Composition range and hydrogen-induced decomposition of Ca4Al3Mg

The effect of composition on the structural stability of Ca4Al3Mg has been studied. It was found that the Ca4Al3Mg structure stabilizes in a narrow composition range. In the Ca4Al4−xMgx alloys, the single Ca4Al3Mg phase exists in an approximate composition range from x = 0.8 to 1.2. Further decreasing x to 0.5, the alloy contains two phases Ca4Al3Mg and Ca13Al14. Increasing x to 1.5, however, the alloy consists of Ca4Al3Mg, CaMg2 and Ca. The effect of temperature on the structural stability of Ca4Al3Mg under hydrogen atmosphere has also been investigated. The ternary compound Ca4Al3Mg can react with hydrogen to form CaH2 and Al starting at about 373 K. The Mg atoms dissolve in CaH2 and Al after the hydrogen-induced decomposition of Ca4Al3Mg.