Growth behavior of intermetallic compounds during reactive diffusion between aluminum alloy 1060 and magnesium at 573-673 K

A potential new research reactor fuel design proposes to use U-Mo fuel in a Mg matrix clad with Al. Interdiffusion between the Mg containing fuel core and Al cladding can result in the formation of intermetallic compounds that can be detrimental to fuel element performance. The kinetics of the reactive diffusion in the binary Al-Mg system was experimentally studied. Layers of the intermetallic compounds, beta (Al3Mg2) and gamma (Al12Mg17) phases, were formed between the Al alloy 1060 and Mg during annealing. The beta layer was observed to grow faster than the gamma phase. The thickness of each layer can be expressed by a power function of the annealing time with the exponent n close to 0.5 for the beta phase and less than 0.5 for the gamma phase. The results suggest that the growth of beta phase is controlled by lattice diffusion and that of the gamma phase by grain boundary and lattice diffusion. Metallographic examination showed the grain boundary diffusion in the form of columnar growth of gamma phase during annealing. Based on the reactive diffusion equation developed in this work, in the absence of irradiation effects, it will take more than 110 h to consume a half thickness of 400 mu m of the cladding. Crown Copyright (C) 2014 Published by Elsevier B.V. All rights reserved.