AlZnMgCuMn高熵合金的微观组织、力学和耐腐蚀性能及其机理

Microstructure, mechanical properties, corrosion resistance and mechanism analysis of AlZnMgCuMn high-entropy alloy

摘要:

为探究轻质高熵合金AlZnMgCuMn的微观组织、力学性能、耐腐蚀性能及合适的热处理工艺,本研究采用XRD、SEM、EDS分析了合金的微观组织,通过电子万能试验机和维氏硬度计测试其力学性能,利用动电位极化测试、阻抗谱、CLSM和AFM对耐腐蚀性能及其机理进行分析。结果表明,AlZnMgCuMn高熵合金由Al-Mn准晶体相和HCP相组成,前者表现为枝晶形貌,后者分布于枝晶间。热处理对两相形貌、分布和体积分数的影响较小。铸态AlZnMgCuMn的抗压强度、压缩率和维氏硬度分别为415 MPa、4.4%、461.2 HV_0.5,自腐蚀电位和电流分别为-726.344 mV和1.882 μA/cm^₂。电化学腐蚀之后合金表面产生明显的腐蚀坑,其深度约为12 μm,枝晶Al-Mn相具有较低的电位作为阳极而优先被腐蚀,随着腐蚀的加剧,腐蚀微区彼此连接并发展成为大面积的腐蚀坑。

Abstract:

The study aims to investigate the heat treatment process of light high-entropy alloy AlZnMgCuMn and its effect on microstructure, mechanical properties and corrosion resistance. The microstructure of this alloy was characterized by XRD, SEM and EDS. The mechanical properties were evaluated by electronic universal testing machine and Vickers hardness tester. The corrosion resistance and mechanism were analyzed by potentiodynamic polarization test, impedance spectrum test, CLSM and AFM. The results show that AlZnMgCuMn alloy is composed of Al-Mn quasicrystalline phase and HCP phase, and the effect of heat treatment on the morphology, distribution and volume fraction of two phases is small. The compression fracture strength, fracture strain and Vickers hardness of as-cast AlZnMgCuMn are 415 MPa, 4.4% and 461.2 HV0.5, respectively. The Ecorr and Icorr of as-cast alloy are -726.344 mV and 1.882 μA/cm2. After electrochemical corrosion, obvious corrosion pittings are formed on the surface of alloy, the depth of which was about 12 μm. The dendritic Al-Mn phase has a lower potential as an anode and is preferred to be corroded. As the corrosion intensifies, the corrosion microdomains are connected with each other and develop into a large corrosion area.