AZ91D镁合金热处理与微弧氧化的交互作用

Interaction of heat-treatment and micro-arc oxidation on AZ91D magnesium alloys

随着AZ91D镁合金微弧氧化反应的进行,膜层逐渐增厚,膜层表面的喷射孔洞和喷射沉积物粗大化,膜层表面粗糙度增大.微弧氧化反应时膜层内部的应力集中会使膜层萌生微裂纹.对基体进行固溶处理后可以改善其微弧氧化膜层中微裂纹的数量和形态以及膜层表面的粗糙度,并能提高微弧氧化膜层的生长速率,同时降低微弧氧化过程的能耗.时效处理会使微弧氧化膜层中的残余应力得以释放,微弧氧化膜的形貌没有发生明显改变,即膜层表面的微裂纹在数量和形态上仍好于未经热处理基体膜层.微弧氧化处理不会引起基体组织的显著变化.在硅酸盐溶液体系中,AZ91D镁合金表面参与微弧氧化反应的Al比Mg少得多,同时还伴随着一个溶液中的Si向镁合金基体内部渗透的过程.

With the micro-arc oxidation process of AZ91D magnesium alloys going, the thickness of coatings increases gradually. The coarser the discharging channels and the ejecting deposition are, the rougher the coating surface is. The micro-cracks on coatings are resulted from the stress concentration in coatings. The amount and morphology of micro-cracks, surface roughness and growth rate of coatings are improved after substrates have been treated with the solid-solution that also benefit to energy saving of the micro-arc oxidation process. The residual stresses are released during the aging treatment, and the coating morphology is kept almost unchanged in terms of the amount and morphology of micro-cracks. And the microstructure of substrates has not been changed after the micro-arc oxidation treatment. More magnesium elements in AZ91D have participated in the micro-arc oxidation reaction conducted in silicate electrolyte. And silicon elements from the electrolyte also have diffused into magnesium substrates at the same time.