Search

In this paper, the microstructure and mechanical properties of Al-6.5Si-5.5Cu-0.2Zr-0.01Sr-0.06Ti-0.2Ce cast aluminum alloys were investigated in multistage solid solution systems. The microstructure of the alloy was characterized using an optical microscope (OM), scanning electron microscope (SEM), energy-dispersive spectrometer (EDS), x-ray diffraction (XRD) and transmission electron microscope (TEM), respectively. The hardness and conductivity of the alloy were measured using a Vickers hardness and eddy current conductivity testers, respectively, and the tensile properties were described by a drawing machine. The results showed that the mechanical properties of the alloy are the worst under the four-stage solid solution system (G1). With the increase in multistage solution temperature and holding time, θ phase (Al2Cu) was gradually dissolved into α-Al matrix to enhance the effect of dislocation strengthening. When the solution temperature reached 510 °C, the mechanical properties of the alloy were the best, and the tensile strength and elongation were increased to 354.90 MPa and 9.02%, respectively. With the increase in temperature, eutectic Si agglomeration and large area of insoluble phase between metals were found, resulting in the decrease in mechanical properties. [ABSTRACT FROM AUTHOR]

The microstructure and properties of an AlSi10Mg alloy produced by selective laser melting were examined using optical microscopes, scanning electron microscopes, electron backscattered diffraction, and x‐ray diffraction. The results show that the mechanical characteristics of selective laser melting formed AlSi10Mg alloy is superior to those of traditional sand cast AlSi10Mg alloy due to fine grain strengthening and solid solution strengthening. AlSi10Mg alloy formed by selective laser melting is mainly composed of α‐aluminum solid solution, eutectic silicon with network structure and a small amount of Magnesium silicon precipitated phase, and different cross‐sections have unique microstructures and properties. The XOY plane is composed primarily of equiaxed grains with an average grain size of 7.34 μm and a {001} <100> cubic texture, and it has a hardness value of 130.7 HV 0.2. The majority of the YOZ plane, which has a {111}<110> brass R texture and a hardness value of 108.9 HV 0.2, comprises columnar crystals with an average grain size of 8.42 μm. [ABSTRACT FROM AUTHOR]

In the aircraft industry, the high-strength aluminum alloys AA7075 and AA2024 are extensively used for the manufacture of structural parts like stringers and skins, respectively. Additive manufacturing (AM) of the AA7075-T6 aluminum alloy via friction stir deposition to build continuously multilayered parts on a substrate of AA2024-T4 aluminum has not been attempted so far. Accordingly, the present work aimed to explore the applicability of building multilayers of AA7075-T6 alloy on a substrate sheet of AA2024-T4 alloy via the additive friction stir deposition (AFSD) technique and to optimize the deposition process parameters. The experiments were conducted over a wide range of feed rates (1–5 mm/min) and rotation speeds (200–1000 rpm). The axial deposition force and the thermal cycle were recorded. The heat input to achieve the AFSD was calculated. The AA7075 AFSD products were evaluated visually on the macroscale. The microstructures were also investigated utilizing an optical microscope and scanning electron microscope (SEM) equipped with an advanced EDS technique. As well as the presence phases, the mechanical performance of the deposited materials in terms of hardness and compressive strength was also examined. The results showed that the efficiency of the deposition process was closely related to the amount of heat generated, which was governed by the feeding rate, the rotational speed, and the downward force. AA7075 defect-free continuously multilayered parts were produced without any discontinuity defects at the interface with the substrate at deposition conditions of 1, 2, 3, and 4 mm/min and a constant 400 rpm consumable rod rotation speed (CRRS). The additively deposited AA7075-T6 layers exhibited a refined grain structure and uniformly distributed fragment precipitates compared to the base material (BM). The gain size decreased from 25 µm ± 4 for the AA7075-T6 BM to 1.75 µm ± 0.41 and 3.75 µm ± 0.78 for the AFSD materials fabricated at 1 and 4 mm/min deposition feeding rates, respectively, at 400 rpm/min. Among the feeding rates used, the 3 mm/min and 400 rpm rod rotation speed produced an AA7075 deposited part possessing the highest average hardness of 165 HV ± 5 and a compressive strength of 1320 MPa. [ABSTRACT FROM AUTHOR]

Novel HEAp-Ti/Al laminated composites embedded with particles of the high-entropy alloy Al0.5CoCrFeNi (HEA) were fabricated by vacuum hot-press sintering at 730 °C. The phase composition and microstructure of the composites were studied with X-ray diffractometer (XRD), scanning electron microscope SEM, energy dispersive spectrometer (EDS), transmission electron microscope (TEM), and electron backscattering diffraction (EBSD) techniques. At this temperature, it has been observed that Al3Ti intermetallic compound is the favored phase and the reaction results in the dispersion of Al3Ti in the original Al layer. A large number of interfaces are formed between Al3Ti and Al. The deformed Al3Ti grains are concentrated in the interface near the Ti side. The mechanical properties, including tensile and compressive properties at room temperature, were analyzed. The tensile test results indicate that the composite exhibited an average tensile strength of 258 MPa and an average yield strain of 9.86%. Compression test results show that when a load perpendicular to the layer is applied, the yield strain and yield stress of the material are 9.67% and 474.09 MPa, respectively. Moreover, under a load parallel to the layer, the material fails due to interfacial debonding. [ABSTRACT FROM AUTHOR]

This work investigates the microstructure characterization and mechanical properties of Al alloy fabricated by additive friction stir deposition (AFSD). Microstructure characterizations of the Al alloy 5B70 base material (BM) and build were compared using optical microscope (OM) and electron back scattered diffraction (EBSD). The hardness distribution in the direction perpendicular to the cross-section of the deposited area was systematically evaluated. Tensile tests were performed on the BM and the build using digital image correlation (DIC), and the real-time stress distribution states of the specimens were analyzed. After the tensile tests, the fracture micromorphology was characterized using scanning electron microscope (SEM). The results indicated that a high degree of recrystallization occurred in the deposition zone, where fine, equiaxed, and differently oriented grains are formed. It was found that the strength of the deposition layer was lower compared to that of the BM, but its toughness was significantly improved. Also, obvious anisotropy of mechanical properties was identified in the deposition layer. [ABSTRACT FROM AUTHOR]

