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The microstructure, phase composition, precipitates evaluation, casting, and mechanical properties of the novel cast Al-4Cu-2.1Er-1Mg-0.2Zr-0.2Cr-0.15Fe-0.15Si-0.1Ti alloy were analyzed using by optical microscope, scanning and transmission electron microscopes, differential scanning calorimetry, thermodynamic calculations, hot cracking and mechanical properties measurements. The positive effect of Cr as a substitution of Mn on plasticity and precipitation strengthening was demonstrated. The 0.2Zr, 0.2Cr and 0.1 Ti as a grain refiners provide a fine grain size of 25 μm in the as-cast state due to primary Al 75–80 Cu 10–12 Er 3–4 Cr 7 phase particles formation as a nucleation centers of Al. The hot cracking index (HCI) of the AlCuErMgCr alloy was 12–14 mm which is similar with HCI of the cast Al-Si-Cu-Mg alloys. The good casting properties in the AlCuErMgCr alloy achieved due to a fine grain structure and narrow solidification range. The contribution of the Al 3 (Zr,Er) (40 nm), Al 45 Cr 7 (6 nm), and S'(θ') (100/5 nm) precipitates is 38.5 MPa, 140.4 MPa, and 198.9 MPa and the calculated contribution from dislocation and precipitates is 262.3 MPa. The ultimate tensile strength (UTS) and elongation (El.) of the AlCuErMgCr alloy are 372 MPa and 6% which is higher in 16.6% and 150%, respectively, than in the Mn-containing alloy. Novel alloy has an excellent combination of yield strength (YS) and plasticity at 20–250°C. The YS and El. are 301 MPa and 6% and 225–250 MPa and 4.6–11.5% at 20 and 200–250°C, respectively. The rupture strength at 250°C after 100 h (σ 100 250) is 106 MPa. Mechanical and casting properties of the novel alloy are superior to the properties of commercial 201.0 (Al-Cu-Mn-Mg-Ag-Ti) alloy. • Cr, replacing Mn, had a positive impact on both plasticity and precipitation strengthening. • 0.2Zr, 0.2Cr, and 0.1Ti as grain refiners resulted in the formation of primary Al 75–80 Cu 10–12 Er 3–4 Cr 7 phase particles. • The AlCuErMgCr alloy displayed an ultimate tensile strength (UTS) of 372 MPa and an elongation (El.) of 6%. • The rupture strength at 250°C after 100 hours was determined to be 106 MPa. [ABSTRACT FROM AUTHOR]

The microstructure and properties of the aged Cu-Cr-Zr-Nb alloy were studied by means of hardness tester, universal tensile testing machine, conductivity meter, X-ray diffraction, scanning electron microscope, and transmission electron microscope. The results indicated that the hardness and TS (tensile strength) of the Cu-Cr-Zr-Nb alloy increased first and subsequently decreased with increasing the aging temperature. Nevertheless, the electrical conductivity is gradually increasing. The aged Cu-Cr-Zr-Nb alloy was mostly made up of Cu matrix, Cr particles, Cr 2 Nb, and CuZr compounds. Due to the effects of dislocations accumulated by cold drawing and twins produced during the aging process, the softening temperature of the alloy reached 590 ℃. When the Cu-Cr-Zr-Nb alloy was aged at 490 ℃, < 111 > replaced < 110 > in the optimal orientation of the alloy, and the KAM (kernel average misorientation) value inside the alloy was the largest. The alloy exhibited great comprehensive properties at 490 ℃ for 1 h, with a hardness of 144.4 HBW, a TS of 521 MPa, and an electrical conductivity of 78.3%IACS. The contribution value of YS (yield strength) at different aging temperatures was further calculated. The computational results showed that precipitation strengthening was the main strengthening mechanism of the Cu-Cr-Zr-Nb alloy, and fine-grained strengthening and dislocation strengthening simultaneously played a supplementary role. • Due to the effects of dislocations accumulated by cold drawing, precipitation strengthening of Cr and twins produced during the aging process, the softening temperature of the Cu-Cr-Zr-Nb alloy reaches 590 ℃. • The Cu-Cr-Zr-Nb alloy exhibits great comprehensive properties at 490 ℃ for 1 h, with a hardness of 144.4 HBW, a tensile strength of 521 MPa, and an electrical conductivity of 78.3 %IACS. • The computational results show that precipitation strengthening is the main strengthening mechanism of the Cu-Cr-Zr-Nb alloy. [ABSTRACT FROM AUTHOR]

Developments in engineering and medicine have allowed patients' health and quality of life to be supported by implants. Unfortunately, widely used titanium-based alloys with aluminum and vanadium are not ideal materials. The first problem is a mechanical mismatch between human bone and the implant material, and the second issue is the presence of Al or V, which are harmful for the human body and health. This article focuses on the holistic design and production of titanium-based materials with vital elements. The zoned, gradient element can exhibit better mechanical properties and improve the connection between the implant and the bone. The samples in two constructions were built with two different zones. The powders for samples were prepared using the powder metallurgy technique with sieve separation. Phillips X-ray X′Pert diffractometer and PDF4 + database performed the phase composition analysis. The Scanning electron microscope allow the samples observation. Stereological methods assessed porosity and PAR M370 Scanning Electrochemical Workstation. The designed technology based on the powder metallurgy method allows for producing functional, two-zoned graded materials with variable porosity. The phase composition analysis confirmed partially synthesis. Additionally, the observation of the microstructure of the sintered samples revealed the presence of two permanently connected zones. Preliminary mechanical research was conducted to evaluate the potential use of the material as an implant material. The proposal to use two-zone construction of components for implants is dictated by the possibility of personalizing implants for patients, taking into account personal characteristics and needs. [Display omitted] • The functionally graded materials based on vital elements were successfully fabricated using powder metallurgy method. • Highly porous FGM with interconnected porosity was prepared by powder metallurgy. • The porous and microstructure evolution in each gradient layer of FGM is revealed. • The effect of Tin use as Process Control Agent were confirmed and allow to obtain more uniform powders. [ABSTRACT FROM AUTHOR]

High anti-corrosion Mg alloys is desirable to expand their industrial applications. Herein we report an outstanding corrosion resistance of dual-phase Mg-8Li-Y alloy using ultrahigh pressure (UHP) technology. The average corrosion rate is ∼0.47 mm/y, overwhelming the majority of Mg-Li alloys reported hitherto. In-situ X-ray diffraction and scanning electron microscope observation demonstrate that a unique multiple-film on UHPed Mg-8Li-Y alloy attributes to the excellent corrosion resistance, which origins from the dynamic dissolution/regeneration of Li 2 CO 3 -rich composite film, thus effectively prohibiting corrosion solution permeation. These results provide some implications to design good anti-corrosion coating for Mg, ever stainless Mg alloys. ● Y-rich particle dimension is reduced by ultrahigh pressure treatment. ● The corrosion rate of Mg-8Li-Y-UHP-700 is only ∼0.47 mm/y. ● The compact composite oxide film attributes to outstanding corrosion resistance. ● Oxide film bestows dynamic dissolution/regeneration and self-repair characters. [ABSTRACT FROM AUTHOR]

The structure of a series AB 2 Laves-type metal hydride alloys, in which Ce was doped into Ti 0.24 Zr 0.76 Ni 1.15 Mn 0.7 V 0.15 and annealed the alloys, was studied and correlated to hydrogen storage properties and electrochemical performances. X-ray diffraction, scanning electron microscope, and energy-dispersive spectroscopy results revealed that Ce formed a CeNi 3 secondary phase instead of entering the Laves phases. The synergistic effect of the CeNi 3 and (Ti,Zr)Ni phase improved the hydrogen storage and electrochemical discharge properties of the Ce-doped (Ce 0.02) alloy. Especially, the secondary phases could decrease the hydrogen absorption plateau, reduce the hysteresis phenomenon, and increase the hydrogen storage capacity (from 0.9 wt% to 1.4 wt% at 25 ℃). The formation of CeNi 3 H x hydride on the surfaces of alloy electrodes led to a higher discharge capacity (∼500 mAh/g) and a faster activation rate. The Ce 0.02 alloy also showed a good cyclic stability ∼82.08%, after 500 charge-discharge cycling, which could be ascribed to the good corrosion resistance of the CeNi 3 phase on the surface of alloy. In addition, annealing treatment promoted the depletion of (Ti,Zr)Ni secondary phase and the transformation from the C14 to C15 phase. The Ce-doped AB 2 alloy can be used as a hydrogen storage and hydride battery electrode material. • Annealing resulted in the transformation from the C14 to C15 Laves phase. • Full discharge capacity of Ce 0.02 alloy as an anode reaches 500 mAh/g at 10 mA/g. • Synergistic effect of the CeNi 3 and (Ti,Zr)Ni phases on the Laves phases. • Secondary phases improves discharge and hydrogen storage capacity, and HRD ability. [ABSTRACT FROM AUTHOR]

