SCR技术半固态制浆及组织形成机理

采用单辊搅拌冷却技术(Shearing-Cooling-Rolling,简称SCR)制备A2017合金半固态浆料,对SCR工艺参数对半固态浆料组织的影响以及组织形成机理进行了研究.结果表明,熔体浇注温度和辊靴型腔高度对半固态浆料组织的影响显著,降低熔体浇注温度或减小辊靴型腔高度,半固态浆料组织从粗大的枝晶和菊花晶转变为细小的等轴晶或球形晶.组织形成机理分析表明,熔体首先在工作辊和靴子表面形核生长,在液流冲击及剪切搅拌的作用下晶核脱落游离进入残余液相区长大成菊花晶,在强烈剪切搅拌作用下,菊花晶断裂破碎最终形成非枝晶组织.

Manufacturing Semi-solid Slurry by SCR Technology and Formational Mechanism of Microstructures

The SCR(Shearing-Cooling-Rolling)technology was adopted to manufacture A2017 alloy semi-solid slurry, the effects of SCR process parameters on semi-solid microstructure and the formational mechanism of semi-solid microstructure were studied. Results shows that the effects of both the pouring temperature of molten alloy and the distance of roll-shoe cavity on semi-solid microstructure are mostly evident. Reducing the pouring temperature or decreasing the distance can transform the semi-solid microstructure from coarse dendrites into fine equiaxed or net-globular grains. The analysis of formational mechanism of semi-solid microstructure shows that nuclei form on the surface of roll and shoe firstly and then these nuclei are broken and distribute into residual molten alloy under the impact of liquid flow and laminar shearing and grow into rosette-shaped grains. Finally, the arms of rosette-shaped grains are broken by the severe shearing and stirring and become fine non-dendrites.