Influence of the microstructure on the interreaction of Al/Ni investigated by tomographic atom probe

In order to obtain a detailed understanding of the different stages of interreaction, tomographic atom probe (TAP) investigations were performed on Al/Ni-interreaction couples in the as-prepared state, and on couples annealed at various temperatures. To investigate the influence of the microstructure on the early interreaction stages, specimens were prepared by in situ electron beam evaporation and by sputter deposition, for comparision. Because of the outstanding resolution of the TAP, the formation of a metastable phase prior to the formation of the first intermetallic phase predicted for the equilibrium phase diagram of the Binary system AlNi was directly proved by chemical analysis. The observation of grain boundary penetration of Ni solute into Al in sputter deposited layers shows that the microstructure of the specimens is a very important factor in the initial phase formation during the early interreaction stages.