EFFECTS OF HOT FORGING TEMPERATURE ON MICROSTRUCTURE AND MECHANICAL PROPERTY OF TG6 HIGH TEMPERATURE TITANIUM ALLOY

Near-isothermal forging experiments of the TG6 titanium alloy have been conducted at the deformation temperatures ranging from 850 to 1075 degrees C with a constant strain rate and deformation degree. The primary alpha phase content in the alloy after solution, deformation and heat treatment, and the thickness of lamellar alpha phase in the alloy after heat treatment were measured by OM and image analyzer. The results show that compared to solution state, both forging and forging + heat treatment cause the decrease or increase of primary alpha phase content when forging temperatures are below or over 1000 degrees C The thickness of the lamellar alpha phase increases with the increase of forging temperature, which is caused by the decrease of nucleation density of secondary alpha phase The beta phase grains are so big when the forging temperature is 1075 degrees C while their microstructures are non-uniform The room temperature and 600 degrees C tensile properties; impact property and fracture toughness of TG6 alloy have also been measured. It is found that the tensile strength of the TG6 alloy is not very sensitive to forging temperature The plasticity decreases but the fracture toughness increases with the increase of forging temperature. There is no obvious change in the impact toughness when forging in the alpha and beta double phase field, however it decreases when forging temperature is near the beta transformation temperature. The change in mechanical property was explained by SEM, TEM and OM experiments