TiC/AlSi10Mg alloys were successfully fabricated by laser additive manufacturing under high-frequency micro-vibration. The application of high-frequency micro-vibration during laser processing could accelerate the melt flow, promote the floating of gas and slag in the molten pool and significantly reduce the pores in the alloys, which could obtain refined and homogenous microstructure with superior alloy density as well as good performances with relatively high production efficiency. The effects of different vibrational frequencies on the microstructure and properties of the alloys have been systematically investigated. The microstructure, chemical composition, phase constituent, hardness distribution and tensile properties of the TiC/AlSi10Mg alloys were investigated by optical microscope (OM), scanning electron microscope (SEM), energy dispersive X-ray analysis (EDAX), X-ray diffractometer (XRD), Vickers micro-hardness tester, and high-precision electronic universal testing machine, respectively. The results shows that the structures of the TiC/AlSi10Mg alloys are refined by high-frequency micro-vibration. The size of the cellular grain is decreased from 4 to 13 μm to 2–4 μm. The overlap region of the molten pool could be divided into three parts: fine zone, coarse zone and heat affected zone (HAZ). The number of pores in the alloys is reduced by high-frequency micro-vibration and the density of the alloys is effectively improved. When the vibration frequency is 969 Hz, the structure is more compact and the defect in the alloy is the lowest, providing a good density (99.1%). In addition, the maximum average hardness is 183.3 HV 0.05 at the vibration frequency of 969 Hz, and the maximum tensile strength and elongation are 314.7 MPa and 8.81% respectively at this vibration frequency, which are higher than those at other vibrational frequencies. Image 1 • The microstructure of the TiC/AlSi10Mg alloys is refined by the vibration. • The maximum density of the alloy reaches 99.1% at a vibration frequency of 969 Hz. • The hardness of the TiC/AlSi10Mg alloys is enhanced by the vibration. • The tensile strength of the TiC/AlSi10Mg alloys is improved by the vibration. [ABSTRACT FROM AUTHOR]

A cost-effective iron-rich non-equiatomic Fe 50 Mn 20 Al 15 Ni 10 Co 5 medium entropy alloy (MEA) was synthesized by vacuum induction melting. The as-cast alloy exhibits a multiphase microstructure with the ordered B2 (a= 2.90 ± 0.01 Å), disordered body-centred cubic (BCC) (a= 2.89 ± 0.01 Å) and face-centred cubic (FCC) (a= 3.61 ± 0.02 Å) phases. X-ray diffraction (XRD) and transmission electron microscope (TEM) were used to confirm the structure of the evolved phases. The columnar dendrites having a width in the range of 120–300 µm were observed in the as-cast structure. The formation of Ni-Al rich B2 precipitates in the BCC matrix was confirmed based on detailed microstructural characterization using scanning electron microscope (SEM) and TEM. The phase separation in the form of modulated structure of ordered B2 and disordered BCC phase was related to the spinodal decomposition. The formation of the FCC phase at and near the grain boundaries is linked to simultaneous nucleation and growth mechanisms, which occur during the solidification. The as-cast alloy has shown an average compressive yield strength of ∼1250 MPa and ultimate strength of ∼1675 MPa, along with a compressive strain of ∼42%. The optimum balance of strength and ductility is achieved due to the formation of the hard (B2, BCC) and soft (FCC) phases and their interplay during the deformation process. These encouraging results of the alloy in the as-cast state have provided the direction to design and develop such economically viable alloys, which could be produced at industrial scale. • A novel cost-effective Fe 50 Mn 20 Al 15 Ni 10 Co 5 MEA was synthesized by vacuum induction melting. • Alloys exhibits two phase structure of BCC and FCC in as-cast state. • The modulated structure of B2 and BCC was related to spinodal decomposition. • The optimum balance of strength and ductility is achieved in the alloy. [ABSTRACT FROM AUTHOR]

Laser powder bed fusion (LPBF) is one of the most widely used additive manufacturing (AM) methods to produce metal parts with new functionalities, but it still suffers from a low built rate. Increasing the powder layer thickness is an efficient way to augment LPBF productivity. The objective of this study is to investigate the influence of the powder layer thickness during the LPBF of F357 alloy on the microstructure and age-hardening response during T5 heat treatment. Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations show that microstructure differences are negligible between samples printed at 30 µm and 50 µm layer thicknesses in the as-built condition. Samples built with both layer thicknesses and subjected to T5 heat treatments at 150 °C, 160 °C, and 170 °C also show similar microstructures and their α-Al cells contain large Si precipitates and small Si clusters and no β"-Mg 2 Si precipitates. Therefore, β"-Mg 2 Si precipitation hardening is not the dominant mechanism, and strengthening appears to be mainly due to the small Si clusters. With the help of the Johnson-Mehl-Avrami (JMA) model, the activation energy of the precipitation process of the samples built at 30 and 50 µm layer thicknesses is calculated to be 142 kJ/mol and 139 kJ/mol, respectively. These comparable values suggest a similar evolution of the precipitation hardening for both layer thicknesses, which is consistent with the observed microstructures. Consequently, the production efficiency of LPBF-printed F357 alloys can be enhanced by using higher layer thickness and the T5 heat treatment. • The as-built 30 µm sample exhibits higher hardness than the 50 µm sample. • T5 HT can strengthen both 30 µm and 50 µm samples at 150 °C, 160 °C, and 170 °C. • Hardness difference between 30 µm and 50 µm sample is reduced after T5 peak aging. • Similar T5 precipitation evolution of 30 µm and 50 µm samples is shown by TEM. • The apparent activation energy for both 30 µm and 50 µm samples is ∼140 kJ/mol. [ABSTRACT FROM AUTHOR]

The effect of δ-Al 3 CuNi phase and thermal exposure on microstructure and mechanical properties of Al-Si-Cu-Ni alloy is investigated by optical microscopy, scanning electron microscope, and tensile test. The alloys with different volume fractions of δ-Al 3 CuNi phase are designed according to the thermodynamic calculation, which is confirmed by the microstructure characterization. The mean diameter of primary Si increases while the eutectic Si decreases with increasing the volume fraction of δ-Al 3 CuNi phase. The eutectic Si is coarsening during thermal exposure at 350 °C. Both strip-shape and fishbone-shape δ-Al 3 CuNi phase are observed in the as-cast alloys. In addition, the fishbone-shape δ-Al 3 CuNi phase is composed of many independent short rods. Parts of the thin short rods of δ-Al 3 CuNi phase change into γ-Al 7 Cu 4 Ni phase after thermal exposure at 350 °C for 200 h. The ultimate tensile strength and yield strength increase while the elongation decreases with increasing the volume fraction of δ-Al 3 CuNi phase. Comparing with the as-cast alloys, the ultimate tensile strength and yield strength are reduced after thermal exposure at 350 °C for 200 h, but the elongation of the alloys is increased. The failure mechanism of the alloys tested at 25 °C is quasi-cleavage fracture and ductile fracture is the dominant fracture mechanism tested at 350 °C. • The Al 3 CuNi with thin short rods shape changes into Al 7 Cu 4 Ni at 350 °C for 200 h. • The eutectic Si is coarsening during thermal exposure at 350 °C. • The Al 3 CuNi phase with strip-shape is thermal stable at 350 °C. • The ultimate tensile strength and yield strength increase with the Al 3 CuNi phase. [ABSTRACT FROM AUTHOR]

The aim of the present study was to assess the influence of the milling time (10 h, 15 h and 20 h) on the structure and properties of Ti-10Ta-8Mo (wt.%) and Ti-10Ta-8Mo-3Sn (wt.%) alloys for potential biomedical application. In addition, the influence of the addition of 3 wt% Sn on the structure and properties of the milled and sintered materials was investigated. X-ray diffraction confirmed the partial synthesis and formation of the β phase during the milling process. The transmission electron microscope analysis of the bright and dark field images and the diffraction image proved the nanocrystalline nature of the material after being subjected to 20h milling duration. The scanning electron microscope observation of the sintered samples confirmed the influence of the milling time and presence of Sn on the microstructure of the obtained material. Furthermore, a small addition of Sn led to better size homogenization by establishing a better balance between the cold-welding and agglomeration processes. At the same time yielding different structures of pores for the sintered samples. The dry sliding tests revealed the excellent friction properties and wear rate of the samples previously milled for 15 h, with the addition of Sn. • The milling and sintering enables the preparation of porous Ti-Ta-Mo-(Sn) alloys. • The presence of Sn led to the finer, flake-like particles after ball milling. • The α, β and Mo nanocrystalline phases were prepared by ball milling. • For the Sn15 + HT sample the friction process and a COF that was three times lower. • The sample Sn15 + HT sample was characterized by the lowest specific wear rate. [ABSTRACT FROM AUTHOR]

