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The effects of V element on microstructural evolution and soft magnetic properties of FeSiBCuNbV (x = 0, 0.5,1, 1.5 and 2, at.%) nanocrystalline alloys annealed at one-step and two-step state were investigated. As a result of an adequate addition of V, the microstructure and soft magnetic properties of the nanocrystalline alloys have greatly changed. The alloys with higher V content are prone to form large grain size nanocomposite structure with better thermal stability but slightly worsen soft magnetic properties. However, the strategy of two-step annealing technique effectively refines grain and thereby improves the soft magnetic properties of the alloys. The nanocrystalline alloy with V = 1.5 after two-step annealing exhibits combined excellent soft magnetic properties, including a lower coercivity ( H = 0.89 A/m), enhanced saturation magnetization ( B over 1.3 T), high effective permeability? µ = 26,400 at 1 kHz) and low core loss. The work shows that adopting a preheating procedure before the primary nanocrystallization stage, viz. to use two-step annealing technique instead of the routinely used one-step nanocrystallization stage,is an effective solution to the disadvantage of the decrease of Nb. [ABSTRACT FROM AUTHOR]

FeCuNbSiB nanocrystalline alloys were prepared by using conventional one-step annealing process and two-step annealing process. It was found that two-step annealing process can effectively improve soft magnetic properties and optimize microstructure. By separately controlling the formation of Cu clusters and further optimize the nanocrystalline structure, Bcc α-Fe with the grain size of 13 nm is formed in samples pretreated at 400 °C and nanocrystallized at 560 °C for 1 h. The samples exhibit excellent magnetic properties, such as lower coercive force of 0.7 A/m, higher initial permeability of 9.16 × 10, lower core loss of 0.18 W/kg at 0.7 T and 400 Hz, and 0.5 W/kg at 0.7 T and 1 kHz, respectively. The microstructure and magnetic structure evolution during different annealing processes were investigated. Correlation among the magnetic properties, magnetic structures and the microstructures changes in two different crystallization processes was studied systematically. [ABSTRACT FROM AUTHOR]

The microstructure of the interfa ce zone is the most important factor to determine the properties of the Cu/Al clad metal sheet joint. The composition distribution and phase constitution at the interface of the double-sided electron beam welding (DSEBW) joint of 6.5 mm thick Cu (1.5 mm)/Al (5 mm) clad metal sheet were revealed by means of technologies of scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was confirmed that there formed a distinct transition zone with a length of about 5.8 mm at the interface, and it consisted of a thin layer of IMC and a large area eutectic structures. Moreover, the thickness distribution of IMC layer in the center and edges of the interface zone was nonuniform, and gradually decreased from the center (7.5 μm) to the edges (1.5 μm and 2.6 μm) by means of SEM and EBSD. Furthermore, the eutectic structure performed the superior laminar, and the grey IMC dispersed in Al-rich dendrites inside the eutectic structure. In addition, the interface zone mainly consisted of two slices, including Cu/IMC interface (Interfaces I and III) and IMC/eutectic structure interface (Interfaces II and IV). For interfaces I and III, this IMC was Al 2 Cu, and there was no other IMCs between Cu and Al 2 Cu IMC by means of TEM; For interfaces II and IV, the eutectic structure was composed of Al 2 Cu and α-Al, while there was also no other IMCs between Al 2 Cu IMC and (Al 2 Cu + α-Al) eutectic structure. In short, the microstructure characterizations at the whole interface of the DSEBW joint were Al 2 Cu IMC and (Al 2 Cu + α-Al) eutectic structure. • Cu/Al clad metal sheet was joined by double-sided EBW, and there formed a distinct transition zone at the interface. • The composition distribution and phase constitution of the interface zone were revealed by means of SEM, EBSD and TEM. • The microstructure characterizations at the overall interface were Al 2 Cu IMC and (Al 2 Cu + α-Al) eutectic structure. • This study provided some theoretical guidance for the research of EBWed Cu/Al clad metal sheet to some extent. [ABSTRACT FROM AUTHOR]

