人工时效与自然时效对Al-7Si-0.6Mg铝合金组织与力学性能的影响

研究了人工与自然双重阶段时效对铸造Al-7Si-0.6Mg合金的力学性能影响.试验结果表明:A1-7Si-0.6Mg合金经535℃×10h(固溶)+水淬+165℃×1 h(人工时效)+24h(自然时效)+165℃×5 h(人工时效)热处理工艺后,其抗拉强度321MPa、伸长率12％,相对T6热处理工艺试样其抗拉强度及伸长率分别提高了7.7％和140％；其室温拉伸断口中存在大量的等轴韧窝,尺寸细小且分布均匀,属于韧性断裂方式；人工与自然双重阶段时效对A1-7Si-0.6Mg力学性能提高的机制主要是共晶硅的球粒化与分布、Mg2Si沉淀强化、析出相Si相与位错间的交互作用.

Effect of Artificial Aging and Natural Aging on Microstructure and Mechanical Properties of Al-7Si-0.6Mg Aluminum Alloys

The effects of the combination use of artificial aging and natural aging on mechanical properties of Al-7Si-0.6Mg cast aluminum alloys were investigated in detail.The experimental results reveal that the mechanical properties can be improved when the alloys were treated as follows:solution treatment at 535 ℃ for 10 h,followed by water quenching,then artificial aging at 165 ℃ for 1 h,followed by natural aging,and then artificial aging at 165 ℃ for 5 h.The best mechanical properties were reached with σb=321 MPa and δ=12%,which is 7.7% and 140% larger than that of the T6-treated alloys.Many fine equiaxial dimples were uniformly distributed in fracture of sample,which implied ductile rupture of the sample.The improvement of mechanical properties was ascribed to the spheroidization and distribution of eutectic silicon,Mg2Si-phase precipitation strengthening,and the interaction between Si precipitates and dislocation.