A novel continuous and controllable combustion synthesis process for fabrication of TiAl alloy from TiO 2 , Al, KClO 3 and CaO was developed in this paper. The effects of different material ratios on the composition of alloy and the separation effect of alloy and slag were studied. Based on the mass action concentration model, the phase equilibrium composition of Ti- O -Al system at 1800 K was also investigated. The as-cast TiAl alloys were analyzed by X-ray diffractometer, scanning electron microscope, inductively coupled plasma emission spectrometer and Oxygen/Nitrogen/Hydrogen analyzer. According to the comparison between theoretical calculation and experimental results, the variation trends for the alloy composition from experiment are well consistent with calculation results along the increase of Al addition amounts in raw materials. The analyzed composition of alloy for Ti, Al and O are 56.53, 40.99 and 1.09 (wt. %), respectively. This present method hopefully supplied an efficient way for preparation of Ti- or Al-based alloys. • The ratio of raw materials can be supplied by mass action concentration calculation. • Phases, compositions of TiAl alloy can be predicted from theoretical calculation. • A continuous and controllable smelting procedure can be conducted. • Integration of metallurgy and materials preparation process has been realized. [ABSTRACT FROM AUTHOR]

Abstract Al-6Cu-6Mg-5Sn-3Ga- x In (x = 0, 0.5, 1, 3, 5. mass. fraction) alloys were prepared using melting and casting technique. The microstructures and properties of the alloys were investigated by X-ray diffraction, scanning electronic microscope/EDX, electron microprobe analysis, Vickers hardness, compression properties, immersion tests and electrochemical measurements. The results show that the main phases of the alloys with the indium element consist of α -Al, Al 2 MgCu, Mg 2 Sn and Al-In eutectic phases. The Al-In phases segregates in α -Al grain boundaries. The gallium elements solid solution in the matrix alloys. When the addition of In contents is 1 mass.%, the hardness of the Al-6Cu-6Mg-5Sn-3Ga-1In alloy reaches to 142HV, and the compressive strength up to 582 MPa. The Mg 2 Sn and the Al-In eutectic phases are the source of the degradation reaction, and the driving force to continue is the concentration of Al in the eutectic phase. The relationship between the degradation corrosion rate and temperature, indium element content and other factors were also discussed in this paper. Graphical abstract Image 1 Highlights • Microstructure, mechanical properties and corrosion behavior of Al-6Mg-6Cu-5Sn-3Ga- x In alloys were firstly investigated. • The investigated alloys mainly consist of α -Al matrix, Al 2 MgCu, Mg 2 Sn and Al-In eutectic phase. • The investigated alloy has a maximum degradation rate reaches 98.51 mg/(cm2 h) at 93 °C. [ABSTRACT FROM AUTHOR]

The effect of neodymium (Nd) additions from 0 to 0.2 wt.% on microstructure, mechanical properties at room and high temperature, as well as corrosion resistance of 2A70 alloy were studied by optical microscopy (OM), scanning electron microscope (SEM), transmission electron microscopy (TEM) in this paper. The results show that appropriate addition of Nd (0.15 wt.%) refines the size and enhances the density of the aging precipitates S′ phase, which lead to the increasing of mechanical properties at room and elevated temperatures. The newly formed Al8Cu4Nd compound, dispersed along grain boundary, which hinders the movement of grain boundaries at elevated temperature and improves the high temperature performance of 2A70 alloy. Compared with traditional 2A70 alloy, the intergranular corrosion of the peak-aged alloy with 0.15 wt.% Nd has also been effectively enhanced. [ABSTRACT FROM AUTHOR]

It is well known that high entropy alloys (HEAs) have a wide range of potential applications as radiation shielding due to their superior properties. The CoNiFeCr-Ti/Al compositions were chosen for their low cost as HEA in this study. The HEAs were successfully produced using the mechanical alloying (MA) method with equimolar CoNiFeCr, CoNiFeCrAl, and CoNiFeCrTi compositions. The production and structural properties of the alloys were investigated in detail. Besides, the photon and particle radiation shielding properties of the HEAs were calculated with the help of Phy-X/PSD, SRIM (10 keV-20 MeV), and ESTAR (10 keV-20 MeV) programs. The photon-matter interaction parameters were calculated in both specific photon energies emitted from 241Am, 133Ba, 109Cd, 60Co, 137Cs, 131I, and 22Na nuclides and a continuous energy range of 15 keV-15 MeV. The characterization of the alloys was investigated by using X-ray diffraction (XRD) and scanning electron microscopes (SEM) attached to an energy dispersive spectroscopy (EDX). It was found that the HEAs have a highly amorphous structure due to the selected production method. The crystal size of the alloys was calculated as 70, 35, and 20 nm for CoNiFeCr, CoNiFeCrAl, and CoNiFeCrTi, respectively. In terms of shielding properties, it has been determined that the produced HEAs have better shielding characteristics for photon and particle radiations than standard shielding concretes. In addition, the results demonstrated that CoNiFeCr alloy, which has the best shielding ability among the HEA alloys, can be used as a shielding material application requiring photon, electron, proton, alpha, and neutron radiations. • Low-cost CoNiFeCr-Al/Ti high entropy alloys (HEAs) were produced by mechanical alloying. • Crystal sizes were calculated as 70, 35, and 20 nm for CoNiFeCr, CoNiFeCrAl, and CoNiFeCrTi, respectively. • All manufactured HEAs have a better radiation shielding capacity than conventional OC, SS, SM. • CoNiFeCr alloy can be used as an alternative shielding material for all radiation types. [ABSTRACT FROM AUTHOR]

The single-phase TiNbZrMo x (x = 0, 0.3, 0.5, 0.7, 1) high-entropy alloys (HEAs) were prepared by arc melting. The relation between molybdenum, microstructure, mechanical properties and wear resistance was investigated by X-ray diffractometer (XRD), scanning electron microscope (SEM), universal tensile tester, hardness tester, friction tester, and wear tester. The results showed that TiNbZrMo x alloys were composed of a single BCC phase. With the increase of Mo elements, the crystallite size of the as-cast alloy decreased first and then increased, both the alloy strength and hardness were increased and compressive strain plasticity was decreased. TiNbZrMo 0.5 has the best comprehensive performance with a yield strength of 1.0 GPa, compressive strength of 1.3 GPa, and hardness of 429 HV; compared with TiNbZrMo 0 , yield strength increased by 77.32%, compressive strength increased by 25.14%, and hardness increased by 70.24%; and its specific wear rate decreased by 50%, while it's compressive plasticity only decreased by 5%. • The addition of appropriate amounts of molybdenum improves the strength, hardness and wear resistance of TiNbZrMo x HEAs. • Compared to TiNbZr, TiNbZrMo 0.5 has the best overall performance. • The main wear mechanisms of TiNbZrMo x (x = 0, 0.3, 0.5, 0.7, 1) are abrasive wear and oxidative wear. [ABSTRACT FROM AUTHOR]

In this study, the porous carbon-based materials loaded with Fe, Co, and Cu nanoparticles were fabricated by chemical blow molding carbonization to ameliorate the hydrogen storage performances of as-milled Mg 91 Al 5 Y 4 alloy. The Sievert apparatus was utilized to test the isothermal hydrogen absorption/desorption curves and P-C-T (Pressure-composition-temperature) curves. The microstructure characterizations of the specimens were completed by using XRD (X-ray diffraction), SEM (scanning electron microscope), TEM (transmission electron microscope), etc. Besides, Raman spectrum and Nitrogen adsorption/desorption isotherms have been applied to characterize the defect density, specific surface area and dominant pore diameter of the catalysts. Based on the results, the catalysts Tm@C (Tm = Fe, Co, Cu) with porous lamellar structure have the specific surface area of 156.9, 190.9, 106.4 m2/g and the diffraction intensity ratio (I D /I G) of 1.06, 1.09, 0.96, respectively, showing great catalytic influence on hydrogen storage performances of as-milled Mg-Al-Y alloy Concretely, the composite Mg 91 Al 5 Y 4 + 5 wt% Co@C with the minimum dehydrogenation activation energy of 84.8 kJ/mol can absorb a small amount of H 2 at 323 K, besides, the initial hydrogen desorption temperature of it is about 521.5 K. The catalytic functions of Tm@C can be ascribed to the following aspects: the enhancement of milling efficiency and the following particle/grain refinement of alloy; the introduction of great number of defects (active sites); the loaded transition metals (with high electronegativity and multi-valence) or their derivative nanoparticles, etc. • Tm@C (Tm Fe, Co, Cu) are prepared to improve Mg-Al-Y hydrogen storage alloy. • The Mg 91 Al 5 Y 4 -5 wt%Co@C composite has the minimum E a de value of about 84.8 kJ/mol. • The Tm nanoparticles supported by the catalysts and inner defects play a catalytic role. [ABSTRACT FROM AUTHOR]

