时效热处理对水下搅拌摩擦加工WE43镁合金的微观组织及力学性能影响

Effect of Aging Treatment on Microstructure Evolution and Mechanical Properties of Submerged Friction Stir Processed WE43 Alloy

摘要:

研究了铸造WE43镁合金在水下搅拌摩擦加工（SFSP）过程中的微观组织演变、后续时效热处理对SFSP试样微观组织及力学性能的影响。研究结果表明，SFSP显著细化了铸造WE43镁合金的晶粒尺寸，同时也将粗大的第二相破碎成细小弥散的不规则状颗粒。SFSP后，由于微观组织的细化及均匀化，材料的强度和伸长率均得到大幅提升。经过后续时效热处理后，由于β′′和β1相的大量析出，峰值时效试样的强度得到了进一步提高，伸长率则有所降低。断口形貌分析表明，SFSP试样的拉伸断裂模式更倾向于韧性断裂，而峰值时效试样的拉伸断裂模式为韧–脆混合断裂。

Abstract:

In this study, as-cast WE43 alloy was subjected to submerged friction stir processing (SFSP). Microstructural evolution during SFSP and effect of aging treatment on mechanical properties of SFSP specimens were investigated. The results showed that the microstructure of cast WE43 alloy was significantly refined and the mechanical properties were greatly enhanced. After subsequent artificial aging treatment at 66 h for 150 ℃ and 54 h for 180 ℃, strengths of the peak–aged specimens were further increased, which was attributed to the large quantity of β′′ and β1 precipitates, respectively. Meanwhile, elongations of the peak-aged specimens were both decreased, since more crack nucleation sites were provided with the increased precipitates. The failure mechanism of SFSP specimen was ductile fracture mode, while the peak-aged specimens were all mixed ductile–brittle fracture mode.