MICROSTRUCTURE EVOLUTION OF LAMINATED MAGNESIUM - INTERMETALLICS COMPOSITE

Magnesium-intermetallics laminated composites have been fabricated through reactive bonding at 490 degrees C in vacuum using magnesium sheets and copper foils. Investigations were concerned with the structural transformations of a Mg-Cu couple boundary. Holding for only a few minutes resulted in the formation of thin layers at the investigated interface. Prolongation of the heating time lead to reactions in the liquid state and completely disappearing of copper layers. Therefore, the final microstructure consisted of alternating layers of unreacted magnesium and intermetallics. The microstructure was revealed in optical and scanning electron microscopy (SEM). The study exhibited the presence of different reaction products in the diffusion zone and their chemical compositions were determined by X-ray microprobe analysis. The occurrence of two different intermetallic compounds Cu2Mg and CuMg(2)was predicted from the Cu-Mg binary phase diagram. The predominant part of the intermetallic layers was the hypoeutectic mixture of CuMg(2)and solid solution of copper in magnesium, since a liquid front of reaction was moving into the magnesium sheets. The microhardness of the reaction products and the elemental components was comparatively measured.