In this paper, aluminum alloy doped with Mg, In, Sn and Bi (Al-0.02Mg-0.01Sn-0.004Bi-0.003In) is prepared via melting and casting process. The influence of rare earth elements Bi and In on electrochemical performance of aluminum alloy anode is studied. The self-corrosion of hydrogen evolution and the electrochemical performance are investigated for the prepared alloy in 4 M NaOH electrolyte. The scanning electron microscope is used to study the surface morphology of the prepared alloy after discharge. It shows that synergistic effect between the alloy elements significantly reduces the self-corrosion rate of aluminum anode. Discharge experiments display that the prepared alloy outputs high capacity density and energy density of 2857.14 A h kg−1 and 4805.71 W h kg−1 at a high discharge rate (50 mA cm−2), respectively. It can also obtained considerable anodic utilization of 95.94 %. The prepared aluminum alloy is a desirable candidate anode material for the high-performance Al-air battery. • The prepared alloy exhibits an equiaxed grain structure with an average grain size of 70 µm. • The prepared alloy outputs high capacity density and energy density. • The prepared alloy has low self-corrosion rate of hydrogen evolution. • The prepared alloy has considerable anodic utilization of 95.94 %. [ABSTRACT FROM AUTHOR]

The interface between LPSO and β' in the Mg-Gd-Al alloys is investigated by the high-angle annular dark-field scanning transmission electron microscope (HAADF-STEM) imaging and first-principles calculation. The formation energies of interface structures with different rare-earth-depleted layers (REDL) indicate that the interface structure with three-layer REDL is the most stable. The interfacial phase diagram with the chemical potential of Gd is obtained by the first-principles molecular dynamics analysis of interface energies, indicating that the β'/Mg interface layer in the three-REDL structure is the most stable, and the REDL is not only the Mg atomic layer, but also part of the LPSO phase. Moreover, it is also indirectly proved that the β'/Mg interface layer with three-layer REDL in Mg-Gd-Al alloys will form strong covalent and metallic bonds, and the bond energy is larger and more stable. Therefore, the characterization and calculations of the LPSO and β' interfaces provide a theoretical basis for future interface property analysis and interface design. • The interface between long-period stacking-ordered (LPSO) and β' phases by HAADF-STEM and first-principles calculation. • The first-principles molecular dynamics analysis and bond relationship of the rare-earth-depleted layer (REDL). • The interface with three REDLs (partof the LPSO phase) is the most stable structure. [ABSTRACT FROM AUTHOR]

• Effects of pre-strain on precipitation kinetics and strengthening mechanisms of γ'-strengthened HEAs were studied. • Pre-strain can accelerate precipitation kinetics but shows a non-monotonous feature with the increase of pre-strain. • The shortened defects existing time by recrystallization can weaken the acceleration effect at high pre-strain. • Strengthening mechanisms can be tuned by different pre-strain to realize targeted properties. Pre-strain is often used as a powerful pre-treatment to tailor the microstructures and mechanical properties of traditional alloys. However, in high-entropy alloys (HEAs), the effect of pre-strain degree on the precipitates is still unclear. In this paper, we investigated the effects of pre-strain degree on the precipitation of Ni 2 CoCrFeTi 0.18 Al 0.12 high-entropy alloys. The HEAs were cold-rolled with different thickness reduction of 30%, 50%, and 70% and annealed at 800 °C for 30 ~ 60 min, followed by high-resolution scanning electron microscope (SEM) analysis. Counter-intuitively, we discovered a non-monotonous effect of pre-strain on the precipitation behavior, that low pre-strain can accelerate the precipitation behavior while such accelerating effect is weakened under high pre-strain. This non-monotonous effect is attributed to the shortened defects existing time by recrystallization under high pre-strain. In addition, pre-strain can controllably tailor the precipitation strengthening, dislocation strengthening, and grain boundary strengthening of HEAs. These results not only uncover the mechanism of the non-monotonous pre-strain effect on the precipitates but also provides a pre-strain mediated scheme for tuning the precipitation-strengthened HEAs to targeted properties. [ABSTRACT FROM AUTHOR]

• The mechanical properties of microstructures depend on mesoscopic slip and fracture behavior. • There exist many long slip traces directly passing through the microtextured regions. • Blocked slip arouses a high stress concentration in microtextured region. • Slip transmission is related to alignment between two slip systems and their Schmidt factors. In this paper, the tensile behavior and deformation mechanism of two typical bimodal microstructures in Ti6242S alloy were investigated through the in-situ scanning electron microscope (SEM) test and electron backscatter diffraction (EBSD). The results showed that the two microstructures presented different mechanical properties due to the different microscopic slip and fracture behaviors. In the homogeneous microstructure (with homogeneous crystallographic orientation), most of the slip traces were restricted within the grains because the slip transmissions between neighboring grains were blocked. The slip deformation was relatively homogeneous. Therefore, the fracture mechanism was micro-void accumulation fracture. In the inhomogeneous microstructure (with many microtextured regions), there existed many long slip traces directly passing through the microtextured region (the region of α phase with similar crystallographic orientation), the slip behavior was closely related to the same basal slip. The blocked slip aroused a high stress concentration in microtextured region, which was easy to induce the formation of microcrack, and then the microcrack propagated along the slip band. This can be attributed to the fact that slip transmission behavior was closely related not only to the alignment between slip planes and slip directions in two neighboring slip systems , but also to their Schmidt factors (SFs). Thus, the fracture mechanism was the coexistence of micro-void accumulation facture and cleavage fracture. [ABSTRACT FROM AUTHOR]

The Mg-12Gd-2Er-0.4Zr (GE122K) is fabricated by double extrusion, and the effects of grain refinement and precipitate evolution on the mechanical performance of the extruded alloys are deeply analyzed. Scanning electron microscope results spectacle that some bulky precipitates in the single extruded alloy are fragmented to fine precipitates during double extrusion and distribute linearly along the extrusion direction (ED). The fine precipitates exhibit the strongest dispersion strengthening effect, whereas the bulky precipitates act as crack resources and decrease the elongation. After double extrusion, a refined grain structure with an average grain size of 2.7 µm is achieved, which is attributed to dynamic recrystallization (DRX). Moreover, double extrusion boosts the content of rare-earth elements into the matrix by dissolving the fine precipitates. During aging, extensive β′ precipitates form in the double extruded alloy than in the single extrude alloy. As a result, refined grains and strong precipitation strengthening make a significant contribution to a high yield strength (YS) of 422 ± 1.59 MPa with an elongation (EL) of 6.5 ± 0.89% in the double extruded+peak-aged alloy (ACX2). The possible strengthening mechanisms are discussed, and it is found that grain refinement and precipitate strengthening are the main contributors to the high strength of the GE122K alloy. Fabrication of Mg-12Gd-2Er-0.4Zr (wt%) alloy via double extrusion+aging with excellent mechanical performance. [Display omitted] • A facile and robust fabrication mechanism is adopted to attain an excellent balance of yield strength and elongation. • Grain refinement and precipitates have different effects on the strength of Mg-12Gd-2Er-0.4Zr alloy. • The β′ precipitate strengthening is the dominate strengthening mechanism during aging treatment of the extruded alloys. [ABSTRACT FROM AUTHOR]

• Phase transformation upon cooling Ti 2 AlNb alloy was investigated. • The critical rate to completely depress α 2 and O phases is 0.5 and 4 °C/s, respectively • The phase transformation of B2/β→O occurs in a temperature range of 729–925 °C. • A higher cooling rate makes the phase transformation occur in a narrower temperature range. • The alloy cooled at 0.1 °C/s has the highest microhardness due to the fine but numerous precipitates. Phase transformation and microstructure evolution of a Ti 2 AlNb alloy upon cooling from B2/β phase at rates of 0.02–100 °C/s were investigated by using X-ray diffractometer, scanning electron microscope, and thermal dilatometer. At the lowest cooling rate of 0.02 °C/s, both α 2 and O phases precipitate from the B2/β phase. The precipitation is prior to occur at the grain boundary of the parent phase, which even makes α 2 phase almost disappear from the interior of the grain. Cooling the alloy at a higher rate results in a decreasing amount of the precipitates. The critical rate for the complete depression of α 2 and O phase precipitation is 0.5 °C/s and 4 °C/s, respectively. According to the established continuous cooling transformation (CCT) diagram, the temperature interval for B2/β→O phase transformation decreases with increasing cooling rate. The alloy cooled at the rate of 0.1 °C/s has the highest microhardness for the appropriate size and amount of the precipitated phases. [ABSTRACT FROM AUTHOR]

• Ti-6Al-4V were manufactured by the DMLS technique with different laser powers. • Effect of the microstructure and surface modifications on apatite formation ability was investigated in the SBF solution. • Ca and P ions ratios were calculated to determine the formation of apatite layer. • The samples 3 exhibited a higher apatite formation ability. [Display omitted] In this study, Ti-6Al-4V alloys were additively manufactured (AM) with different laser powers. The goal was to investigate the effect of different surface modifications on apatite formation ability. Four types of surface modifications, namely, sandblasting (S), acid etching (E), anodic oxidation (AO) and anodic spark oxidation (ASO), were achieved on the Ti-6Al-4V samples. The microstructure, phase, morphology, roughness and wettability properties were examined by optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD), surface profilometer and contact angle techniques. The bioactivity analysis was performed in simulated body fluid (SBF) for 2 weeks. The results indicated that the microstructure, surface topography, roughness and wettability influenced the apatite formation were affected by the production laser power. Generally, the samples 3 showed higher Ca and P ion ratio value because of percentage of β phase amount, the presence of bioactive phases on the surfaces. The E3 sample resulted in the best apatite formation theoretically. The etching procedure of AM Ti-6Al-4V in the acidic solution can be applied to improve the apatite formation ability of Ti-6Al-4V alloys. [ABSTRACT FROM AUTHOR]

