预时效对Al-5.2Mg-0.45Cu-2.0Zn合金室温稳定性的影响

Effect of pre-aging treatment on the stability of Al-5.2Mg-0.45Cu-2.0Zn alloy sheet at room temperature

摘要:

本文详细研究了预时效对Al-5.2Mg-0.45Cu-2.0Zn合金时效析出行为的影响。预时效不仅提高了合金的室温稳定性,避免了合金烤漆软化,同时提高了合金的烤漆时效响应速度。合金经T4处理后,再峰时效处理后的组织包括粗大的T-Mg₃₂(AlZn)₄₉相以及针状的S-Al₂MgCu相。然而合金经T4P处理后,再峰时效处理的组织只含有细小而高密度的T-Mg₃₂(AlZn)₄₉相而不包括S-Al₂MgCu相。自然时效后不稳定的原子团簇在180℃时效后会回溶到基体中, 从而抑制了合金的时效析出强化。而预时效后生成的稳定的原子团簇会成为180℃时效的形核点,显著提高了合金的时效响应速度。

Abstract:

In this research, pre-aging treatment has been performed on our newly developed Al-5.2Mg-0.45Cu-2.0Zn alloy. Results show that pre-aging treatment not only improves the stability of the alloy sheet at room temperature, which avoids the paint-baking softening, but also enhances the age hardening response during subsequent artificial aging at 180℃. The microstructure of the T4 sample in peak aged condition consists of coarse lath-like T-Mg32(AlZn)49 phase and needle-like S-Al2MgCu phase. However, the microstructure of the T4P sample in peak aged condition only consists of high density of finer and equiaxed T phase with the S phase disappeared. Unstable clusters formed during natural aging dissolve when imposed on 180℃, which retards the precipitation process of the alloy. Stable clusters formed during pre-aging treatment serves as the nucleis of the T phase during aging at 180℃, which enhances the age hardening response of the alloy.