The effects of La and Y on the microstructure and mechanical properties of cast Al-Si-Cu alloys were investigated by X-ray diffractometer (XRD), optical microscope (OM), and scanning electron microscope (SEM). The results indicated that the addition of La and Y had a great effect on the refinement of α-Al grains, the modification of eutectic Si phase, and the reduction of β-Al5FeSi length in Al-Si-Cu alloys. The A380 + 0.6 wt.% La/Y alloy exhibited the best microstructure and mechanical properties. The UTS and EI of the A380 + 0.6 wt.% La/Y alloy were 215.3 MPa and 5.1%, which were 22.9% and 37.8% higher than those of the matrix alloy, respectively. In addition, neither Al11La3 nor Al3Y generated by the addition of La and Y could not serve as the nucleation core of α-Al grains, so the grain refinement of α-Al originated from the growth limitation and constitutional supercooling. Since La and Y promote twinning generation and constitutional supercooling, the eutectic Si phase also changed from stripe-like to short fibrous or even granular and was significantly refined. Furthermore, thermodynamic calculations indicated that the Al11La3 phase was formed first and the Al3Y phase was generated on the Al11La3 phase. [ABSTRACT FROM AUTHOR]

The structure and mechanical properties of non-equiatomic Al8Co30Cr18Fe9Ni31Nb4, Al8Co30Cr18Fe9Ni31Nb2Ti2 and Al8Co30Cr18Fe9Ni31Ti4 high entropy alloys (HEAs) were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), hardness and tensile testing. TEM and XRD analyses revealed the formation of γ''-Ni3Nb/γ (FCC), double FCC and γ'-Ni3Al/γ (FCC) structure for as-cast Al8Co30Cr18Fe9Ni31Nb4, Al8Co30Cr18Fe9Ni31Nb2Ti2 and Al8Co30Cr18Fe9Ni31Ti4 HEAs, respectively. The hardness and yield strength values were found to increase with the addition of Nb while the ductility of alloys increased with the increase in Ti concentration, significantly. The as-cast Al8Co30Cr18Fe9Ni31Ti4 alloy exhibited an excellent combination of ultimate tensile strength of 844 MPa and an elongation of 29.8% due to the coherent phase relation between γ' precipitates and γ matrix. The fractured surfaces of as-cast Al8Co30Cr18Fe9Ni31Nb4, Al8Co30Cr18Fe9Ni31Nb2Ti2 and Al8Co30Cr18Fe9Ni31Ti4 HEAs showed typical dimple type ductile fracture under tension test. [ABSTRACT FROM AUTHOR]

This study investigated the microstructure, hardness, tensile and tribological behaviour of a cooling slope Al--Si--Mg alloy following ECAP and T6 heat treatment. The optical and scanning electron microscopes were applied to investigate the microstructure of the as-cast material and heattreated ECAPed Al--Si--Mg alloy. The dry sliding wear test was tested with three different loads of 10 N, 50 N, and 100 N with constant sliding speed and sliding distance at 1.0 m/s and 9000 m, respectively, using the pin-on-disc tribometer. The hardness and tensile properties were evaluated through microhardness, UTS, and YS measurement for the as-cast Al--Si--Mg alloy, both heat-treated with and without ECAPed alloys. Moreover, wear rate and COF in the Al--Si--Mg alloy with different loads were analysed and linked with microstructural and strength behaviour after the ECAP process. Meanwhile, these analyses of results were correlated with the behaviour of the as-cast Al--Si--Mg aluminium alloy and heat-treated non-ECAPed alloy. Results demonstrated that a combination of ECAP processing and T6 heat treatment improves the mechanical behaviour, while the COF and wear rate are improved at a load of 100 N. [ABSTRACT FROM AUTHOR]

FeCrMnNi high-entropy alloys prepared by vacuum induction melting were tested and characterized using an X-ray diffractometer, a scanning electron microscope, a micro hardness tester and a universal tensile tester to investigate the effects of the heat treatment temperature on the microstructure and mechanical properties of the alloys and the heat-resistant corrosion properties of FeCrMnNi alloy after annealing at 800 °C. It is a high-entropy alloy with a typical dendritic (DR) morphology. With the increase in the heat-treatment temperature, the amount of ultrafine precipitates with the BCC structure in the matrix increased; furthermore, the amount of ultrafine precipitates started to decrease at temperatures above 900 °C, and the DR structure gradually weakened. After heat treatment at temperatures above 800 °C, the alloy showed a tensile strength of 721.1 MPa and an elongation at break of 26.7%, which indicates improved strength of the alloy while maintaining good plasticity, mainly because a large amount of nanoscale particles precipitated between the DR structures and enabled fine grain strengthening. Therefore, an appropriate heat-treatment temperature helps to improve the overall mechanical properties of the high-entropy alloy. [ABSTRACT FROM AUTHOR]

A novel aluminum matrix composites (AMCs) reinforced by multiphase intermetallic compounds were fabricated through a conventional casting approach. The microstructure, compression properties and tribological behavior of the AMCs were detailed studied by the scanning electron microscope (SEM), x-ray diffraction (XRD), and electron probe microanalysis (EPMA). The results demonstrated that the fraction of precipitated multiphase intermetallic compounds gradually increased with the increase of high-entropy alloy (HEA) adding content, and the grain size of α-Al obviously was reduced. The irregular multiphase intermetallic compounds, such as Al70Cr20Ni10 and AlTiCrSi, are distributed in the Al matrix. However, the Al2Cu and Al7Cu4Ni distributed in inter-dendrites of α-Al. In addition, the compression strength of AMCs reinforced by 20.0 wt.% HEA addition was significantly enhanced to 530 MPa due to the precipitation of multiphase intermetallic compounds. Meanwhile, its compression strain was higher than 25%. Compared with pure Al, the microhardness of AMCs was extremely increased to 160 HV when the addition content of HEA was up to 20.0 wt.%. When the addition amount of HEA reached 10.0 wt.%, the COF of the ACMs was decreased by 51.6% from 0.766 to 0.371. When the HEA content was up to 20.0 wt.%, the wear rate reached the minimum of 4.87 × 10−5 mm3/N·m, which was reduced by 31.9% compared with pure Al. Furthermore, the strengthening effect and wear mechanism of AMCs reinforced by HEA addition was also discussed. [ABSTRACT FROM AUTHOR]

