Laser Powder Bed Fusion of Titanium Matrix Composites

Abstract

Laser powder bed fusion (L-PBF) is an additive manufacturing (AM) process in which an object is manufactured in a layer-by-layer manner from a batch of loose powder using a mobile laser beam as the heat source. Due to the layer-wise nature of the L-PBF process, it is capable of producing objects with complex shapes and unique geometries in bulk, porous, or cellular forms with potential applications in various industries, including aerospace, biomedical, and automotive, among others. The AM technology has recently attracted a great deal of attention in fabricating metal matrix composite (MMC) components with improved mechanical and functional properties than the non-reinforced metallic counterparts. However, full implementation of this promising technology in manufacturing high-quality MMCs is rather challenging in many aspects, such as preparing the starting material, obtaining defect-free parts, and finding suitable post-processing treatments. This research deals with the fabrication of high-performance titanium matrix composites (TMCs) by L-PBF processing of the B4C/Ti-6Al-4V(Ti64) composite powders. Results revealed that almost fully dense TMC samples could be achieved by optimizing the process variables. To tailor the mechanical properties of the fabricated TMCs, various heat treatment cycles were employed for both TMC and monolithic Ti64 parts. The microstructures of the as-built and heat-treated TMC and Ti64 samples were thoroughly examined and correlated to the microhardness, nanohardness, wear, scratch, compression, and short-term creep properties. In addition, the strengthening mechanisms were investigated, and each mechanism's contribution to the compressive yield strengths was identified. Results revealed that the optimum heat treatment cycle for the fabricated TMC samples differs from that of the Ti64 alloy.