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TiAl alloys possess excellent properties, such as low density, high specific strength, high elastic modulus, and high-temperature creep resistance, which allows their use to replace Ni-based superalloys in some high-temperature applications. In this work, the traditional TiAl alloy Ti-48Al-2Nb-2Cr (Ti4822) was alloyed with additional Nb and fabricated using laser metal deposition (LMD), and the impacts of this additional Nb on the microstructure and mechanical and tribological properties of the as-fabricated alloys were investigated. The resulting alloys mainly consisted of the γ phase, trace β0 and α2 phases. Nb was well distributed throughout the alloys, while Cr segregation resulted in the residual β0 phase. Increasing the amount of Nb content increased the amount of the γ phase and reduced the amount of the β0 phase. The alloy Ti4822-2Nb exhibited a room-temperature (RT) fracture strength under a tensile of 568 ± 7.8 MPa, which was nearly 100 MPa higher than that of the Ti4822-1Nb alloy. A further increase in Nb to an additional 4 at.% Nb had little effect on the fracture strength. Both the friction coefficient and the wear rate increased with the increasing Nb content. The wear mechanisms for all samples were abrasive wear with local plastic deformation and oxidative wear, resulting in the formation of metal oxide particles. [ABSTRACT FROM AUTHOR]

The microstructures, mechanical properties and precipitation behavior of a high-Ti low-C weathering steel obtained by thermo-mechanical controlled process were investigated by means of electron backscatter diffraction and transmission electron microscope. The cooling rates have a significant effect on the continuous cooling transformation structure of deformed austenite in the tested steel, and the higher cooling rate is conducive to the formation of bainite. The grain orientation and precipitates of the steel at different cooling rates were discussed in detail. There were some large size precipitates which may lead to negative effect on the mechanical properties at the grain boundaries and within the grains at cooling rate of 0.5 °C/s. However, the higher cooling rate of 30 °C/s was favorable to obtain dispersive nano-scale precipitates. There is a greater degree of plastic deformation and dislocation density in the microstructures at 30 °C/s than 0.5 °C/s. The roles of precipitates, grain boundaries and sub-grain boundaries on the hindrance of dislocations movement were discussed. The precipitation strengthening effect of the precipitates can be brought into full play when the coiling temperature is about 610 than 560 °C. The yield strength of the high-Ti low-C weathering steel plate is 777 MPa at 610 °C. [ABSTRACT FROM AUTHOR]

This paper focuses on the effect of melting modes on microstructural evolution and tribological properties of AlSi10Mg alloy fabricated by selective laser melting (SLM). The results showed that the microstructures of SLM AlSi10Mg consisted of primary α-Al surrounded by cellular Si networks (∼500 nm) when fabricated in conduction mode, but has a finer cellular-like Si phase (∼200 nm) when fabricated in keyhole mode. The strong convection caused by the melt reflow and Marangoni convection under keyhole mode also resulted in deposition of nano-scale Si particles at the bottom of the molten pool. The SLM AlSi10Mg fabricated in keyhole mode exhibited better wear resistance than that fabricated in conduction mode. Compared to traditional as-cast specimens, both SLM specimens showed better wear resistance due to the unique cellular-like networks. The SLM technique offers a new approach for material processing that can be used to refine microstructures for improved tribological properties. [ABSTRACT FROM AUTHOR]

A near-equiatomic FeCoNiCuAl High-entropy alloy (HEA) was produced using laser powder bed fusion (L-PBF) pre-alloy powder. Microstructural characteristics and tribological properties of L-PBF specimens under various volumetric energy densities (VEDs) were investigated in detail. The results showed that the phase of L-PBF specimen consisted of BCC matrix + Cu-rich B2 precipitate. The microstructure of L-PBF specimen largely consisted of columnar grains perpendicular to the melt pool boundary (MPB) direction owing to the epitaxial growth along the temperature gradient. The preferred orientation of the L-PBF specimen was gradually transformed from the order of <001> to <101> as the VED rose. Larger size precipitates re-appeared and wider MPB were formed upon faster remelting and steeper cooling as a result of higher VED. Compared to the components produced by Spark Plasma Sintering, L-PBF specimens presented better wear resistance owing to the ultra-fine substructure and nano-scaled precipitates. In addition, the L-PBF specimen produced with 83 J/mm3VED exhibits the highest elastic strain to failure (H/Er) and yield stress (H2/Er3). [ABSTRACT FROM AUTHOR]

Laser-cladding CeO2-doped Ni-based composite coatings were prepared on the surface of a titanium alloy, and the effects of CeO2 addition on the microstructure, microhardness, and corrosion resistance of the prepared coatings were studied. The results showed that TiC, NiTi, Ni3Ti, and Ti2Ni phases were formed on the prepared coatings. Moreover, the addition of CeO2 in laser-cladding coatings effectively refined the microstructure and reduced the number of cracks generated in the laser-cladding process. When the amount of CeO2 was 2%, the number of cracks in the laser-cladding coating was significantly reduced compared with that of 0%. When the content of CeO2 was 2% or 3%, the microhardness of laser-cladding coatings reached the maximum value. At the same time, it was found that the appropriate addition of CeO2 was helpful to improve the corrosion resistance of the laser-cladding coating. However, excessive CeO2 addition could reduce the corrosion resistance of the laser-cladding coating. [ABSTRACT FROM AUTHOR]

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External magnetic field (EMF) has a strong effect on the welding arc shape, droplet transfer, weld forming, microstructure, and properties of joint metal. This paper defines the types of external magnetic field and reviews the development of magnetically controlled arc welding process, particularly, the effect of external magnetic field parameters on the welding process. It is found that the welding productivity, the weld formation, the ductility, and toughness of welded metal can be improved; and the welding residual stresses, the chemical inhomogeneity, and the welding defects can be reduced. Finally, the development trend is discussed in the later sections of the paper. [ABSTRACT FROM AUTHOR]

