Simultaneous Densification and Improvement of Cold Spray Additively Manufactured Ti-6Al-4V Properties via Electro Plastic Treatment

Abstract

Abstract Large-scale industrial application of additively manufactured (AM) components in general, and specifically cold sprayed additive manufactured (CSAM), is limited due to the nature of this technology and the resulting product’s porosity and embrittlement. To improve the final properties of additive manufactured material, many lengthy, complex, or expensive post-treatments have been proposed. Reducing the environmental impact, cost and time required for additive manufacturing will allow for greater use in industrial applications. A novel thermomechanical treatment known as in-situ electro-plastic treatment (ISEPT) is used in this study to treat CSAM Ti-6Al-4V alloy known as grade 5 titanium. The Ti-6Al-4V alloy has approximately three times the strength and hardness of Commercial Purity Titanium (CP-Ti) with lower ductility and a dual-phase (α + β) microstructure that poses challenges during for the CSAM process. Compared to CP-Ti, the results showed that CSAM Ti-6Al-4V presented double the porosity and triple the number of ISEPT passes that presented ~ 2 µm ultra-fine grain microstructure. The ultrafine structures strength of the ISEPT material was superior to that of CSAM Ti-6Al-4V. The ISEPT passes consolidated the CSAM (α + β) dual-phase Ti-6Al-4V and allowed for nucleation of equiaxed grains at the vicinity of former CSAM splats boundaries. Formation of lamellar colonies within the splat’s inner regions was observed. The role of ISEPT conditions on rapid elimination of porosity and evolution of cold spray splat boundaries via dynamic recrystallization of Ti-6Al-4V were discussed.