In the paper, the synergic effects of hot deformation temperature and pre-straining on microstructure and mechanical properties of 2014 Al alloy were investigated by tensile test combined with X-ray diffraction, electron backscattered diffraction and transmission electron microscopy. Results show that low-temperature deformation alloy presents lower yield strength compared with high-temperature deformation alloy due to the formation of high area fraction recrystallized grains and low-density coarse ageing precipitates. The pre-straining significantly improves yield strength for low-temperature deformation alloy, which was ascribed to the presence of high-density fine and uniform ageing precipitates. The combined mechanisms have been discussed in detail. • Low-temperature deformation alloy presented lower yield strength compared with high-temperature deformation alloy. • Pre-straining can significantly improve yield strength for low-temperature deformation alloy. • The mechanism of hot deformation temperature and pre-straining has been discussed. [ABSTRACT FROM AUTHOR]

The influences of Si (0.65–1.28 wt%) on the microstructure, mechanical, impact toughness and local corrosion behaviors of an Al–Cu–Mg–Si with high Cu/Mg ratio has been investigated. The results showed that the area fraction of insoluble particles Q phase increased with the increase of Si content, and a small amount of Si phase appeared at high Si content. The ageing precipitates was θ′ and Q′ phase, and the number of Q′ phase significantly increased with the increase Si content. Si didn't obviously accelerate age-hardening response, nor effectively improve peak hardness in the range of 0.65 ≤ Si ≤ 1.28 wt%. The strength of the alloy first increased and then decreased, while the impact toughness and local corrosion properties decreased with the increase of Si content. The fracture and corrosion mechanism have been discussed in detail. • The role of Si on microstructure and properties of AA2014 have been investigated • The particles Q phase and Q′ was increased with the increase of Si content. • The ageing precipitation of the alloy was θ′ and Q′ phase. • The impact toughness decreased with the increase Si content. [ABSTRACT FROM AUTHOR]

In this study, heat treatment was employed to enhance the mechanical properties of an as-cast CrFeNiAl 0.28 Si 0.09 Ti 0.02 Cu 0.01 high entropy alloy (HEA) with the heterostructure consisting of face-centered cubic (FCC), body-centered cubic (BCC) and B2 phases. It was observed that, after heat treatment at 873 K for 1 h followed by water-quenching, well-dispersed L1 2 and L2 1 nano-precipitates could be formed in FCC phase and BCC phase of this as-cast HEA, respectively. Furthermore, it is worth noting that despite a noticeable reduction in dislocation density, this heat treatment process significantly enhances yield strength, ultimate tensile strength, plasticity and hardness simultaneously, which could be attributed to the formation of nano-scale precipitates mentioned above. These findings provide a novel approach for fabricating high-performance HEAs by introducing complex multi-level heterogeneity. • A method to break strength-plasticity trade-off in (FCC + BCC)-type HEAs was proposed. • Heat-treatment lead to the formation of L1 2 /L2 1 nano-particles in FCC/BCC phase. • Strength, plasticity and hardness enhance simultaneously after heat-treatment. • Nano-precipitation leads to more prominent heterostructure effect in the HEAs. [ABSTRACT FROM AUTHOR]

Face-centered cubic (FCC) high-entropy alloys (HEAs) are commonly confronted with a fundamental issue of inadequate strength. In this pursuit, the present work develops a dual-heterogeneous structure via micro-scale and nano-scale design in Al 0.3 CoCrFeNi HEA, i.e., partially recrystallization and precipitated body-centered cubic (BCC) particles through annealing and aging treatments. As a result, the HEA can achieve a high yield strength of ∼1200 MPa while still retain a uniform elongation of ∼8 %. The yield strength is improved to even higher than that of rolled sample with profuse dislocations and the other most Al 0.3 CoCrFeNi or CoCrFeNi-based HEAs reported in previous works. Such high strength can be ascribed to combination of pre-existing dislocations in non-recrystallized regions and nano-size BCC precipitates in recrystallized regions, which can, in turn, carry the plastic deformation, leading to a certain degree of plasticity. This study provides valuable insights for future research in enhancing the strength of FCC HEAs. • A novel dual-heterostructure was designed in Al 0.3 CoCrFeNi HEA. • Introducing nano-size precipitates into partially recrystallized microstructure. • The alloy with dual-heterostructure shows yield strength of ∼1200 MPa and elongation of ∼8 %. • The Ni–Al type BCC precipitate is the one reason for strengthening. • The partially recrystallization in another reason for strengthening. [ABSTRACT FROM AUTHOR]

