Al-9.6%Mg合金高压凝固组织及稳定性

High pressure solidification microstructure and stability of Al-9.6%Mg alloy

利用扫描电镜、X射线衍射仪和透射电镜对6GPa高压下凝固的Al-9.6%Mg合金的显微组织以及组织的稳定性进行研究,对高压亚稳相形成机理进行探讨。结果表明:常压下枝晶间大量存在的Al3Mg2相在高压凝固时消失,形成另一密排六方结构相;经300℃,11h时效处理后,组织变得不稳定,六方结构相消失,转变成稳定的Al3Mg2相,但其形态由常压下三岔分界形式转变成团状,由此推断该六方结构相为亚稳相;在高压凝固条件下Mg在Al基体中的固溶度由7.74%增大到11.3%,Al相的晶格常数增加,在XRD图中表现为Al相衍射峰左移,但经时效处理后,Al相衍射峰基体又回复到常压时的位置。

The microstructure and its stability were investigated when Al-9.6%Mg alloy was solidified under 6GPa high pressure using SEM, XRD and TEM. The formation mechanism of high pressure metastable phase was discussed. The results show that a hexagonal phase forms under high pressure solidification conditions instead of a great amount of interdendritic Al3Mg2 phases under normal pressure. This phase disappears after aging treatment （300℃, 11h）, and they are transformed into the stable Al3Mg2 phase, but its morphology changes from the branching to agglomerate. So it is deduced that the hexagonal phase formed at 6 GPa pressure is a metastable phase. In addition, the solid solubility of Mg in Al matrix increases from 7.74% to 11.3%, and the lattice constant of a（Al） phase also increases, the diffraction peaks of Al move to the left in XRD patterns. However, the position of the diffraction peaks of Al is almost the same as that of normal pressure after aging treatment.