热机械处理Al-Co-Fe-Ni共晶高熵合金组织性能研究

Effect of Thermomechanical Processing on the Microstructure and Mechanical Properties of Al-Co-Fe-Ni Eutectic High-entropy Alloy

共晶高熵合金具有优异的强塑性匹配,同时还兼具传统共晶合金良好的铸造性能,对高熵合金的实际化应用有着重大的意义。而如何进一步提升共晶高熵合金的强塑性能,成为了高熵合金领域的研究热点。本文以Al-(21)Co_(19.5)Fe_(9.5)Ni_(50)共晶高熵合金为研究对象,探究了热机械处理对合金微观组织和拉伸力学性能的影响规律。并结合合金微观组织和相结构对合金应变硬化能力的影响,阐明了热机械处理条件下合金的变形机制及其对合金力学性能的影响。结果表明,经过热机械处理后合金由共晶层片组织转变为近完全等轴晶组织,且FCC相中析出L1_(2)相。热机械处理后合金在拉伸变形过程中,随着应变量的增加FCC相内位错密度增加,B2相发生应力诱发马氏体相变而形成具有相互交错孪晶结构的L1_(0)相,最终在FCC相与B2相双重强化机制下,表现出更高的屈服强度(551 MPa)和断裂伸长率(10.2%),加工硬化率曲线出现显著变化。

Eutectic high-entropy alloys have excellent strength and plasticity,and also have the good casting performance of traditional eutectic alloys,which is of great significance for the practical application of high-entropy alloys.However,how to further improve the strong plasticity of eutectic high-entropy alloys has become a research hotspot in the field of high-entropy alloys.In this paper,an Al_(21.5)Co_(19.5)Fe_(9.5)Ni_(50)eutectic high-entropy alloy was used as the research object,and the influence of thermomechanical treatment on the microstructure and tensile mechanical properties of the alloy was investigated.The deformation mechanism of the alloy under thermomechanical treatment conditions and its influence on the mechanical properties of the alloy were also elucidated in relation to the influence of the microstructure and phase structure of the alloy on its strain hardening ability.The results show that after thermomechanical treatment,the alloy transforms from a eutectic lamellar structure to a nearly complete equiaxial crystalline structure,and the L12 phase precipitates out of the FCC phase.During the tensile deformation of the alloy after thermomechanical treatment,with increasing strain,the dislocation density in the FCC phase increases,and a stress-induced martensitic phase transformation occurs in B2 phase to form the L1_(0)phase with an interlocking twin structure.Finally,under the dual strengthening mechanism of the FCC phase and the B2 phase,the alloy exhibits a higher yield strength(551 MPa)and elongation at break(10.2%),and the work hardening rate curve shows significant changes.