• A novel Fe-rich low-cost MEA was designed. • FCC+BCC+B2 heterostructures emerge in this MEA simply by casting. • This as-cast MEA shows excellent mechanical properties and low cost. • Complex interaction between solid solution and B2 nano-particles exists in this MEA. A novel FCC+BCC+B2 heterostructure Fe 2.5 CrNiAl 0.3 Si 0.3 medium entropy alloy (MEA) was successfully designed and fabricated via arc-melting. The micron-to-submicron-scale FCC and BCC phases and nano-scale B2 particles in both phases realize complex heterostructure effect, leading to superb ultimate tensile strength and high plasticity of this as-cast MEA, and its Fe-rich Co-free characteristic is beneficial for the combination of excellent mechanical properties and low raw material expenses. This work provides valuable insight and a novel route into developing new cost-effective and high-performance as-cast MEAs. [ABSTRACT FROM AUTHOR]

• C microalloying was used for structure modification of as-cast heterostructure HEAs. • Minor C leads to coarsening of FCC phase formation and increase FCC/BCC ratio. • C microalloying greatly enhances plasticity and slightly reduces strength. An as-cast CrFeNiAl 0.28 Si 0.08 Ti 0.02 Cu 0.01 C 0.01 high-entropy alloy (HEA) was designed via minor C substitution for Si in a high-strength CrFeNiAl 0.28 Si 0.09 Ti 0.02 Cu 0.01 HEA with FCC + BCC dual-phase heterostructure. Compared to its C-free counterpart with fine sideplate structure, this HEA has higher proportion of FCC phase with relatively coarser island-like structure, and exhibits remarkable increase in production of ultimate tensile strength (UTS) and plasticity with ∼ 25 %, while maintaining its UTS to > 1GPa, which has excellent comprehensive mechanical properties in as-cast heterostructure HEAs. High dislocation storage ability is possibly the main reason for high UTS and plasticity of this HEA. This work provides a novel insight for the optimization of microstructure and mechanical properties of heterostructure HEAs in as-cast state. [ABSTRACT FROM AUTHOR]

In this paper, a novel strategy for designing high entropy alloys (HEAs) with low cost and high mechanical properties was proposed. Accordingly, a Fe-rich Co-free Fe 2 CrNiSi 0.3 Al 0.2 HEA was designed and fabricated by arc-melting. The results show that this HEA is mainly composed of FCC dendrites, while BCC phase locates at the inter-dendrite regions. Moreover, this HEA exhibits outstanding comprehensive mechanical properties among dual-phase HEAs produced via various fabrication methods considering its product of strength and plasticity as well as raw material cost. It is interesting that, compared to its Al-free FCC counterpart, this HEA has significant enhancement in yield strength and ultimate tensile strength, while its plasticity is merely slightly reduced. Further investigation reveals that the heterostructure in this HEA plays an important role in this phenomenon. This work provides a novel insight into the development of high-performance HEAs with broad applications. • A novel strategy for designing high-performance low-cost HEA is proposed. • A Fe-rich Co-free HEA is designed based on this method. • This low-cost dual-phase HEA has superb comprehensive mechanical properties. • Heterostructure plays a vital role in its mechanical properties. [ABSTRACT FROM AUTHOR]