The effect of different laser scanning speeds on the microstructural evolution and associated tribological and corrosion behavior of Ti-23Nb alloys produced by laser metal deposition (LMD) was systematically investigated. The microstructures of all specimens were composed of equiaxed β grains, acicular α″ phases, and unmelted Nb particles. With the increase of scanning speed, the volume fractions of the α″ phase and unmelted Nb particle increased, while the volume fraction and grain size of the β phase decreased. This results in a high hardness (∼ 304 HV) for the specimen with a high scanning speed (2.6 mm/s). Although the hardness of the specimen produced at 2.0 mm/s is slightly lower (∼ 296 HV), it possesses less unmelted Nb particles (soft phases, low hardness of ∼ 107 HV), resulting in a lower wear rate (∼ 4.9 × 10−4 mm3N−1 m−1). Compared to fully alloyed areas, unmelted Nb particles corrode preferentially. The specimen produced at 2.6 mm/s possesses a lower corrosion potential (E corr) value owing to the presence of more α″ phase and unmelted Nb particles. Grain size is a critical factor in determining the corrosion current density (i corr). The high scanning speed specimen (2.6 mm/s) with small grain sizes has high resistance and low i corr. • The microstructures of LMD Ti-23Nb alloys were composed of equiaxed β grains, acicular α″ phases, and unmelted Nb particles. • Localized partitioning of solutes is the underlying reason for the formation of α″ martensite during LMD processing. • Grain size and unmelted Nb particles are two main factors for the properties of LMD Ti-23Nb alloys. [ABSTRACT FROM AUTHOR]

[Display omitted] • A multi-phase-field model was used to study the austenite-acicular ferrite transformation process. • The role of different influencing factors on the austenite-ferrite transformation is investigated. • Different strategies for refining the acicular ferrite grain sizes have been discussed. • The current simulation results provide guidelines for the experimental utility of acicular ferrite. The excellent combination of strength and toughness renders acicular ferrite to be a desirable microstructural contexture in C-Mn and high-strength low-alloy steels. The formation of acicular ferrite in steels is generally affected by factors such as composition, cooling rate, prior austenite grain size (PAGS), and impurity inclusions. Due to the complexity of multi-factor coupling, it is difficult to explore the influence of a single factor through actual experiments. In the current work, the influences of cooling rates, PAGS, and impurity inclusion density on the microstructure evolution of austenite-acicular ferrite transformation in low alloy steels are quantitatively evaluated by multi-phase-field simulation. The numerical results demonstrate that reducing PAGS during austenite-ferrite transformation, increasing cooling rate and increasing inclusion nucleation density can effectively refine acicular ferrite grain size. Moreover, the C element diffuses from acicular ferrite to austenite and accumulates at the phase interface during the phase transformation from austenite to ferrite. The findings in the current work contribute to better regulating and designing acicular ferrite in steels. [ABSTRACT FROM AUTHOR]

• A crack-free AlCoCuFeNi was fabricated by spark plasma sintering and hot roling. • The specimen consisted of BCC, FCC, nano-sized L1 2 , and Al 2 O 3 phases. • The specimen possessed good anti-wear ability and good corrosion resistance. In this work, a high hardness, crack-free AlCoCuFeNi high-entropy alloy with good corrosion resistance was successfully produced by spark plasma sintering at 1000℃ and 30 MPa for 10 min, followed by hot rolling to a thickness reduction of 10 % after holding at 600℃ for 30 min. The microstructure of the alloy was composed of fine equiaxed grains of (Fe, Co, Ni, Al)-enriched BCC, Cu-enriched FCC, nano-sized L1 2 , and Al 2 O 3 phases. The maximum texture index of the material is only 1.53, indicating a low anisotropy. The alloy possessed a high hardness (599 HV), a low friction coefficient (0.1), and a low corrosion current density (1.13 μA/cm2), implying both good wear and corrosion resistance. In addition, the creep mechanism was found to be grain boundary sliding. [ABSTRACT FROM AUTHOR]

Metallic glass composite coatings Ti 45 Cu 41 Ni 9 Zr 5 and Ti 45 Cu 41 Ni 6 Zr 5 Sn 3 (at.%) on a Ti-30Nb-5Ta-7Zr (wt.%) (TNTZ) alloy were prepared by laser cladding. The microstructures of the coatings were characterized by means of X-ray diffractometry (XRD), scanning electron microscopy (SEM) equipped with energy dispersive X-ray analyzer (EDXA), and transmission electron microscopy (TEM). Results indicated that the coatings have an amorphous structure embedded with a few nanocrystalline phases and dendrites. A partial substitution of Ni by Sn can improve the glass forming ability of Ti-base metallic glass system, and induce the formation of nano-sized Ni 2 SnTi phase during the cyclic laser heating. The tribological behavior of both the substrate and the coatings was investigated in detail. A significant improvement in both the hardness and the wear resistance of the coatings was achieved with the addition of Sn. The relationship between the wear resistance and the microstructures of the coatings was discussed. [ABSTRACT FROM AUTHOR]

Both a novel Ti-5Cu alloy (in wt%) and a Ti-5Cu in situ composite containing 1 wt% B 4 C were fabricated by laser powder bed fusion, and their microstructures, mechanical and tribological properties were systematically investigated. The microstructure of the Ti-5Cu was mainly composed of α Ti laths, Ti 2 Cu and retained β phases, while the B 4 C/Ti-5Cu composite was composed of α Ti laths, Ti 2 Cu, TiC, TiB and TiB 2 phases. Both the Cu and B 4 C additions promoted a transition from columnar to equiaxed grains for prior-β and α phases. The B 4 C/Ti-5Cu composite was found to have a higher hardness (467 HV) than the Ti-5Cu (417 HV). Further, the composite exhibits a yield strength of 1100 MPa and an ultimate tensile strength of 1250 MPa. Values which are higher than those of the Ti-5Cu that exhibits a yield strength of 750 MPa and an ultimate tensile strength of 900 MPa. However, this strength increase comes at the expense of a reduction in elongation to failure from 6.2% to 1.5%. Even though the composite is significantly stronger, the two materials exhibited very similar wear rates (ω B4C/Ti-5Cu = 4.95 × 10−4 mm3 N−1 m−1 and ω Ti-5Cu = 4.85 × 10−4 mm3 N−1 m−1). • The LPBFed Ti-5Cu was mainly composed of α Ti laths, Ti 2 Cu and retained β phases. • The LPBFed B 4 C/Ti-5Cu composite was composed of α Ti laths, Ti 2 Cu, TiC, TiB and TiB 2 phases. • Both the addition of Cu and B 4 C can refine the grain and promote columnar to equiaxed transition of prior-β phase. • The LPBFed Ti-5Cu exhibit a strong combination of hardness, tensile properties and wear resistance. • Although the composite is significantly stronger, the two materials exhibited very similar wear rates. [ABSTRACT FROM AUTHOR]

