Novel Co-free high performance TRIP and TWIP medium-entropy alloys at cryogenic temperatures

Recently, high- and medium-entropy alloys (HEAs and MEAs) have been found to exhibit excellent cryogenic mechanical properties, but most of them contain high-priced Co element. Therefore, developing HEAs or MEAs with high strength and ductility and relatively low cost is urgent. In this work, novel Co-free FexMn75-xNi10Cr15 (x = 50 and 55 at.%) MEAs were developed, which exhibit a good combination of low cost, high strength and ductility at cryogenic temperature. It was found that the Fe50Mn25Ni10Cr15 MEA exhibits a combination of cryogenic tensile strength of ∼ 0.98 GPa and ductility of ∼ 83 %. The excellent cryogenic mechanical properties were attributed to joint of twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP) effects. The present study sheds light on developing low cost MEAs with high performance for cryogenic-temperature applications.