Achieving synergistic improvement of wear and mechanical properties in Ti–6Al–4V alloy by multiple cryogenic treatment

Abstract

Ti–6Al–4V alloy was subjected to cryogenic treatment at −196 °C followed by single and multiple treatment cycles. Compression tests revealed that, despite a decrease in yield strength, cryogenically treated samples (especially by multiple cryogenic treatment) exhibited noteworthy improvements, with a 10.2% failure strain and 9.4% rise in compressive strength compared to the as-received state. The cryogenically treated samples were further refined and exhibited a reduced β-phase volume fraction, showed higher dislocation density and microstrain in X-ray diffraction results. Remarkably, the surface hardness was significantly improved by the cryogenic treatment, leading to enhanced wear resistance with lower coefficients of friction. This was attributed to the formation of smaller wear debris and a decrease in abrasive wear under sliding conditions. Electron backscatter diffraction (EBSD) findings demonstrate that the friction-induced localized deformation layers exhibit the high density of low angle grain boundaries (LAGBs) with deformation-induced sub-grains. The synergistic improvement of wear resistance and mechanical properties is ascribed to the intricate microstructural alterations induced during cryogenic treatment, particularly accentuated in multiple cryogenic treatment. These findings highlight the efficacy of cryogenic treatment in improving both mechanical and wear properties of Ti–6Al–4V alloy.