Ultra-high strength and ductile powder metallurgy (PM) binary Ti-20at.%Ta alloy has been fabricated via sintering from elemental Ti and Ta powders and subsequent hot swaging and annealing. The microstructural evolution and mechanical properties in each stage were evaluated. Results show that inhomogeneous microstructures with Ti-rich and Ta-rich areas formed in the as-sintered Ti-Ta alloys due to limited diffusion of Ta. In addition, Kirkendall porosity was observed as a result of the insufficient diffusion of Ta. Annealing at 1000°C for up to 24 h failed to eliminate the pores. Hot swaging eliminated the residual sintering porosity and created a lamellar microstructure, consisting of aligned Ta-enriched and Ti-enriched phases. The hot-swaged and annealed PM Ti-20Ta alloy achieved an ultimate tensile strength of 1600 MPa and tensile elongation of more than 25%, due to its unique lamellar microstructure including the high toughness of Ta-enriched phases, the formation of α phase in the β matrix and the refined lamellae. [ABSTRACT FROM AUTHOR]

In this paper, we describe the effects of different scanning speeds (600–900 mm/s) on the microstructure, mechanical properties and corrosion behavior of biodegradable bone-substitution alloys produced from 80:20 (by wt.) Fe:Mn powders using laser powder bed fusion (LPBF). Both the Mn content (18.9–15.1 wt% Mn) and density (7920–7730 kg/m3) of the LPBFed samples decreased slightly with increasing laser scanning speed, while the oxygen content increased (0.12–0.40 wt%). Increasing scanning speed also led to increased porosity (from 0.27% to 2.5%) and increased cracking. The specimen produced at the lowest scanning speed of 600 mm/s, which consisted of only the HCP ε-martensite phase, showed by far the highest yield strength (YS) at 644 MPa and the highest ultimate tensile strength (UTS) at 857 MPa, but the lowest elongation to failure (El) of only 13.7%. Specimens produced at higher scanning rates consisted of both BCC α′-martensite and ε-martensite phases. The sample fabricated at a scanning speed of 700 mm/s showed the best balance of mechanical properties with a YS of 330 MPa, a UTS of 839 MPa, and an El of 36.1%. Electrochemical testing showed corrosion rates from 0.09 mm/yr (600 mm/s specimen) to 0.22 mm/yr (700 mm/s specimen), which are higher than those of both pure Fe and most Fe–30Mn and Fe–35Mn alloys reported in the literature. The work demonstrates that the meso-/micro-scale structure, and, hence, the mechanical properties and corrosion rates of Fe–Mn alloys can be tailored by varying the scanning speed during LPBF processing. It also demonstrates the potential of LPBFed Fe–Mn alloys with low Mn content for use as biodegradable bone substitutes. [ABSTRACT FROM AUTHOR]

Highlights: [•] Systematically and comparative microstructure analysis for the SrIrO3 thin films. [•] Meta-stable orthorhombic SrIrO3 phase was obtained under normal conditions. [•] The stabilization of meta-stable orthorhombic SrIrO3 was quantitatively understood by lattice mismatch strain. [ABSTRACT FROM AUTHOR]

Abstract: This study demonstrates the feasibility of improving the optical properties of a vertically aligned quantum dot (QD) structure and the performance of a quantum dot intermediate band solar cell (QD-IBSC) by capping a GaAsSb layer on the InAs QDs. Experimental results indicate that dot-size uniformity is significantly improved due to the strain modification in the evolution of the successive vertically aligned dot layer growth. A solar cell device with an InAs/GaAsSb columnar dot structure increases the short-circuit current density (J sc ) by 8.8%, compared to a GaAs reference cell. This dot structure also increases quantum efficiency by up to 1200nm through the absorption of lower-energy photons. The InAs/GaAsSb QD-IBSC also improves the open-circuit voltage (V oc ), indicating a reduction in misfit defect density and recombination current density. The results of this study confirm the ability of a columnar InAs/GaAsSb QD structure to enhance the device performance. [Copyright &y& Elsevier]

Abstract: Organophosphorylated titania submicrospheres (OPTi) are prepared and incorporated into a chitosan (CS) matrix to fabricate hybrid membranes with enhanced methanol resistance and proton conductivity for application in direct methanol fuel cells (DMFC). The pristine monodispersed titania submicrospheres (TiO2) of controllable particle size are synthesized through a modified sol–gel method and then phosphorylated by amino trimethylene phosphonic acid (ATMP) via chemical adsorption, which is confirmed by XPS, FTIR and TGA. The morphology and thermal property of the hybrid membranes are explored by SEM and TGA. The ionic cross-linking between the –PO3H2 groups on OPTi and the –NH2 groups on CS lead to better compatibility between the inorganic fillers and the polymer matrix, as well as a decreased fractional free volume (FFV), which is verified by positron annihilation lifetime spectroscopy (PALS). The effects of particle size and content on the methanol permeability, proton conductivity, swelling and FFV of the membranes are investigated. Compared to pure CS membrane, the hybrid membranes exhibit an increased proton conductivity to an acceptable level of 0.01Scm−1 for DMFC application and a reduced methanol permeability of 5×10−7 cm2 s−1 at a 2M methanol feed. [Copyright &y& Elsevier]

