挤压变形AZ81镁合金的疲劳变形与断裂行为

Fatigue deformation and fracture behavior of as-extruded AZ81 magnesium alloy

研究镁合金的疲劳行为,可为镁合金的抗疲劳设计和合理使用提供可靠的理论依据.通过总应变幅控制的疲劳实验和断口形貌分析,确定了挤压变形AZ81镁合金的循环应力响应行为、疲劳寿命行为和断裂机制.结果表明:在应变控制的疲劳加载条件下,挤压变形AZ81镁合金呈现明显的循环应变硬化,其弹性应变幅、塑性应变幅与断裂时的载荷反向周次之间的关系可分别用Basquin和Coffin-Manson公式来描述,得到了拉伸滞后能的理论计算值与应变疲劳寿命之间呈线性关系、疲劳裂纹的萌生和扩展均以穿晶模式进行的结论.

The investigation on fatigue behavior of magnesium alloys can provide a reliable theoretical foundation for both fatigue resistant design and reasonable application of magnesium alloys. Through total strain-controlled fatigue tests and analysis on fracture surfaces of fatigued specimens, the cyclic stress response and fatigue life behaviors as well as fracture mechanism were identified for as-extruded AZ81 magnesium alloy. The experimental results show that the extruded AZ81 alloy exhibits significant cyclic strain hardening. For extruded AZS1 alloy, the relations between elastic strain amplitude, plastic strain amplitude and reversals to failure can be described by Basquin and Coffin-Manson equations, respectively. A linear relation between calculated tensile hysteresis energy and fatigue life has been noted. In addition, it has been found that fatigue cracks initiate and propagate in a transgranular mode.