Regulation Mechanism of Friction Stir Processing Parameters on Microstructure and Properties of Laser Metal Deposited TC4 Titanium Alloy

To enhance the microstructure and mechanical properties of TC4 titanium alloy formed by laser metal deposition (LMD), friction stir processing (FSP) was employed to modify the surface of the as‐deposited TC4 titanium alloy. This study systematically investigates the effects of FSP parameters—rotational speed (250–1050 rpm) and travel speed (50–210 mm min −1 )—on the microstructural evolution and mechanical performance of LMD‐formed TC4 titanium alloy. Results indicate that FSP effectively refines the coarse as‐deposited microstructure into uniform equiaxed grains, eliminates the internal defects such as porosity, and enhances phase homogeneity. Microhardness increased from 305.2 HV 1 (LMD) to a maximum of 345.2 HV 1 at 850 rpm and 210 mm min −1 . Grain refinement was confirmed by broadening XRD peaks and increased β‐phase content at higher rotational speeds. The β‐phase stabilizing element V increased from 3.8% to 5.0% with higher heat input, while Al content varied between 5.2% and 6.3% depending on thermal exposure. Wear resistance improved significantly: wear rate decreased from 5.9 × 10 −4 mm 3 N −1 m −1 (LMD) to 2.22 × 10 −4 mm 3 N −1 m −1 at 850 rpm and 210 mm min −1 . These findings validate that suitable FSP parameters can effectively tailor the microstructure and substantially enhance the mechanical properties of LMD‐formed TC4 alloy, offering a viable route for additive‐equivalent hybrid manufacturing.