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通过Pandat软件模拟了Al-11.91Si-3.5Cu-1.69Ni-0.75Mg合金的平衡凝固相图,测量了其DSC曲线。结果表明,合金的第一个吸热峰开始于502.7℃,结合相图可知该吸热峰对应于Al2Cu的转变温度。基于此,设计了495℃×(6、10、14)h单步固溶。发现495℃×2h固溶后最低吸热峰的开始温度提高到了522.1℃。基于此设计了495℃×2h+515℃×(4、8、12)h两步固溶,并与单步固溶作对比。固溶完成后在200℃时效得到合金不同热处理状态下的时效曲线,并测量了对应峰时效态的拉伸力学性能。得到最佳热处理方案为:(495℃×2h+515℃×8h)固溶+(200℃×4h)时效,时效后合金的抗拉强度从铸态的212 MPa提高到367 MPa,伸长率从0.44%提高到0.66%。
The equilibrium solidification phase diagram of Al-11.91Si-3.5Cu-1.69Ni-0.75Mg alloy was simulated by Pandat software and its DSC curve was measured. The results show that the first endothermic peak of the alloy begins at 502.7 ℃, and the phase diagram shows that the endothermic peak corresponds to the transition temperature of Al2Cu. Based on this, a one-step solution of 495 ℃ × (6,10,14) h was designed. The initial temperature of the lowest endothermic peak after 495 ℃ × 2h solution was found to be 522.1 ℃. Based on this, a two-step solution at 495 ℃ × 2h + 515 ℃ × (4,8,12) h was designed and compared with single-step solution treatment. After the solution was completed, the aging curves were obtained at 200 ℃ for different heat treatment conditions, and the tensile mechanical properties of the corresponding aging peak were measured. The optimum heat treatment schedule was: (495 ℃ × 2h + 515 ℃ × 8h) solution + (200 ℃ × 4h) aging. After aging, the tensile strength of the alloy increased from 212 MPa to 367 MPa, elongation Increased from 0.44% to 0.66%.