Ultrasonic Energy Field-Induced Recrystallization-Driven Grain Refinement and Mechanical Property Enhancement in Ti5321G Alloy Manufactured via Laser Melting Deposition

The influence of the ultrasonic energy field (UEF) on the microstructure and mechanical properties of Ti5321G alloy fabricated by laser melting deposition (LMD) was systematically investigated. The application of UEF promotes the transformation of coarse columnar grains into fine and uniform equiaxed grains, reducing the average grain size from 400.3 μm to 145.2 μm, a reduction of 63.7%. Concurrently, the proportion of high-angle grain boundaries increases, and the crystallographic texture is significantly weakened, with the maximum MUD value decreasing by approximately 51.8%. EBSD analysis reveals that the recrystallization fraction substantially increases from 5.3% to 28.1% upon UEF application. As a result, the yield strength, ultimate tensile strength, and total elongation are improved by 6.2%, 5.2%, and 33.8%, respectively. These property enhancements are mainly ascribed to grain-boundary strengthening from grain refinement and improved strain coordination ability of the equiaxed grain structure. The findings demonstrate that UEF-assisted LMD is an effective approach for achieving simultaneous enhancement of strength and ductility in titanium alloy components.