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采用MTS809型电液伺服疲劳试验机、扫描电镜研究了不同冷却速度对A319铝合金圆形加载路径下的疲劳特性.结果表明:当冷速为10℃·s~(-1)时,材料中二次枝晶臂间距、硅颗粒及孔洞尺寸较冷速为0.1℃·s~(-1)时要小.二次枝晶臂间距较小时,滞后回线面积小,材料应力应变近乎同相,且附加强化效果明显.不同冷速条件下裂纹萌生位置不同,在冷速为10℃·s~(-1)的材料中,裂纹在大硅颗粒处萌生,随着冷速降低至0.1℃·s~(-1)时,裂纹位于孔洞处萌生.对于A319铸造铝合金来说,冷速的变化对其轴向与切向循环特性并无直接影响,轴向表现为先硬化再软化,切向表现为先硬化后稳定的趋势.
The fatigue behavior of A319 aluminum alloy under circular loading was studied by means of MTS809 electro-hydraulic servo fatigue tester and scanning electron microscope.The results show that when the cooling rate is 10 ℃ · s ~ (-1) The secondary dendrite arm spacing, the size of silicon particles and the hole size are smaller than the cooling rate of 0.1 ℃ · s ~ (-1) .The secondary dendrite arm spacing is small, the hysteresis loop area is small, the material stress and strain are nearly in phase, And the additional strengthening effect is obvious.Where the crack initiation locations are different under different cooling rates, the crack initiation occurs at the large silicon particles in the cooling rate of 10 ℃ · s -1, with the cooling rate decreasing to 0.1 ℃ · s ~ (-1), the crack is initiated at the hole.For the A319 cast aluminum alloy, the change of cooling speed has no direct effect on the axial and tangential circulation characteristics, To the performance of the first hardening after the trend of stability.