热处理对ZM51镁合金高周疲劳性能的影响

Effect of heat treatment on high⁃cycle fatigue properties of ZM51 magnesium alloy

采用升降法和成组法对挤压态、固溶态、T6欠时效态及T6峰时效态ZM51镁合金进行应力比为-1的疲劳性能测试,获得了ZM51镁合金在不同热处理状态下的疲劳强度(循环周次为1×10^(7))和S-N曲线,研究了不同热处理工艺对ZM51镁合金高周疲劳性能的影响;同时,通过疲劳断口分析获得ZM51镁合金的高周疲劳断裂机理。结果表明,经过固溶处理(320℃×1 h+380℃×3 h)后,ZM51镁合金疲劳强度明显下降,由挤压态的124 MPa降低为94 MPa,经过后续的T6时效处理,合金疲劳强度升高,T6欠时效态(90℃×32 h+175℃×2 h)疲劳强度为107 MPa,T6峰时效态(90℃×32 h+175℃×14 h)疲劳强度为130 MPa。疲劳断口分析表明,ZM51镁合金高周疲劳断裂机理为“拉伸孪生-退孪生”。

Fatigue properties of ZM51 magnesium alloy in as⁃extruded,as⁃solution⁃treated,T6 under⁃aged and T6 peak⁃aged states were tested with a stress ratio of-1 by the lifting method and the group method,respectively.The fatigue strength(1×10^(7) cycles)and S⁃N curves of ZM51 magnesium alloy in different heat treatment states were obtained.The effects of different heat treatments on high⁃cycle fatigue properties of ZM51 magnesium alloy were studied.Meanwhile,the high cycle fatigue fracture mechanism of ZM51 magnesium alloy was revealed by fracture analysis.The test results show that the fatigue strength of ZM51 magnesium alloy decreases significantly from as⁃extruded 124 MPa to 94 MPa after solution treatment(320℃×1 h+380℃×3 h).After subsequent T6 aging treatment,the fatigue strength of the alloy increases to 107 MPa in under⁃aging state(90℃×32 h+175℃×2 h)and 130 MPa in peak⁃aging state(90℃×32 h+175℃×14 h).Fatigue fracture analysis shows that the high cycle fatigue fracture mechanism of ZM51 magnesium alloy is“tensile twinning⁃detwinning”.