Effect of Aging Temperature on Microstructural Evolution and Mechanical Properties of a Novel β Titanium Alloy

A beta titanium alloy Ti-6Mo-5V-3Al-2Fe (wt%) was designed in terms of d-electron alloy design method. Aging treatment was performed at various temperatures ranging from 450 degrees C to 600 degrees C for 4 h to study the effect of aging temperature on microstructure evolution and tensile properties. The results show that the secondary alpha phase with smaller size and inter-particle spacing forms under omega-assisted nucleation mechanism at the aging temperature of 500 degrees C. The highest ultimate tensile strength of 1510 MPa is obtained due to the strengthening of fine acicular secondary alpha phases within beta grains, while poor elongation of 4.6% is found as a result of the inevitable precipitation of alpha phase at grain boundaries and the formation of precipitate free zone near grain boundaries. Fine secondary alpha precipitates tend to coarsen with increasing the aging temperature. Coarse alpha precipitates can bring about broad inter-particle spacing and result in less alpha/beta interfaces that act as effective dislocation barriers. The increase of aging temperature leads to the variation of tensile properties, i.e. the strength decreases while ductility changes in an opposite way. A considerable improvement of elongation to 12.2% is achieved by increasing the aging temperature to 600 degrees C, in association with the formation of parallel alpha colony near beta grain boundaries and broad inter-particle spacing of secondary a phases within beta grains.