We report the mechanical and microstructural characteristics of a medium-entropy alloy, Co_17.5Cr_12.5Fe₅₅Ni₁₀Mo₅ (atomic percent, at%) at cryogenic temperatures, down to a record low temperature of 0.5 K. The alloy exhibits excellent strength and ductility combined with a high strain-hardening rate in the entire temperature range investigated. Its property profile, including the yield strength, ultimate tensile strength, strain hardening capability, and absorbed mechanical energy, is better than those of most alloys and HEAs used in cryogenics. Within the interval of extremely low temperatures considered (0.5–4.2 K), the alloy exhibits several unusual features, including anomalies of the temperature dependence of the yield strength and tensile ductility, discontinuous plastic deformation (DPF), and a change in the propensity for the deformation-induced martensitic transformation. While the occurrence of these effects in the same temperature interval may be fortuitous, we hypothesize that they are interrelated and provide a tentative explanation of the observed phenomena on this basis.

我们报告了中等熵合金 Co _17.5 Cr _12.5 Fe ₅₅ Ni ₁₀ Mo ₅的机械和显微结构特征（原子百分比，at%）在低温下，低至 0.5 K 的创纪录低温。该合金在所研究的整个温度范围内都表现出优异的强度和延展性以及高应变硬化率。其性能特征，包括屈服强度、极限抗拉强度、应变硬化能力和吸收的机械能，优于大多数用于低温的合金和 HEAs。在考虑的极低温度区间 (0.5-4.2 K) 内，合金表现出几个不寻常的特征，包括屈服强度和拉伸延展性的温度依赖性异常、不连续塑性变形 (DPF) 以及变形诱发马氏体相变。