A variety of microstructures in Mg/Cu super-laminate composites caused by competitive reactions during hydrogenation

Abstract

A variety of microstructures in Mg/Cu super-laminate composites (SLCs) caused by competitive reactions during hydrogenation has been shown experimentally. Two types of MgCu2 structures, three-dimensional (3-D) network and layer, were observed after initial hydrogenation of Mg/Cu SLCs under the conditions of 573K, 86.4ks in H2 of 3-3MPa. It was proposed that Mg/Cu SLCs could be hydrogenated by two kinds of processes. The one is alloying Mg with Cu to form Mg2Cu followed by hydrogenation of Mg2Cu, leading to the formation of 3-D network of MgCu2. The other is hydrogenation of Mg followed by the reaction of MgH2 to Cu, leading to the formation of layer MgCu2. SEM observations revealed that there existed Mg2Cu nano-crystals at the interface between Mg and Cu in as-rolled Mg/Cu SLCs, and layer MgCu2 at the interface between MgH2 and Cu in pellets of MgH2 powder and Cu powder heated under the conditions of 673K, 86.4ks in H2 of 8.0 MPa. The existence of Mg2Cu nano-crystals enables alloying Mg with Cu at low temperatures (<473K).