Quasi-Static Mechanical Properties of Post-Processed Laser Powder Bed Fusion Ti6Al4V(ELI) Parts under Compressive Loading

Abstract

The Ti6Al4V structures in aircraft and biomedical industries are usually exposed to quasi-static loads. Therefore, understanding the quasi-static behaviour of this alloy manufactured by an additive manufacturing process is paramount. This paper documents an investigation of the quasi-static mechanical properties of various microstructures of heat-treated Ti6Al4V(ELI) parts manufactured by laser powder bed fusion (LPBF). The effects of different quasi-static strain rates on different microstructures of these samples and their strain hardening are also presented. The test samples were produced using an EOSINT M280 direct metal laser sintering (DMLS) machine and, thereafter, subdivided into three major groups, namely samples C, D and E, for high-temperature annealing at different heat treatment strategies. A universal hydraulic testing machine (UTM) was used to carry out tests at strain rates of 0.001 s−1, 0.005 s−1 and 0.1 s−1. The three forms of LPBF Ti6Al4V(ELI) were found to be sensitive to quasi-static strain rate, whereby values of yield and flow stresses in each form of alloy increased with increasing strain rate. The order of the strength at each strain rate from the highest to the lowest was found to be samples C, D and E. The effects of strain rate on flow hardening were found to be significant in samples C and insignificant in samples D and E.