• AlSi10Mg components were fabricated by SLM under different VED ranges, i.e. conduction, transitional, and keyhole modes. • The KDP was consisted of α-Al, with less than 15 μm grain size, and enclosed by ~200 nm eutectic Si cellular networks. • No preferential crystallographic orientation could be observed within the KDP. • The high-stress exponents indicate that the creep behavior is controlled by dislocation-particle interactions. • The SLM AlSi10Mg fabricated in the transition mode exhibits a high tensile strength combined with reasonable ductility. The effect of the volumetric energy density (VED) on the keyhole formation, microstructural evolution and associated mechanical properties of AlSi10Mg fabricated by selective laser melting (SLM) has been systematically investigated. The results indicated that three melting modes could be distinguished during the laser melting process, corresponding to different VED ranges, i.e. conduction mode (<50 J mm-3), transitional mode (~50–65 J mm-3), and keyhole mode (>65 J mm-3). A high VED not only produced keyhole defects and hydrogen pores, but also generated two types of molten pool, i.e. a general shallow molten pool (GSP) and a keyhole-induced deep molten pool (KDP). The GSP was mainly consisted of an α-Al matrix, with ~30 µm grains size, and enclosed by a ~500 nm eutectic Si cellular network. The grain size of the KDP was less than 15 µm, and it has both a finer Si network (~200 nm) and nano-scale Si particles. No preferential crystallographic orientation could be observed within the KDP, while a strong texture along<111>orientation was exhibited in the GSP. These were responsible for the different mechanical properties of the SLM parts under different melting modes. The related mechanisms of the GSP and the KDP formation are comprehensively discussed and a correlation between the microstructure and the mechanical properties is also outlined. [ABSTRACT FROM AUTHOR]

The layered IVV 2 Te 4 -based compounds have recently received significant attention due to their intrinsically low lattice thermal conductivities. However, the influence of microstructure regulation and halogen doping on their thermoelectric properties has been scarcely studied. In this work, we systematically investigated the anisotropic thermoelectric transport properties of pristine SnSb 2 Te 4 compounds with varied microstructures manipulated by ball milling. With the help of thermoelectric transport models, the optimal ball milling time is estimated based on the calculation of quality factor. Furthermore, the remarkably improved Seebeck coefficient is achieved by the introduction of halogen elements into Te sites, which is attributed to reduced carrier concentration and converged carrier pockets. As a result, a maximal zT ∼0.4 at 725 K is achieved in SnSb 2 (Te 0·94 I 0.06) 4 sample aligned with the SPS pressure direction with a ball-milling time of 1 h, which demonstrates a 35 % enhancement over the pristine sample. This work provides an insightful guide to elevate the thermoelectric properties of layered IVVI 2 Te 4 -based compounds. [ABSTRACT FROM AUTHOR]

Ti-23Nb (at.%) coatings on an NiTi alloy with metallurgical bonding were prepared by laser cladding (LC) technology using Ti-Nb mixture powders. The effects of laser processing parameters on the microstructure and mechanical properties of the coatings were systematically investigated and the corrosion resistance of the coatings was assessed. The coatings were composed of TiNb, (Ti, Nb)2Ni, and β-Nb phases. The coatings increased the hardness of the NiTi alloy by a combined strengthening effect of the eutectics and fine microstructure. The corrosion resistance of the coated part was improved. The coatings with great corrosion resistance could keep the coated parts inert in an aggressive environment, and effectively restrain the release of toxic Ni ions, which means that the Ti-Nb alloy coatings are likely to be used as a biomaterial for medical applications. [ABSTRACT FROM AUTHOR]

Recent studies have suggested that high-entropy alloys (HEAs) possess high fracture toughness, good wear resistance, and excellent high-temperature mechanical properties. In order to further improve their properties, a batch of TiC-reinforced FeCoNiCuAl HEA composites were fabricated by mechanical alloying and spark plasma sintering. X-ray diffractometry analysis of the TiC-reinforced HEA composites, combined with scanning electron microscopy imaging, indicated that TiC particles were uniformly distributed in the face-centered cubic and body-centered cubic phases. The room temperature hardness of the FeCoNiCuAl HEA was increased from 467 to 768 HV with the addition of TiC, owing to precipitation strengthening and fine grain strengthening effects. As the TiC content increased, the friction coefficient of the FeCoNiCuAl HEA first increased and then decreased at room temperature, due to the transition of the wear mechanism from adhesive to abrasive behavior. At higher temperature, the friction coefficient of the FeCoNiCuAl HEA monotonously reduced, corresponding well with the transition from adhesive wear to oxidative wear. [ABSTRACT FROM AUTHOR]

In this study, Zr–Al–Ni–Cu bulk metallic glass composites (BMGCs) were successfully fabricated by laser rapid prototyping and systematically characterized using x-ray diffractometry (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicate that the studied BMGCs exhibit periodical microstructure along the deposition direction. According to the microstructural characteristics and phase composition, three identified regions are identified, which are classified as the amorphous zone, NiZr 2 nanocrystals + amorphous matrix zone and Cu 10 Zr 7 dendrites + CuZr 2 nanocrystals zone. The nanomechanical behaviors were investigated by nanoindentation and nanoscratch tests. The elastic modulus and nanoindentation hardness are in the following order: NiZr 2 nanocrystals + amorphous matrix zone > Cu 10 Zr 7 dendrites + CuZr 2 nanocrystals zone > amorphous zone. This is mainly attributed to the structural relaxation and crystallization of BMG caused by the effect of heat treatment during the repeated processes of laser heating. Moreover, NiZr 2 nanocrystals can effectively inhibit the movement of shear band in amorphous matrix, resulting in the enhancement of their strength and hardness. [ABSTRACT FROM AUTHOR]

A (Fe 40 Co 50 Ni 10) 94 (TaNbZrVC 2) 6 multi-element alloy (MEA) was developed. The alloy is composed of a multi-component carbide (MCC) phase and two BCC solid solution phases. The compressive yield strength is about 1373 MPa, while the compressive plasticity is over 60% at room temperature, which is mainly contributed by the MCC strengthening phase. [ABSTRACT FROM AUTHOR]

