Si相对铸造Al-Si合金低温拉伸断裂行为的影响

Effect of silicon phase on tensile fracture of Al-Si alloys at low temperature

对Al-1Si-0.3Mg和Al-7Si-0.3Mg合金在-80~20℃拉伸过程中的断裂行为进行研究。结果表明:随着温度的降低Al-1Si-0.3Mg合金的抗拉强度、屈服强度及伸长率均呈上升趋势;Al-7Si-0.3Mg合金的抗拉强度和屈服强度上升,伸长率却明显下降;拉伸过程中Al-1Si-0.3Mg合金中位错在晶界塞积,易使相邻晶粒内位错源启动,使合金具有较高的塑性;Al-7Si-0.3Mg合金的位错在Si相边界塞积,使相邻晶粒内位错源难以启动,从而造成合金具有较高的强度。

The tensile mechanical properties of Al-7Si-0.3Mg and Al-1.0Si-0.3Mg alloys at-80-20 ℃were investigated.The mechanisms of crack initiation and extension at low temperature were analyzed.The results show that the tensile strength,yield strength and ductility of Al-1.0Si-0.3Mg alloy increase with decrease of temperature.The tensile strength and yield strength of Al-7Si-0.3Mg alloy increase,but the ductility of Al-7Si-0.3Mg alloy decreases with the decrease of temperature.During the low temperature tensile process,the dislocations pile up along the boundaries of grains in Al-1.0Si-0.3Mg alloy,which make dislocation sources to trigger easily in the adjacent grains,so the ductility of Al-1.0Si-0.3Mg alloy is improved.But the dislocations pile up at the Si particles in Al-7Si-0.3Mg alloy,which prevents the dislocation sources to trigger in the adjacent grains,so,the strengths of Al-7Si-0.3Mg alloy is greater.