Enabling alloy screening via multi-material printing using a production PBF-LB machine

The development of novel functional alloys is often constrained by the onerous and costly discovery to validation process. Herein, we present a set-up to enable multi-material production of specimens through in-situ alloy formation using a production laser-based powder bed fusion (PBF-LB) printer. Multi-material samples were achieved through the combined use of a reduced build volume unit, to minimise material requirements (~ 16% powder volume of full build volume), and custom spacers to screen a Ti-Cu biomedical alloy design space allowing for identification of performance thresholds. Multi-material specimens were designed from 0 to 20 wt% Cu in 5% increments and rapidly assessed using high-throughput methods for mechanical and biological properties. Specifically, microhardness and non-destructive ultrasound analysis showcased a significant enhancement in hardness, from 199.24 ± 5.97 to 428.53 ± 26.75 HV, and reduction in longitudinal modulus, from 166.59 ± 4.95 to 148.37 ± 7.54 GPa, as copper content increased. Simultaneously, confocal imaging of pre-osteoblasts (MC3T3s), mesenchymal stem cells (hMSCs), and gram-positive Staphylococcus aureus bacterium after 24 h of contact, suggested 10% Cu as the breakpoint to maintain cytocompatibility and antimicrobial efficacy. Designed Ti-10Cu was identified as the region of interest for further alloy refinement, demonstrating the ability of this screening system to narrow down a material design space according to critical functional properties. This proof-of-concept study presents a feasible alloy discovery tool that utilises a production PBF-LB system without any machine modification.