形变热处理对Al-Si-Mg铸造合金组织与性能的影响

Effects of thermomechanical treatment on microstructure and properties of Al-Si-Mg cast alloy

通过Brinell硬度和拉伸测试以及OM,SEM和TEM的组织观察,研究了形变热处理对Al-12.0%Si-0.2%Mg合金组织与力学性能的影响。结果表明,通过形变热处理可以显著提高试验合金的硬度、强度及伸长率。该合金经500℃热挤压、(535±5)℃固溶、160℃时效12h处理后Brinell硬度可达85.7HBS,抗拉强度为256.3MPa,伸长率为15.0%。热挤压过程加速共晶Si相发生碎断与球化,细小的Si颗粒分布均匀,结合强化相在时效过程中弥散析出,导致形变热处理条件下合金的强度及伸长率同时提高。SEM和TEM观察显示,合金在热挤压过程中发生了基体Al的再结晶及Si和Mg2Si相的析出。

Effects of thermomechanical treatment on microstructure and mechanical properties of Al-12.0% Si-0.2% Mg alloy were investigated by means of Brinell hardness measurement,tensile test,OM,SEM and TEM observations.Results show that Brinell hardness and tensile properties of the Al-12.0% Si-0.2% Mg alloy after thermomechanical treatment are improved,especially the elongation.Brinell hardness of 85.7HBS,tensile strength of 256.3 MPa and elongation of 15.0% are obtained by a process of hot extrusion at 500 ℃ and aging at 160 ℃ for 12 h after solid solution at 535 ℃ .Hot extrusion accelerates the breaking and spheroidizing of the eutectic Si particles.The uniform distribution of fine Si particles and dispersive precipitation of fine harden phases （Mg2 Si） during subsequent aging improve both the strength and plasticity of the alloy.Microstructure observation by SEM and TEM indicates that dynamical recrystallization of Al matrix occurs and phases of Si and equilibrium Mg2 Si are precipitated during hot extrusion.