Investigations on friction stir composite processing and picosecond laser-induced surface modification on mechanical properties of β-titanium alloy

This work introduced a new surface modification method of titanium alloy Ti-35Nb-2Ta-3Zr alloy by friction stir machining (FSP) and picosecond laser-induced surface modification (PsLSM). The results show that the properties of the alloy are the best when the picosecond laser scanning speed is 50 mm/s, the laser power is 0.5 W. Compared with the untreated, the microhardness is increased by 68.7%, Young's modulus is reduced by 40%, the friction coefficient is reduced by 81.8%, and the friction loss is reduced by 62.5%. Among them, the experimental results show that the effect of PsLSM on performance improvement is higher than that of FSP, but the performance of samples treated with FSP+PsLSM is higher than that of samples treated with PsLSM. It was found that the LIPSS formed on the sample's surface after PsLSM treatment is the main reason for the improvement of mechanical properties, and the ultra-high temperature remelting effect of FSP treatment makes the surface grains refined. This study provides a new idea and method for surface modification of β titanium alloy to improve its mechanical properties.