时效及冷热循环对Al2O3增强2A12铝合金尺寸稳定性的影响

采用压铸方法制备了体积分数为30%的Al₂O₃/2A12复合材料,对其残余应力松弛及尺寸变化进行了研究,分析了时效和冷热循环处理对复合材料尺寸稳定性的影响规律。结果表明,复合材料的残余应力松弛量随时效时间的延长而增加;冷热循环处理不仅能导致高密度位错的形成,还能够促进时效析出,并能够降低复合材料中的残余应力,从而提高了复合材料在交变温度场下的尺寸稳定性。伴随着冷热循环处理循环下限温度的降低,即上下限温差越大,复合材料中的残余应力持续减小,微变形抗力提高,对基体析出的加速作用增大,复合材料的尺寸稳定性获得明显改善。本文提出的3种工艺中,160℃×10 h时效+（-196～160℃）冷热循环4次是提高Al₂O₃/2A12复合材料尺寸稳定性的最佳工艺。 

Effect of aging and thermal-cold cycling on dimensional stability of Al_2O_3 reinforced 2A12 alloy

Al2O3/2A12 alloy composite with 30% volume fraction was prepared by means of die casting method,and then its residual stress relaxation and size change were studied,the effect of aging and thermal-cold cycling treatment on the dimensional stability of the composite was analyzed. The results show that the residual stress relaxation of the composite increases with the extension of aging time,and the thermalcold cycling treatment can not only lead to the formation of high density dislocations,but also promote the aging precipitation,as well as reduce the residual stress in the composite,thus improving the dimensional stability of the composite under the alternating temperature field.With the decrease of the lower limit temperature of the thermal-cold cycling treatment,that is,the greater the temperature difference between the upper and lower limits,the residual stress in the composite material continues to decrease,the micro-deformation resistance increases,the acceleration effect on the matrix precipitation increases,and the dimensional stability of the composite material shows significant improvement. Among the three processes proposed in this paper,the optimum process for improving the dimensional stability of Al2O3/2A12 composite is to age at 160 ℃ for 10 h accompanied with thermal-cold cycling treatment in the temperature range from-196 ℃ to 160 ℃ for four times.