镁合金电子束焊接接头微观组织特征

Joint microstructures of magnesium alloy for electron beam welding

镁合金熔点低、热导率高、线膨胀系数大、表面张力小,焊接后易出现夹杂、脆性相和气孔等。针对以上问题,进行AZ61镁合金真空电子束焊接研究。对优化工艺条件下电子束焊接接头的微观组织、相结构和硬度分布进行了详细分析研究。结果表明,AZ61镁合金电子束焊接接头成形良好,没有明显的热影响区,焊缝狭窄,焊缝为细小的等轴晶,晶粒尺寸5～10μm;焊缝区域主要由细小的α-Mg和Mg17Al12相组成。焊缝硬度高于母材,说明电子束焊接是焊接AZ61镁合金厚板材料的有效方法。

The magnesium alloy is characterized with low melting point,high heat conductivity,high linear expansion coefficient,low surface tension,and easy occurrence of impurities,brittle phase and cavities after welding.To overcome such problems,the vacuum electron beam welding（EBW） for AZ61 magnesium alloy was carried out.The mierostructure and phase structure of joints were investigated under certain process conditions.The microhardness measurement was conducted for joints.The results show that the joints with good appearance have been formed.A fine equiaxed grained with 5-10 μm size weld region is observed and no obvious heat effeeted zone is found,the weld zone mainly consists of small α -Mg phase and Mg17Al12 phases.The test results indicate that the mierohardness of weld zone are higher than those of the base metal.Therefore,electron beam welding can provide an effective method to weld the AZ61 magnesium alloys.