Al_(0.3)CoCrFeNi高熵合金高压扭转过程中的组织结构演变

对面心立方(FCC)结构的Al_(0.3)CoCrFeNi高熵合金进行不同应变量的高压扭转实验,利用维氏硬度仪、电子背散射衍射、X射线衍射仪以及透射电镜系统分析变形引起的组织结构演变。结果表明:高压扭转过程中合金晶体结构并未发生改变,仍然保持为FCC结构,但引发其晶粒纳米化,平均晶粒尺寸达到30nm。晶粒细化主要是通过孪晶(包含初次孪晶与二次孪晶)、去孪晶(包含初次去孪晶与二次去孪晶)以及孪晶界分割晶粒的过程实现。孪晶和随后去孪晶的竞争作用导致孪晶宽度先减小后增大,初次孪晶和二次孪晶的最小宽度分别为2.7nm和0.9nm。

Microstructure Evolution of Al0.3 CoCrFeNi High-entropy Alloy During High-pressure Torsion

An as-cast Al0.3 CoCrFeNi high entropy alloy with face-centered cubic (FCC)structure was processed by high-pressure torsion (HPT)to different strain values.This deformation-induced micro-structure evolution was investigated by using Vickers hardness,electron backscatter diffraction, X-ray diffraction and transmission electron microscopy.The results show that,during HPT process-ing,the crystal structure is not changed,remaining FCC structure,while nanocrystallization of grains is induced by HPT to 30nm of average grain size;grain refinement is achieved through twinning (in-cluding primary and secondary twinning),de-twinning (including primary and secondary de-twinning) and twin boundary subdivision;competition between twinning and de-twinning processes contributes to the decrease and subsequent increase in twin boundary spacing,while the minimum spacing of pri-mary and secondary twins reach 2.7nm and 0.9nm,respectively.