两种不同加工状态CrCoNi中熵合金的微观组织和力学性能研究

Study on Microstructure and Mechanical Properties of CrCoNi Medium Entropy Alloy with Two Different Processing States

中熵合金是近年来材料研究的热点,一般对中熵合金采用“铸造-轧制-热处理”的加工工艺。采用XRD、金相显微镜、万能试验机、扫描电镜对铸态、轧制+热处理的CoCrNi中熵合金的金相组织、硬度、室温、低温(77 K)力学性能以及拉伸断口进行分析。结果表明:对铸态CoCrNi合金轧制+热处理,两种不同状态合金均稳定保持面心立方(FCC)相,其中铸态组织为典型的树枝晶,但是无明显第二相存在,轧制+热处理对铸态组织有明显的细化和均匀化作用,对材料的拉伸强度和硬度有明显提升。两种不同加工状态的合金在低温下拉伸性能均发生明显提升,其中轧制后热处理中熵合金在液氮温度下抗拉强度达到1262.9 MPa、拉伸延伸率能达到89.6%,且两种状态下中熵合金在不同温度下均发生塑性断裂。在室温下CoCrNi合金的塑性变形行为以滑移为主,低温下CoCrNi合金塑性变形行为以孪生为主。

Medium entropy alloy is a hot topic in material research in recent years.The process of casting-rolling-heat treatment is generally adopted for medium entropy alloy.XRD,metallographic microscope,universal testing machine and scanning electron microscope were used to study the metallographic structure,hardness,mechanical properties at room temperature and low temperature(77 K)and tensile fracture of entropy alloy in CoCrNi as cast and rolling+heat treatment.The results show that of as-cast CoCrNi alloy rolling+heating processing,two different state alloy are stable face-centered cubic(FCC)phase,the as-cast microstructure for typical dendrites,but there are no obvious second phase.The rolling+heat treatment has obvious effect on the microstructure of refining and homogenizing effect,the tensile strength and hardness of the material has obvious improvement.The tensile properties of the two alloys in different processing states improves obviously at low temperature.The tensile strength and elongation of the entropy alloy can reach 1262.9 MPa and 89.6%at liquid nitrogen temperature in the post-rolling heat treatment,and the plastic fracture of the entropy alloy in the two states occurs at different temperatures.The plastic deformation behavior of CoCrNi alloy is mainly slip-slip at room temperature,and twinning at low temperature.