Mechanical alloying of the Pd-Si system in controlled conditions of energy transfer

The conditions of milling are of crucial importance in determining the kind of solid state reaction that can take place, among various possible paths, in a given system submitted to the mechanical alloying (MA) process. A model correlating the energy transfer during milling with the experimental parameters (rotation speed, mass and diameter of the balls) has been verified with the Pd-Si system. The composition Pd₈₀Si₂₀ has been milled, starting from pure elemental powders, in different milling conditions and the MA process followed by X-ray and differential scanning calorimetry measurements. It has been found that for high levels of energy transfer the system evolves towards the formation of the intermetallic Pd₃Si. At lower levels of energy transfer, formation of a stable intermetallic phase is hindered and the reaction product is a fully amorphous phase. The amorphous structure of the MA sample has been compared with an amorphous melt-spun ribbon of the same composition.