Study on the New High Strength and Creep Resistance of Magnesium Alloy

　　Study on the New High Strength and Creep Resistance of Magnesium Alloy
　　Since Magnesium alloys have such advantages as low density, high specific strength and rigidity、good damping performance and electromagnetic shielding ability, they have been found more and more applications in the fields of automobile、aerospace and electronic products . However they have low strength and poor creep resistance at high temperature, which have blocked them from being used as structural materials to produce heat-resistant parts in Ring neodymium magnet automotive, aerospace and other industries. In this paper, Zr and rare-earth element Nd are added into Mg-Zn based alloy and the new Mg-Zn-Nd-Zr alloy is fabricated. The microstructures of the new alloys are evaloated by Optical Microscope、X-ray Diffraction (XRD)、Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS), and their mechanical properties are systemically studied.
　　The optimum components of alloy under experimental conditions are obtained and the effects of additional elements on alloy’s mechanical properties and creep property are discussed.The results show that: (1) The addition of Zr can obviously refine grains of Mg-Zn-Nd alloy and the refining effect is the best when the Zr content is at 0.8wt%. It is mainly because thatα-Zr is precipitated in the inner of grains, which can serve as theα-Mg nucleation so as to refrain the growth of grain through heterogeneous nucleation.(2) The alloy’s tensile strength gradually increases with Zr addition at room temperature, and both the tensile strength and elongation reaches the maximum values when the http://www.chinamagnets.biz content of Zr is up to 0.8wt%. The analysis of XRD and SEM(EDS) showed that compounds such as Mg12Nd、Mg7Zn3 and Mg2Zn11 are precipitated along the grain boundaries of MgZn5Nd3.5Zrx alloy, which can effectively lock dislocation so as to strengthen alloy and improve the mechanical properties of alloy by grain refining.(3) The creep resistance of Zn5Nd3.5Zr0.8 alloy is good under 50MPa at 175℃, but it drops when the temperature is higher than 200℃. The improvement of creep resistance is mainly caused by the addition of high melting-point elements of Zr and Nd, which can refine the metallographic structure of alloy and the strengthening phases of Mg12Nd, Mg7Zn3 and Mg2Zn11 can stop the cross slip of grain bounders so as to improve the creep property.Under this experimental conditions, the optimum components of Mg-Zn-Nd-Zr alloy with