Effect of rotationally accelerated shot peening on the microstructure and mechanical behavior of a metastable β titanium alloy

Abstract

Microstructural evolution and deformation mechanism of a metastable β alloy (Ti-10V-2Fe-3Al) processed by rotationally accelerated shot peening (RASP) were systematically investigated with optical microscopy, X-ray diffraction, electron backscatter diffraction and transmission electron microscopy. Different gradient hierarchical microstructures (gradients in α″ martensite and β phase, and hierarchical twins range from the nanoscale to microscale) can be fabricated by RASP via changing the shot peening time. The hardening behavior and tensile mechanical properties of gradient hierarchical microstructure were systematically explored. Novel deformation twinning systems of {112}α″ and {130}<310>α″ in the kinked α″ martensite were revealed during the tensile deformation. It was found that stress-induced martensitic transformation, twinned α″ martensite and the related dynamic grain refinement contribute to hardness and work hardening ability. Simultaneous improvement of strength and ductility of the metastable β titanium alloy can be achieved by introducing a gradient hierarchical microstructure.