Microstructure And Properties Of Mg-Gd-Y-Zr Heat-Resistant Magnesium Alloy

Magnesium alloys with high specific strength,good damping and shock absorption,good thermal conductivity,good electrostatic shielding and low density,is the lightest metal material.Magnesium alloy has good application prospects in aerospace,automotive,medical equipment,3C and so on.However,due to its poor corrosion resistance and poor high temperature resistance,it limits the application of magnesium alloys in high temperature and corrosive environments.Therefore,the development of heat resistant alloys has become a research hotspot.Some effective means,such as alloying,fine grain strengthening,second phase strengthening,deformation strengthening and so on,can improve the comprehensive performance of magnesium alloys.In addition,the centrifugal casting process can also improve the microstructure,thereby improving the heat resistance of the alloys.Based on this,the Mg-10Gd-2.5Y-0.1Zr alloy is designed and constructed.The Mg-10Gd-2.5Y-0.1Zr alloy is prepared by centrifugal casting method,and the alloys are hot rolled.The microstructure and phase composition of the as-cast and as-rolled test alloys are observed and analyzed by optical microscopy?OM?,scanning electron microscopy?SEM?,X-ray diffraction?XRD?and EDS spectrometer.The mechanical properties of the alloy at different temperatures are tested.The main research work and results are as follows:?1?The microstructure and phase composition of conventional as-cast and centrifugal as-cast Mg-10Gd-2.5Y-0.1Zr alloys are systematically analyzed.The as-cast Mg-10Gd-2.5Y-0.1Zr alloy is mainly composed of?-Mg phase,Mg₂₄?Gd,Y?₅ phase,and Mg₃?Gd,Y?phase.Compared with the conventional as-cast alloy,the centrifugally as-cast alloy has finer grains and segregation of the compound.?2?Centrifugal as-cast Mg-10Gd-2.5Y-0.1Zr alloy was prepared by different centrifugal speeds.The microstructure of the as-cast Mg-10Gd-2.5Y-0.1Zr alloy at different speeds and different radius is different.At the same rotation speed,the content of the compound phase in the alloy gradually increases with the increase of the centrifugal radius.At the same radius,with the increase of the rotational speed,the content of the compound phase in the alloy gradually increases,and the difference in the content of the near and far end compound phases increases,and the finer the alloy grains are.?3?The room temperature mechanical properties of the centrifugally as-cast and conventional as-cast Mg-10Gd-2.5Y-0.1Zr alloys are tested.The results show that the tensile strength of Mg-10Gd-2.5Y-0.1Zr alloy reaches 200 MPa at 600 r/min,which is25 MPa higher than that of the alloy under conventional casting.?4?The as-cast Mg-10Gd-2.5Y-0.1Zr alloys are rolled at a process temperature of500�C and a deformation of 30%.The results show that compared to the as-cast alloy,the grains of the as-cast Mg-10Gd-2.5Y-0.1Zr alloy are remarkably refined and a large amount of twins have appeared.At room temperature,the 900r/min alloy has the highest tensile strength of 321 MPa.At 300�C,the 900 r/min alloy has the best tensile properties of 284 MPa and the highest elongation of 22.1%,which exhibits good heat resistance.?5?The as-cast Mg-10Gd-2.5Y-0.1Zr alloys are rolled at a process temperature of500�C and a deformation of 60%.The results show that the alloys have more twins and the grains are finer.When the centrifugal speed exceeds 600r/min,the effect of increasing the rotational speed on microstructure and mechanical properties of the alloy is weakened.At room temperature,the 900r/min alloy has the highest tensile strength of345 MPa.At 300�C,the tensile properties of the alloy at 600 r/min are 290 MPa,which exhibits good heat resistance.