Aluminium alloys have low density and good mechanical properties, making them suitable for the manufacture of mechanical structures where low weight is critical. However, when these alloys are subjected to elevated temperatures, their mechanical properties deteriorate significantly. The aim of this study is to investigate the effect of temperature on the mechanical properties of aluminium alloy, EN AC-Al Si12CuNiMg. For this purpose, an experimental investigation was performed at ambient and elevated temperatures on aluminium alloy samples prepared by casting. Tensile and hardness tests were carried out to characterize the mechanical properties of this material. Additionally, an optical microscope was used to examine the microstructures of this alloy. Finally, a scanning electron microscope was used to analyze the fracture modes of this material. The results show that the mechanical properties such as tensile strength, yield strength, and Young's modulus of this alloy dramatically decrease when the temperature exceeds 250oC. The microstructural investigation reveals several factors that are detrimental to the mechanical properties of this alloy. This includes coarse-grained structures, micro-pores, and several intermetallic compounds. Furthermore, fractography reveals a minor cleavage-like pattern and micro-cracks on the fracture surface of all failed samples under various temperatures, indicating semi-brittle fracture mode. [ABSTRACT FROM AUTHOR]

The effects of Ag content and hot-rolling on the microstructure and mechanical properties of Zn-1.5Cu-xAg-0.1Zr(x = 0, 0.1, 0.5, 1.0) alloys were investigated. The microstructure, phase composition and fracture morphology of the alloys were observed and analyzed by optical microscope, x-ray diffraction, scanning electron microscope, energy dispersive spectrometer and universal mechanical testing machine. The results show that Ag has the effect of grain refinement. After alloying, the grain size of as-cast Zn-1.5Cu-xAg-0.1Zr alloy decreased first and then increased, and the minimum grain size of as-cast Zn-1.5Cu-0.5Ag-0.1Zr alloy was refined to 64.18 μm. At the same time, new phase AgZn3 began to precipitate, the yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) of alloys were also up to 97.35 MPa, 139.25 MPa and 7.60%, respectively. After hot-rolling, the grain of Zn-1.5Cu-xAg-0.1Zr alloy was broken and new phase CuZn5 was precipitated. The mechanical properties were significantly improved, and the maximum YS, UTS and EL of as-rolled Zn-1.5Cu-1.0Ag-0.1Zr alloy were 218.14MPa, 244.83MPa, 64.50%, respectively. [ABSTRACT FROM AUTHOR]

The development of magnesium alloys with superior plasticity and favorable strength is still challenging in aerospace industry. Herein, hot extruded Mg-xNd-2.0Sm-0.4Zn-0.4Zr alloys (x = 0, 0.5, 1.0, 1.5, 2.0 and 2.5 wt.%) were rationally designed and easily prepared in order to implement the favorable combination of strength and plasticity. The effects of Nd element addition on the microstructure and mechanical properties of the hot extruded alloys were systematically investigated by optical microscopy (OM), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The OM results indicated that the grain size of the hot extruded alloys decreased from 27.1 to 14.1 μm with increasing Nd addition from 0 to 2.5 wt.%. Some coarse β phases existed at the grain boundary when the addition of Nd element increased to 2.0 wt.%. The TEM results showed that the nanoscaled basal lamellar precipitates, granular precipitates and prismatic lamellar precipitates formed in α-Mg matrix. And the amount of precipitated phase increased obviously with the increase of Nd element addition. The ultimate tensile strength increased significantly from 203 ± 3.0 to 237 ± 2.5 MPa, and the elongation decreased from 30.5 to 21.2 % when the Nd elements increased from 0 to 2.5 wt.%. The fractographs of the hot extruded alloys could be classified as ductile fracture. [ABSTRACT FROM AUTHOR]

In this study, a new alloy material Mg-Zn-Zr (ZK60) was designed for the connecting rod. It was found that the blanks sampled along the vertical direction of an extruded bar crack during the roll forging process. The microstructure and precipitates of the extruded bar were observed and analyzed using optical microscope (OM), scanning electron microscope (SEM) and x-ray diffraction (XRD). The result showed that the Zn, Zr, and MnZn2 precipitates were elongated along the extrusion direction. The mechanical anisotropy was investigated by testing the mechanical properties of the specimens sampling from different angles. Hot deformation behavior was further studied using the Gleeble 3500 thermal-mechanical simulator. The tensile and yield strengths were the highest along the extrusion direction, reaching 347 MPa and 301 MPa, respectively. The deformation resistance was also higher in the extrusion direction than that in the vertical direction. Fracture mechanisms of the sample from different directions were discussed. The ZK60 alloy was more susceptible to failure if the deformation direction was parallel to the bands of segregation area and precipitates. [ABSTRACT FROM AUTHOR]

Liquid metallurgy method based aluminum matrix composites (AMCs) are extensively utilized in diverse engineering applications including shipbuilding, structural, nonstructural, automotive, and aerospace owing to their superior strength, weightless, low density, excellent corrosion, and wear resistance. In the present investigation, liquid state technique was employed to prepare the LM4/aluminum nitride (AlN) composites containing four different mass proportion of AlN filler particles content. The weight proportion of filler particles from 0 to 12 wt% at 4 wt% intervals. Scanning electron microscope (SEM) images demonstrated a even dispersal of filler particles in the matrix. The test outcomes discovered that the LM4/12 wt% AlN AMCs had revealed extreme hardness, tensile, compression strength than the nonreinforced base matrix alloy. A considerable enrichment in the tensile strength is associated with the incorporation of AlN particles into LM4 matrix. The manufactured composites reveal high mechanical properties when compared with the alloy without reinforcement. The improvement of those lightweight AMCs with superior mechanical characteristics has a extreme potential to be employed for aircraft, structural and automobile applications. [ABSTRACT FROM AUTHOR]