Ti–36Nb–2Ta–3Zr–0.35O (wt.%) (TNTZO, also called gum metal) alloy was surface treated by electron beam melting (EBM), in order to improve wear properties. The microstructures and phase constitutions of the treated surface were characterized by optical microscopy (OM), scanning electron microscopy (SEM), grazing incidence X-ray diffraction (GIXD) and electron backscattered diffraction (EBSD). The results showed that the martensitic phase and dendrites were formed from the β phase alloy after the EBM treatment, and microstructures in the surface changed with the processing parameters. Compared with the untreated TNTZO alloy, the surface modified TNTZO alloys exhibited higher nano-hardness, 8.0 GPa, and the wear loss was also decreased apparently. The samples treated at a scanning speed of 0.5 m/s exhibited the highest wear resistance due to the fast cooling rate and the precipitation of acicular α″ phase. The relationship between the wear property and the surface microstructure of TNTZO alloy was discussed. [ABSTRACT FROM AUTHOR]

An AlCoCuFeTi high-entropy alloy with excellent wear resistance and high hardness was successfully produced by arc melting. The effects of annealing on the microstructure, nanomechanical behaviors, tribological properties, and corrosion resistance were systematically investigated. The results showed that the AlCoCuFeTi consisted of a Co-enriched L2 1 phase, a Cu-enriched FCC phase, and a (Fe, Ti)-enriched Laves phase. Annealing promoted the formation of FCC and Laves phases but decreased the volume fraction of the L2 1 phase. The high hardness of AlCoCuFeTi is attributed to the formation of L2 1 and Laves phases. The highest hardness (14.1 ± 1.3 GPa) and reduced Young's modulus (256 ± 11 GPa) were achieved in the 1100 °C annealed and 900 °C annealed specimens, respectively. All specimens exhibited excellent wear resistance compared to typical HEAs due to the mild-oxidational wear mechanism. The 1100 °C annealed specimen possessed the highest elastic strain to failure (H/E r) and yield pressure (H3/E r 2), corresponding to its best-measured wear resistance. The segregation of Cu led to galvanic corrosion during the polarization tests, and the area ratio of cathode to anode (A c /A a) determined the corrosion rate. The 1100 °C annealed specimen exhibited good corrosion resistance due to its low A c /A a value. • The AlCoCuFeTi high-entropy alloy exhibits high hardness due to the formation of L2 1 and Laves phases. • Annealing promotes the formation of FCC and Laves phase while decreasing the volume fraction of L2 1 phase. • The AlCoCuFeTi high-entropy alloy obtains an outstanding wear resistance because of the mild-oxidational wear mechanism. [ABSTRACT FROM AUTHOR]

Titanium alloys produced by additive manufacturing show excellent mechanical properties at room temperature. However, their deformation behavior at low temperature is still not fully understood. In this study, the microstructural evolution and tensile behavior of the near-α titanium alloy Ti-6.5Al-2Zr-Mo-V (TA15), fabricated via laser powder bed fusion (LPBF), were determined at both 25 °C and −196 °C. The LPBFed TA15 alloy shows the microstructure of α laths and acicular α′ martensite due to the rapid cooling rate during LPBF processing. Pyramidal slip and numerous twins, including nano-twins and triple twins, were activated at cryogenic temperature, leading to the high ultimate tensile strength (UTS) up to 1750±8 MPa and yield strength (YS) up to 1548±25 MPa, which is higher than the strength at room temperature (YS∼1103 MPa, UTS∼1281 MPa). The dominant deformation mechanism changes from dislocation slip to twinning with decreasing temperature, leading to uniform deformation with an elongation of 5.2±0.1 %. The results can guide the control of the microstructure of LPBFed near-α titanium alloys at cryogenic temperature. • The LPBFed TA15 showed excellent tensile strength (YS∼1548 MPa, UTS∼ 1750 MPa, elongation∼5.2±0.1 %) at −196 °C. • A large number of 10 1 ̅ 1 < 10 1 ̅ 2 > nano-twins, including the nanotwins and triple twins, were activated at cryogenic temperature. • The dominant strengthening mechanism varies from dislocation strengthening to twin boundary strengthening. [ABSTRACT FROM AUTHOR]

ZrC/ZrB 2 in-situ reinforced composite coatings were prepared by laser cladding on zirconium alloy. The effect of WC content on microstructure and properties of in-situ reactive ZrC/ZrB 2 composite coatings were investigated experimentally. The dilution rate and the inhomogeneity of reinforcements distribution were increased by increasing WC content. The increment of WC content contributed to the refinement of the fishbone dendrites. The microhardness and corrosion resistance of the composite coatings decreased with increasing WC content. When the WC content was 15 wt%, the average microhardness of the coating was the highest as 529 HV 0.5. Meanwhile, the corrosion potential was the highest and the corrosion current density was the lowest, which were − 0.660 V and 1.627 × 10 − 8 A cm −2 , respectively. • ZrC/ZrB 2 in-situ reinforced composite coatings were successfully prepared on zirconium alloys by laser cladding. • The increment of WC content contributed to the refinement of the fishbone dendrites. • The addition of WC enhanced the corrosion resistance of the coating. [ABSTRACT FROM AUTHOR]

• A new method for preparing Zn and its alloys has been devised. • The relationship between Zn and CuZn 4 phase is [-1–120] ε // [01–11] Zn. • Zn-2Cu-0.1Ti alloy has high mechanical properties and slow degradation rate. • Zn-2Cu-0.1Ti alloy has excellent osteogenesis properties. Bioresorbable implants are intended to be biocompatible, mechanically stable, and to corrode gradually in response to an appropriate host response. In this work, a Zn-2Cu-0.1Ti (ZCT) alloy was fabricated by a combination of casting and hot-rolling. X-ray diffraction analysis revealed the presence of both TiZn 16 phase and a CuZn 4 phase in the alloy. ZCT showed an extraordinary increase in yield strength compared with the unalloyed Zn to 248 MPa (from 100 MPa) and a similar elongation to failure (33–34%). The alloy also possesses a relatively low corrosion rate when immersed in simulated body fluid. The 50 % extract of ZCT alloy exhibits excellent biocompatibility for MC3T3-E1 cells. These results indicate that the ZCT alloy has potential for clinical applications. [ABSTRACT FROM AUTHOR]

