Effect of Zn Plating on the Sinterability and Mechanical Properties of Magnesium Powders

Displacement-plated Zn on Mg powder forms a eutectic liquid during sintering, wetting interparticle contacts, and promoting capillary densification. In simple powder mixtures (5 mass% Zn), the diffusion rate imbalance created Kirkendall voids on the Zn side, leaving pores that acted as stress concentrators and reduced the transverse rupture strength. For plated powders, the persistence of the liquid determines their final microstructure. At low Zn loadings (60 s, 4 mass%), the liquid was largely depleted during the 700 K hold (transient liquid-phase sintering), producing a nearly single-phase Mg matrix containing only discontinuous intermetallic compounds. At high Zn loadings (120 s, 14 mass%), the liquid persisted at lower temperatures. During cooling, the liquid phase formed a continuous Mg7Zn3 morphology. This leads to embrittlement of the compact and reduced bending strength. Overall, Zn coating is an effective method for improving the sinterability of Mg powders; however, controlling the Zn content is essential to avoid a continuous brittle intermetallic network and to optimize the mechanical performance.