Microstructure and surface analysis of friction stir processed Ti-6Al-4V plates manufactured by electron beam melting

In this paper, the feasibility and capability of friction stir processing to enhance material structure and surface properties of additively manufactured Ti6Al4V plates is investigated. The base material was produced by electron beam melting process and then friction stir processed using a pin less tool to compensate the provides poor surface finishing, reduced mechanical properties and internal porosity defects affecting the outer layer. A reduction by 80% of surface roughness was achieved. Internal porosity decreased as well. Microstructural analysis evidenced that the heating and stirring effects promoted the formation of distinct metallurgical zones, namely a stirred zone (SZ), a transition zone (TZ) and a heat affected zone (HAZ). The SZ exhibits a fully recrystallized microstructure, whereas highly deformed but not recrystallized grains and coarser grains were detected in the TZ and HAZ, respectively. Within the treated zone the hardness increased up to 450 HV with respect to 380 HV of the base material.