The effect of powder recycling on the mechanical properties and microstructure of electron beam melted Ti-6Al-4 V specimens

Additive manufacturing (AM), also called 3D-printing, is an innovative technology, as the printing of objects is performed by layer-by-layer deposition. A wide variety of materials can be used to produce a variety of shapes that cannot be achieved using any other technology. AM started as a prototyping in plastics, and now it is successfully implemented with metals. AM in metals, first of all, in Titanium alloys, offers the potential to not only generate net-shape, complex geometrical and light-weight objects, but also to achieve enhanced mechanical properties, even better than achieved by traditional mass production, like casting. However, the priority of achieving good non-porous microstructure and the desired mechanical properties is a challenge for the main fields of applications of Titanium AM, such as the aerospace industry and production of medical implants. Thus, the quality of the powder and standardization of the AM process are the top priority. The potential recycling of the Ti-6Al-4 V powder as an inextricable part of the AM process needs to be explored. The influence of powder recycling on Ti-6Al-4 V additive manufacturing, the correct number of cycles, the requirements of the recycling procedures, and possible post processing procedures – are still open questions. This research aims to answer these questions. Two identical test cylinder sets were printed, one from recycled powder and one from the new powder batch. The cylinders were printed by the Arcam EBM A2X machine using a start platform of 210 x 210 mm in size. Electron Beam Melting (EBM) is a well-known effective manufacturing process. This AM technology utilizes high power electron beam to produce layer-by-layer metal parts for various applications, such as fabrication of biomedical implants and aerospace components. The microstructure and mechanical properties of the printed specimens from the two sets (new and recycled Ti-6Al-4 V powder) were investigated before and after heat treatment.