淬火温度对Al_(0.5)CoCrFeNiSi_(0.2)高熵合金组织结构的影响

采用真空电弧熔炼的方法制备了高熵合金Al0.5CoCrFeNiSi0.2。对其进行600℃到1100℃保温10h后淬水的淬火处理。通过金相显微镜、扫描电镜及附带的能谱仪、X射线衍射仪和透射电镜观察分析合金的组织结构。用显微硬度计测定合金的显微硬度。结果表明:铸态和淬火态的合金组织均呈典型的枝晶形貌,枝晶含有非晶相和纳米级颗粒。在淬火加热温度低于800℃时,随着淬火温度升高,晶粒细化、fcc相含量减少,硬度随淬火温度的升高而提高;当温度升高至900℃后,枝晶相长大,fcc相含量增加,大块枝晶中析出一种富含Al、Ni的θ相,硬度下降。

Effect of Quenching Temperature on the Microstructure of High-entropy Al0.5CoCrFeNiSi0.2 Alloy

High-entropy Al0.5CoCrFeNiSi0.2 alloy was prepared by the arc melting and casting method.As-cast alloy was heated at 600℃-1 100℃ for 10h and subsequently quenched into water.Microstructure of the alloy was characterized by optical microscopy(OM),scanning electron microscopy(SEM),X-ray energy-dispersive spectrometry(EDS),X-ray diffractometry(XRD) and transmission electron microscopy(TEM).Hardness of the alloy was measured by a Vickers hardness tester.The results showed that the microstructures of as-cast and as-quenched alloy exhibited typical dendrite and inter-dendrite structures.Dendrites contained an amorphous phase and nano-scale precipitates.When the quenching temperature is lower than 800℃,the hardness of the as-quenched alloy increased with increasing quenching temperature,this can be attributed to dendrite refinement,inter-dendrite phase increase and decrease of the fcc phase.When the quenching temperature is higher than 900℃,the dendrite phase grew up,the fcc phase increased and a Ni-Al rich phase precipitated in the dendrites,which resulted in the hardness of alloy to decrease.