剪切/振动耦合作用下连续流变轧制成形A2017合金组织演化及动态凝固

摘要

A novel semisolid rheo-rolling process of A2017 alloy was achieved by combining the shape rolling mill with the vibrating sloping plate device.The microstructure evolution and solidification behaviors during the process were investigated.The high cooling rate caused by the sloping plate and stirring action caused by the vibration and metal flow lead to a high nucleation rate as well as two primary grain growth pattems,direct globular growth as well as dendrite growth and subsequent breakage,which causes the formation of fine spherical or rosette primary grains.During the rolling process,the grains of the strip were elongated.The primary grain size of A2017 alloy strip increases with the increment of casting temperature.When the casting temperature was between 650 C and 660 ℃,A2017 alloy strip with good quality was produced by the proposed process.The microstructures of the strip are mainly composed of spherical or rosette grains.%将振动倾斜板制浆技术与轧制技术有机结合,开发新型连续流变轧制成形技术,利用该技术制备A2017合金板材.研究连续流变轧制成形过程中A2017合金组织演化及动态凝固行为.结果表明,在振动倾斜板制浆过程中,由于倾斜板的强冷却及振动作用,熔体内部形核率较高,晶粒有两种长大方式:一是直接球形长大,二是先枝晶生长然后断裂球化,因此促进了球形晶和玫瑰晶的形成.在半固态浆料轧制过程中晶粒被拉长.随着浇注温度升高,晶粒尺寸逐渐变大.当浇注温度为650-660℃时,可以制备表面形貌和内部组织较好的A2017合金板材,其内部组织主要由球形晶和玫瑰晶组成.