Highlights • Addition of special fat availably improved the quality of non-fermented frozen dough. • Adding special fat increased gelatinization and reduced degree of retrogradation. • Frozen dough added with special fat showed better texture and rheological property. • Freezable water content and mobility of free water reduced when special fat was added. • Starch granules covered by gluten existed in frozen dough added with special fat. Abstract To better understand the effect of interesterified blend-based fast-frozen special fat (IBSF) on the quality of frozen dough, the physical properties and microstructure of frozen dough were investigated. The presence of IBSF in the frozen dough increased the gelatinization enthalpy (from 0.16 to 0.26 J/g) and decreased the degree of retrogradation (from 81.3% to 53.8%). The frozen dough added with IBSF also exhibited enhanced extensibility and greater flexibility. Data of DSC and Low-field NMR demonstrated that addition of IBSF significantly reduced the freezable water content and mobility of free water. SEM analysis showed that the starch granules were arranged in the gluten network of frozen dough. Compared with the corresponding physical blend-based special fat and commercial special fat, IBSF not only exhibited favorable influence on the quality of frozen dough, but didn't have trans-fatty acid. These results suggest that IBSF is promising in the preparation of prefrozen fast food. [ABSTRACT FROM AUTHOR]

Abstract A TiC-Fe surface gradient coating was prepared on the surface of pure titanium by a simple two-step heat-treatment process (1150 °C × 5 min + 1000 °C × 10 h). The phase composition, microstructure, nanoindentation hardness, elastic modulus, fracture toughness, and adhesion strength of the TiC-Fe surface gradient coating were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), nanoindentation testing, and scratch testing. The results reveal that the TiC-Fe surface gradient coating was composed of dense TiC grains and a small amount of α-Fe. The TiC-Fe surface gradient coating was divided into three zones according to the variation in the volume fractions of TiC particulate and α-Fe phase. These zones were labeled as follows: a columnar TiC zone (I zone), a large particle TiC zone (II zone) and a large bulk TiC zone (III zone). The formation process and mechanism of the TiC-Fe surface gradient coating include the nucleation growth of TiC grains, followed by diffusion and in situ reactions between titanium and carbon. The nanoindentation hardness and elastic modulus for cross section of the TiC-Fe surface gradient coating ranged from 19.1 to 31.7 GPa and from 368.1 to 464.3 GPa, respectively. The fracture toughness values of I zone, II zone and III zone are 3.5, 1.6 and 3.1 MPa m1/2, respectively, and these values largely depend on composition and microstructure. Investigations of crack surface morphologies indicate that radial cracks at the corners of the indentation originate from the crossing of slip bands and that the toughening mechanism was mainly crack deflection and bridging. In addition, the scratch testing indicated that the coating exhibited excellent coating/substrate adhesion strength. Highlights • A TiC-Fe coating was fabricated by a simple two-step heat-treatment process. • The grain size and volume fraction of TiC presented a graded distribution. • The formation mechanism of the coating was the in situ solid phase diffusion reaction. • The fracture toughness values of the coating were 1.6–3.5 MPa m1/2 with 76%–99% TiC content. [ABSTRACT FROM AUTHOR]

Abstract Tantalum-tantalum carbide (Ta-TaC) core–shell rod-reinforced iron-based composites were designed and fabricated by in situ solid-phase diffusion reaction at 1150 °C for 5, 10, 15, 20, and 80 min, respectively. Phase composition, microstructure, impact toughness, micro-hardness, and elastic modulus of the composite, morphologies and grain sizes of TaCs were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, impact test, and nano-indentation test. Furthermore, formation kinetics of TaC-Fe shell layer was analyzed by measuring the thickness of pure TaC layer as a function of heat treatment time and temperature. Results indicated the generation of dense and compact TaC layer around the Ta rod by in situ solid-phase diffusion reaction, and together they were designated as the Ta-TaC core–shell rod. Predominant features of the Ta-TaC core–shell rod included a gradient nanostructured TaC-Fe shell layer and a Ta core. Predominant phases of the Ta-TaC core–shell rod-reinforced iron-based composite were Ta, TaC, and α-Fe phases. Kinetic results of TaC-Fe shell layer exhibited parabolic relationship between the thickness of pure TaC layer and annealing time, and growth rate constant for pure TaC layer was estimated to be 6.25 × 10−8 cm2 s−1. TaC particles in TaC-Fe shell layer preferred a perfect cube morphology enclosed by {100} facets with minimized total surface free energy. Grain size of TaC increased gradually from about 150 to 500 nm with the increasing distance from the interface of Ta core/TaC-Fe shell layer to the substrate. The Ta-TaC core–shell rods play an important role in improving the mechanical properties of the composite. Micro-hardness of the TaC-Fe shell layer was in the range of 10.4–24.8 GPa, which is 3–8 times than that of the substrate due to the dense and compact TaC. Impact toughness of the composite was 100.6 J cm−2, which is markedly higher than that of the gray cast iron (7.8 J cm−2). Excellent impact toughness of the composite is mainly attributed to Ta core of Ta-TaC core–shell rod, which undergoes a large plastic deformation under external forces. Moreover, the compact TaC distributed around Ta rod reduced split action to the matrix, and the matrix absorbed large amount of crack propagation energy. Highlights • Ta-TaC core–shell rod was in situ synthesized by solid-phase diffusion reaction. • The Ta-TaC core–shell rod includes a gradient TaC-Fe shell layer and a Ta core. • The maximum hardness was 24.8 GPa attributed the dense and hard TaCs. • The impact toughness was about 12 times higher than that of the gray cast iron. • High impact toughness of the composite was due to the Ta core with high toughness. [ABSTRACT FROM AUTHOR]

