Enhancing the dealloying kinetics and microstructural control of Mg–Ti composites through Ca addition to the Mg melt

Liquid metal dealloying (LMD) is an effective method for fabricating three-dimensional bicontinuous Mg–Ti composites. However, conventional LMD using pure Mg melts is limited by the sluggish kinetics of Cu dissolution, which restricts processing efficiency. This study investigates the influence of 1 wt% Ca addition to the Mg melt on dealloying kinetics and microstructural evolution, using a Ti 30 Cu 70 (at%) precursor alloy. Short-duration dealloying trials (10 s immersion) reveal that the Ca-containing melt produces a considerably deeper dealloyed region (∼262 μm) than the Ca-free melt (∼168 μm), indicating enhanced Cu dissolution. Morphological observations reveal that Ca addition transforms the interfacial structure from a linear, lamellar TiCu ligament to a blob-like, fragmented morphology, driven by interfacial instability associated with the increased Cu flux. The final Mg–Ti composite obtained from the Mg–1Ca melt exhibits a higher Mg matrix fraction (53 %), narrower Ti matrix width (1.6 μm), and reduced internal connectivity compared to the Ca-free counterpart (45 %, 2.4 μm). Moreover, Ca addition induces substantial grain refinement in the Mg matrix (from >92 μm to 10–30 μm) and suppresses deformation twinning in the Ti matrix, resulting in an increased effective Ti grain size (from 2.1 μm to 3.2 μm). These changes are attributed to altered phase separation kinetics and interfacial stress distributions arising from the modified chemical potential landscape introduced by Ca. This study demonstrates that minor Ca addition in the Mg melt enhances the thermodynamic driving force for dealloying, thereby reducing LMD completion time and enabling microstructural control of Mg–Ti composites.