To obtain a robust diffusion-bonded joint at a relatively low temperature, Nb foil was applied as an interlayer to the diffusion bonding of Zr-4 alloy, and a wide process parameter involving the bonding temperature of 720–820 °C and holding time of 30–120 min was investigated to reveal the evolution of interfacial structure and mechanical properties of the joints. The β-(Zr, Nb) and Widmanstädter microstructure formed at the interface induced by the eutectoid transformation of the diffused Zr and Nb at the bonding temperatures over 740 °C. The phase structure and the thickness of β-(Zr, Nb) layer were not considerably influenced by the increase in diffusion parameters while the Widmanstädter zone thickened significantly. Moreover, the tensile strength and elongation of the resultant joints could be stabilized above 433 MPa and 7.8%, respectively, when the bonding temperature exceeded 760 °C with a holding time of 30 min. By extending the holding time to 60 min at 760 °C, the tensile strength and elongation could reach 454 MPa and 12.6%, respectively, comparable to those obtained at an elevated temperature of 820 °C for 30 min. Additionally, the samples fractured at the diffusion layer were characterized by the in-situ tensile test under the scanning electron microscope, and it was discovered that the crack initiation and propagation process occurred mainly between the β-(Zr, Nb) and Widmanstädter diffusion zone. • The well-bonded Zr-4 joints were achieved by the application of Nb interlayer. • The diffusion layer consisted of β-(Zr, Nb) and Widmanstädter microstructure. • The Nb addition lowered bonding temperature without weakening tensile properties. • The fracture occurred between the β-(Zr, Nb) and Widmanstädter diffusion zone. [ABSTRACT FROM AUTHOR]

A hybrid composite material was obtained by stacking carbon fiber reinforced plastic (CFRP) onto 7075‐W Al alloy sheet. Mechanical properties of the CFRP/Al hybrid composite material were measured by tensile and flexural tests. To investigate the flow of the epoxy, the thinning was measured using an optical microscope and the defects were observed by a scanning electron microscope. A finite element model was established to predict the thickness and the contact pressure distributions of the CFRP/Al hybrid composite material during the forming process. The results showed that the tensile strength (TS) of the CFRP/Al hybrid composite was increased by 10% and the fracture strain was increased by 24% compared with the single 7075 Al alloy. The flexural strength (FS) and the displacement of the loading nose were improved by 13% and 75%, respectively. According to the microstructure observation, large cracks in the epoxy could be found on the side wall of the U shape part. The results of numerical analysis indicated that the low contact pressure at side wall was the main reason for the decrease of the tensile and FS and the delamination between laminates. [ABSTRACT FROM AUTHOR]

Continuous research into critical functional property enhancement of materials employed in artificial intelligence systems is imperative to overcome performance limitations. This study investigated the thermal and mechanical properties of stir-cast fabricated Al-Cu alloy modified with addition of iron-millscale (IMS) particles varied from 2-6 wt.%. The alloys microstructure was analysed using both optical and scanning electron microscope coupled with energy dispersive spectroscopy (SEM/EDS). PerkinElmer Thermogravimetry/Derivative thermal analyser was used to assess the alloys thermal characteristics while the mechanical properties were evaluated using relevant state of the art equipment. Results show that the best thermal and mechanical properties comparable to established standards were achieved at 6 wt.% IMS particle addition. Contributions to the alloy enhanced performances stemmed from the structure refining propensity of IMS particles. Based on the thermal and mechanical properties demonstrated, the alloy is recommended for application in pneumatic offshore valve actuator used in oil and gas flow process lines. [ABSTRACT FROM AUTHOR]

In this paper, the hot deformation behavior of A357 alloy was investigated by hot compression tests. Isothermal hot compression simulation tests for A357 alloy were carried out at the conditions of deformation temperature of 350-470 °C, strain rate of 0.001-10 s−1 and engineering strain of 50%. Based on the Prasad instability criterion and dynamic material model, the hot processing maps of A357 alloy were constructed. The microstructure of compressed samples at different areas of the hot processing map was characterized by metallographic and scanning electron microscope and transmission electron microscope. The experimental results showed that the unstable processing zone of A357 alloy was mainly distributed in the high strain rate (10 s−1) and low-temperature (350, 380 °C) region. With an increase in the strain, the unstable zone expanded from low temperature to high temperature (470 °C). The ideal deformation conditions were deformation temperatures of 380-410 °C and strain rates of 0.001-0.01 s−1, and deformation temperatures of 440-470 °C and strain rates of 0.01-1 s−1. When the A357 alloy was extruded with the optimal hot processing parameters, the results suggested that hot extrusion could make the microstructure uniform and fine, thereby improving mechanical properties, especially when the elongation was up to 19.5% higher than the as-cast A357 alloy. [ABSTRACT FROM AUTHOR]

There has been great attention on high-entropy alloys (HEAs) over the past decade. Unlike conventional alloy systems, HEAs commonly include at least five principal elements with equiatomic or near-equiatomic ratio. HEAs with their superior mechanical, magnetic, and thermal properties are promising materials for critical engineering applications. Medium-entropy alloys (MEAs), which consist of less than five principal elements, have very similar structural features with HEAs such as robust thermodynamic stability and exceptional mechanical performance. The insights of MEAs have not been fully revealed yet. In the present study, novel MEAs (Cu20Ni20Al30Ti30, Cu25Ni25Al25Ti25, Cu34Ni22Al22Ti22, and Cu35Ni25Al20Ti20) have been designed using thermo-physical calculations and Thermo-Calc software. These MEAs were then produced using copper heart arc melting and suction cast into cylindrical rods with 3 mm diameters. X-ray diffraction (XRD), optical microscope (OM), transmission electron microscope (TEM), scanning electron microscope (SEM), and energy-dispersive spectroscopy (EDS) were used for structural characterization. The corresponding results reveal that the Cu20Ni20Al30Ti30, MEA, consists of a body-centered cubic (BCC-B2) phase with intermetallic compounds (ICs), whereas Cu25Ni25Al25Ti25 has single BCC-B2 phase. When the amounts Cu and Ni are increased, system drives itself toward a face-centered cubic (FCC) structure. A dual BCC and FCC composite Cu35Ni25Al20Ti20 has been detected as the most promising MEA among the others with 820 and 1338 MPa measured yield and compressive strength, respectively. [ABSTRACT FROM AUTHOR]

