Effect of Ca content in Mg melt on dealloying kinetics and microstructural evolution of Mg–Ti composites fabricated via liquid metal dealloying

Liquid metal dealloying (LMD) has emerged as an effective technique for producing Mg–Ti composites with three-dimensional bicontinuous architectures, making them suitable for lightweight structural and biomedical applications. This study systematically examines the effect of Ca addition (1, 5, and 10 wt.%) to the Mg melt on the dealloying kinetics, microstructural evolution, and mechanical properties of Mg–Ti composites, using a Ti–Cu precursor. Increasing Ca content markedly accelerates dealloying, reducing the time for complete Cu removal from 40 min (Mg–1Ca) to 20 min (Mg–10Ca). The early-stage dealloying depth and the duration of rapid dissolution increase with Ca content, indicating a sustained dissolution rate. Post-dealloying analysis reveals progressive Ca incorporation into the Mg matrix, with retained contents of 0.4 wt.% (Mg–1Ca), 1.3 wt.% (Mg–5Ca), and 3.5 wt.% (Mg–10Ca). When Ca exceeds its solubility limit, a fine Mg₂Ca intermetallic phase forms, primarily as a eutectic phase. Ca also refines the Ti matrix, reducing its average width from 2.2 µm (Mg–1Ca) to 1.9 µm (Mg–10Ca). Morphologically, low Ca levels promote fragmentation of the Ti matrix, while higher Ca facilitates partial reconnection of the matrix. These compositional and structural changes enhance mechanical performance. The Vickers hardness increases from 109 Hv (Mg–1Ca) to 117 Hv (Mg–5Ca) and 152 Hv (Mg–10Ca). Collectively, the findings confirm that Ca alloying in the Mg melt enhances both processing efficiency and composite performance by accelerating dealloying and controlling microstructural characteristics, thereby providing a versatile route for optimizing bicontinuous Mg–Ti composites fabricated via LMD.