The synergy effect of Si addition and pre-straining prior to artificial aging heat treatment on microstructure and mechanical properties of Al–Cu–Mg alloys with a medium Cu/Mg ratio have been investigated by Vickers hardness, room temperature tensile test combined with X-ray diffraction and transmission electron microscopy characterization. It is indicated that the strength was greatly enhanced via adding Si and introducing pre-straining due to the formation finer θ′ precipitates. The pre-straining was more effective for Si-free alloys on improving strength compared with Si-containing alloys. The combined mechanism of Si addition and pre-straining has been discussed in detail. [ABSTRACT FROM AUTHOR]

To improve the performances of engineering components is a hot topic for materials science and engineering communities. In the present work, the Co-free FeCrNiSi 0.4 medium entropy alloy (MEA) coating was manufactured onto a Q235 steel substrate using laser cladding. Then, the microstructure, hardness and corrosion resistance of the MEA coating were carefully examined. The results indicate that the MEA coating, without obvious cracks and pores, exhibits a duplex phase microstructure consisting of majority face-centered cubic (FCC) phase and minor hexagonal close-packed (HCP) phase. In 3.5 wt% NaCl solution, the MEA coating displays superior corrosion resistance with a pitting potential of 1.19 V (vs. SCE), which is much higher than that of 304 stainless steel. The remarkable anti-corrosion performance can be attributed to the multiple kinds of oxidation (NiO, Fe 2 O 3 , Cr 2 O 3 and SiO x (x < 2)) formed on the passive film and the small difference of Volta potential (∼40 mV) between FCC phase and HCP phase. Moreover, the microhardness of the coating reaches 346 HV, which is 2.1 times higher than that of the Q235 steel. These findings offer an effective route to fabricate a MEA coating with superior corrosion resistance and mechanical property, which thus can improve the service stability of industrial components. • FeCrNiSi 0.4 coating on Q235 steel substrate is synthesized by laser cladding. • The metallurgical bond between MEA coating and Q235 steel substrate is formed. • The MEA coating exhibits duplex phase microstructure including FCC phase and HCP phase. • The MEA coating displays superior anti-corrosion performance. • The small Volta potential difference for FCC and HCP phases and the formed various oxides cause good corrosion resistance. [ABSTRACT FROM AUTHOR]

• A novel as-cast Fe-rich Co-free high-entropy alloy (HEA) is designed. • This ductile HEA has excellent ultimate tensile strength and low-cost. • High mechanical properties closely correlates with heterostructure in this HEA. A novel Fe 2 CrNiSi 0.3 Al 0.28 high-entropy alloy (HEA) was designed and produced via arc-melting. This Co-free Fe-rich HEA mainly consists of bulky body-centered cubic (BCC) structure and branches of fine needle-like face-centered cubic (FCC) particles. Moreover, this as-cast HEA exhibits the ultimate tensile strength (UTS) of ∼1.3 GPa and plasticity of ∼9%. Compared to the typical ductile as-cast HEAs, it shows among the highest UTS and lowest cost. Heterostructure exhibits positive influence on its high mechanical properties. This work provides a novel insight for propelling broad applications of HEAs. [ABSTRACT FROM AUTHOR]

In this paper, a novel Co-free CrFeNiAl 0.28 Si 0.09 Ti 0.02 Cu 0.01 high entropy alloy (HEA) was designed and fabricated by casting. It is found that, this as-cast HEA has complex multi-phase microstructure including fine FCC sideplates with ultrafine wheathead-like substructures, as well as nano-precipitates in the fine BCC inter-sideplate regions. Further, it shows excellent comprehensive mechanical properties combining ultimate tensile strength (UTS) of over 1.2 GPa and plasticity of ∼22% in as-cast state, while cold rolling with the reduction rate of 60% further increases UTS to ∼1.7 GPa and maintain good plasticity. Moreover, it is found that the formation of FCC sideplates in this HEA in as-cast state is possibly resulted from solid-state phase transformation. Besides, dislocation and heterogeneous structure play important roles in mechanical properties of this HEA under different fabrication conditions. This work provides a novel route in the design of high-performance low-cost HEAs that could be fabricated in simple ways, which is beneficial for further application and development of this series of advanced materials. • A novel Co-free CrFeNi-based multi-phase HEA was designed. • Complex fine/ultrafine/nano-scale structures form in this HEA via casting. • Such microstructure closely correlates with solid-state phase transformation. • This HEA shows superb mechanical properties in as-cast and cold-rolled states. • Heterostructure and dislocation play vital roles in high mechanical properties. [ABSTRACT FROM AUTHOR]

