Mechanical behavior assessment of the Ti6Al4V alloy obtained by additive manufacturing towards aeronautical industry

Abstract

Nowadays the dynamics of markets, technology advances, and companies’ competition have brought changes in metal processing. Recent technical improvements of additive manufacturing (AM) processes have shifted their application from prototyping to the production of end-use parts either as customised or series. The extended geometric flexibility, coupled with the reduced time of production and the improved efficiency in resources utilization inherent of Selective laser melting (SLM) are the characteristics sought by aircraft industry in order to develop and progress. This thesis aims to contribute to the study and analysis of the new strategy of production Selective Laser Melting in the manufacture of metallic components for aeronautical use. Specifically the mechanical characterization of the titanium alloy Ti6Al4V is performed. For this purpose several samples and specimens were manufactured in the SLM equipment at Centre for Rapid and Sustainable Product Development (CDRSP) and the mechanical tests were carried out at the Instituto Superior Técnico (IST) for further analysis of the results. SLM is an additive manufacturing technique through which components are built by selectively melting powder layers using a focused laser beam. With the proper setting of the SLM process, a relative density above the required value in the aircraft industry (above 99%) is achieved. Specifically in this work, relative densities of around 99.6% were achieved. However the process is characterized by short laser-powder interaction times and localized high heat input, which leads to steep thermal gradients, rapid solidification and fast cooling resulting in a specific microstructure. In order to obtain optimal mechanical properties, heat treatments are necessary due to the original martensitic microstructure. Moreover finishing mechanical process is required, firstly due to the need of remove the parts from the platform and secondly to decrease the surface roughness of the parts.