The Research Of Extruction Process, Microstructure And Mechanical Properties Of The Heat-resistant Mg Alloy Containing With RE

As the lightest metal in the practical application of structural materials, magnesium alloy is more and more widely used in the automotive, electronics and other industries. However, the intensity of magnesium alloy significantly decreased accompanying temperature rise when the temperature exceeds120℃, which limits its application as automotive engine components and drive member. Clearly, the development of high-strength and heat-resistant magnesium alloy can make it be more fully used in the automotive industry. Therefore, in order to improve the heat resistance of the alloy, and to broaden the field of application of magnesium alloy, the Mg-Zn alloy contained Si, Ca, Nd, heart treatment process and extraction process were studied.In this paper, the different state Mg-Zn-Si-Ca-xNd alloy microstructure and mechanical properties are studied in order to determine the extrusion process parameters, the heat treatment process parameters as well as the content of alloying elements of the alloy.The results showed that the grain of the alloy was refine, the morphology of Mg2Si phase transformed from Chinese characters form into globular form, and twins existed through extrusion. The size of alloy grain smaller at first and then larger with the increase of the extrusion temperature, however the twins were redurced with the increase of the extrusion temperature. The grain organization of the alloy was the most uniform and fine under the320℃extrusion. The mechnical properties of extrusion state alloy under room temperature and high temperature were excellent than as-cast alloy. The mechanical properties of extrusion state alloy were further improved by aging treatment. The mechanical properties of the alloy were the most outstanding through the process of320℃extraction and190℃×8h ageing, and the corresponding room temperature tensile strength were348MPa and tensile strength at200℃temperature were214MPa.The microstructure of as-cast and extrusion state alloy were refined with the Nd addition, and the morphology and distribution of MgZn phase were also changed. The as-cast mechanical properties, especially in high temperature mechanical properties were improved significantly with the increase of Nd contention. The tensile strength at150℃of as-cast alloy which content1.6%Nd was145MPa, increased20.5%in the contrast of based alloy(112MPa). The room temperature and high temperature mechanical properties of extrusion+aging state alloy were improved with the increase of Nd contention. When the alloy content1.6%Nd, the room temperature tensile strength were378MPa and tensile strength at200℃were244MPa.The study of the subject not only as a basis for the development of new high-strength heat-resistant magnesium alloy, but also lay the foundation for the application of high-strength heat-resistant magnesium alloy in the automotive sector and provide technical support for the development of lightweight automobile market.