Microstructural and Mechanical Analysis of High-Performance Parts Produced by Hybrid Additive Manufacturing of Powder LMD on Forged Base Components

Abstract

Ti-6Al-4V is used as a high-performance material in many industries (mainly automotive and aerospace, but also the medical industry) and traditionally produced by hot forging, with subsequent extensive post-processing and machining, leading to a material yield far from 100 % [1]. New production chains, such as additive manufacturing, enable the near net shape production of high-performance parts, however, still with long production cycles and high manufacturing costs, especially for larger parts [2]. Therefore, an efficient and feasible production is often limited to low quantities and/or small pieces. In the present study, we propose a hybrid manufacturing route, combining additive laser metal deposition (powder LMD) on hot forged base components, enhancing material efficiency, but still enabling the production of industrial quantities. Primary investigations on the microstructure and mechanical properties of the material show results similar to conventional hot forged material, but reduce the number of processing steps and increase the material yield.In more detail, the relationship between the primary beta grain size and the secondary alpha phase characteristics was investigated and moreover, related to the cooling history of the material. Furthermore, the influence of the microstructure and phase characteristics on the mechanical properties of the material was analyzed. For the determination of the primary beta grain size, the programming language MATLAB as well as its integrated open-source toolbox MTEX were used, where a GUI has been developed for the reconstruction of the primary beta grain orientations and sizes from recorded EBSD data of the secondary alpha (Ti) phase, using the Burger’s orientation relationship (BOR, [3-7]).