铝硅合金热疲劳过程的应力应变分析

对铝硅合金进行了热疲劳模拟实验和应力、应变分析。铝硅合金的导热系数高,高温弹性模量低,温度涨落过程产生的宏观热应力低于同一温度下合金的屈服应力和疲劳极限;而铝、硅热膨胀系数的差异将在铝硅相界等局部区域产生远大于宏观热应力的微观热应力,并因此萌生热疲劳裂纹。通过变质工艺改变硅相形态,可改善合金的抗热疲劳性能。

ANALYSIS OF STRESS AND STRAIN IN PROCESS OF THERMAL FATIGUE OF ALUMINIUM SILICON ALLOY

The simulating test of thermal fatigue for aluminium silicon alloy has been done and the fields of temperature and stress have been analysed. Because the thermal conductivity of aluminium silicon alloy is high and the modulus of elasticity at high temperature is low,the macro-stress produced in temperature change process is smaller than yield stress and fatigue limit of alloy at same temperature. The difference of expand coefficients between aluminium and silicon produces micro-stress at same areas where aluminium matrix and silicon phase is adjacent. The micro stress is larger than macrostress,it is the micro-stress that initiates thermal fatigue cracks. Alloy resistance to thermal fatigue can obviously be improved by different modification techniques.