冷轧钛绝热剪切带演变和机理研究

Study on evolution and mechanism of adiabatic shear bands of cold rolled titanium

对冷轧条件下钛绝热剪切带形态、显微硬度、局部剪切应变和局部温度增量的演变进行了系统研究和估计,揭示了冷轧钛绝热剪切带的演化规律和机理。结果表明,冷轧变形量从50%增至83%,冷轧钛板边缘首先形成变形区,在变形区内形成与轧制方向呈40°的局部剪切带,剪切带宽约25μm。在剪切带中心观察到尺寸范围为20~160 nm的细小纳米晶粒,平均尺寸约为70 nm。显微硬度测试表明剪切带内的硬度明显高于周围基体。计算得到的剪切带内的剪切应变和最大温度增量远高于整体变形样品。局部化剪切带起源于微观结构的几何失稳而不是热扰动。

In order to study the evolution law and mechanism of titanium adiabatic localization shear band under cold rolling conditions,conclusions were drawn by exploring and analyzing the cold rolling process.Firstly,the morphology of the shear band was analyzed,followed by the microhardness,and finally the evolution of local shear strain and local temperature increment.The results show that after deformation from 50%to 83%in cold rolling,the edge of the cold rolled titanium plate first forms a deformation zone,in which a local shear band with an angle of 40°to the rolling direction is formed,and the width of the shear band is about 25μm.In the center of the shear band,there are ultrafine nanocrystals with the size of 20-160 nm and the average size of 70 nm.Through the microhardness test reslut,it can be concluded that the hardness in the center of the shear band is significantly higher than that around the matrix.The calculated shear strain and maximum temperature increment in the shear zone are much higher than that of the whole deformed sample localized shear bands originate from the geometrical instability of the microstructure rather than thermal disturbance.