Effects Of Heat-treatment Technology On The Microstructures And Properties Of Semisolid Forming ZA52Magnesium Alloy

ZA series magnesium is widely studied because of its good characteristic such as satisfied cast ability, good properties, low cost and so on. Low alloying ZA52magnesium maintains good over-all properties; furthermore, the density is low. It is quite valuable to profound study the microstructure and properties of ZA52magnesium series magnesium.We use ZA52magnesium alloys which prepared by ourselves as experimental material, using C and Ca, Sr as modifications’to improve the alloys. Both the C and Ca, Sr can make a-Mg phase smaller, but the refine mechanization is differ from them, and the alloys’properties are uneven, the comprehensive properties are improved with C and Ca, Sr combined, they distribute mainly in Mg-Zn-Al phases. We get the best properties:the (?)b is235MPa and the δ is14.6%.The DSC curve shows that the liquids is599.9℃, the interval between liquids and solidus is57℃, these are basis for isothermal treatment. Holding temperature is the most important factor during isothermal treatment, we learn that the alloys’structure develop heavy when the holding temperature is near liquids, but the shape will be uneven easily, longer holding time can make the grains more rounder. We can get complete parts in almost each thixoforging, the30%liquid ratio forging parts are more ideal; the properties will increase with higher holding pressure, and the remolding force will increase at the same time. Thixoforging parts have higher properties than other forgings, the (?)b is254MPa and the δ is13.8%.The effects of solution and aging treatment on microstructure and properties of ZA52magnesium alloy were investigated, and the best heat treatment process is determined. Semisolid die forging ZA52magnesium alloy after aging (Tl), solid solution (T4) and solid solution plus aging treatment (T6) can improve its mechanical properties. When the aging temperature is170℃,aging time of8h.the tensile strength and hardness of the alloy is reached maximum, but elongation slightly down. When the solid solution temperature is350℃,solid solution time of5h.the tensile strength and elongation reached its highest, but the macro hardness fell. Further to solid solution plus aging treatment of alloy, the comprehensive mechanics performance of the alloy is the best when the solid solution treatment process of355℃,8h,and aging treatment at 170℃,8h.