Effect Of Sm And Zr Composite Addition On Microstructure And Mechanical Properties Of Mg - Cu Alloy

Magnesium with their unique advantages,such as high specific intensity,high specific rigidity,high damping,strang electromagnetic shielding and, radioresistance, free-machining,easy recovery,etc, has very important application value and wide application prospect.However,its disadvantages including poor plastic deformation abiliry,low toughness at room temperature,low yield strength and corrosion resistance,have provented their application and development.Adding alloying elements to improve the comprehensive performance of magnesium alloy is currently the most common and most effective way to improve the performance of magnesium alloy. In this paper, adding the Sm、 Zr generated toughness B2 (CsCl structure)-typle alloy phase in order to improve Mg-based alloy’ phase mechanical properties with Cu.Element Zr is the most effective elements of fine grains in magnesium alloys,also could reduce segregates of alloy’ phase on boundary and make them more dispersive and homogeneous, so effection of compound addtion of Sm、Zr on the microstructure and mechanical properties of Mg-Cu alloy have been studyed. In order to analyze the influence of solidification parameters process convolution on alloy phase character,the effection of 3 cooling ways including air-cooling,water-cooling,furnance-cooling,on the microstructure and mechanical properties of Mg-Cu alloy have been studyed. The results show that:(1) Mg2Cu phase was formed mainly on the grain boundary in Mg99Cu alloy.By adding Sm, Cu reacting with Sm generated small amounts of CuSm phase. Sm elements tended to be partial in Mg2Cu phase, and changed the distribution features of Mg2Cu, made the amount of intracrystalline precipitated phase increased.(2) Mg99Cu adding Zr alloy elements, besides formed Mg2Cu phase, also formed CuZr2 phase. Zr elements can purify the melt, and reduce the number of the intracrystalline exhalation phase. Make grain boundary straight into positively polygon, and grain boundary’ angle was 120°.(3) The compound addtion of Sm、Zr, for the interaction between elements, integrated and improved the Sm, Zr of different roles. Addtion content and different cooling ways changed the location Cu element and number of precipitated phase, With the reduce of adding element,boundry got fine, precipitated phase got more.(4) Lamellar structure were formed in alloys at AC, and dendrites were formed in alloys at water-cooling,and isometric polygon grainswere formed at furnance-cooling. The compressive strength was the highest at water-cooling, the plasticity was the best at air-cooling. Because of the severe oxidation plasticity and compressive strength were the worst generally at furnance-cooling. With the reducing of the cooling rate, the grain size increaseed gradually, the compressive strength of the alloy decreaseed gradually.Intracrystalline precipitation pointlike particles gradually reduced, almost disappeared when furnace cooling.(5) The plasticity, strength and comprehensive performance of Mg99Cu0.5Sm0. 25Zr0.25 turned out the best,which strain was32%, the compressive strength was 270Mpa at air-cooling. The compressive strength of Mg99Cu0.5Sm0.25Zr0.25 was 325Mpa compressive strain was 27% at water-cooling. Grain was bulky, and oxygen evolution was more serious, plastic and compressive strength were relatively poor at furnance-cooling.