Effect of Zn addition to Mg melt on microstructural characteristics of Mg–Ti composites fabricated via liquid metal dealloying

• Effects of Zn addition to Mg melt on LMD-fabricated Mg–Ti composites were investigated. • Zn preferentially partitions into the Mg matrix, forming a supersaturated solid solution. • Increasing Zn content refines Ti-matrix width and grain size via twin-induced subdivision. • {11–22} contraction twinning in Ti is promoted by CTE-mismatch-induced residual stresses. • Vickers hardness increases by 56% at 10 wt.% Zn due to combined strengthening mechanisms. This study investigates the effect of Zn addition (1, 5, and 10 wt.%) to the Mg melt on the microstructure and mechanical properties of Mg–Ti composites fabricated via liquid metal dealloying (LMD). The addition of Zn effectively refines the Ti matrix while preserving the characteristic three-dimensional bicontinuous structure of dealloyed composites. Quantitative analysis shows that increasing Zn content reduces the Ti matrix width and effective grain size by up to 18% and 44%, respectively. Microstructural observations further reveal the formation of lamellar {11–22} contraction twins within the Ti matrix, with twin density increasing proportionally with Zn addition in the absence of external mechanical loading. As a result, the Vickers hardness increases monotonically from 130 HV in the Zn-free composite to 203 HV in the Mg–10Zn composite, corresponding to a 56% improvement. These results demonstrate that Zn alloying of the Mg melt is an effective strategy for enhancing the mechanical performance of bicontinuous Mg–Ti composites produced by LMD.