Effect of rapid solidification,impurity level,and further alloy additions on dissolution rate of Mg–Mn alloys in 3%NaCl solution

Abstract

Gravimetric and hydrogen evolution methods have been used to determine the effect of binary Mn and ternary Nd, Y, Ni, Cu, and Si alloy additions on the dissolution rate x of splat quenched Mg in 3%NaCl solution, using the ingot or chill cast condition as a reference condition. The results indicate that splat quenching leads to a reduction in x for Mg, Mg–Mn, and Mg–Mn–Nd, the presence of Mn resulting in a decrease in x with time of immersion to values <1 mpy (1 mpy ≍ 24 μm/year) for Mg–Mn–Nd. In marked contrast, the presence of Ni and Cu in Mg–Mn–Ni, results in high values of x, which initially increase with time of immersion, attributed to microgalvanic action between the Mg–Mn matrix and interpenetrating network of Mg₂X (X = Ni or Cu). The presence of Mn in Mg–Mn–Nd alloys gives rise to a relative insensitivity to residual Fe content for the splat quenched condition compared with the much stronger effect found previously for rapidly solidified Mg–15 wt-%Al.

MST/1823