Abstract: Electroless nickel plating on Mg–8Li alloy was studied, and an appropriate molybdate pretreatment was proposed. The pretreatment layer acted as an effective barrier and catalytic layer for the subsequent Ni–P plating. The coating was characterized by its structure, morphology, micro-hardness and corrosion resistance. Scanning Electronic Microscope (SEM) observation showed that the Ni–P coating was compact, uniform. The presence of molybdate pretreatment layer could reduce the potential difference between the Ni–P coating and the substrate, and enhanced the corrosion resistance of the alloy to certain extent. The electrochemical measurements showed that the sample with Ni–P film exhibited lower corrosion current density and more positive corrosion potential than the substrate. The hydrogen evolution tests further proved that the Ni–P coating provided good protection to the substrate. [Copyright &y& Elsevier]

• In this study, we have successfully used the LMD technique to fabricate a γ-TiAl/Ti 2 AlNb graded alloy, which is fully dense without cracks and pores. • We carried out detailed phase and microstructure analysis on the transition zone from the Ti 2 AlNb substrate to the γ-TiAl alloy: Three layers are observed in the transition zone. • We employed a novel high-speed nanoindentation technique, for the first time, to statistically study the microstructure-property relationship in the transition zone. [Display omitted] Additive manufacturing (AM) is a transformative technology to the aerospace industry. As one of the AM techniques, laser metal deposition (LMD) enables the fabrication of engine blades and a disk, as a single component, known as blisk. In this study, we use the LMD technique to fabricate a γ-TiAl/Ti 2 AlNb graded metallic alloy by depositing γ-TiAl powder on a Ti 2 AlNb alloy substrate. High-resolution scanning electron microscope (SEM) and high-speed nanoindentation are employed to characterize the microstructure and mechanical properties of the transition zone from the Ti 2 AlNb substrate (disk) to the γ-TiAl alloy (blade). The results show that the transition zone includes three layers (I, II and III) with gradient compositions and phases: (I) mainly β/B2 matrix with randomly distributed α 2 and γ phases, (II) (α 2 + γ) lamella with γ and β/B2 phases, and (III) similar microstructure with Layer II but finer γ and β/B2 phases. The results of nanoindentation mapping show good correlations between the mechanical properties (nanohardness and elastic modulus) and microstructure in the transition zone. Attributing to the rule of mixtures, the nanohardness and elastic modulus gradually increase from the substrate Ti 2 AlNb to Layer I, and gradually decrease from Layer I to γ-TiAl. This work demonstrates that the microstructure and phase analysis in combination with high-speed nanoindentation offers a new opportunity to study graded materials made using LMD. [ABSTRACT FROM AUTHOR]

• γ 2 -Al 8 Mn 5 phase transformed to LT -Al 11 Mn 4 phase due to uphill diffusion of Al. • Shell type structure developed where LT -Al 11 Mn 4 shell encapsulated γ 2 -Al 8 Mn 5 phase. • Higher volume of LT-Al 11 Mn 4 phase resulted in cracks in the shell. • Si, Fe and Mg content decreased in the LT-Al 11 Mn 4 during solutionizing. [Display omitted] γ 2 -Al 8 Mn 5 intermetallic particles are generally present in commercial Mg-Al-Zn alloys. The present study is concerned with the effect of solutionizing on the morphology and phase stability of the γ 2 -Al 8 Mn 5 particles in an as-cast AZ91 alloy. Analysis using energy dispersive spectroscopy (EDS) and electron back scattered diffraction (EBSD) in a scanning electron microscope (SEM), transmission electron microscopy (TEM) and atom probe tomography (APT) suggests that solutionizing resulted in uphill diffusion of Al from the α-Mg matrix resulting in the phase transformation of γ 2 -Al 8 Mn 5 to Low Temperature (LT) -Al 11 Mn 4 phase. This leads to a shell type structure of LT-Al 11 Mn 4 encapsulating γ 2 -Al 8 Mn 5 and the formation of cracks in the LT-Al 11 Mn 4 phase. These can propagate during external loading, affecting the mechanical properties. Additionally, the content of Fe and Si decreased in the LT-Al 11 Mn 4 , which could potentially decrease locally the corrosion resistance. [ABSTRACT FROM AUTHOR]

In this work, stoichiometric Pb 1−x Ge x Te (x = 0.0, 0.03, 0.06, 0.09, 0.12) crystalline alloys were synthesized using the monotonical temperature melting technique. The synthesized alloys were examined using x-ray diffraction and scanning electron microscope. It was revealed that the crystal structure in all samples is a cubic phase of PbTe. In terms of Seebeck coefficient and electrical conductivity, thermoelectric measurements were carried out in the temperature range of 83–373 K. The Seebeck coefficient of the compounds showed a positive sign, which refers to p-type conduction. The thermoelectric power factor (PF) was studied as a function of temperature, with different amounts of Ge content (x). The highest PF was recorded for the highly Ge-doped samples at higher temperatures (373 K). The maximum PF was observed at 3.2 × 102 µW/m K2 for the sample with x = 0.09, which is quite high for the studied compounds. The electronic part of thermal conductivity was calculated using the Wiedemann-Franz law. A noticeable reduction of this thermal conductivity was detected due to stronger point defect scattering introduced by Ge doping. The reduction in the electronic thermal conductivity can led to a considerable enhancement in the thermoelectric figure of merit. • Pb 1−x Ge x Te alloys were synthesized by monotonical temperature melting technique. • Thermoelectric measurements were carried out in the temperature range 83–373 K. • The thermoelectric power factor was studied as a function of temperature and Ge content. • The maximum power factor was observed at 3.2 × 102 µW/m.K2. [ABSTRACT FROM AUTHOR]

Abstract: Faceted nanoparticles of zinc oxide were successfully achieved via thermal annealing of hydrozincite (Zn5(CO3)2(OH)6) powder at different annealing temperatures, i.e. 300, 500 700 and 900°C in air for 2h using sol–gel method by refluxing for 6h at 70°C. Zinc acetate dihydrate (Zn(CH3COO)2·2H2O) was used as precursor with urea (NH2CONH2) for the synthesis of hydrozincite. The morphological observations by field emission scanning electron microscope indicated increase in particle size from 20 to 300nm with increase in the annealing temperatures. High resolution TEM and SAED measurement indicate the distance between two lattice fringes is ∼0.52nm corresponding to (0001) fringes. A standard peak of zinc oxide was observed at 457cm−1 from the FTIR analysis. Thermo gravimetric analysis (TGA) revealed that the primary weight loss starts at ∼130°C due to solvent evaporation and the secondary weight loss due to phase transition from hydrated zinc oxide to zinc oxide was observed at ∼290°C. [Copyright &y& Elsevier]

Abstract: Ag/ZnO contact material was prepared by gas atomization internal oxidation forging technology (AIOF technology). The granularity, morphology and component of gas atomized Ag/Zn alloy powder were studied; the phase constitution, microstructure and physical performance were analyzed by X-ray diffraction (XRD), optical microscope (OM) and scanning electron microscope (SEM), respectively. Furthermore, the oxidation mechanism of Ag-based alloy was also discussed. The results showed that 82% gas atomized Ag/Zn alloy powders were less than 125μm in diameter of irregular shape. The microstructure was homogeneous with electrical contact resistance equal to 2.10μΩcm and of 98% relative density and hardness of 102.8HV. The performance was much better than that prepared by conventional powder metallurgy method. The oxidation of Ag-based alloy was considered to be controlled by oxygen diffusion. [Copyright &y& Elsevier]

Abstract: The effects of mechanical ball-milling on the hydriding/dehydriding behaviors of La1.8Ca0.2Mg14Ni3 alloy were investigated. The time of ball-milling under an argon atmosphere is 10, 15 and 20h, respectively. The changes in phase structure and morphology of the samples were analyzed through XRD and scanning electron microscope (SEM). The results show that mechanical ball-milling can improve the hydrogen absorption/desorption kinetics of La1.8Ca0.2Mg14Ni3 alloy. The milled alloys of La1.8Ca0.2Mg14Ni3 show much better hydriding/dehydriding behaviors than the as-cast alloy. Among the alloys studied, the alloy milled for 20h shows the best overall property. [Copyright &y& Elsevier]

