含碳FeCoCrNiMn高熵合金的异质显微组织和力学性能

Heterogeneous microstructure and mechanical properties of carbon-doped FeCoCrNiMn high-entropy alloy

利用可控热机械处理工艺,在含0.5%C(摩尔分数)的FeCoCrNiMn高熵合金中获得具有纳米析出相和双峰晶粒尺寸分布的异质显微组织。粗大的M23C6碳化物倾向于在细晶粒的晶界处形成。与具有均匀显微组织的样品相比,异质结构FeCoCrNiMn−0.5%C(摩尔分数)高熵合金具有相似的平均晶粒尺寸(约4.8μm)。然而,它具有晶粒双峰结构且粒径<3μm的细晶粒的体积分数更高,从而使屈服强度从552 MPa提高到632 MPa。具有异质结构的样品在不同的区域呈现不同的力学性能和变形显微组织,导致在拉伸变形过程中产生明显的应变局域化和高密度的几何必要位错。这些变形特征有利于提高应变硬化能力,从而促进强度−塑性的协同作用。

Heterogeneous microstructure with nano-precipitate and bimodal grain size distribution was obtained in a FeCoCrNiMn high-entropy alloy(HEA)doped with 0.5 at.%C by a controlled thermo-mechanical treatment.The coarse M23C6 carbides tend to aggregate along the fine grain boundaries.Compared to the sample with homogenous microstructure,the heterostructure FeCoCrNiMn−0.5at.%C HEA has approximately the same average grain size of 4.8μm.However,it shows bimodal grain size distribution and higher volume fraction of the fine grains(<3μm),resulting in the increase of yield strength from 552 to 632 MPa.The sample with heterostructure presents different mechanical responses and deformed microstructures in different regions,accounting for significant strain localization and high density of the geometrically necessary dislocations during tensile deformation.These deformation characteristics are beneficial to the enhancement of strain hardening capacity,thereby promoting strength−ductility synergy.