稀土元素参与下az91d镁合金亚快速凝固组织及其热稳定性研究-材料工程专业论文.docx

AbstractAs the lightweight structural materials in the 21st century, magnesium alloy has broad application prospects in the automotive and electronics fields due to its advantages of high specific strength, specific stiffness and superior damping capacity and good electromagnetic shielding. However, the magnesium alloy produced by conventional casting process exhibits coarse grain, and the continuous network eutectic phase at grain boundary is incline to coarsening under high temperature, which leading undesirable strength and poor creep performance. Consequently, the further application of magnesium alloys is restricted. It is well known that grain refinement can effectively improve the mechanical properties of magnesium alloy. As one of the most valuable elements in magnesium alloys, rare earth can increase the strength via grain refinement and improve the high temperature creep property. With the addition of rare earth, the needle-like phase is formed, which generates a strong fragmentation effects on matrix and thus influence the improvement of mechanical properties. As an important technology for the fabrication of novel high-performance structural materials, sub-rapid solidification technology can not only greatly refine grain, eliminate needle-like phase structure, but also improve mechanical properties, processability and corrosion resistance significantly. Therefore, the combination of rare earth alloying and sub-rapid solidification technology can increase high temperature strength and creep resistance of cast metal, which provide theoretical basis for development of high performance magnesium alloys.In this study, sub-rapidly solidified AZ91D magnesium alloy containing RE element is fabricated by copper mould spray-casting technique on high vacuum induction melting equipment. Not only the refinement effect of rare earth and sub-rapid solidification on AZ91D magnesium alloy is researched, but also the effects of different and its content on the primary