微量Zr对Al-Cu-Mg合金时效硬化行为及显微结构的影响

Effect of trace Zr on aging hardening and precipitation microstructure of Al-Cu-Mg alloy

本文应用维氏硬度仪和透射电镜研究了微量Zr添加对Al-Cu-Mg合金180℃时效硬化行为及对应显微组织的影响。结果表明,Zr元素的添加对时效初期合金的硬度提升影响不大,但对峰值及过时效阶段合金的硬度有明显的增强作用。具有较高空位结合能的Zr容易与合金的空位结合,限制了时效初期合金中其它溶质原子的析出速率。而随着时效时间的延长,Zr元素的存在趋向促进细小的S及θ′相的弥散析出,提高合金的峰值硬度;同时Zr添加能够有效地抑制θ′相的过度粗化,并在过时效阶段使Al-Cu-Mg合金基体中的θ′相保持较高的径厚比,可有效提高过时效合金的硬度及热稳定性。

The effects of trace Zr addition on the age-hardening behavior and the precipitation microstructure of Al-Cu-Mg alloy were investigated by Vickers hardness testing and transmission electron microscopy in this work.The results show that the addition of Zr appears to have little effect on the hardness of the alloy at the initial stage of aging,but has a significant enhancement effect on the hardness of the alloy at the peak-aging stages and over-aging stages.Zr has a high vacancy binding energy and is easy to combine with the vacancies in the alloy matrix,which will limit the precipitation rate of other solute atoms at the initial stage of aging.With the extension of the aging time,the presence of Zr element is conductive to promoting dispersive precipitation of fine S andθ′phases,which increases the peak hardness of the aged alloy significantly.Also,the addition of Zr can effectively suppress excessive coarsening of theθ′phase during the over-aging stage,allowing theθ′phase to maintain a high diameter-to-thickness ratio,which will effectively improve the hardness and thermal stability of the Al-Cu-Mg alloy.