The Microstructure And Mechanical Properties Of Mg-Y-Ce-Zr Magnesium Alloy

Magnesium alloy is one of the most lightest commercial metal structure material,with good seismic damping performance, superior specific strength and specific stiffness and widely used in the automotive industry, electronics industry and aviation industry. Most of the magnesium alloys are hexagonal close-packed structure and can hardly deform in room temperature with only three slip systems. The prismatic slip system and cone slip system of magnesium can be activated by raising the deformation temperature,however,magnesium alloy burns and oxidizes easily at high temperature.Thus it is necessary to enlarge deformation in order to raise deformation temperature and improve flame retardant performances.The four different test groups,Mg-Y-Ca-Zr,Mg-Y-Ce-Zr,Mg-Y-Sm-Ce-Zr,Mg-Y-CeZr-Ca series alloys, were selected, smelted, rolled and heat treated, and the microstructure, mechanical properties, element distribution and fracture morphology of the four different test groups were studied by optical microscopy, tensile test and scanning electron microscopy. The first group includes Mg-3Y-0,9Ca-0.6Zr,Mg-3Y-0.7Ce-0.6Zr and Mg-3Y-3Sm-0.7Ce-0.6Zr alloys.The study shows that the microstrucure and the mechanical property of magensium alloy are improved by the addition of element Y and Ce. With addition of element Ca, the grain boundary of magnesium alloy is more continueous. The strength of the alloy is improved but the plasticity of alloy is poor. The grain of Mg-3Y-1.5Ce-0.6Zr alloy is the tiniest in the as-cast groups. The big grains are 16-18?m, and the small grains are 4-6?m. The grains are refined by 60%.The comprehensive mechanical property of Mg-3Y-1.5Ce-0.6Zr is the best of the four selected as-cast groups. The yield strength, tensile strength and elongation of Mg-3Y-1.5Ce-0.6Zr alloy are 203.8MPa, 143.4MPa and 19 % and increased by 33%,39% and 79%, respectively.With the addition of rare element Y and Ce, especially with the addition of element Ce, the deformation of magnesium alloy is improved. With addition of element Ca,the deformation of magnesium alloy is reduced. The deformation of Mg-4.5Y-1.5Ce-0.6Zr alloy is largest of the four groups. The maximum reduction ratio of single pass, the rolling pass and the total reduction were 14.3%, 18 pass, 65.2%. The single pass reduction ratio is three times and the total pressure ratio is six times that of the alloy without adding element Ce.