In the present study, effect of ZrC vol.% on mechanical properties of AA6061 metal matrix composites (MMCs) produced via stir casting technique was investigated. The vol.% of ZrC particles was varied as 5,10 and 15. The composites were characterized for its microstructure and mechanical properties and their relationships were obtained. The scanning electron microscope (SEM) images revealed uniform distribution and good bonding between the AA6061 alloy and the ZrC particles. The mechanical properties of the AA6061 alloy was found to significantly improve with the addition of ZrC particles from 5 to 15 vol.%, the hardness increased from 32 to 68 HV, yield strength increased from 50 to 86 MPa and the ultimate tensile strength increased from 118 to 165 MPa. However, the % of elongation of the composite samples decreased with 15 vol.% addition of ZrC particles. Sliding wear behaviour of the composites was investigated using a pin-on-disc wear tester at a load of 9.8 N and addition of ZrC particles was significantly found to reduce the wear rate of AA6061 alloy. [ABSTRACT FROM AUTHOR]

• 1 second-resolved strain mapping in scanning electron microscope (SEM) is realized. • Dynamic microscale strain distribution of Ti-6Al-4V in SEM is first reported. • Strain rates of average and maximum strains of Ti-6Al-4V in dwell fatigue are measured. • Strain evolution on grains and concentration near crack tip are visually observed. • Experimental plastic strain increment is a benchmark to establish simulation models. Towards clarifying underlying behavior of dwell fatigue in Ti alloys, we here present the first example of 1 second- and 1 μm-resolved full-field dynamic strain mapping. It has been realized by developing a video sampling moiré method combined with a video acquisition way in a scanning electron microscope (SEM). Monotonic strain increments during displacement holding for 10 min in dwell fatigue are visually characterized in both smooth and cracked Ti-6Al-4V specimens. The strain rates from 10−6 to 10−5 s−1 of average and maximum strains, as well as the remaining plastic strain were experimentally measured in both specimens. The strain distributions are coupled with grain boundaries to discuss the strain evolution characteristics. Experimental results indicate that both crack initiation and growth in the Ti-6Al-4V alloy are sensitive to even several tens of second-scale load/displacement holding. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The Mg-Zn-Gd-Zr alloy is one of the important aerospace alloys in the aircraft gearbox applications. The complex geometry of the gearbox introduces several stress concentration points with various intensities. These regions are susceptible to catastrophic failure under mixed loading condition. Therefore, it is important to understand the deformation and failure mode of this alloy for various plastic constraint conditions. In the present work, Mg-4%Zn-1.5%Gd-0.5%Zr alloys were prepared with four different increasing notch root radii (1, 2, 4 and 8 mm). These samples were tested for tensile properties and compared with the smooth condition. In addition, notch sensitivity was determined analytically. The microstructure and fracture samples of the alloy were characterized with the aid of an optical/scanning electron microscope. Tensile test results show that the alloy is notch sensitive and shows notch-strengthening effects. The notch strength ratio increases with the decrease in the notch root radius due to the strong plastic constraint. The predicted and experimental results of the fracture strain with the notch root radius are in qualitative agreement. The void growth rate prediction is qualitatively in agreement with the tensile and fractography results and suggests that the notch geometry has a significant influence on the plastic strain of the alloy. The microstructure of the alloy has equiaxed grains of 74 ± 24 µm with the grain boundary eutectic. The eutectic is composed of Gd-rich Mg phase. The fracture surface has a distinct change from mixed mode to complete cleavage with the increasing notch root radius. The fractography results show that the fracture mode is predominantly intergranular for all the cases. [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]

Selective laser melting (SLM) allows for manufacturing intricate and accurate component designs that are challenging, expensive, or impossible to achieve using traditional methods. To achieve a high-quality final product with SLM, it is necessary to optimize the process parameters carefully. This optimization helps to minimize internal structural defects and control the microstructure. In this study, the optimum production parameters of Ti6Al4V alloy were determined using the Response Surface Method (RSM). The micro-CT analysis was utilized to calculate the relative densities of the samples fabricated using different production parameters. Furthermore, the influence of heat treatment, conducted below and above the β transformation temperature, on the mechanical properties was examined. The results were analyzed by considering the microstructure images obtained from Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) analysis. The optimum production parameters for the SLM method were found to be 80W laser power, 1125 mm/s scanning speed, 25 μm layer thickness, and 45 μm hatch distance. Samples created with these optimized parameters achieved 99.919% relative density, 1050 MPa ultimate tensile stress, and 13.8% elongation, surpassing the minimum standards outlined in ASTM F3001-14. Additionally, the systematic parameter reduction approach used in the study led to savings in both powder consumption and time in SLM, a method that could be applied to various metallic materials. • Ti6Al4V-ELI alloy was manufactured with selective laser melting method. • The response surface method was used to determine the optimum production parameters. • Micro-CT analysis was performed and density ratios were calculated. • Mechanical properties were improved with post processing operation. [ABSTRACT FROM AUTHOR]

(Mo 1-x Cr x) 5 Si 3 alloys were prepared by vacuum arc melting technique. The microstructure and mechanical properties of (Mo 1-x Cr x) 5 Si 3 alloys were characterized using a scanning electron microscope (SEM), X-ray diffraction (XRD) and nano-indentation tests. The tribocorrosion characteristics of the alloys were investigated using a tribocorrosion tester in 3.5 wt% NaCl solution. The results revealed that the thermal expansion anisotropy ((CTE(c)/CTE(a))) of the (Mo 1-x Cr x) 5 Si 3 alloys decreased from 2.25 to 1.45 with increasing Cr content. The Cr-alloyed (Mo 1-x Cr x) 5 Si 3 alloys exhibited a high hardness, and their fracture toughness, ratios of H3/E2 and H/E were improved. (Mo 1-x Cr x) 5 Si 3 alloys showed a strong wear-corrosion combined effect, and an opposite trend between friction coefficient and OCP values was observed during the tribocorrosion tests. The tribocorrosion resistances of (Mo 1-x Cr x) 5 Si 3 alloys were better than that of 0Cr18Ni9 stainless steel due to the formation of Cr 2 O 3 -MoO 3 -SiO x protective films. The (Mo 0.8 Cr 0.2) 5 Si 3 alloy exhibited the best tribocorrosion characteristics with a low friction coefficient and wear rate. For the 0Cr18Ni9 and Mo 5 Si 3 alloy, pure wear (V w) was dominant, nevertheless, corrosion-induced wear (V cw) was the main tribocorrosion mechanism of (Mo 0.8 Cr 0.2) 5 Si 3 alloy. • Tribocorrosion behaviors of the (Mo 1-x Cr x) 5 Si 3 alloys were investigated. • The fracture toughness of Mo 5 Si 3 alloy was improved by Cr alloying. • Oxide films (MoO 3 , Cr 2 O 3 and SiO x) enhance the tribocorrosion properties. • Tribocorrosion resistances of the alloys were better than that of 0Cr18Ni9. [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]

