Effect of Isothermal Annealing on the Microstructure and Impact Properties of TC10 Titanium Alloy

Abstract

The microstructure and impact properties of TC10 titanium alloy bar after isothermal annealing are studied by metallographic microscope, SEM and impact properties test. The results show that there were two forms of a phases in the original microstructure of TC10 titanium alloy forging bar, one was primary equiathetic a phases, the other was secondary a phases. After the alloy was annealed with isothermal temperature, the content of the equiaxed a phases in the metallographic structure decreased with the increased of temperature, and disappeared after reaching the transformation point. While the number of platelet a in the structure increased with the increased of temperature, and the size increased. The impact toughness of the alloy shows a trend that first increases and then decreases with the increase of heating temperature. When the temperature exceeded the transformation point, the impact toughness decreases significantly. With the increase of heating temperature, the fracture morphology of the alloy mainly changes from a large number of relatively deep dimples to a few relatively shallow dimples, and dissociation steps appear. After the whole investigation, it can be concluded that the best heat treatment system in this experiment was 920°C×1.5h/FC→800°C×1.5h/AC+560°C×4h/AC, and the maximum impact toughness was 49.5 J/cm2.