电子束焊接热效应对镁合金焊缝显微硬度的影响

Influence of thermal effect upon micro-hardness of magnesium alloy weld of vacuum electron beam welding

摘要:

研究了真空电子束焊接热效应对AZ91D和AZ31B镁合金焊缝显微硬度的影响机制，实验结果表明，真空电子束焊接热效应对AZ91D、AZ31B镁合金焊缝均有不同程度的强化作用。当焊接热输入较大时，影响AZ91D镁合金焊缝硬度的主要因素为因Mg元素烧损而产生的强化相变化，焊接热输入越大，焊缝中的Mg元素烧损增加，使Al元素质量百分含量逐渐增加，从而在焊缝中生成了更多的强化β相，使焊缝硬度得到提高，产生的强化相越多，焊缝硬度相对越大；当焊接热输入较小时，影响AZ31B镁合金焊缝硬度的主要因素为焊后冷却速度，焊接热输入越小，焊后冷却速度越快，焊缝晶粒越细小，焊缝硬度相对越大。

Abstract:

The impact mechanisms of the thermal effect of vacuum electron beam welding on the micro-hardness of AZ91D and AZ31B magnesium alloy weld were studied. The experiment results showed that the welding thermal effect exerts its influence on weld hardness differently for AZ91D and AZ31B magnesium alloy. Two factors affecting the micro-hardness of the weld should be included, which are the cooling rate after welding and the burning loss of alloying elements after the action of welding thermal effect. When the welding heat input is large, the main factor affecting the weld hardness of AZ91D magnesium alloy is the increase of strengthening phases because of the burning loss of Mg elements. A larger welding heat input induces more strengthening phases in weld and the weld hardness increases relatively. When the welding heat input is small, the main factor affecting the weld hardness of AZ31B magnesium alloy is the cooling rate after welding. The smaller welding heat input induces faster cooling and solidification rate after welding and then forming fine grains, so the weld hardness is relatively high.