• A novel Fe-rich Co-free anti-bacterial HEA was produced by casting and cold-rolling. • It has fully FCC structure with segregation of Cu, Cr and Fe. • It combines excellent mechanical properties and high anti-bacterial rate. In this work, a novel cold-rolled Fe 1.3 CrNiCu 0.7 Si 0.2 high entropy alloy (HEA) was designed and fabricated, and its microstructure, mechanical properties and anti-bacterial properties were systematically investigated. The results show that, this cold-rolled HEA is composed of FCC phase with significant segregation of Fe, Cr and Cu. Moreover, it has high anti-bacterial rate of ∼98% against E. coli , and exhibits excellent ultimate tensile strength of ∼1100 MPa and good plasticity of over 10%. This work provides a new approach for designing low-cost HEAs with superb comprehensive properties combining high mechanical properties and anti-bacterial properties, which is beneficial for the development of this series of HEAs. [ABSTRACT FROM AUTHOR]

The microstructure, mechanical properties, and corrosion resistance of Fe 50 Mn 25 Cr 15 Ni 10-x Co x medium-entropy alloys (MEAs) with varying Co and Ni contents were investigated in this study. With increasing Co concentration, the microstructure of the MEAs changes from FCC single phase to FCC + HCP dual-phase. At room temperature, a rise in Co concentration increases the strength and ductility of the MEAs, while at liquid nitrogen temperature, the ductility, and the product of tensile strength and ductility of the MEAs decrease significantly. Furthermore, the corrosion resistance of the MEAs decreases significantly with increasing Co content. This work provides a research object for the further development of low-cost MEAs with excellent mechanical properties and corrosion resistance. • The microstructure of Fe 50 Mn 25 Cr 15 Ni 10-x Co x changes from FCC to FCC + HCP with increasing Co. • The mechanical properties of the MEAs at 298K were enhanced with increasing Co. • The ductility and tensile strength × ductility of the MEAs at 77 K decrease with increasing Co. • The corrosion resistance of the MEAs was deteriorated with increasing Co. [ABSTRACT FROM AUTHOR]

• Co-free anti-bacterial Cr-Fe-Ni-Cu-Si HEAs were designed. • These HEAs have high mechanical properties and good corrosion resistance. • Increasing Si would lead to the enhancement in strength but decrease in plasticity. [Display omitted] In this work, a series of Co-free CrFeNiCuSi x (x = 0.2, 0.3) high entropy alloys (HEAs) were designed and fabricated by suction casting, and their microstructure, mechanical properties, corrosion resistance and anti-bacterial behaviors have been systematically investigated. It is found that, all these HEAs are composed of FCC phase and have dendrite structure, while the dendrite and inter-dendrite regions are Cu-deplete and Cu-rich, respectively. Moreover, the increase in Si leads to the strengthening of this series of HEAs but would reduce their plasticity. The corrosion resistance is closely correlated with the distribution of Cu in these HEAs. The anti-bacterial rate against E. coli. is ~97% when x = 0.2, while that is ~90% when x = 0.3, indicating high anti-bacterial properties of these HEAs. This work indicates that these designed Co-free HEAs could have excellent comprehensive properties combining high ultimate tensile strength and plasticity, as well as good corrosion resistance and anti-bacterial properties, which provides a novel route in designing high-performance and low-cost anti-bacterial HEAs. [ABSTRACT FROM AUTHOR]

