谐波异质结构AlCoCrFeNi高熵合金的制备、组织演化与力学性能

Preparation,Microstructure Evolution and Mechanical Properties of AlCoCrFeNi High-entropy Alloys with Harmonic Heterostructure

结合机械球磨与放电等离子烧结工艺制备了一种由外层细小晶粒与内层粗大晶粒构成的谐波异质结构AlCoCrFeNi高熵合金(High-entropy alloys,HEAs),测试了其准静态压缩力学性能,并对该合金的相结构与微观组织进行了表征。结果表明,球磨后烧结的AlCoCrFeNi高熵合金的屈服强度为1686 MPa,压缩应变率为16.5%;未球磨直接进行烧结的AlCoCrFeNi高熵合金的屈服强度仅为1371 MPa,压缩应变率为16.2%;铸态AlCoCrFeNi高熵合金的屈服强度为1363 MPa,压缩应变率为18.7%。与其他两种制备方法相比,球磨和烧结工艺制备的AlCoCrFeNi高熵合金的综合力学性能最佳。烧结制备的AlCoCrFeNi高熵合金在相组成上与原始粉末一致,未发生变化,均由BCC+B2+FCC相构成;机械球磨细化了AlCoCrFeNi高熵合金粉末外层的晶粒,外层小晶粒与内层大晶粒形成谐波异质结构,这种特殊的结构在变形时起到背应力强化作用,显著提高了AlCoCrFeNi高熵合金的屈服强度。

A kind of AlCoCrFeNi high-entropy alloy(HEA)with harmonic heterostructure composed of outer fine grains and inner coarse grains was prepared by mechanical ball milling and spark plasma sintering.The quasi-static compressive mechanical properties of the alloy were tes-ted,and the phase structure and microstructure of the alloy were characterized.The results show that the yield strength of sintered AlCoCrFeNi HEA after ball milling is 1686 MPa and the compressive strain rate is 16.5%.The yield strength and the compressive strain rate of the sintered AlCoCrFeNi HEA without ball milling are only 1371 MPa and 16.2%,respectively.The yield strength and the compressive strain rate of the as-cast AlCoCrFeNi HEA are 1363 MPa and 18.7%,respectively.Compared with the other two methods,the AlCoCrFeNi HEA prepared by ball milling and sintering has the best comprehensive mechanical property.The phase composition of the AlCoCrFeNi HEA prepared by sintering is consistent with that of the original powder,both composed of BCC+B2+FCC phase.The outer grains of the AlCoCrFeNi HEA powder were refined by mechanical ball milling,and formed harmonic heterostructure with the inner large grains.This special structure plays a role of back stress strengthening,and significantly improves the yield strength of the AlCoCrFeNi HEA.