Effects of press down volumes on the microstructure and mechanical properties of hybrid in situ point-mode forging and laser additive manufactured Ti-6Al-4V.

[Display omitted] • Ti-6Al-4V samples were fabricated through hybrid in situ point-mode forging and laser additive manufacturing techniques. • Effects of press down volume (PDV) on microstructure evolution and mechanical properties were investigated. • The equiaxed grain sizes were decreased with the increase in the PDV. • The microstructure with fine equiaxed grains and a bimodal morphology was achieved via the PDV of 0.25 mm. The intrinsic high cooling rates and high thermal gradients of laser additive manufacturing leaded to a tendency towards columnar grains. Hybrid in situ point-mode forged and laser additive manufacturing (HFAM) was a newly-developed printing technique with the capability of full transition from columnar grains to fine equiaxed grains in the HFAM-processed samples. Press down volume (PDV) of point-mode forging, an important parameter in the HFAM technique, affected the microstructure of the HFAM-processed samples. The effects of PDVs on the microstructure and mechanical properties of the HFAM-processed Ti-6Al-4V were investigated. The HFAM-processed samples showed equiaxed grains. The grain sizes were decreased with the increase in the PDV. The higher PDV contributed to the generation of the equiaxed primary α-Ti phase. The microstructure with fine grains and a bimodal morphology was achieved via the PDV of 0.25 mm, providing excellent comprehensive mechanical properties. The tensile strength and elongation at break of 0.25 mm PDV sample were ∼20.6% and ∼115.1% higher than that of un-forged one. [ABSTRACT FROM AUTHOR]