Oxide dispersion strengthened tungsten (ODS-W) alloys are promising plasma facing material in future fusion reactors. In this study, composite powders of W-Er 2 O 3 were prepared by co-deposition method and hydrogen reduction, and then consolidated by spark plasma sintering (SPS). Microstructure evolution during co-deposition process was investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM) and Fourier transform infrared spectrometer (FTIR). Also, simulation using DMol3 module in Materials Studio was carried out to understand the co-deposition mechanism. The results showed that H+ of W-OH bond in white tungstic acid was replaced by Er3+ due to coordination reaction during co-deposition process, leading to formation of ring-like chelate of (WO) n Er. This indicates that doping of Er3+ was achieved at a molecular level. Consequently, Er 2 O 3 particles were relatively uniformly distributed in W-Er 2 O 3 alloy, and the hardness and compressive strength reached 627 ± 19 HV and 1640 ± 40 MPa, respectively. • Thermodynamic diagram of W-H 2 O was calculated to optimize co-deposition process. • Co-deposition mechanism was analyzed by simulation and experimental methods. • W-Er 2 O 3 alloy was prepared by co-deposition method and two-step SPS. • Er 2 O 3 particles were relatively uniformly distributed in alloy. • Hardness and compressive strength reached 627 HV and 1640 MPa, respectively. [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]

In this work, individual influences of Al, Fe and Ni on the microstructure, wear resistance and mechanical properties of high-entropy alloys (Al x CrFe y Ni z Ti 0.2) were studied. Microstructures and phase constituents of the alloys with different values of x, y and z were characterized via Scanning Electron Microscope, Energy Disperse Spectroscopy, and X-ray diffraction. Mechanical properties and wear resistances of the alloys were evaluated, including hardness, micro-hardness, and resistance to abrasive wear. It was shown that with increasing Al content, the FCC phase was replaced by disordered BCC (A2) and ordered BCC (B2) phases, leading to an increase in micro-hardness by ∼73% and a decrease in wear volume loss by ∼78%. Fe also increased the fraction of A2 phase, but reduced hardness by ∼41% and led to a considerable decrease in wear resistance. In contrast, Ni helped form a FCC phase, resulting in a decrease in hardness by ∼35%, and an increase in wear volume loss by ∼73%. Abrasive wear appeared to be the dominant wear mechanism, while the formed oxide scale played a role in improving the wear resistance. Efforts were made to correlate the changes in hardness and wear resistance with changes in microstructure. Among all specimens, AlCrFeNiTi 0.2 and Al 0.5 CrNiTi 0.2 reached the highest wear resistance. The results obtained help shed light on the development of advanced wear-resistant high-entropy alloys via the favorable addition of Al. • Influences of Al, Fe and Ni on microstructure, hardness and wear of AlxCrFeyNizTi0.2 high-entropy alloy were investigated. • Increasing Al content led to a significant increase in hardness by 73% and a decrease in wear volume loss by 78%. • Increasing Fe content lowered hardness and consequently increased the wear volume loss. • Varying Ni of low fraction had little effect on wear of the alloy, which markedly increased as Ni fraction rose to 1.25. [ABSTRACT FROM AUTHOR]

The AlFeCoNiCrTi high-entropy alloy (HEA) powders were prepared by high-energy ball milling. The ultrafine-grained WC–HEA and WC–Co-cemented carbides were fabricated through planetary ball milling and heat-pressure sintering. The microstructures and properties of the sintered alloys were compared using scanning electron microscope, X-ray diffraction, mechanical property testing and electrochemical testing. It has been shown that the AlFeCoNiCrTi HEA can be used as a binder for the ultrafine-grained WC-based cemented carbide. The WC–HEA-cemented carbide has better performances than the WC–Co-cemented carbide. The suitable contents of HEA can inhibit the WC grain growth and improve the mechanical properties and corrosion resistance of cemented carbides. [ABSTRACT FROM PUBLISHER]

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]

Powder metallurgy Cu–1Cr–0.65Zr (wt%) alloy was fabricated using Cu, Cr, and ZrH 2 powders as initial materials by hot pressing at 950 °C for 4 h under 27.7 MPa. Microstructure was observed by scanning electron microscope (SEM) and transmission electron microscope (TEM). Mechanical and electrical properties were also analyzed. It was found that an appropriate heating treatment could result in the formation of fine and homogeneously dispersed coherent nano-precipitates, relative to Cr phase with BCC structure and Cu 5 Zr.The aging treatment induced the first increase and then decrease of hardness with the prolongation of aging time. The highest hardness of 141 HV was achieved when aging at 450 °C for 4 h, following the strength of 397 MPa with an elongation of 23%. However, the electrical conductivity was only 78.3% IACS (International Annealing Copper Standard). It was determined that the effect of Cr particles on strength was more important than that of Cu 5 Zr. [ABSTRACT FROM AUTHOR]

