TA2纯钛帽型试样显微组织对绝热剪切演化过程的影响

Effect of microstructure on adiabatic shear evolution of TA2 pure titanium hat-shaped specimen

以70%轧制变形量和70%轧制变形量500℃/120 min退火处理后的TA2纯钛板为试验材料,基于帽型试样和限位环变形控制技术,在分离式霍普金森压杆装置上对试样进行动态冲击“冻结”试验,研究轧制组织和再结晶组织对绝热剪切变形过程的影响。结果表明:随剪切应变增加,轧制组织的帽型试样先在剪切区两端形成裂纹,降低了试样的承载力,随后试样发生变形局部化。再结晶组织的帽型试样由于存在作为软组织的再结晶晶粒,使试样先在剪切区两端发生变形局部化,后诱发剪切区内的变形局部化。明显的绝热温升效应出现在剪切带发展后期,促进了剪切带内形成二次再结晶。绝热温升可能不是剪切带形成的主要因素,相反剪切带的形成使试样发生应变高度局部化导致温升。

The experimental materials were TA2 pure titanium plate with 70%rolling deformation and TA2 pure titanium plate with 70%rolling deformation 500℃/120 min annealing.Dynamic impact"freezing"tests were carried out using a split Hopkinson pressure bar set up based on a hat-shaped specimen and a limit ring deformation control approach to examine the influence of rolling and recrystallization microstructure on the adiabatic shear local development process.The results show that as shear strain increases,cracks emerge at both ends of the shear area,reducing the hat-shaped specimen′s bearing capacity,followed by deformation localization.The recrystallization grains of the hat-shaped specimen with soften structure recrystallization cause deformation localization at both ends of the shear area,and then cause deformation localization in the shear area.The adiabatic temperature rise effect comes later in the development of the shear zone and promote secondary recrystallization in the shear band.Although adiabatic temperature rise may not be the primary cause of shear band formation,it does result in highly localized strain and temperature rise.