6063铝合金的TTP曲线与淬火敏感性

采用中断淬火技术测定了6063铝合金的时间-温度-性能(TTP)曲线,透射电镜研究了6063铝合金的淬火敏感性.结果表明,6063铝合金的淬火敏感性低于6061和6082铝合金的,合金的鼻尖温度为360℃,淬火敏感区间为300～410℃.微观组织观察表明,在敏感区间内,β-Mg2Si平衡相优先在(AlxFeySiz)相上非均匀形核而析出,且在360℃鼻尖温度时的长大速度最快.平衡相的析出导致合金溶质原子的浓度下降,减少了时效时的β"强化相的数量,降低了强化效果.因此,对于6063铝合金大型材的淬火,一方面,在淬火敏感区间(410～300℃)应加大冷却速率以抑制平衡相的析出,从而获得较佳的时效强化效果；另一方面,适当减小从固溶温度到410℃以及低于300℃时的冷却速率,从而减小淬火应力.

Time-temperature-property curves for quench sensitivity of 6063 aluminum alloy

The quench sensitivity of 6063 alloy was investigated via constructing time–temperature–property (TTP) curves by interrupted quenching technique and transmission electron microscopy (TEM) analysis. The results show that the quench sensitivity of 6063 alloy is lower than that of 6061 or 6082 alloy, and the critical temperature ranges from 300 to 410 °C with the nose temperature of about 360 °C. From TEM analysis, heterogeneous precipitate β-Mg₂Si is prior to nucleate on the (Al_xFe_ySi_z) dispersoids in the critical temperature range, and grows up most rapidly at the nose temperature of 360 °C. The heterogeneous precipitation leads to a low concentration of solute, which consequently reduces the amount of the strengthening phase β‘’ after aging. In the large-scale industrial production of 6063 alloy, the cooling rate during quenching should be enhanced as high as possible in the quenching sensitive temperature range (410–300 °C) to suppress the heterogeneous precipitation to get optimal mechanical properties, and it should be slowed down properly from the solution temperature to 410 °C and below 300 °C to reduce the residual stress.