Al–Si base composites reinforced with different mixtures of Ni and nano-Al 2 O 3 particles have been fabricated by squeeze casting and their metallurgical and mechanical characterization has been investigated. A mixture of Ni and nano-Al 2 O 3 particles of different ratios was added to the melted Al–Si piston alloy at 700 °C and stirred under pressure. After the Al-base-nano-composites were fabricated by squeeze casting, the microstructure and the particle distribution inside the matrix have been investigated using optical and scanning electron microscopes. Moreover, the hardness and the tensile properties of the resulted Al-base-nano-composites were evaluated at room temperature by using Vickers hardness and universal tensile testers, respectively. As a result, in most cases, it was found that the matrix showed a fine eutectic structure of short silicon constituent which appeared in the form of islands in the α-phase around some added particle agglomerations of the nano-composite structures. The tendency of this structure formation increases with the increase of Ni particle addition. As the ratio of the added particles increases, the tendency of these particles to be agglomerated also increases. Regarding the tensile properties of the fabricated Al-base-nano-composites, ultimate tensile strength is increased by adding the Ni and nano-Al 2 O 3 particles up to 10 and 2 wt.%, respectively. Moreover, the ductility of the fabricated composites is significantly improved by increasing the added Ni particles. The composite material reinforced with 5 wt.% Ni and 2 wt.% nano-Al 2 O 3 particles showed superior ultimate tensile strength and good ductility compared with any other added particles in this investigation. [ABSTRACT FROM AUTHOR]

Aggregation of Y 2 O 3 particles with relatively large size along grain boundaries is a main limiting factor for performance improvement in W–Y 2 O 3 alloys. In order to tailor the distribution and achieve size refinement of Y 2 O 3 dispersoids, W–Y 2 O 3 alloy was prepared using ball milling with extended milling time and subsequent spark plasma sintering (SPS) in this study. Microstructure evolution of Y 2 O 3 during the preparation process was characterized in detail using X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM). Mechanical properties of SPSed alloy were evaluated in terms of microhardness, three-point bending and compression tests. Structure transformation of Y 2 O 3 from BCC to FCC during the process of ball milling and subsequent sintering was first identified in W–Y 2 O 3 alloy in this study. Compared with the raw micron sized Y 2 O 3 powders, the transformed Y 2 O 3 dispersoids experienced significant size refinement. Around 76% of the nanosized Y 2 O 3 dispersoids were distributed inside grain interior, and they exhibited semi-coherent relationship with tungsten matrix. These microstructural characteristics contributed to the high compressive strength of 1804.2 MPa and microhardness of 625.7 HV in the SPSed W–Y 2 O 3 alloy. • W–Y 2 O 3 alloy were prepared by extended ball milling and SPS. • Structure transformation of Y 2 O 3 from BCC to FCC was identified in W–Y 2 O 3 alloy. • Y 2 O 3 also experienced size refinement and 76% of them were inside grain interior. • The nanosized Y 2 O 3 exhibited semi-coherent relationship with tungsten matrix. • Y 2 O 3 dispersoids contributed to improved strength mainly through grain refinement. [ABSTRACT FROM AUTHOR]

In the present paper, the Mg-11Gd-2Y-1Zn alloys with different Al addition were fabricated by the gravity permanent mold method. The effect of Al content on microstructure evolution and mechanical properties of as-cast Mg-11Gd-2Y-1Zn alloy was studied by metallographic microscope, scanning electron microscope, XRD and tensile testing. The experimental results showed that the microstructure of as-cast Mg-11Gd-2Y-1Zn alloy consisted of α-Mg phase and island-shaped Mg3 (RE, Zn) phase. When Al element was added, Al2RE phase and lamellar Mg12REZn (LPSO) phase were formed in the Mg-11Gd-2Y-1Zn alloy. With increasing Al content, LPSO phase and Mg3 (RE, Zn) phase gradually decreased, while Al2RE phase gradually increased. There were only α-Mg and Al2RE phases in the Mg-11Gd-2Y-1Zn-5Al alloy. With the increase of Al content, the grain size decreased firstly and then increased. When the Al content was 1 wt.%, the grain size of the alloy was the minimum value (28.9 μm). The ultimate tensile strength and elongation increased firstly and then decreased with increasing Al addition. And the fracture mode changed from intergranular fracture to transgranular fracture with increasing addition. When Al addition was 1 wt.%, the maximum ultimate tensile strength reached 225.6 MPa, and the elongation was 7.8%. When the content of Al element was 3 wt.%, the maximum elongation reached 10.2% and the ultimate tensile strength was 207.7 MPa. [ABSTRACT FROM AUTHOR]

To enhance the mechanical properties (e.g., strength and elongation) of the face-centered cubic (fcc) α-phase in the Au-Cu-Al system, this study focused on the introduction of the martensite phase (doubled B19 (DB19) crystal structure of Au2CuAl) via the manipulation of alloy compositions. Fundamental evaluations, such as microstructure observations, phase identifications, thermal analysis, tensile behavior examinations, and reflectance analysis, have been conducted. The presence of fcc annealing twins was observed in both the optical microscope (OM) and the scanning electron microscope (SEM) images. Both strength and elongation of the alloys were greatly promoted while the DB19 martensite phase was introduced into the alloys. Amongst all the prepared specimens, the 47Au41Cu12Al and the 44Au44Cu12Al alloys performed the optimized mechanical properties. The enhancement of strength and ductility in these two alloys was achieved while the stress plateau was observed during the tensile deformation. A plot of the ultimate tensile strength (UTS) against fracture strain was constructed to illustrate the effects of the introduction of the DB19 martensite phase on the mechanical properties of the alloys. Regardless of the manipulation of the alloy compositions and the introduction of the DB19 martensite phase, the reflectance stayed almost identical to pure Au. [ABSTRACT FROM AUTHOR]

• The secondary acicular β-phase appeared after a 650 °C–1000 h aged process and significantly increased in quantity for 3000 h. • The morphology and quantity of the primary β phase changed significantly with the prolonged aging time. Taking the GH783 alloy bolt of intermediate pressure main stop valve used in 1000 MW ultra-supercritical unit as the research object, the optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD) and mechanical performance tests were carried out to study the microstructure transformation and mechanical properties of GH783 alloy bolts at different aging stages under 650 °C aging environment. The results showed that the secondary needle β phase began to appear in the bolts aged for 1000 h, and the density of secondary β-phases in bolts aged for 3000 h significantly increased. When the aging time reached up to 20,000 h, the secondary β phase coarsened significantly. At the same time, as the aging time prolonged, the morphology and quantity of the primary β phase changed significantly. In terms of mechanical properties, the tensile strength and impact toughness of the bolts gradually decreased. This was due to the growing γ' phase, the formation of Ni 5 Al 3 phase and the Nb-rich Laves phase in the structure during the aging process. [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]

