ZrTiAlV alloy grain refining under high-pressure torsion and electric field-assisted heat treatment

Abstract

To reduce grain size, shorten heat treatment time, and guarantee good comprehensive mechanical properties of ZrTiAlV alloy, we proposed a grain refining technology, which is a combination of electric field-assisted heat treatment and high-pressure torsion. And using this technology we studied ZrTiAlV alloy grain refining. The original material consists of pure phase α, which will be changed into pure phase β at temperatures exceeding 700°C during electric field-assisted heat treatment. The temperature required for the phase α of the high-pressure torsion material to be completely changed into phase β increases obviously. When the torsion pressure is 5GPa, the initial heat treatment temperature is higher than 700°C and the final heat treatment temperature reaches 800°C, only then can the phase α be completely changed into a phase β structure. When the initial heat treatment temperature is higher than 600°C, the large grains of phase β contain a large amount of sub-grain boundaries, and the sub-grains are smaller than 100μm. When the initial temperature is 700°C, the grains are completely refined and re-crystallization is quite complete. The difference in the orientation angle of the large and small grains is small, indicating continuous dynamic re-crystallization. The original material consists mainly of lath-shape phase α structure; after high-pressure torsion at 4GPa and electric field-assisted heat treatment at 800°C, the phase β structure becomes nearly pure and only a few minor α phase structures are created.