The current study investigates the effects of ultrasonic treatment on the gravity segregation and dendritic segregation of the Mg–8Gd alloys. Corresponding microstructures and mechanical properties at different heights of the ingots were analyzed. Without ultrasonic treatment, the microstructures and mechanical properties at different heights of the ingot were significantly different. The content of Gd in the bottom sample reached up to 11.4% and a large number of network eutectic structures could be observed along the coarse dendrites, which was confirmed to be the main reason for the brittle fracture with a poor elongation of 2.75%. In addition, there were also some cubic phases proved to be α-Gd, MgGd and Mg 2 Gd. When the ultrasonic was introduced into the melt, the cavitation effect and acoustic streaming occurred, resulting in the uniformities of temperature and Gd content in the alloy melt. As a consequence, the microstructures at different heights tend to be similar with the equiaxed α-Mg matrix containing Mg 5 Gd in homogeneous dispersion state and both the strength and the elongation of the samples were improved obviously. [ABSTRACT FROM AUTHOR]

The electrochemical oxidation behavior of high-entropy alloys (HEAs) is supposed to be different from that of traditional Ti-based alloys due to the presence of multi-principal elements. In this work, equi-atomic Ti-Nb-Ta-Zr-Hf bio-HEA (PEO-free) was subjected to plasma electrolytic oxidation (PEO) at 150 (PEO-150 V), 200 (PEO-200 V) or 250 V (PEO-250 V). Due to substrate oxidation, the PEO-formed coatings were composed of multiple metallic oxides in their complete oxidation states. Moreover, elements such as Ca, Si, Na and O from the electrolyte were also introduced into the coatings. Different from the amorphous nature PEO-150 V coating, the microstructures of PEO-200 V and PEO-250 V coating were characterized by Hf 0.5 Zr 0.5 O 2 nano-crystals homogeneously dispersed in amorphous coating matrices, with PEO-250 V group (∼20 μm in diameter) possessing larger nano-crystals than PEO-200 V group (∼6 μm in diameter). The dry-sliding test identified an order of PEO-200 V > PEO-250 V > PEO-150 V > PEO-free group for the wear resistance. The corrosion resistance evaluated by electrochemical impedance spectroscopy followed the trend of PEO-150 V > PEO-200 V > PEO-250 V > PEO-free group. The in vitro experiments confirmed the favorable cyto-compatibility of PEO-treated surfaces. Together, the results indicate that the coating with appropriate amorphous/crystalline dual-structure on Ti-Nb-Ta-Zr-Hf bio-HEA surface is promising for biomedical applications. [Display omitted] • Plasma electrolytic oxidation was performed on Ti-Nb-Ta-Zr-Hf biomedical high-entropy alloy. • The PEO-150 V coating was amorphous, while PEO-200 V and PEO-250 V coating were dual-structured. • The wear resistance was in an order of PEO-200 V > PEO-250 V > PEO-150 > PEO-free group. • The corrosion resistance followed a trend of PEO-150 V > PEO-200 V > PEO-250 > PEO-free group. [ABSTRACT FROM AUTHOR]

• Unalloyed Tantalum was processed successfully by LPBF with high laser power (600 W). • The convert from columnar grain to equiaxed grain was obtained by high laser power. • A high-density sample with good mechanical properties was fabricated. The effect of laser energy density on the microstructural evolution and the mechanical properties, including tensile property and nanoindentation creep behavior of Ta parts were investigated. A high laser power strategy (600 W) was used to obtain Ta part with high density. The microstructure of Ta fabricated with 200 W comprised columnar grains with strong 〈1 1 1〉 texture, while equiaxed grains with random orientation were found in Ta fabricated with 600 W. The elongation to failure of the specimen fabricated at 600 W was higher than that of the specimen fabricated at 200 W, which stemmed from pore elimination and equiaxed grains. Nanoindentation creep results showed that the movement of dislocations was the main creep mechanism and the influence of laser energy density was discussed. [ABSTRACT FROM AUTHOR]

Mg is a potentially biomaterial for bone implant due to its biodegradability and biomechanical compatibility. However, the too fast degradation rate limits its clinical application. In the study, both alloying treatment and laser rapid melting were applied to slow down its degradation rate. The microstructure, mechanical properties and degradation behavior of the Mg x Sn ( x = 0–7 wt %) alloys were investigated. With Sn content increasing, the grain sizes decreased, while the new Mg 2 Sn phase increased. The refined grain slowed the degradation rate due to the reduced segregation. While the Mg 2 Sn phase accelerated the degradation rate owing to the couple galvanic corrosion. Thus, the optimal degradation behavior was obtained with a balanced grain size and Mg 2 Sn phase volume fraction. Besides, the compression strength increased firstly (up to 5 wt %) and then decreased with Sn increasing. [ABSTRACT FROM AUTHOR]

Due to their bioinert nature, titanium alloys show poor bone-implant integration and insufficient osseointegration in vivo. In this study, a series of low elastic modulus bioactive titanium alloys with a nominal composition of Ti-13Nb-13Zr-1.25 Mg (wt%) were prepared using mechanical alloying and spark plasma sintering techniques. The microstructures, mechanical properties, degradation behaviors and in vitro bioactivities of these alloys were systematically investigated. After sintering at 700 °C, the α-Ti, β-Ti and Nb (Zr)-rich phases were present, and the Mg was uniformly distributed. In addition to above-mentioned phases, the α″ phase was found after sintering at 800 °C or 900 °C. The density, elastic modulus, yield strength, ultimate compressive strength and corrosion resistance all increased with increasing sintering temperature. After sintering at 900 °C, the alloy exhibited high density (99.8%), good compressive strength (1417.2 MPa) and excellent corrosion resistance. In addition, it had a lower elastic modulus (~69 GPa) than that of the biomedical alloy Ti–13Nb–13Zr (~80 GPa). In vitro experiments showed that the alloys sintered at either 800 °C or 900 °C promoted cell adhesion and proliferation. However, the alloy sintered at 700 °C inhibited cell proliferation, which was due to the greater release of Mg2+. Thus, the optimally-processed Ti-Nb-Zr-Mg alloy sintered at 900 °C shows immense potential as a biomedical material. [Display omitted] • Ti-Nb-Zr-Mg alloys with low modulus were fabricated by MA and SPS. • Higher sintering temperature promoted the formation of α″ phase. • Mg element reduced the corrosion resistance of Ti-Nb-Zr matrix. • The mode of Mg2+ release was affected by sintering temperature. • The sustained release of Mg2+ was beneficial to the cell viability and proliferation. [ABSTRACT FROM AUTHOR]

