In-Situ Tensile Testing Combined with EBSD Analysis of Ti-6Al-4V Samples from Components Fabricated by Additive Layer Manufacture

Abstract

ALM-based production of Titanium components shows great promise in supplying cost-effective products within industries such as energy, chemical processing and aerospace. In common for all is high quality demands. This necessitates extensive research into the intricacies of this production process. Complex microstructures comprised of columnar remnants of directionally solidified β-Titanium, with interior inhabited by colonies of finer α-plate structures were found in samples produced by layered plasma welding of alloy Ti-6Al-4V. Utilising the powerful characterisation tool of in-situ tensile tests combined with EBSD analysis allowed qualitative correlation between microstructural features and deformation characteristics. Non-uniform deformation occurs due to a strong variation of strain response between colonies. Prismatic and basal slip systems are active, with the prismatic systems contributing to the most severe deformation through coarse, widely spaced slip bands. Certain colonies behave as microstructural units, with easy slip transmission across the entire colony. Other colonies show significant deformation mismatch, with local build up of strain gradients and stress concentration. Segmentation occurs due to the growth morphology imposed by the columnar grains. Tensile tests perpendicular to columnar structures reveal strong deformation localization. Connections are made between the peculiarities of the production process and the observed microstructure and deformation mechanisms.