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The effect of Mo addition of Fe50Mn25Ni10Cr15 medium‐entropy alloy (MEA) on its cryogenic mechanical properties is investigated. It is found that the optimized (Fe50Mn25Ni10Cr15)99.5Mo0.5 MEA exposes the yield strength, tensile strength, and ductility of 690 MPa, 1148 MPa, and 63% at 77 K, respectively. Especially, the yield strength increases by 29% after Mo addition. Herein, the solid‐solution strengthening, twinning‐induced plasticity, and transformation‐induced plasticity are beneficial to reveal the high work hardening capability and good strength‐ductility synergy at 77 K. This research can offer guidance for the design of low‐cost and high‐performance MEAs for cryogenic applications. [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]

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]

• A novel Fe-Co-Ni-Cr soft-magnetic HEA was designed. • This HEA shows high corrosion resistance comparable to stainless steel. • This HEA exhibits high soft-magnetic properties and malleability. • High (Fe, Co) and Cr contents ensure the balance of B s and corrosion resistance. In this paper, a soft-magnetic Fe 40 Co 40 Ni 10 Cr 10 high entropy alloy (HEA) was designed and fabricated, and its microstructure, magnetic properties, corrosion resistance and mechanical properties have been systematically investigated. It is found that, this HEA is composed of single FCC structure and shows homogeneous compositional distribution. This HEA has good soft-magnetic properties as well as excellent corrosion resistance comparable to stainless steel. Besides, this HEA has high malleability with compressive plasticity of > 60% without fracture. The homogeneous compositional distribution and single FCC phase in this Cr-containing HEA is possibly the main reason for the combination of the above-mentioned properties. This work provides a novel route for designing functional HEAs with enhanced comprehensive material properties. [ABSTRACT FROM AUTHOR]

The design of medium-entropy alloys (MEAs) with low-cost and high-performance is a hot topic in the field of metal materials. Here, low amount of Co and Ni element is employed to prepare Fe–Co–Ni–Cr MEA, resulting in a reduced material cost of MEA, which also lead to low stacking fault energy and subsequently promote phase transformation in the alloy system. The achieved cost-effective Fe 65 Co 10 Ni 10 Cr 15 MEA has excellent cryogenic strength of 1.6 GPa and strain of 56%, which has the highest strength-price ratio among the reported MEAs so far. The significant strengthening of the alloy is attributed to the hetero-deformation and the accelerated deformation-induced phase transformation. • Microstructure and mechanical properties of novel Fe 65 Co 10 Ni 10 Cr 15 MEA was studied. • The alloy shows a well combination of strength and ductility both at 293 K and 77 K. • Hetero-deformation and TRIP effect are the main strengthening mechanism. [ABSTRACT FROM AUTHOR]