Phase transformations induced by mechanical alloying of Ag-28 at.-%Al alloy

A Ag-28 at.-%Al alloy was obtained by mechanical alloying in a SPEX 8000D mill from elemental Ag and Al powders. Two vials with different internal volume and two ball powder weight ratios were used to analyse the phase evolution. Microstructural characterisation was carried out by X-ray diffraction, SEM and TEM. The sequence of phase transformation during the milling process was as follows: Ag+Al (powders)→α→α+ζ→α+ζ+μ→μ+ζ→μ. The formation of the α and ζ phases is favoured by the energy of the impacts in the early stage of milling, while the formation kinetics rate of the μ phase was faster for the higher vial volume and ball/powder weight ratio. TEM images confirm the presence of the μ phase with a nanometric grain size.