大挤压比制备高强Mg-Gd-Y-Zn-Zr合金的显微组织及强韧化机理

Microstructure and strengthening-toughening mechanisms of a high-strength Mg-Gd-Y-Zn-Zr alloy processed by large-strain hot extrusion

通过大挤压比热挤压工艺制备出含有长周期堆垛有序(LPSO)相的高强塑性Mg-8.34Gd-2.32Y-1.04Zn-0.07Zr合金。通过金相显微镜、EBSD、TEM等显微检测方法及数学模型研究了合金显微组织与力学性能之间的关系。结果表明,合金经热挤压后形成了双峰结构,在时效处理后同时存在14H-LPSO相和β′析出相。合金获得了较好的力学性能,抗拉强度、屈服强度和伸长率分别达到463.1 MPa,392.6 MPa和13.3%。合金屈服强度以细晶强化、析出强化和固溶强化的贡献为主。高占比的细小再结晶晶粒、弱织构以及LPSO相的存在对合金塑性的提升有重要作用。

The Mg-8.34Gd-2.32Y-1.04Zn-0.07Zr alloy containing long-period stacking order(LPSO)phase with good combined strength and ductility was prepared by large-strain hot extrusion.By the analysis via optical microscopy,EBSD,TEM and mathematical models,the relationship between microstructure and mechanical properties of the alloy was studied.The results show that a bimodal structure forms after hot extrusion.After an artificial ageing treatment,the 14-H LPSO phase andβ′phase are both observed.The alloy exhibits good mechanical properties.The tensile strength,yield strength and elongation are 463.1 MPa,392.6 MPa and 13.3%,respectively.Grain boundary strengthening,precipitation strengthening and solid solution strengthening provide the most significant contribution to the yield strength of the alloy.The high ratio of fine recrystallized grains,the weak texture as well as the presence of LPSO phase play important roles in the enhancement of ductility of the alloy.