搅拌摩擦加工AZ31镁合金低周疲劳性能研究

Low-cycle fatigue properties of friction stir welded joint of AZ31 magnesium alloy

摘要:

作为新型大塑性变形技术，搅拌摩擦焊接技术（FSW）已成功应用于超细晶材料的制备。本文采用FSW对热轧态AZ31镁合金进行连接，对母材和焊接接头的低周疲劳性能进行了研究。结果表明：在疲劳测试和单轴拉伸测试过程中，焊合区和前进侧热机械影响区交界处为性能薄弱区域。FSW AZ31接头的低周疲劳寿命，屈服强度，抗力强度以及断后延伸率均低于母材。AZ31镁合金疲劳测试过程种的主要变形机制为位错滑移，疲劳断口表面呈现出明显的疲劳纹。最终，我们发现母材和FSW接头低周疲劳行为符合Coffin-Manson和 Basquin关系

Abstract:

Friction stir welding (FSW) has been validated to be a severe plastic deformation method for development of ultrafine-grained metals. In this study, hot-rolled AZ31 magnesium alloy plate was processed by FSW, and the effect of FSW on the low-cycle fatigue (LCF) behavior of AZ31 magnesium alloy was analyzed. Results showed that the interface between the stir zone and thermo-mechanically affected zone at the advancing side is the weakest region, in which the monotonic tensile and fatigue fracture occur. Compared with the base metal (BM), the LCF fatigue life, the yield strength, the ultimate tensile strength and the elongation of FSW specimen decrease. The main deformation during LCF was dislocation slip deformation. The fracture surface exhibited a typical fatigue characteristic with the fatigue striations. Finally, we found that the LCF behavior of BM and FSW specimens can be well described by the Coffin-Manson and Basquin’s relations.