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]

Serration behavior is a kind of plastic instability phenomenon of materials, which widely exists in the high-entropy alloys and has influence on microstructure and mechanical properties. In this work, the microstructure and mechanical properties of a NiCrFeCoMn high-entropy alloy (HEA) were studied under high-speed impact. The microstructure of a NiCrFeCoMn HEA were investigated by optical microscope (OM), scanning electron microscope (SEM), electron backscatter diffraction (EBSD), and transmission electron microscope (TEM). The dislocation density increased with the true strain at high-strain-rate deformation, and the dislocations can be hindered and released continually by the twin layers, resulting in serration on the true stress—true strain curve. When values of the strain rates are 1250, 2000 and 4800 s−1, the yield strength of the deformed NiCrFeCoMn HEA are 510, 525 and 680 MPa, respectively. Moreover, the fluctuation of the serration became more serious with the increasing of the strain rate. Compared with the as-cast NiCrFeCoMn HEA, the true stress—true strain curve of the deformed NiCrFeCoMn HEAwas smoother. [ABSTRACT FROM AUTHOR]

In this paper, the temperature sensitivity of mechanical properties and microstructure of the additive manufactured Ti-6Al-4V alloy via selective laser melting was investigated in the deformation temperature range between room temperature (RT) and 550 °C. Mechanical properties and microstructure were characterized by the means of tensile testing, optical microscope, scanning electron microscope and transmission electron microscope. The results show that the ultimate tensile strength (UTS) of the experimental Ti-6Al-4V alloy exhibits two-stage temperature sensitivity, which is reflected in the fact that the temperature sensitivity of UTS below 500 °C is conventional, whereas, the UTS decreases drastically from 834 MPa to 562 MPa as the temperature increases from 500 °C to 550 °C. Compared with the Ti-6Al-4V alloys prepared by conventional processing methods and other additive manufacturing methods, this experimental Ti-6Al-4V alloy exhibits a competitive strength below 500 °C and possesses excellent comprehensive mechanical properties at RT. The analysis shows that the microstructure is composed of α′ martensite with plenty of twinning structures when the as-built samples are deformed below 500 °C. However, above 500 °C, martensite gradually transformed into equilibrium α phase, the microstructure changed from acicular to lamellar, and β and α 2 (Ti 3 Al) appear due to the elemental distribution homogenization and martensite decomposition, which account for the dramatic decrease of the tensile strength of the experimental Ti-6Al-4V alloy above 500 °C. Unlabelled Image • SLM Ti-6Al-4V samples deformed below 500 °C had excellent tensile strength. • α′ martensite, twins and dislocations played a significant role on tensile properties. • The ultimate tensile strength of the alloy exhibited two-stage temperature sensitivity. • β phase and α 2 phase precipitated in the samples which were deformed above 500 °C. [ABSTRACT FROM AUTHOR]

Grain refinement is one of the effective methods to improve the yield strength and toughness of Al-Cu alloys. The effects of Sc addition (0.2%, 0.4%, 0.6%, 0.8% and 1.0 wt%) on the microstructural evolution and mechanical properties of as-cast Al-5%Cu alloys were studied. The as-cast samples were characterized by optical microscope (OM), transmission electron microscopy (TEM), scanning electron microscope (SEM) and electron probe microanalysis (EPMA). The results revealed the primary α-Al occurred to obvious change from developed dendrites to fine equiaxed grains with the increasing Sc content in Al-5%Cu alloy. When the addition concentration of Sc reaches 0.8%, the developed α-Al dendrites were significantly refined and the average size of α-Al decreased from 218.3 μm to 29.6 μm. Moreover, the morphology and size of θ-Al 2 Cu phases of Al-5%Cu alloy caused noticeable changes with the increase of Sc concentration. Mechanical properties test illustrated that the ultimate tensile strength (UTS), yield strength (YS) and elongation (El) increased by 61.59%, 66.82% and 57.20%, respectively, which could be attributed to microstructure refinement and fine Al 3 Sc particle precipitate. • Sc can significantly refine the α-Al phase from coarse dendrites to uniform fine equiaxed grains in Al-5%Cu alloy. • The addition of Sc change the morphology of θ-Al 2 Cu from discontinuous to continuous tissues. • The YS and UTS was improved by 61.59% and 66.82% and the El was enhanced by 57.20% when the addition of Sc reached 0.8%. [ABSTRACT FROM AUTHOR]

In this work, the effect of Mo addition on phase evolution and mechanical properties of as-cast FeCoNiCuMo x (molar ratio X = 0.2, 0.4, 0.6, 0.8, 1) high entropy alloy systems (HEAs) have been investigated. It has been found that with increasing Mo concentration, atomic size difference (δ), geometrical parameter (∧) and enthalpy of mixing (ΔH mix) of this multi-component alloy systems decrease. However, the mixing entropy (ΔS mix), electronegativity difference (ΔX), d-orbital energy level parameter ( M d ‾), root mean square residual strain (RMS) and critical parameter (Ω) increases which clearly indicates the formation of the solid solution with no intermetallic compounds. X-ray diffraction and scanning electron microscope analysis also confirm that FCC solid solution phases are formed at X = 0.2 to 0.6. Further, on increasing the Mo concentration beyond 13 at % (X > 0.6), FCC1 and FCC2 phase were detected due to large positive enthalpy of mixing between Cu and others (Fe, Co, Ni, and Mo) elements. Moreover, the segregation of Cu in the FeCoNiCuMo x (X = 0.8 and 1) alloy can be well predicted via φ and λ parameters. The Compressive strength and hardness were found to increase with Mo concentration in FeCoNiCuMo x HEAs due to solid solution strengthening. • Synthesized the novel FeCoNiCuMo x HEAs via Vacuum arc melting and suction casting. • Phase evolution has been studied and correlate with thermodynamic criterion with segregation parameter. • A novel Mo based high entropy alloy exhibit good compressive strength and ductility. [ABSTRACT FROM AUTHOR]