Predeformation Effects on Shear Response and Microstructure in Pure Titanium -TA2

摘要

Adiabatic shear properties of pure titanium-TA2 have been investigated using specially designed specimen in a Hopkinson pressure bar at high strain rate of 10~3s~(-1). Microstructural characteristics was investigated using scanning electrion microscopy as well as transmission and high resolution transmission electrion microscopy .The results showed that the shear stress and adiabatic sensitivity for rolled 45% TA2 are higher than forged TA2. Comparing the adiabatic shear bands (ASB) both in the forged and rolled TA2, no evidence in morphology alteration was found except to shear band widths. The transmission electron micrograph of the ASB in forged and rolled TA2 showed the grain size reduction from～20μm to 200nm. No deformation twins have been observed in ASB. The selected area electron diffraction patterns of the ASB showed reflections of multiple grains, forming discontinuous rings which can be indexed as h.c.p. structure of α-Ti. This indicates that the ASB consists of fine grains of α-Ti and the α-Ti→ β-Ti transformation did not occur.