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研究了添加微量钒对AZ91D镁合金显微组织的影响。在AZ91D镁合金熔炼过程加入AlV55中间合金引入钒元素,用光学显微镜、扫描电镜、能谱仪和X射线衍射等分析研究了加钒前后合金组织的变化以及钒在合金中的存在形式。结果表明:钒的引入使β-Mg17Al12相由不连续网状逐渐离散化,钒在AZ91D合金中主要以新相Al3V形式溶解或分散于β-Mg17Al12相和α-Mg基体中。高熔点的新相Al3V在AZ91D镁合金凝固过程中先于其他相生成聚集在固液界面前沿,抑制晶粒的长大;同时由于α-Mg相细化而使晶界面积增加,相应的单位面积晶界处发生共晶反应的熔液体积减少,生成的β-Mg17Al12相变得细小。同时由于晶粒尺寸减小以及晶界处Al3V相的强化作用,AZ91D合金的硬度随着添加钒含量的增加呈增大趋势。
The effect of adding trace vanadium on the microstructure of AZ91D magnesium alloy was studied. The AlV55 master alloy was added into the AZ91D magnesium alloy during the melting process to introduce vanadium elements. The changes of the alloy structure before and after the addition of vanadium and the existing forms of vanadium in the alloy were studied by optical microscope, scanning electron microscope, energy dispersive spectrometer and X-ray diffraction. The results showed that the introduction of vanadium gradually dispersed the β-Mg17Al12 phase from the discontinuous network, and the vanadium dissolved or dispersed in the β-Mg17Al12 phase and α-Mg matrix mainly in the form of new phase Al3V. The new phase Al3V with high melting point formed earlier than other phases in the solidification process of AZ91D magnesium alloy and aggregated at the front of the solid-liquid interface to restrain grain growth. At the same time, the grain boundary area increased due to the refinement of α-Mg phase. Corresponding units The area of the grain boundary eutectic reaction of the melt volume decreases, the resulting β-Mg17Al12 phase becomes small. At the same time, the hardness of AZ91D alloy increases with the addition of vanadium due to the decrease of grain size and strengthening of Al3V phase at the grain boundaries.