Microstructural Evolution of Ti-6Al-4V Alloy During Water Quenching Under Different Processing Conditions

It is important to understand the microstructural evolution of Ti-6Al-4V alloy during water quenching under different processing parameters in order to obtain optimum mechanical properties of the alloy. The thermal simulation of Ti-6Al-4V alloy was conducted using a thermomechanical simulator. The results have shown that a fully martensitic microstructure was obtained after solution treatment. Water-quenching after solution resulted in hardness increase, and this was attributed to the presence of alpha' and alpha ''. The lamellar structure formed when the specimen was water-quenched after isothermal holding at 850 degrees C, and the hardness further increased. Colony appeared after deformation at 850 degrees C with subsequent water quenching, and the Vickers hardness HV reached the maximum value (5840 MPa) because of the grain boundary strengthening. The microstructure was composed of a phase, lamellar colonies alpha/beta and colony when the specimen was isothermally held at 600 degrees C after deformation at 850 degrees C. Cooling and isothermal holding after deformation increased the width of a phase and colony, which was in the range of 324-706 nm for equiaxed grains. This caused a decrease in hardness.