(中南大学 材料科学与工程学院，长沙 410083)
摘 要: 采用热模锻工艺制备了Mg-8.94Gd-1.80Y-0.42Zr-0.21Ag(质量分数，%)合金大型锥形壳体，对壳体不同部位的显微组织与力学性能进行了分析。结果表明：沿锥形壳体高度方向及壁厚方向的显微组织均存在明显差异，沿高度方向，锥形壳体顶层与中层比底层具有更高的再结晶程度；沿壁厚方向，由内至外再结晶程度先降低后升高。顶层与中层的内部均近乎发生完全动态再结晶，而其余部位为粗晶、细晶构成的混晶组织。锥形壳体顶层与底层部位均表现出明显的力学性能各向异性，中层部位的力学性能则近乎各向同性，这与试样不同晶体取向所导致的变形机制差异密切相关。合金经时效处理后，强度得到显著提高，力学性能各向异性程度降低，但室温拉伸断裂方式由韧性断裂与脆性断裂的混合断裂方式转变为单一的脆性断裂。
关键字: 镁合金；模锻；显微组织；力学性能；时效处理
（School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The microstructure and mechanical properties of different parts of the Mg-8.94Gd-1.80Y-0.42Zr-0.21Ag (mass fraction, %) alloy large conical shell prepared by the hot die forging process were analyzed. The results show that there are obvious differences in microstructure along the height direction and thickness direction of the conical shell. Along the height direction, the top and middle layers of the conical shell have higher degree of recrystallization than the bottom layer. Along the thickness direction, the recrystallization degree first decreases and then increases from inside to outside. The interiors of the top and bottom layers are almost completely dynamic recrystallization, while others are mixed microstructure composed of coarse and fine grains. The top and bottom layers of the conical shell show obvious anisotropy in mechanical properties, while the middle layer is nearly isotropic, which is closely related to the difference in deformation mechanism caused by different crystal orientations of the samples. After aging treatment, the strength of the alloy is increased significantly, and the mechanical anisotropy is weakened, but the tensile fracture mode at room temperature changes from the mixed fracture mode of ductile fracture and brittle fracture to a single brittle fracture.
Key words: magnesium alloy; die forging; microstructure; mechanical properties; aging treatment
