In-house processing and characterisation of bioresorbable Mg-Sr / Ca alloy Powders: The effects of powder size / morphology and composition on densification

• Liquid content plays a more dominant role than powder characteristics in pore closure. • Powder morphology and size control densification via solid-state sintering. • Higher Ca content enhances Mg sinterability by facilitating liquid formation. • α-Mg enriched in Ca causes localised melting, increasing liquid densification. • Ca lowers the liquidus temperature of liquid-forming phase during sintering Low-temperature additive manufacturing (AM) technologies can reduce the safety risks of magnesium (Mg) alloys for producing patient-specific bioresorbable bone implants, however, the sinterability of Mg-based alloys, which control the resultant properties, is ambiguous. The characteristics of Mg-based powder feedstock are critical for the densification of the low-temperature AM fabricated parts through the sintering process. In this study, we have processed and characterised Mg-based powder in-house using cryo-milling of Mg turnings obtained from castings. The effects of size / morphology of in-house processed Mg-Sr / Ca-based powder on sinterability were investigated using Powder Metallurgy (PM). It was determined that the highest densification (i.e., 98.15 %) was achieved by using the lowest Sr / Ca ratio with a narrow solidification range (∼ 4 °C). Broader particle size distribution also enhanced green part compaction. The role of liquid-phase sintering (LPS) process on the densification was also analysed by changing Sr / Ca ratio in the powder mixture.