Abstract: The microstructures of Fe2Si5 based alloys fabricated by spark plasma sintering and the subsequent heat treatment were investigated by X-ray diffraction (XRD) analysis and scanning electron microscope (SEM). The results showed that a two-phase structure consisting of β-FeSi2 and Si dispersoids was obtained by the eutectoid decomposition of α-Fe2Si5 phase during annealing. The thermoelectric properties of Fe2Si5 based alloys were also investigated as compared with the stoichiometric FeSi2 based alloys. It was found that Fe2Si5 based alloys have the same conduction mechanism with stoichiometric FeSi2 alloys doped with Mn and Co, respectively. An increase in carrier scattering caused by Si particles was observed in both Mn- and Co-doped alloys. The effect of Si dispersoids on Seebeck coefficient and electrical resistivity was discussed. Results show that the excessive Si dispersoids in Fe2Si5 based alloys could improve the transport properties of the material, especially for the Co-doped alloys. [Copyright &y& Elsevier]

Three-component Cu68.5Ni12P19.5 alloy was prepared using 99.95 wt.% Cu, Cu–P and Ni–P master alloys. The precursors were encapsulated in quartz tubes under vacuum (10-2 bar) and melted in a resistance furnace. The microstructure of the alloy was investigated using a light microscope and a scanning electron microscope (SEM) with energy dispersive spectroscopy (EDS). An analysis of the morphology was carried out and the volume fraction of microstructural constituents in the as-cast state was assessed. The melt spinning was used to produce ribbons from the alloy. The ribbons were then investigated by means of differential scanning calorimetry and differential thermal analysis. High-temperature X-ray studies of melt-spun ribbons as a function of temperature were carried in order to characterize the thermal stability of the alloy. The results were discussed and compared with other experimental data. [Copyright &y& Elsevier]

Ti–Al–Si powders with different Al and Si combinations were mechanically alloyed by ball milling in order to investigate the roles of Al and Si elements in the formation of a Ti supersaturated solid solution or amorphous phase. The results demonstrate that Al plays an active role in promoting the formation of Ti(Al,Si), which can be attributed to the development of a lamellae structure with alternating layers of deformed Ti and Al in the case of Ti–21Al–4Si (at.%) powder. No such lamellae structure could be formed during the milling of Ti–4Al–21Si (at.%). Though SEM observations indicated fine granular structure after 40 h milling in both types of powder mixtures, EDS analyses showed that the fine milled particles were of homogenous composition in the case of Ti–21Al–4Si only. [Copyright &y& Elsevier]

The hydriding combustion synthesis (HCS) is well known as a revolutionary process to produce the hydrogen storage alloy directly from the metal powder mixture with many benefits. In a previous paper, recently focused, hydrogen storage alloy of ternary Mg–Ni–Cu system was successfully produced based on this method, to improve the property of a typical hydrogen storage alloy, Mg2Ni. However, since there are still many operating parameters for that production, relationship between operating conditions and the product property is not still well explained. Therefore, the effect of synthesis temperature, as important operating condition, on the hydrogen storage capacity and hydriding rate of the product was mainly examined in this study. Products synthesized at extremely different temperatures of 753, 773, 798 and 823 K and hydrogen pressure of 4.0 MPa were analyzed, identified and characterized by means of the hydriding curve at 573 K, the patterns of X-ray diffraction and the images of scanning electron microscope. The results revealed that the synthesis temperature in a ternary system of hydrogen storage alloys by HCS is more sensitive and more significant than in a binary system to balance two aspects; the product activity for hydriding reaction and the reaction completion of combustion synthesis. The results also indicated that the HCS process was very attractive to produce the ternary Mg–Ni–Cu system of hydrogen storage alloy from the viewpoints of saving energy, saving time and controlling the specific composition of the products. [Copyright &y& Elsevier]

• Laser-deposition technique was employed for the fabrication. • The influence of laser process parameters on the corrosion resistance was investigated. • The scanning speed had more influence on corrosion behaviour than the laser power. • The Ti-based HEAs was more resistant to corrosion than the Cu-based HEAs. Corrosion is a conservational occurrence that has a large economic impact on most metals and its alloys because it destroys and deteriorates most materials by an electrochemical process through the reaction of these materials with the environment. High Entropy Alloys in aerospace applications react with the environment in applications such as jet engines, especially at elevated temperatures. Thus, the capacity of high entropy alloys to resist corrosion must be investigated to expand the application of this advanced material in the aerospace industry. In this comparative study, AlCoCrFeNiCu and AlCoCrFeNiTi High Entropy Alloy samples were fabricated by Laser Additive Manufacturing, particularly direct energy deposition and the corrosion behaviour of both alloys were examined and compared. The influence of the laser processing parameters on the microstructure and corrosion responses of the high entropy alloys in 3.5 wt% NaCl solution was also investigated. The microstructural morphologies were examined using an X-ray diffraction system (XRD) and Scanning electron microscope (SEM) equipped with Energy Dispersion Spectroscopy (EDS). The results showed that the Scan speed had the most influence on the microstructure and corrosion behaviour of the alloys. There was a strong relationship between the phase structure of the alloys and their susceptibility to localized corrosion. Therefore, it has been proposed in this study that the phase distribution within the alloys also influences the corrosion behaviour of laser deposited high entropy alloys. [ABSTRACT FROM AUTHOR]

The present study demonstrates the direct observation of pore formation by rapid release of vacancies in ultrafine grain (UFG) Al-0.4at%Zr alloy during in-situ annealing in a scanning transmission electron microscope. The ultrafine grain structure was preliminary obtained by high pressure torsion processing at a hydrostatic pressure of 6 GPa up to 10 revolutions. In-situ annealing reveals the rapid formation of pores in triple junctions (TJs) of grain boundaries (GBs) during the first few minutes followed by their subsequent slow resorption with the complete disappearance of some of them. During annealing, no noticeable displacement of GBs is observed. By considering the evolution of non-equilibrium GBs inherited by the severe plastic deformation, a theoretical description is suggested which describes: (i) the pore formation at disclinated TJs as a thermodynamically driven process of free volume dissolution through generation of vacancies, which then migrate to the TJs and coagulate at them with growth of the pores diminishing the strain energy of the TJ disclinations, and (ii) further decrease of the TJ disclination strain energy through the climb of extrinsic GB dislocations towards the disclinated TJs, accompanied with dissolution of the TJ pores by emission of vacancies which provide the dislocation climb. The rapid release of excess vacancies during the early stage of heat treatment is consequently identified as a phenomenon responsible for accelerated atomic mobility. This work hence provides a new perspective for understanding the accelerated precipitation kinetics observed in severely deformed alloys. ga1 • It is demonstrated that grain structure of a severely deformed Al-alloy store large amounts of vacancies. • Vacancy release by the rearrangement of near equilibrium grain boundaries is followed by in-situ annealing in STEM. • The kinetics of pore formation and dissolution has been followed by in-situ STEM observations. • Theoretical models are provided that reproduce the formation and dissolution of pores formed by vacancy condensation. • A proportion of stored vacancies may be responsible for faster precipitation kinetics in severely deformed alloys. [ABSTRACT FROM AUTHOR]

The effect of Zr and Er on the microstructure, electrical conductivity and mechanical properties of Al-0.4Fe alloy was investigated using optical microscope (OM), scanning electron microscope (SEM), electron back-scattered diffraction (EBSD), transmission electron microscope (TEM) and energy dispersive x-ray spectroscopy (EDS). It is revealed that both of the Zr and Er could inhibit the recrystallization process of Al-0.4 wt %Fe alloy due to the formation of Al 3 Zr or Al 3 Er particles. Zr is more recrystallization-resistant than Er due to the preferential precipitation of Al 3 Zr. Both of the Zr and Er could modify the morphology of Al 3 Fe particle from needle-like to sphere-like or rod-like, which reduce the negative effect of Al 3 Fe phase. Zr could significantly refine dendrites of the Al-0.4Fe alloy, while Er shows a negligible effect on dendrite refining due to the delayed formation of Al 3 Er during solidification. However, the low solubility of Er is beneficial for strength and electrical properties of Al-0.4Fe alloy. In consideration of strength and electrical conductivity, the Al-0.4Fe-0.2Er is selected as the best alloy among the four alloys, which shows a yield strength of 145 MPa, elongation at fracture of 8% and electrical conductivity of 61.2 %IACS after cold-rolling. The results provide an insight in design high strength, high conductive aluminum conductor material. • The coarse needle-like Al 3 Fe phases could be modified into sphere- and rod-like small particles by Zr and Er additions. • Synergetic improvement of strength and conductivity in Al-0.4Fe-0.2Er alloy is gained. • Co-adding Zr and Er improves recrystallization resistant capability of the Al-0.4Fe alloy better than the single one. [ABSTRACT FROM AUTHOR]

