动态塑性变形纯钛的绝热剪切带研究

Study on Adiabatic Shear Band in Pure Titanium Subjected to Dynamic Plastic Deformation

利用动态塑性变形(DPD)技术对纯钛圆柱样品进行动态压缩试验,研究了高应变下出现的绝热剪切带(ASB)及两侧过渡区的显微组织和硬度分布。结果发现:ASB仅出现在动态压缩应变大于等于0.6的DPD样品中,在准静态压缩对比试验中未出现,表明其受应变速率和应变两者共同影响。剪切带内部硬度略低于基体,而过渡区硬度明显低于基体。通过Zerilli-Armstrong本构模型和热扩散距离计算分析表明,计算的过渡区与绝热温升热影响区宽度与试验结果基本相符,初始晶粒动态再结晶形成等轴晶组织并引起组织软化。

The cylindrical pure Ti specimens were compressed by dynamic plastic deformation （DPD）. The microstructure and microhardness of adiabatic shear bands （ASB） and transitional zones were investigated at high strains. The results show that ASBs are only found in DPD samples at high strains （ε≥0.6）, but not found in low-strain or quasi-static compression samples. These suggest that the ASBs are affected by both strain rate and strain. The hardness of ASBs is slightly lower than that of the matrix; however, the hardness of transitional zones is obviously lower than that of the matrix. These results are researched by Zerilli-Armstrong constitutive model and heat diffuse equation. The computational widths of the heat-affected zone and the transitional zone are consistent with the experimental results. The formation of equiaxed grains is due to dynamic recrystallization of deformed grains. This process results in hardness reduction of the transitional zone.