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研究由SiC和Sr改性的原位Mg_2Si_p/AM60B复合材料在部分重熔过程中的组织演变和相变。结果表明:SiC和Sr可以有效地细化初生α-Mg晶粒和Mg_2Si颗粒。部分重熔以后,可以获得具有细小球状初始α-Mg颗粒的半固态组织。部分重熔过程中的组织演变可以分为4个阶段:快速粗化、组织分离、球状化和最终的粗化。组织演变的实质是因为发生相变:β→α,α+β→L和α→L,α→L,α→L和L→α。Mg2Si颗粒对于组织演变步骤没有太大影响,但会减慢演变进程且改变粗化机制。复合材料部分重熔时,由于Mg_2Si颗粒的边角优先熔化,颗粒首先变钝,然后呈球状化,最后在Ostwald熟化作用下粗化。
The microstructure and phase transition of Mg_2Si_p / AM60B composites modified by SiC and Sr during partial remelting were investigated. The results show that SiC and Sr can effectively refine primary α-Mg grains and Mg_2Si grains. After partial remelting, a semisolid microstructure with small, spherical, initial α-Mg particles can be obtained. Partial remelting process of organizational evolution can be divided into four stages: rapid coarsening, tissue separation, spheroidization and the final coarsening. The essence of tissue evolution is due to the phase transitions: β → α, α + β → L and α → L, α → L, α → L and L → α. Mg2Si particles have little effect on the evolution of the microstructure, but slow the evolution and alter the coarsening mechanism. Partially remelted composite materials, due to preferential melting Mg_2Si particles corner, the first particles become dull, then spherical, and finally coarsening under Ostwald maturation.