WE94镁合金长寿命疲劳小裂纹萌生和扩展行为研究

Study on initiation and propagation behavior of small cracks in long-life fatigue of WE94 magnesium alloy

镁合金作为结构材料在汽车、航空、航天等领域有广泛的应用前景,在实际服役过程中存在高频振动荷载的长期作用。为解决镁合金结构件在长寿命服役条件下的安全与可靠性问题,基于旋转弯曲和超声振动加载两种疲劳实验方法,研究WE94镁合金在高周与超高周区间(104~109周次)的疲劳强度与失效机制。结果表明,疲劳裂纹萌生于沿基面的滑移带并在断裂面上形成解理状“小平面”形貌;而在疲劳小裂纹扩展初期,裂纹面存在大量细小平行状条带,该条带于裂纹尖端与孪晶带的交互作用过程中形成。因此,镁合金疲劳小裂纹的萌生与扩展过程对材料局部微结构形态与变形机制表现出密切的相关性。

As a structural material,magnesium alloy has a wide application prospect in the fields of automobile,aviation,aerospace and so on.There is a long-term effect of high-frequency vibration load in the actual service process.In order to solve the safety and reliability problems of magnesium alloy structural parts under the condition of long-life service.Based on rotary bending and ultrasonic vibration loading,the fatigue strength and failure mechanism of WE94 magnesium alloy in high cycle and ultra-high cycle range(104-109 cycles)were studied.The results show that the fatigue crack originates from the slip band along the base plane and forms a cleavage“small plane”shape on the fracture surface.At the initial stage of fatigue small crack propagation,there are a large number of small parallel bands on the crack surface,which are formed during the interaction between the crack tip and the twin band.Therefore,the initiation and propagation of small fatigue cracks in magnesium alloys are closely related to the local microstructure and deformation mechanism.