固溶处理对铸造Al-Si合金相选择再结晶的影响

Effect of Solid Solution Treatment on the Phase-Selective Recrystallization of Cast Al-Si Alloy

相选择再结晶在Al-Si合金中基于应变分配原理实现对软相进行再结晶、硬相进行回复从而球化硅相和细化铝相。相选择再结晶处理后合金呈现出高的加工硬化率和伸长率。固溶处理是实现铝合金强韧化的重要环节,与相选择再结晶互相影响。一方面,初始组织对相选择再结晶的应变分配有一定影响;另一方面铝合金固溶过程会影响析出强化作用。因此,本文探究铸造Al-7Si-0.65Mg合金固溶过程中共晶硅相的形貌对相选择再结晶的影响,结合时效析出实现合金的强韧化。结果表明,0.5 h短时间固溶处理可以保持相选择再结晶合金中清晰且不分散的共晶硅颗粒骨架状结构,同时增加基体中Si和Mg含量促进强化相Mg2Si析出,使合金屈服强度达到300 MPa,断后伸长率为9.5%,显著优于传统T6态。

Phase-selective recrystallization in Al-Si alloys is based on the principle of strain distribution to achieve recrystallization of the soft phase and recovery of the hard phase,thereby spheroidizing the silicon phase and refining the aluminium phase.After phase-selective recrystallization treatment,the alloy exhibits a high work hardening rate and elongation.Solid solution treatment,which interacts with phase-selective recrystallization,is an important step in strengthening and toughening aluminium alloys.On the one hand,the initial structure has a certain influence on the strain distribution of phase-selective recrystallization;on the other hand,the solid solution process of aluminium alloys can affect the precipitation strengthening effect.Therefore,the influence of the morphology of the eutectic silicon phase on phase-selective recrystallization during the solid solution process of a cast Al-7Si-0.65Mg alloy was explored in combination with aging precipitation to increase the alloy strength and toughness.The results show that a 0.5 h short solid solution treatment can maintain a clear and non-dispersed framework structure of eutectic silicon particles in phase-selective recrystallized alloys,while increasing the Si and Mg contents in the matrix promotes the precipitation of the Mg2Si strengthening phase,resulting in a yield strength of 300 MPa and an elongation after fracture of 9.5%,which is significantly better than that of the traditional T6 state.