Evaporation-coupled wetting of ZrO₂ by molten Mg in Ar atmosphere

Abstract

The wetting behaviors of molten Mg drops on polycrystalline ZrO₂ substrate surfaces were studied in a controlled Ar atmosphere at 948–1173 K using an improved sessile drop method. The ZrO₂ substrate is virtually not wetted by molten Mg at temperatures below 1173 K. The wetting and evaporation stages according to different variation behaviors of contact angle, contact diameter and drop height were identified. Six representative modes were proposed to describe the evaporation-coupled wetting behaviors during different stages. The competitions between surface oxidation, chemical reaction and drop evaporation were discussed to account for the mechanisms for various wetting behaviors at different temperatures. The chemical reaction leads to the formation of more wettable MgO phase at the interface; however, it yields only an inconspicuous improvement in the wetting due to enhanced Mg evaporation.