淬火条件对砂铸A356合金疲劳裂纹扩展速率的影响

Effect of Quenching Condition on Fatigue Crack Growth Rate of Sand Casting A356 Aluminum Alloy

在相同固溶和时效条件下 ,选择 3种不同温度的水对砂铸A35 6合金进行了淬火处理 ,并对这 3种不同淬火态下的合金进行了拉伸及疲劳裂纹扩展性能研究。结果表明 ,随淬火介质温度的降低 ,淬火冷却速率提高 ,合金的强度增加 ,塑性下降 ;当应力比R较低时 ,淬火条件对合金疲劳门槛区的裂纹扩展有明显影响 ,降低淬火介质温度可以提高合金的疲劳裂纹扩展阻力。此外 ,不同淬火态合金的疲劳裂纹扩展均明显地表现出与应力比R的相关性 。

The tensile performance and fatigue crack growth behavior of sand casting A356 aluminum alloy samples with three different quenching conditions in same solution heat treatment and ageing condition were investigated.The results show that the ultimate tensile strength and yield strength of the alloy samples rise but the total elongation decreases as the temperature of quenching medium drops.When stress ratio R is relatively low,quenching condition influences on the near threshold crack growth behavior of the alloy obviously.Raising cooling rate can increase the fatigue crack growth resistance of the alloy,and the fatigue crack growth rates of the alloys with different quenching conditions are all affected by stress ratio R ,which could be explained by crack closure.