To simultaneously obtain superior superelasticity and biological properties, single- and multi-layer Ti–23Nb coatings were deposited on a cold-rolled NiTi substrate using laser metal deposition (LMD). The microstructure of the single-layer coating consisted of a cellular structure with a grid size of ∼300 μm in the eutectic layer, strip structures and prior β-(Ti, Nb) phases surrounded by the Ti 2 Ni(Nb) phase in the Ni diffusion zone. In contrast, the microstructure of the multi-layer coating consisted of α′, α′′, and prior β phases, which arise from the partition of Nb. Compared with the NiTi substrate, the Ni ion release concentration of the single-layer coating is reduced by 45% with similar nano-mechanical behavior, i.e. a nanohardness, H , of ∼4.0 GPa, a reduced Young's modulus, E r , of ∼65 GPa, an elastic strain to failure, H / E r , of ∼0.06, a yield stress, H 3/ E r 2, of ∼0.016 GPa, and a superelastic strain recovery, η sr , of ∼0.3. The reduction of Ni ion concentration for multi-layer coating after 35 days is even better at up to 62%, but at the cost of a degradation in the mechanical properties. The LMD coatings have a high dislocation density, and their creep is controlled by dislocation movement. • The diffusion of Ni during laser melting leads to the formation of cellular and strip subgrains. • α″ martensite is critical for the properties of the TiNb binary alloys produced by LMD. • The single-layer coating can suppress the release of Ni ions while preserving the superelasticity of substrate. [ABSTRACT FROM AUTHOR]

In this study, three medium entropy alloys (MEAs), TiNbZr, Ti1.5Nb1.5Zr and Ti1.5NbZr1.5 were designed and investigated to be applied as biomedical materials. The results showed that the alloys prepared by arc melting have a typical dendrite microstructure, caused by elemental segregation during solidification. With composition changes, the partition of the constituting elements behaves differently. The microstructure inhomogeneity and chemical segregation could be greatly reduced by homogenization treatment. The MEAs show good compressive ductility (>40%) and yield strength comparable to or even superior to those of the commercially used biomedical alloys (e.g., 316 stainless steel and pure titanium), which are mainly contributed from the solid-solution strengthening effect. In addition, these MEAs exhibit acceptable Young's modulus ranging from 80 to 93 GPa by nano-indentation tests. The alloys also show excellent corrosion resistance in the phosphate buffer saline (PBS) solution and favorable cyto-compatibility, which are comparable to or even superior to pure titanium and/or Ti-6Al-4V alloys. Based on these properties, the Ti-Nb-Zr MEAs show a promising potential in biomedical applications. The results in this study could be instructive for further alloy design of such biomedical MEAs. • Three medium entropy alloys (MEAs) for biomaterials were designed. • The microstructure of the MEAs is composed of a single bcc phase. • The MEAs exhibit excellent corrosion resistance in PBS. • The MEAs manifest excellent biocompatibility comparable to CP-Ti. [ABSTRACT FROM AUTHOR]

FeCoCrNiMo high-entropy alloy (HEA) has attracted great interests due to its excellent corrosion resistance, but it suffers relatively low hardness and poor tribological performance. In this work, a systematic study on microstructural evolution and tribological behavior of equiatomic FeCoCrNiMoSi x (x = 0.5, 1.0, 1.5) HEA coatings prepared by laser cladding (LC) on Q235 steel substrates is reported. Confirmed by X-ray diffraction analysis (XRD) and energy dispersive spectrometry (EDS) results, these coatings mainly consist of Fe-rich FCC and FeMoSi phases. The increase of Si content leads to greater lattice distortion and promotes the formation of Si-rich intermetallics, which can significantly improve the hardness and the wear resistance of the FeCoCrNiMoSi x coatings. The best wear resistance is achieved in FeCoCrNiMoSi 1.0 coating, which the wear mechanism is a combined abrasive and adhesive wear. • FeCoCrNiMoSi x (x = 0.5, 1.0, 1.5) HEA coatings were fabricated by laser cladding. • Single track experiments were used to figure out the optimal process parameters. • The FeCoCrNiMoSi x HEAs mainly consisted of Fe-rich FCC, FeMoSi phases and Si-rich intermetallics. • Hardness of 943 HV was obtained in FeCoCrNiMoSi 1.5. • Wear mechanism changed from abrasive and adhesive wear to delamination wear. [ABSTRACT FROM AUTHOR]

Abstract: In this work, a novel process that combines infiltration casting with subsequent heat treatment was applied to fabricate in situ vanadium carbide (V8C7) ceramic particulates-reinforced iron matrix composites. Based on the differential scanning calorimetry (DSC) data, the as-cast samples were subjected to heat treatment at 1164°C for different dwelling times (0, 10, 15, and 20min). The effects of different heat treatment times on the phase evolution, microstructure, and microhardness of the as-prepared composites were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS), and Vickers hardness tester, respectively. The experimental results revealed that only graphite, α-Fe, and V8C7 phases dominate in the composite samples after heat treatment at 1164°C for 20min. The average microhardness of the as-prepared composites varied among the different regions as follows: 458 HV0.05 (vanadium wire), 1055 HV0.05 (composite area), and 235 HV0.05 (iron matrix). The microhardness of the composite region is four times higher than that of the iron matrix and two times higher than that of the vanadium wire because of the formation of the vanadium carbide phases (V2C and V8C7) as reinforcement within the iron matrix. [Copyright &y& Elsevier]