Effect of ECAP processing on microstructure and mechanical behaviour of Ti-6Al-4V manufactured by directed energy deposition

Additive manufacturing (AM) is an innovative technology allowing faster and cheaper production of complex -shaped parts in comparison to conventional methods. On the other hand, equal channel angular pressing (ECAP), belonging to severe plastic deformation (SPD) methods, induces large amounts of strain and dislocations to the material, which cause its strengthening and densification. In this study, the unique combination of directed energy deposition (DED) and four-pass ECAP processing was investigated. The experimental material is DED-processed titanium alloy Ti-6Al-4 V in as-deposited and ECAP-ed states. The material in both states was sub-jected to microstructure investigation using light (LM) and scanning electron microscopy (SEM) with electron backscattered diffraction (EBSD), porosity and hardness measurement and mechanical testing, which included evaluation of tensile properties. The fracture surfaces of the specimens after testing were observed using SEM. The ECAP processing led to significant deformation of original grains and refinement of microstructure. In the case of ECAP-processed specimens, a significant improvement of mechanical properties in terms of strength and elongation was observed.

Automated summary

Additive manufacturing (AM) allows faster and cheaper production of complex-shaped parts. Equal channel angular pressing (ECAP) induces strain and dislocations, leading to material strengthening. This study investigates the combination of directed energy deposition (DED) and ECAP processing on titanium alloy Ti-6Al-4V. The ECAP-processed specimens show significant improvement in mechanical properties.