• A Co-free corrosion-resistant HEA with high hardness was designed. • This HEA has fully BCC structure under rapid-solidification condition. • This rapid-solidified HEA has two-stage passivation behavior before pitting. In this paper, a CrFeNiAl 0.2 Si 0.2 high entropy alloy (HEA) was fabricated via laser-surface melting (LSM). The result shows that, this HEA could form fully BCC structure under such rapid-solidification condition. Moreover, it exhibits excellent corrosion resistance in 3.5 wt% NaCl solution with two-stage passivation, and could maintain good protectiveness until 1.06 V vs SCE during electrochemical polarization, which is much higher than stainless steel. In addition, this rapid-solidified HEA shows high hardness of ∼667 Hv. Such excellent corrosion resistance and unique passivation process are possibly caused by the diversity in compositional constitution of the passive films under different electrochemical corrosion conditions. This work provides a novel route for designing low-cost corrosion-resistant HEAs with high hardness for coating applications. [ABSTRACT FROM AUTHOR]

In this paper, a novel Fe 49.85 Cr 10.03 Mn 10.03 Co 10.03 Ni 10.03 Al 10.03 high entropy alloy (HEA) with dual-phase fine-grain structure was designed and fabricated by arc-melting. Its microstructure, as well as mechanical properties at room temperature and cryogenic temperature, have been systematically investigated. It is found that this as-cast Fe-based HEA is composed of face-centered cubic (FCC) and body-centered cubic (BCC) phases, and the stick-like FCC fine grains are derived from solid-state phase transformation of BCC phase during cooling. Moreover, it shows similar tensile strength and good plasticity at room temperature and cryogenic temperature, indicating high and stable mechanical properties at a wide range of temperatures. This work provides a novel route for designing high-performance fine-grain HEAs without mechanical/heat treatment, which is beneficial for further development of HEAs. • A novel fine-grain dual-phase HEA with high mechanical properties was designed. • Fine grains form via solid-state phase transformation during cooling from the melt. • This as-cast HEA has high strength and plasticity at room/cryogenic temperatures. [ABSTRACT FROM AUTHOR]

• Novel ferromagnetic Fe 40 Co 40 Ni 10 M 10 (M = Al, Mn) MEAs were designed. • Al is beneficial for fully BCC structure formation via casting. • Mn leads to dual-phase formation, grain refinement and high mechanical properties. • Heat treatment could increase B s and mechanical properties of these MEAs. The influences of Al and Mn on microstructure, magnetic and mechanical properties of Fe 40 Co 40 Ni 10 M 10 (M = Al and Mn) medium entropy alloys (MEAs) have been systematically investigated. It is found that the Fe 40 Co 40 Ni 10 Al 10 has body-centered cubic (BCC) structure and Fe 40 Co 40 Ni 10 Mn 10 has a mixture of face-centered cubic (FCC) and BCC structures in as-cast state, while the former one changes to FCC + BCC dual-phase structure after heat treatment at 1073 K for 1 h. Fe 40 Co 40 Ni 10 Al 10 displays higher saturated magnetization (B s) as compared to Fe 40 Co 40 Ni 10 Mn 10 in as-cast state, while heat treatment significantly enhances B s of Fe 40 Co 40 Ni 10 Mn 10. Besides, it is intriguing that Fe 40 Co 40 Ni 10 Mn 10 shows higher yield strength and plasticity compared to Fe 40 Co 40 Ni 10 Al 10 , while heat treatment could enhance comprehensive mechanical properties of this series of MEAs. In addition, the B s of heat-treated Fe 40 Co 40 Ni 10 Mn 10 is 187.9 emu/g, which is among the highest in the reported ferromagnetic HEAs/MEAs. The correlation among the composition, phase evolution, magnetic properties, and mechanical properties in these MEAs is discussed in detail. This work provides a novel route for developing high-performance ferromagnetic HEAs/MEAs. [ABSTRACT FROM AUTHOR]

