Mg-8Gd-1Er-0.5Zr合金多向锻造工艺及锻后组织与力学性能研究

为改善和提高Mg-8Gd-1Er-0. 5Zr合金的组织和力学性能,采用不同锻造温度和累积应变量对Mg-8Gd-1Er-0. 5Zr合金进行了等温多向锻造实验,并测试和分析了合金的组织和力学性能。实验结果表明:在实验温度范围内,随着锻造温度的升高,Mg-8Gd-1Er-0. 5Zr合金的可锻性逐步提高;在420℃锻造时,锻造初期产生大量的孪晶以协调变形,随着锻造温度升高至480℃,孪晶数量减少,再结晶晶粒数量增加,且平均晶粒尺寸有一定的增大;在累积应变量Δε=0. 66时,与420℃锻造时相比,450℃锻造后的试样强度略有降低,但伸长率明显增加,其抗拉强度、屈服强度、伸长率分别为295 MPa、252 MPa、13. 8%,但当锻造温度提高到480℃时,强度下降;当锻造温度一定时,随着累积应变量的增加,合金内部组织经历了从原始粗晶到混晶组织、再到由再结晶晶粒组成的细小均匀组织的演变,且合金在Δε=0. 66时的力学性能最佳。最终,确定了Mg-8Gd-1Er-0. 5Zr合金的锻造温度优选为450℃。

Research on multi-directional forging process and microstructure and mechanical properties after forging for Mg-8Gd-1Er-0.5Zr alloy

In order to improve the microstructure and mechanical properties of Mg-8Gd-1Er-0. 5Zr alloy,the isothermal multi-directional forging experiments under various forging temperatures and accumulated strains were conducted,and the microstructure and mechanical properties of alloy were tested and analyzed. The results show that the forge-ability of Mg-8Gd-1Er-0. 5Zr alloy is gradually improved by increasing the forging temperature within the experimental temperature range. When the alloy is forged at 420 ℃,a large number of twins are formed in the initial stage of forging to coordinate the deformation. By increasing the forging temperature to 480 ℃,the volume fraction of twins reduces whereas the number of recrystallized grains increases,and the average grain size becomes larger. Compared with the sample forged at 420 ℃ under the accumulated strain of 0. 66,the alloy forged at 450 ℃ exhibits a slight decrease in strength,but the elongation ratio increases obviously,and its tensile strength,yield strength and elongation ratio are 295 MPa、252 MPa and 13. 8%,respectively. However,the strength decreases when the alloy is forged at 480 ℃ . Furthermore,when the forging temperature is constant,with the increasing of the accumulated strain,the internal structure of alloy evolves from the original coarse grains to the mixed crystal structure,and then to the fine uniform structure composed of recrystallized grains. In addition,the alloy has the best mechanical properties under the accumulated strain of 0. 66,and the optimal forging temperature of Mg-8Gd-1Er-0. 5Zr alloy is preferably 450 ℃.