Post-Fatigue Residual Strength of Abrasiveless Waterjet-Treated Ti6Al4V as a Biomaterial

Ti6Al4V, a material frequently used in biomedical applications, has few reports on its post-fatigue mechanical behavior, which is essential for long-term stability. To investigate these aspects, Ti6Al4V specimens underwent abrasiveless pure waterjet treatment, followed by random spectrum fatigue and post-fatigue tensile tests. The surface microstructure and topography were characterized before and after the random spectrum fatigue tests to explain the material’s post-fatigue mechanical behavior. The results showed that the random spectrum fatigue test altered the mechanical behavior of Ti6Al4V specimens by reducing their ductility, as an indication that the random spectrum fatigue test induced the accumulation of internal defects. After two steps of random spectrum fatigue tests, the fracture surfaces of the uniaxial tensile specimens displayed a decrease in the fibrous region and an increase in the shear lip region. The analysis of surface areal roughness parameters, fractography, and average grain size as well as orientation all revealed that, for the currently selected waterjet processing parameters, the influence of waterjet is greater on the surface topography rather than on the mechanical properties. Random spectrum fatigue loading altered the surface topography, resulting in a roughened, peak-dominant profile with an increased auto-correlation length.