Yb微合金化对Al-Zn-Mg-Cu合金显微组织和性能的影响

Effect of Yb microalloying on microstructure and properties of Al-Zn-Mg-Cu alloy

摘要:

采用熔炼铸造结合热挤压变形等工艺制备了Al-Zn-Mg-Cu和Al-Zn-Mg-Cu-Yb两种合金。利用金相显微镜、扫描电镜、透射电镜对组织结构观察及差热分析仪、拉伸试验机和电化学工作站对性能检测，研究了稀土Yb微合金化对Al-Zn-Mg-Cu合金组织和性能的影响。结果表明：Yb的添加能够明显细化晶粒，显微硬度和抗拉强度分别由125.6 HV、562.9 MPa提高至154.9 HV、616.3 MPa，拉伸断裂形式也由沿晶和韧窝共存的混合型断裂转变为完全的韧窝型断裂。然而基体中Al8Cu4Yb粗大相的析出及晶界处η相的连续分布，对合金耐腐蚀性能不利。

Abstract:

Al-Zn-Mg-Cu and Al-Zn-Mg-Cu-Yb alloys were prepared by melting casting and hot extrusion. The effect of rare earth Yb microalloying on the microstructure of Al-Zn-Mg-Cu alloy was observed by optical microscope, scanning electron microscope and transmission electron microscope, and the properties were tested by differential thermal analyzer, tensile tester and electrochemical workstation. The results show that the addition of Yb can obviously refine the grains, and the microhardness and tensile strength increase from 125.6 HV and 562.9 MPa to 154.9 HV and 616.3 MPa respectively. The tensile fracture mode also changes from intergranular and dimple coexisting mixed fracture to complete dimple fracture. However, the precipitation of coarse Al8Cu4Yb phase in the matrix and the continuous distribution of η phase on grain boundary are unfavorable to the corrosion resistance.