• Oxygen triggers formation of nano-crystalline solid solution in Zr-based CMBMG. • Increasing oxygen causes the change of nanocrystalline structure from BCC to FCC. • Zr-based CMBMG has good mechanical properties containing high oxygen concentration. In this paper, O was added in Zr 50 Ti 4 Y 1 Al 10 Cu 25 Ni 7 Co 2 Fe 1 complex multicomponent bulk metallic glass (CMBMG) with concentrations of 0.12 at.% and 0.45 at.%, and the microstructure, thermal stability and mechanical properties of these O-containing alloys were investigated in detail. It is found that, O element promotes the formation and growth of nanocrystals in the glassy matrix, and the structure of nanocrystalline phase changes from BCC to FCC with the increase in O content. Moreover, even at high Oxygen concentration, the alloy still shows excellent resistance to O-induced brittleness. This work is beneficial for better understanding the correlation between O and nanocrystal formation in CMBMGs, which provides a novel insight for further development of this series of alloys. [ABSTRACT FROM AUTHOR]

• A novel BCC-based Fe-Co-Ni-Si magnetic HEA was designed. • This novel HEA shows excellent B s , T c , σ y and good ε p. • High (Fe, Co) concentration plays a vital role in high B s and T c. • BCC structure and refined grains contribute to high σ y. A novel Fe 40 Co 40 Ni 10 Si 10 high entropy alloy (HEA) was designed and fabricated via copper mold casting. It is found that, this alloy is mainly composed of fine lamella-like BCC phase, as well as minor droplet-like FCC phase. This HEA exhibits excellent yield strength of ~1.1 GPa, compressive plasticity of ~38.3%, saturated magnetization of 172 emu/g and Curie temperature of 1169 K, which has significant improvement compared to those of the reported ferromagnetic HEAs, indicating good comprehensive performance combining excellent mechanical and magnetic properties. This study proposes a new approach for the design of high-performance HEAs for functional applications. [ABSTRACT FROM AUTHOR]

In this work, a rapid-solidification method was utilized on FeCoNiAl 0.2 Si 0.2 high entropy alloy (HEA) and its effects on microstructure, corrosion resistance and magnetic properties were systematically investigated. Rapid-solidified and slowly-cooled FeCoNiAl 0.2 Si 0.2 specimens were produced by melt-spinning and induction melting, respectively. It was found that, slowly-cooled FeCoNiAl 0.2 Si 0.2 exhibits dendrite structure with compositional segregation of Al, Si and Ni, as well as the precipitation of L1 2 -type ordered phase in the solid solution matrix, while rapid-solidification effectively promotes the structural and compositional homogeneity. Moreover, rapid-solidification leads to significant enhancement in the stability of the passive film, and thus results in remarkable increase in corrosion resistance compared to its slowly-cooled counterpart. Besides, the distribution of constituent elements plays an important role in the formation of passive film on the surface of this HEA. In addition, the H c of the rapid-solidified specimen exhibits only nearly 1/5 of its slowly-cooled counterpart, indicating significant positive effect of rapid-solidification on soft magnetic properties of FeCoNiAl 0.2 Si 0.2. This work provides a novel route for further development of HEAs with excellent corrosion resistance and soft magnetism. Image 1 • Rapid-solidification was utilized on an FeCoNiAl 0.2 Si 0.2 HEA. • Rapid-solidification causes high corrosion resistance and low H c of this HEA. • Homogeneity plays a key role in soft magnetism and corrosion resistance. • Rapid-solidification leads to significant change in constitution of passive film. [ABSTRACT FROM AUTHOR]

