| There is no consensus that global energy crisis and more and more serious greenhouse effect are happening on our planet. How to reduce the amount of energy cost in the industry and achieve a low-carbon release and recycling way of develop, is now not only related to develop of China, but also of scientific research hot spots. Due to the advantages of light weight and high specific strength, magnesium alloys have great potential in the aerospace and the automotive industry, the using of magnesium alloys can greatly minimize the weight of structural parts and reduce the energy cost. At present, the study of magnesium alloys is on a wide range, but relatively low operating temperature, poor performance at high temperature is a limitation of the application of magnesium alloys. Now more and more institutions are bending themselves to elevate the performance of magnesium alloys at high temperature. Add rare earth elements in magnesium alloys can refine the grains and significantly enhance the performances at room temperature and high temperature. Particularly, by adding yttrium can make the most obvious effect mentioned above. Yttrium and magnesium both has a close-packed hexagonal structure and similar atomic radius, add yttrium in magnesium alloys can form compounds which dispersed in the matrix and grain boundaries, the compounds can prevent grain boundary sliding and strengthen the grain boundaries.In this paper, phase composition, microstructures and mechanical properties at different temperature of cast and processed by rolling Mg94Zn2Y4 alloy was deeply investigated. Further more, morphologies of the fractures of the deformed Mg94Zn2Y4 alloy was examined. Microstructures and mechanical properties of the rolled and annealed Mg97Zn1Y2 alloy was also investigated in this paper. The purpose of this paper is to serve as a reference for the development of new creep-resistant Mg-Y-Zn alloys and provide a basis for wide application of the magnesium alloys.For the as-cast Mg94Zn2Y4 alloy, firstly, XRD was taken to determine the phase composition, the result shows that the phase composition isα-Mg and Mg12YZn, and then SEM and EDS were used to determine the ingredient and the atomic proportion. Tensile tests were carried out from room temperature to 350℃,the ultimate strength, yield strength and elongation of as-cast Mg94Zn2Y4 alloy at room temperature is 144.3MPa,90.4MPa and 1.736%, respectively. It is 126.3MPa,75.8MPa and 2.51% at 200℃, 133.4MPa,83.2MPa and 2.95% at 250℃, 139.7MPa,83.3.4MPa and 5.34% at 300℃, 110.1MPa,68.9MPa and 14.12% at 350℃. The results indicate that the strength of Mg94Zn2Y4 alloy is very stable at elevated temperature. The ultimate strength at 300℃almost reach to the value at room temperature and that is mostly due to the Mg12YZn phase which is still stable at elevated temperature. The enhancement of the elongation is because of the solution of Yttrium in magnesium is higher when at higher temperature. The deformation mode of as-cast Mg94Zn2Y4 alloy at room temperature is brittle and become a brittle-ductility type when at elevated temperature.Mg94Zn2Y4 alloy was processed by different rolling reductions with 38% and 64%. XRD was taken and the result shows that phase composition was stillα-Mg and Mg12YZn. Tensile tests were carried out at room temperature, the yield strength,ultimate strength and elongation of the 38% rolling reduction Mg94Zn2Y4 alloy is 201.50MPa,439.12MPa,5.52%, respectively. It is 247MPa,443.54MPa,5.02% for the 64% rolling reduction. The results show us that the mechanical properties are improved overall after processed by rolling. The deformation mode of rolled Mg94Zn2Y4 alloy at room temperature is brittle-ductility type after the fracture was examined. The grain of rolled Mg94Zn2Y4 alloy was refined compared to the as-cast Mg94Zn2Y4 alloy and this could explain the elevation of the strength of rolled Mg94Zn2Y4 alloy. Rolling at 400℃makes a large amount of Y and Zn atoms dissolved into the Mg matrix, so the elongation of Mg94Zn2Y4 alloy after rolling is significantly improved compared to the as-cast Mg94Zn2Y4 alloy.The microstructures and properties of Mg97Zn1Y2 alloy processed by 22.3% rolling reduction with one time pass and annealed under different conditions were investigated. After annealed at 500℃for 120 minutes, many acicular structure was found in Mg97Zn1Y2 alloy rolled at 400℃, but very few could be found in the Mg97Zn1Y2 alloy rolled at RT when the same annealing conditions were conducted. The existence of the acicular structure is controlled by the concentration of Y and Zn atoms in the grains, the diffusive mobility of Y and Zn atoms in the Mg97Zn1Y2 alloy rolled at 400℃annealed at 500℃for 120 minutes is better compared to in the Mg97Zn1Y2 alloy rolled at RT, so the acicular structure formed in the in former one and could hardly be found in the other. The hardness of the rolled alloy and annealed was examined and results show that the hardness value of alloy rolled at RT is a little higher than the alloy rolled at 400℃, and when the annealing temperature was elevated, the hardness value of both the two type become lower.Although there are a few shortcomings about Magnesium alloys, but we could still tell the bight future about the Magnesium alloy applications in lots fields. I hope that this paper could do some help among the researches in universities and institutions all over the world, If this paper could make any contribution for The progress of human civilization, I couldn't be more happier.
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