We proposed that there are two kinds of competitive processes in the hydrogenation of Mg/Cu super-laminate composites; the one in which alloying (formation of MgCu2 from Mg and Cu) occurs in advance and Mg2Cu is hydrogenated to form MgH2 and MgCu2, and the other in which Mg is hydrogenated and then MgH2 and Cu react to form MgCu2 together with H2 gas, according to a hypothesis that the reaction of MgH2+2Cu→MgCu2+H2 occurs. In order to confirm that the hypothesis is true, we investigated the conditions such as H2 pressure and temperature at which the above-mentioned reaction proceeds. Well-mixed MgH2 and Cu powder was compacted to form pellet at 1.73 GPa and then heated at various hydrogen pressures and temperatures. Experimental results at 673 K indicated that the above-mentioned reaction occurs at pressures higher than 6.5 MPa, approximately the lower limit for the hydrogenation of Mg2Cu, whereas both Mg2Cu and MgCu2 are formed at 3.3 MPa.
