EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

The objective of this work is to improve the microstructure of the Ti-6Al-4V titanium alloy, especially during the Wire-Arc Additive Manufacturing (WAAM) using Tungsten Inert Gas (TIG) process. Indeed, WAAM processes may dramatically lower material consumption compared to conventional machining from a solid bloc. Although, the thermal gradient during solidification in additive manufacturing highly promotes large columnar grains leading to poor mechanical properties and anisotropy of the manufactured material, especially for titanium based alloys. In this case, the epitaxial solidification of the β grains layer after layer leads to centimetric grains with high aspect ratio lowering the mechanical performances and promoting the material anisotropy. First of all, the purpose of the improvement of additive manufacturing of Ti-6Al-4V alloy is to prevent the epitaxial growth of β grains in order to limit their size and reach the CET (columnar equiaxial transition). To achieve this aim, adding particles oxides which precipitate seems to be an appropriate option to increase the number of nucleation sites and/or hinder grain growth. La2O3 or Y2O3 have a great impact on Ti-6Al-4V microstructure by reducing β grain size and also hindering grain boundary migration of β grains in a first place and α plates during further thermal cycles. In order to characterize the changes related to the addition these particles, hardness testing, OM (optical microscope) and SEM (scanning electron microscope) associated with EBSD (electron back-scattering diffraction) are be used to analyze and compare the process-related preferential orientation and the impact of inoculation.