Using both novel high-throughput screening via combinatorial thin film deposition and conventional bulk alloy synthesis techniques, a large region of the AlCrFeNiTi composition space has been probed for alloys that could serve as low cost alternatives to nickel-base superalloys for medium-to-high temperature structural applications. Phase formation trends in this highly complex alloying system have been determined using characterisation techniques that span multiple length scales—from bulk X-ray diffraction and differential scanning calorimetry to atomically resolved scanning transmission electron microscopy and energy dispersive X-ray spectroscopy. A large region of stability for both disordered A2 and ordered B2/L2 1 type phases is observed, with several compositions exhibiting fine-scaled precipitation structures of these two phases. For alloys with ≥20 at.% Al, the precipitation structure was further refined to a nano-scale lamellar arrangement of A2 and B2/L2 1 phases. Formation of C14 Laves phase, especially for compositions with > 10 at.% Ti, has consistently been observed. We include a screening of the mechanical properties based on nanoindentation and macroscopic hardness test data correlated with scanning electron microscope (SEM) observations of the hardness indents. The phase formation trends observed by both combinatorial thin film deposition and bulk alloy synthesis are discussed in detail for samples in the as-deposited and as-cast conditions, respectively. Image 1 • Thin film concentration gradient reproduces phase formation trends in bulk alloys. • Nanoscale lamellar arrangement of B2/L2 1 forms for >20 at.% Al. • Fully coherent interfaces between A2 and L2 1 observed for lamellar alloy. • L2 1 -ordered phases exhibit mixed Ni 2 TiAl and Fe 2 TiAl character. • Above 10 at.% Ti, significant volume fraction of Laves phase forms. [ABSTRACT FROM AUTHOR]

The thermal stability of magnetron-sputtered Zr-Cu-Ag thin films, presenting key-antibacterial properties against E. coli and S. aureus , is studied by using an in situ multiscale approach. This study is carried out to better understand the general evolution of these amorphous films under thermal constraint, and to determine their limit of use in aggressive conditions. The general crystallization behavior and structural stability are investigated by in situ X-ray diffraction (XRD) in heating mode, and completed at micro- and nano-scale by complementary electron microscopy characterizations. The global crystallization temperature of films, determined by XRD, is found between 200 °C and 400 °C depending on the composition. The in situ HT-ESEM (High Temperature – Environmental Scanning Electron Microscope) observations show that, for the composition with the lowest Zr/(Cu + Ag) ratio (Zr 33 Cu 35 Ag 32), the crystallization process is followed by a total dewetting of the thin film. The Zr 73 Cu 16 Ag 11 film is a thin film metallic glass (TFMG), and was also investigated at the nanoscale. In situ HT-TEM (High Temperature – Transmission Electron Microscope) allows observing the progressive crystallization of the TFMG, describing the different steps of transformation from the amorphous as-deposited structure, the individual formation of intermetallics and to the whole crystalline state. • Zr-Cu-Ag thin film metallic glasses, known for their biocide activity, were synthesized by PVD magnetron sputtering. • Their structural and microstructural thermal stability was characterized through an in situ multiscale approach. • Adopting in situ XRD, SEM and TEM technics, both films crystallization and dewetting processes were directly observed. • The Zr 73 Cu 16 Ag 11 film shows a thin film metallic glass character. • From a chemical viewpoint, the higher the Zr/(Cu + Ag) atomic ratio, the higher their thermal resistance. [ABSTRACT FROM AUTHOR]

The hard anodizing process is one of the best choices to achieve high wear resistance in a 6061-Al alloy, which is commonly used in marine and aerospace applications. In this study, the hard anodizing process was performed by applying several current densities at different times. Two types of electrolytes containing various concentrations of sulfuric acid or oxalic acid were used as the bath. The microhardness of the coatings was measured. Morphology, thickness, and structure of the samples were investigated through a scanning electron microscope (SEM), and an X-ray diffractometer (XRD). Surface roughness and tribological behavior of the optimum samples were also examined. The results revealed that there was an optimum value for the electrolyte concentration, as well as the hard anodizing current density and time at which the hardest coating was obtained. All the oxide films had an amorphous structure. Doing the hard anodizing at 35 mA/cm2 in a sulfuric acid bath for 50 min resulted in a uniform and crack-free coating. The weight loss of this oxide film was 50 and 21 times lower than the substrate and the coating obtained in an oxalic acid bath at the optimum conditions, respectively. • Hard anodizing of 6061-T6 Al alloy in the sulfuric and oxalic acid baths. • Effect of electrolyte concentration, current density, and time on properties. • Sulfuric acid was better electrolyte than oxalic acid for hard-anodizing of 6061-Al. • All the hard-anodized films had higher hardness and wear resistance than base alloy. • Optimum condition to obtain compact, hard and wear resistant coating is proposed. [ABSTRACT FROM AUTHOR]

To understand the effect of Co addition on the modulated structure coarsening and discontinuous precipitation (DP) growth kinetics of Cu–15Ni–8Sn alloy, the experiments are carried out using optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscopy (TEM). Our results showed that the addition of Co in Cu–15Ni–8Sn alloy did not recover with a new second-phase associated with Co. During the aging treatment process, the addition of Co reduced the coarsening kinetics of the modulated structure, which was related to the equilibrium solid solubility (X e) of Ni and Sn in Cu, diffusion coefficient of Ni and Sn in Cu (D), and to the interfacial energy (σ) of α -Cu matrix/L1 2. The decrease in values of Xe , D and σ were resulted in a slowdown of the coarsening kinetics. Further, the suitable addition of Co significantly inhibited the nucleation and growth of discontinuous precipitation (DP). The growth kinetics of DP for Cu–15Ni–8Sn- x Co alloy were evaluated using the Johnson-Mehl-Avrami-Kolmogorov equation. With the combination of the Arrhenius equation, the activation energies (Q) of the samples were 105.45 kJ/mol, 150.76 kJ/mol, 178.44 kJ/mol, 251.53 kJ/mol, and 148.89 kJ. Compared with cobalt-free alloy, cobalt-containing alloys exhibited greater activation energy, which suggested that the addition of Co can greatly inhibit the formation of DP. Furthermore, the addition of Co led to decrease in the thickness of the grain boundary and increase in the interlamellar spacing of the DP, which were considered to be the main reasons for suppressing the growth of DP. • The addition of Co in Cu–15Ni–8Sn alloy was not recovered a new second phase associated with Co. • The coarsening kinetics of the modulation structure in Cu–15Ni–8Sn alloy was reduced with Co addition. • The activation energies (Q) of the Cu–15Ni–8Sn- x Co alloys were calculated by the JMAK equation and the Arrhenius equation. • The inhibition mechanism of Co addition on DP is related to the thickness of grain boundary and interlamellar spacing. [ABSTRACT FROM AUTHOR]

The chemically architectured alloys were proposed as a new concept of microstructure, with a multi-scale architecturation. They are composed of a solid-solution at the atomic scale, grain boundaries and composition gradients at the micronic scale and finally a 3D network of gradients at the mesoscale. Composition gradients are between two phases with the same crystalline structure but different compositions. As a first application of this concept, powders of pure Ni and CoCrFeMnNi high entropy alloy were successfully densified by Spark Plasma Sintering. Then the microstructure and mechanical properties were characterized by scanning electron microscope coupled with energy dispersive spectroscopy and electron backscattered diffraction, X-ray diffraction, nanoindentation and compression tests. The obtained chemically architectured alloys present a homogeneous distribution of the two phases with a 10 μm wide chemical gradient in between. By comparison with reference non architectured materials, the chemical architecturation induces a 35% increase of the yield strength. Thus the concept of chemically architectured metallic alloys and composition gradients was proven as very promising: processing of this complex microstructure is possible and it induces a significant mechanical strengthening. Image 1 • A mixture of CoCrFeMnNi and Ni powders was fully densified by spark plasma sintering. • A chemical gradient of around 10 μm was formed between HEA and Ni phases. • This material is called a chemically architectured alloy. • Mechanical strength is improved compared to an ideal mixture of Ni and CoCrFeMnNi. [ABSTRACT FROM AUTHOR]

There are many means and mechanisms to strengthen alloys, but often at the cost of plasticity. Strength or plasticity? In practice, the two often appear as contradictory relationships. In the current work, the ZrSn 1.5 Al x (x = 6, 8, 10, 12, 14 at. %) alloy obtained by controlling the Al content was smelted and hot-rolled at 890 °C, and then immediately quenched to obtain an alloy containing α + β + AlZr3 multiphase structure. Compared with ZrSn 1.5 Al 6 alloy, ZrSn 1.5 Al 14 alloy reaches a high ultimate tensile strength (1080.84 MPa) and a large elongation at fracture (28.59%) at room temperature, an increase of 27.6% and 86.3%, respectively. The formation of AlZr3 particles pins dislocations, promotes cross-sliding of dislocations, and improves the dislocation nucleation rate by changing the dislocation sliding mode, which increases the dislocation density and promotes uniform plastic deformation, enhance the strain-hardening ability of the alloys, thereby improve its plasticity and strength simultaneously. Optical microscopy (OM) and scanning electron microscope (SEM) were used to observe the metallographic structure and tensile fracture morphology. The transmission electron microscope bright field (TEM-BF) image and scanning transmission electron microscope high-angle annular dark field (STEM-HAADF) image of the sample were observed for detailed analysis. The samples were taken in the rolling direction and the mechanical properties were evaluated by uniaxial tensile tests at room temperature. In summary, the machining process is simple, the cost is low, and it is suitable for large-scale industrial-grade applications. It may have reference significance to other alloy systems. • The strength and plasticity have been improved simultaneously. • ZSA14 shows high ultimate tensile strength (1080.84 MPa) and a large elongation at fracture (28.59%). • FCC AlZr3 phase formed when Al content is over 8 at. %. • AlZr3 particles hinder dislocations, dislocation nucleation rate was increased by changing the dislocation slip mode. • The strain-hardening ability of the alloy improved. [ABSTRACT FROM AUTHOR]