In this paper, a laser surface melting (LSM) method was utilized on CrFeCoNiAl x (x = 0.5, 0.6, 0.7) high entropy alloys (HEAs) with FCC + BCC structure, and the effects of LSM on their microstructure, mechanical properties and corrosion behavior were systematically investigated. It is intriguing that, a layer with BCC + B2 structure formed on the surface of CrFeCoNiAl 0.6 and CrFeCoNiAl 0.7 substrates after LSM, while a monolithic FCC layer formed on that of CrFeCoNiAl 0.5 substrate under the same condition. LSM influences the mechanical properties of CrFeCoNiAl x HEAs to varying degrees including hardness and tensile properties decided by the phase formation in laser-treated surfaces and the substrates. In addition, compared to the substrates, obvious increase in self-corrosion potential and pitting potential were found in the laser-treated surface layers of CrFeCoNiAl 0.6 and CrFeCoNiAl 0.7. Interestingly, the corrosion resistance of laser-treated surface layers has positive correlation with Al content, while that of the substrates shows negative correlation with the concentration of Al, which is possibly resulted from the difference in corrosion mechanism. This work provides a new route for significantly improving surface properties of dual-phase HEAs, which would be very beneficial to their further application as advanced materials. Image 1 • LSM leads to remarkable change in phase formation of dual-phase HEAs. • Al plays a vital role in phase constitution of laser-treated surface layers. • High Al content is beneficial for high corrosion resistance in laser-treated surface. • BCC + B2 layer produced by LSM has much higher hardness than FCC + BCC substrate. [ABSTRACT FROM AUTHOR]

A series of Zr–Ti–Y–Al–Cu–Ni–Co–Fe complex multi-component bulk metallic glasses (CMBMGs) were designed using multi-substitution strategy in Zr 55 Cu 35 Al 10 , Zr 60 Cu 30 Al 10 and Zr 60 Cu 28 Al 12 BMGs, and their crystallization and corrosion behaviors were systematically investigated. It is found that, CMBMGs have higher complexity in crystallization compared to their ternary counterparts, and well-dispersed nano-crystals with diameters of 5–30 nm could be easily formed in CMBMGs in a wide range of annealing temperature, reflecting sluggish crystallization kinetics. Moreover, these CMBMGs exhibit considerable higher corrosion resistance than their ternary counterparts. Besides, both the glass transition temperature (T g) and onset crystallization temperature (T x) decrease compared to their ternary counterparts. In addition, it is interesting that the crystallization behavior and corrosion resistance of these Zr–Ti–Y–Al–Cu–Ni–Co–Fe CMBMGs are mainly influenced by the elements substituted in Zr–Cu–Al alloys, which provides a novel route for compositional optimization of CMBMGs. This work is beneficial to better understand the phase formation and properties of BMGs with complex compositions. • A series of Zr-based CMBMGs were designed via multi-substitution. • Well-dispersed nanocrystals with 5–30 nm in size form in a wide range of temperature. • Zr-based CMBMGs have excellent corrosion resistance in 1 mol/L HCl solution. [ABSTRACT FROM AUTHOR]

Ti–6Al–4V alloy was successfully vacuum brazed with a commercial Ti-37.5Zr–10Ni–15Cu (wt.%) filler metal. The effect of brazing temperature and time on the microstructure and shear strength of the brazed joints were investigated. When the brazing temperature was 905 °C for 10 min, the typical interfacial microstructure of the brazed joint were a single layer of α-Ti with a high concentration of Ti, α-Ti, (Ti, Zr) 2 (Cu, Ni) intermetallic compound and eutectoid microstructure. Increasing the brazing temperature and time are beneficial to eliminate the (Ti, Zr) 2 (Cu, Ni) intermetallic compound that degrades the properties in the brazed joint. The shear strength of the brazed joint increases first and then decreases with brazing temperature, and increases with the extended holding time. The maximum shear strength of the brazed joint is 635.77 MPa at a brazing temperature of 920 °C for 30 min due to the high content of columnar α-Ti. Extending the brazing time is obviously beneficial to increasing the strength. The microstructure and shear strength of the brazed joint are highly dependent on brazing temperature and time. • Sound TC4 brazed joint can be obtained at lower brazing temperature. • The maximum shear strength of the brazed joint exceeded 630.00 MPa by proper brazing technique. • Extending the holding time is obviously beneficial to increasing the shear strength. • Increasing the content of columnar α-Ti is an effective way to obtain a higher strength of TC4 brazed joint. [ABSTRACT FROM AUTHOR]