AlxCoFeNiMo高熵合金的结构演变及力学性能

Microstructural Evolution and Mechanical Properties of AlxCoFeNiMo High-Entropy Alloys

采用真空电弧熔炼法制备了一系列AlxCoFeNiMo合金(x=0、0.3、0.5、0.8、1.0)。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、万能试验机以及显微维氏硬度计,研究了铝元素含量变化对试样的晶体结构、显微形貌、成分、压缩性能和硬度的影响。结果表明,随着铝含量的增加,晶体结构从最开始的由富(Co、Fe、Ni)的FCC和μ双相组成,逐渐转变成FCC、μ和富(Al、Ni)的BCC的三相结构,最后转变成BCC和μ双相结构。CoFeNiMo合金具有较好的综合力学性能,其抗压强度为1997.8MPa,塑性应变为17%。随着铝含量从x=0逐渐增加到x=1.0,抗压强度先增大后减小,维氏硬度值从HV458单调增加至HV750。分析认为,Al元素的固溶强化作用和FCC相转变为BCC相是合金强化的重要原因。

AlxCoFeNiMo(x=0, 0.3, 0.5, 0.8, 1.0) alloys were prepared by vacuum arc melting. The effects of Al element content on the crystal structure, microstructure and mechanical properties were studied by using XRD, SEM, EDS, universal tensile testing machine and HV tester. The results show that, with increasing Al content, the crystal structure transformed from duplex FCC+μ phases to triplex FCC+μ+BCC phases, and finally to duplex BCC+μ phases. The microstructure of the alloys transformed from hypoeutectic structure to non-equiaxed dendrite structure, and finally to hypereutectic structure. CoFeNiMo alloy had good mechanical properties, with compressive strength and plastic strain being 1 997.8 MPa and 17%, respectively. As the Al content increased from x=0 to x=1.0, the compressive strength initially increased and then decreased, and the value of Vickers hardness increased from HV458 to HV750. It is believed that the solution strengthening of Al and the transformation from FCC phase to BCC phase are the main reasons of alloy strengthening.