高应变速率下TB6钛合金在绝热剪切带内的晶粒瞬间细化机制

Grain Instant Refinement Mechanism in Adiabatic Shear Band of TB6 Titanium Alloy under High Strain Rate

采用分离式霍普金森压杆装置对TB6钛合金帽型试样进行室温动态加载试验,通过微观组织表征技术对绝热剪切带内的微观结构特征进行观察,研究高应变速率下TB6钛合金绝热剪切带内的晶粒瞬间细化机制。TEM观察结果表明:绝热剪切带中晶粒的瞬时细化是三种机制共同作用的结果。第一种机制是由于位错的快速运动、增殖以及塞积促使晶粒内部产生应力集中现象,最终在此现象的作用下形成裂纹、断裂以及细晶;第二种机制是通过增大晶粒内部的颈缩程度迫使细晶形成;在转动态再结晶机制的作用下,绝热剪切带的中心区域形成100nm的细小等轴晶。

The dynamic loading test of the TB6 titanium alloy hat-shaped specimen is carried out at room temperature by using a separated Hopkinson pressure bar.The microstructure characteristics in the adiabatic shear band are observed by the microstructure characterization technique.The grain instant refinement mechanism in the adiabatic shear band of TB6 titanium alloy is investigated.TEM results show that the grain instant refinement mechanism in the adiabatic shear band is the result of three mechanisms.The first mechanism is the formation of cracks and fractures as well as fine crystals due to the rapid movement,proliferation and accumulation of dislocations that lead to stress concentrations within the grains.The second mechanism is the fine grain formed by elongating the inner necking mode of the grain.The third is to promote the formation of 100nm fine equiaxed crystals in the shear band by rotating dynamic recrystallization mechanism.