Solubilities of Nickel, Iron, and Chromium in Liquid Magnesium in the Presence of Austenitic Stainless Steel

Steel containers and instruments are used to hold and transport Mg melts. Thus, quantitative analysis of the dissolution of metallic elements from the steel materials into the liquid Mg is important for controlling the impurities in processes such as Mg alloy production and Ti smelting. When austenitic stainless steels containing Cr and Ni come in contact with a Mg or Mg alloy melt, a large amount of Ni and limited amounts of Fe and Cr dissolve into the melt. In this study, the composition of a Mg-Ni-based melt in equilibrium with SUS316 was investigated to determine the maximum amounts of impurities dissolved from SUS316 into the liquid Mg. Mg-Ni melts of different compositions were held in a closed crucible of SUS316 at 1073 K (800 °C) to 1273 K (1000 °C), and the compositions of the inner wall of the crucible and the Mg-Ni alloy were evaluated after quenching. Subsequently, the relationships between the solubility limit of element i (i: Ni, Fe, and Cr) in liquid Mg with the coexistence of SUS316, Csol,i∗ (mass pct), and the temperature, T (K), were determined: log(Csol,Ni∗)=-1.40×103/T+2.57(±0.12),log(Csol,Fe∗)=-5.20×103/T+3.93(±0.16),andlog(Csol,Cr∗)=-5.96×103/T+3.80(±0.05). These solubility limits were compared with those estimated based on the available thermodynamic data for the SUS316 and Mg-i binary systems. The validity of the obtained data and the reliability of the previously reported thermodynamic data were also discussed.