Ball Milling and Consolidation Process of Al-Cr Powder Mixture-Microstructural Characterization

The interest in studying the synthesis of an Al-Cr alloy system by non-equilibria processes is due to the formation of metastable or quasicrystalline phases when rapid solidification has been utilized. Similarly, the formation of quasicrystals has been reported to a much lesser extent when the mechanical alloying technique was applied. In the present research, a mixture of powders of Cr and Al (both elements with a purity of 99.99%) with compositions of Al-5 and 7.5 at. % Cr was subjected to a ball milling process. Afterwards, the powder mixture was subjected to a consolidation process, conducted by pressing and sintering processes. The X-ray diffraction analyses revealed that during 20 h of milling there was no formation of metastable or quasicrystalline second phases detected. In addition, the X-ray diffraction peaks revealed that as milling time increased, the nanometric grain size decreased, and once the sintering treatment was applied, the crystallite size decreased following the same tendency. The dislocation density was estimated using the size of nanometric grains; this computation revealed that the dislocation density grew throughout the ball milling process; even after sintering, the multiplication of dislocations prevailed following the same tendency.