定向凝固AlCoCrCuFeNi高熵合金的组织与力学性能

Microstructure and Mechanical Properties of Directionally Solidified AlCoCrCuFeNi High-entropy Alloy

以AlCoCrCuFeNi高熵合金为研究对象,研究了不同抽拉速度下定向凝固组织的演变规律,Cu偏析及力学性能。结果表明:定向凝固AlCoCrCuFeNi高熵合金仍然为稳定的BCC和FCC两种晶体结构,微观组织由富FeCoCr相,富AlNi相和富Cu相组成。随着抽拉速度增大,所获得的凝固组织由粗大的树枝晶逐渐演变为细长的层状树枝晶,枝晶臂间距显著减小。不同抽拉速度下,富Cu相都偏析于枝晶间,其在富FeCoCr相边界处形成不连续的锯齿状分布,且在富AiNi相中形成富Cu沉淀。随着抽拉速度增大,富Cu沉淀相由亚微米级转变为纳米级,富Cu相中的Cu原子浓度下降。合金中不同区域组织的显微维氏硬度差异随抽拉速度增大而减小,平均显微维氏硬度从358 HV增加到375 HV。

The effect of different drawing rates on microstructure,Cu segregation and mechanical properties of AlCoCrCuFeNi high-entropy alloy prepared by directional solidification was studied.The results show that the directionally solidified AlCoCrCuFeNi high-entropy alloy still has two simple BCC and FCC crystal structures,and its microstructure is composed of FeCoCr-rich,AlNi-rich and Cu-rich phases.With the increase of drawing rate,the solidification microstructure gradually changes from coarse dendrite to thin lamellar-dendrite,and the dendrite arm spacings decrease significantly.Under different drawing rates,the Cu-rich phase is segregated between dendrites and discontinuous zigzag distribution is formed at the boundary of FeCoCr-rich phase,and Cu-rich precipitate is formed in AlNi-rich phase.With the increase of the drawing rate,the Cu-rich precipitate changes from submicron to nanometer scale,and the concentration of Cu atoms in the Cu-rich phase decreases.The microhardness difference of different locations in the alloy decreases with the increase of drawing rate,and the average microhardness increases from 358 HV to 375 HV.