In the present dissertation, series of Al–Mg-Ga-In-Sn alloys were prepared by using arc melting and melt-spinning techniques. Their microstructures were characterized by X-ray diffraction (XRD) and scanning electron microscope with energy dispersed X-ray (SEM/EDX). The generated hydrogen volume of Al splitting water reaction was measured using a water displacement method. The morphology and microstructure of the reaction by-products were also characterized using XRD. The results show that from the comparison of microstructures and Al-water reactions between the as-cast and the rapidly solidified alloys, it was found that the effect of Mg on Al-water reaction was attributed to the induction of segregation of In and Sn and formation of intermetallic compounds on Al surfaces. However, Mg dissolved in Al grains hardly had any effect on the Al-water reaction. The reaction rate and hydrogen yield of the rapidly solidified alloys are significantly enhanced due to the refinement of Al grain. • Mg induces the segregation of In and Sn and formation of phases on Al surfaces. • Al grain of the rapidly solidified Al–Mg-Ga-In-Sn alloys is refined significantly. • Reaction rate and H 2 yield of the rapidly solidified alloys enhance significantly. [ABSTRACT FROM AUTHOR]

The VAlTiCrMo and (VAlTiCrMo)N x coatings were prepared by sputtering V–Al–Ti–Cr–Mo splicing targets. The microstructure and chemical composition were analyzed by means of X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and transmission electron microscope (TEM). The high-entropy alloy coating and the corresponding nitride coating have body-centered cubic (BCC) and face-centered cubic (FCC) structures respectively. Nitriding changes the phase structure and growth mode of the high-entropy coating, and the synthesized high-entropy nitride coatings are more compact. Meanwhile, the introduction of nitrogen leads to severe lattice distortion, which improves the mechanical properties of the high-entropy coating. As the nitriding degree increases, the corrosion resistance of the high-entropy nitride coatings in 3.5 wt% NaCl solution is improved. The synthesized (VAlTiCrMo)N x coating exhibits optimized mechanical properties and nobler corrosion resistance when the N 2 flow is 800 sccm. Corrosion inhibition by the microstructures of the VAlTiCrMo and its nitride coatings. Image 1 • VAlTiCrMo high-entropy alloy coating and its nitride coatings prepared by splicing targets. • The change of coating structure is more obvious with the increase of nitrogen flow rate. • The introduction of nitrogen changed the structure of the coating from BCC to FCC. [ABSTRACT FROM AUTHOR]

Improving the strength of alloy materials and simultaneously retaining high toughness are strongly desirable by various engineering applications. Nanocrystalline@amorphous dual-phase nanostructure consisting of nanocrystalline-cores encapsulated with amorphous-shells has been regarded as one of the most effective routes to achieve high strength yet high toughness, which may overcome the limitation of either single-phase nanocrystalline alloys or single-phase metallic glasses because of reverse Hall-Petch effect or shear-band deformation. Herein, nanocrystalline@amorphous core-shell nanostructure has been successfully assembled in the sputtered TA19 alloy film only by regulating bias voltages (V b), and then V b induced evolution of microstructure and mechanical property was further investigated by combined experiments of X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM), select area electron diffraction (SAED), transmission electron diffraction (TEM) and nanoindentation. The results show that the bombardment of energy ions can promote formation of amorphous zones in TA19 alloy film, successfully achieving ordered core-shell nanostructure at −120 V of V b , while single-phase nanocrystalline occurs at V b = −40 V and amorphous dominated structure appears at V b = −200 V. Maximum hardness value of 11.2 GPa achieves at V b = −120 V when the ordered core-shell nanostructure is formed with invisible shear bands around indenter, but more amorphous result in disappearance of core-shell nanostructure at V b = −200 V, which worsens hardness, accompanying with presence of obvious shear bands around indenter. This novel core-shell-like structure succeeded in achieving high strength or hardness yet high toughness by providing strong resistance to hinder movements of both grains and shear bands due to large amount of nanocrystalline@amorphous interfaces. It is suggested that the V b as a key factor controlling the core-shell-like structure of TA19 films, which may provide a new strategy to improve mechanical properties of alloy films. • The microstructure of TA19 films can be tailored by V b. • High V b can promote the formation of amorphous zones in TA19 alloy films. • The ordered nanocrystalline@amorphous core-shell nanostructure formed at appropriate V b of −120 V. • The maximum H of ∼11.2 GPa appeared in the uniform core-shell nanostructure. [ABSTRACT FROM AUTHOR]

Titanium alloy was extensively used in aerospace industrial field. It has a great significance to directly reveal the deformation process as a function of application conditions. This work investigates the real-time deformation behavior of laser direct metal deposited (LDMD) Ti–6Al–4V alloy at 200 °C, using self-developed high temperature in-situ scanning electron microscope (SEM) tensile stage with a controlled heating system. The results showed that the microstructure of the sample comprised of columnar β grains with zigzag grain boundaries decorated by tilted α plates along the building direction. During uniaxial tensile, slip bands develop along the grain boundaries between α plates with increasing stress. Grain boundary sliding contributes to the high tensile elongation. Compared the mechanical properties along transvers tensile with those at room temperature, the tensile stress decreased and displacement increased at 200 °C. Therefore, higher elongation and reduction in cross-sectional area were identified at 200 °C than those at room temperature. The fracture of specimen at 200 °C shows obvious necking character and deep dimples with thin rims. Coalescence of slip bands at α/α interface creates voids and the coupling of voids nucleates micro-crack. α/α grain boundary interface constitutes path to the crack propagation. The high misorientation angle at columnar β grain boundary hinders the cracks propagation. Finally, the cracks accumulate along the columnar β grain boundary leading to fracture. • The microstructure deformation of LDMD Ti–6Al–4V alloy is studied by high temperature in-situ SEM tensile stage at 200 °C. • Slip bands development, cracks propagation, and columnar β GB hindering at 200 °C are investigated. • Temperature effect on the deformation mode and corresponding mechanical properties have been revealed. [ABSTRACT FROM AUTHOR]

Effects of Bi additions on age-hardening response and precipitation of Mg–2.31Zn–0.31Co (at.%) alloy have been investigated. The addition of Bi can substantially promote the age-hardening response at 200 °C. The precipitates microstructure is characterized using high-angle annular dark-field scanning transmission electron microscope, and the results show that the remarkable improvement is attributed to a much higher number density of β 1 ' rods and the formation of prismatic Mg 3 Bi 2 plates. At the early stage of ageing, Mg 3 Bi 2 precipitates out first and then Zn segregates to the Mg 3 Bi 2 /Mg interface, which could provide chemical environment and heterogeneous nucleation sites for the subsequent precipitation of the β 1 ' phase. Image 1 • The addition of Bi can substantially enhance the age-hardening response of Mg–2.31Zn–0.31Co alloy. • Bi additions result in a higher number density of β 1 ' rods and the formation of prismatic Mg 3 Bi 2 plates. • Zn atoms segregate at Mg 3 Bi 2 /Mg interface. • Rod-like β 1 ' phase heterogeneously nucleates at Mg 3 Bi 2 /Mg interfaces. [ABSTRACT FROM AUTHOR]

In this work we analyse the formation of sigma phase in Al x CrFeCoNi (x = 0–1.5) alloys. In order to characterise the Al x CrFeCoNi system, we decided to investigate 5 additional samples corresponding to the individual phases of alloys for x = 1 and 1.5. They were annealed at 600–1000∘C for 24 h. For each of those five samples scanning electron microscope, SEM, XRD and Mössbauer measurements were performed. The SEM/BSE images allowed identify the number of different phases present in the samples and EDX method gave elemental composition of every phase. The XRD technique helped identify those phases, and thanks to Mössbauer spectroscopy we were able to determine the percentage of each of them. The SEM/EDX measurements also revealed spherical Al precipitations which can be clearly divided into two groups in respect of diameter distribution. The analysis of the Mössbauer spectra revealed magnetically split and a paramagnetic component for phases rich in Cr as well as for a phase rich in Al and Ni. We established that the sigma phase is formed in the phase rich in Cr, and has a secondary character. We also provide the degree of transformation to sigma phase for every sample. • Separate sample series of AlxFeCrCoNi HEA were fabricated, their properties were compared. • FeCrCoNi-rich fcc phase forms a doublet in Mössbauer spectrum. • σ phase transforms from Cr-rich bcc phase only. • Spinodal decomposition was observed in AlNi-rich bcc phase only. • Mössbauer spectra of AlxFeCrCoNi were decomposed into subspectra of respective phases. [ABSTRACT FROM AUTHOR]