Creep properties and effect factors of hot continuous rolled Ti–6Al–4V alloy

By means of heat treatment, measurement of creep properties and contract analysis of dislocations configuration, creep behaviors and effect factors of hot continuous rolled (HCR) Ti–6Al–4V alloy are investigated. Results show that, the microstructure of HCR alloy after solution treatment at temperature lower than β phase transus point consists of the super-saturation equiaxial α phase and “basket weave” structure. The quantity of “basket weave” structure increases with solution temperature, and the fully “basket weave” structure may be obtained after solution treatment at 1000 °C. Compared to the alloy solution treated at 940 °C, the alloy treated at 1000 °C has lower strain rate and longer creep lifetime under the conditions of applied stress of 575 MPa at 420 °C. In the range of the applied stress and temperature, the creep activation energy of the alloy is calculated to be Qa = 249.8 kJ/mol. Deformation mechanism of HCR alloy during creep is double orientations slips of dislocations activated within α phase with HCP structure, while deformation feature of the alloy solution treated at 940 °C is the wave-like 〈a + c〉 dislocations activated on the pyramidal planes in the α phase. Solution treated at 1000 °C, deformation mechanism of the alloy is that the multiple slips of (1/2)〈1 1 1〉 dislocations are activated within β phase with BCC structure, in which V-rich β phase with high volume fraction may enhance creep resistance, which is thought to be the main reason of the alloy possessing the low strain rate and longer creep lifetime.