Papers by Author: Shou Qiu Tang

Abstract: The effect of Sr addition on the as-cast microstructure of AS31 alloy was studied. The experimental results show that the grain size decreased obviously from 1116μm to 221μm for AS31 alloy with addition of 0.05%Sr, and promote the formation of globular grains. The morphology of eutectic Mg₂Si phase is changed from Chinese script to polyhedral shape or fine fibers shape. The grain refinement mechanism is attributed to the enrichment of Sr element at solidification interface front, which restricts the growth of α-Mg primary dendrite. The modification of the eutectic Mg₂Si phases results from the dissociative Sr changing the preferred growth manner of them.

Abstract: Long route and high inclusion content are two common problems existing in the present process for magnesium alloys. To solve these problems, a new process technology, in which the crystalline magnesium is used as the raw material, is developed. The process is melting flux→ adding raw materials in batches → stirring→ holding→ pouring (MASHP). The mechanisms of protection and purification mechanisms are also analyzed. The results show that the MASHP process has high protection and purification effects on magnesium alloys. By the in-batches addition mode of raw materials, no oxidation and evaporation loss of magnesium produce during heating and melting, and the inclusions that self-contained in the crystalline magnesium and that produced by oxidation during heating and melting can be minimized. High quality magnesium alloys can be produced by the new process.

Abstract: The microstructure and tensile properties at room temperature of as-cast, solution-treated and aged samples of a Mg-5Sn-5Zn (wt%) alloy are investigated. The microstructure of the as-cast sample consists of -Mg primary, Mg-MgZn eutectic, divorced eutectic Mg2Sn and secondary precipitation Mg2Sn. After solution treatment, all the MgZn particles and the majority of Mg2Sn phases are dissolved into the matrix and the tensile strength and the elongation of the alloy increase obviously. During aging process many fine particles precipitate which result in the improvement of the yield strength.