Dynamic Compressive Deformation Behavior of Two Damage Tolerance Titanium Alloys at High Strain Rates

Dynamic compression experiments on the two damage tolerance titanium alloys of TC4-DT and TC21 were carried out at strain rates from 1 000 s-1 to 8 000 s-1 by the split Hopkinson pressure bar method respectively, and then the fracture morphology and microstructures were investigated by scanning electron microscopy and optical microscopy. The results show that the two titanium alloys have exhibited a strengthening and plasticity-increasing effect induced by strain rates, and the flow stresses of TC21 titanium alloy were higher than those of TC4-DT titanium alloy at the same strain rate. The two titanium alloys both showed a shear failure characterized by the alternative distribution of dimple area and smooth area at the fracture surface. At the same strain rate, the number of dimples in TC4-DT titanium alloy was more and the elongation was greater than those in TC21 titanium alloy. The adiabatic shear bands were not observed in TC21 titanium alloy but observed clearly in TC4-DT titanium alloy. With the increase of strain rates, the width of the adiabatic shear bands increased, and accompanied by the crack initiation, propagation and polymerization along the direction of the adiabatic shear bands.