Mechanical alloying in the CoSn system

Elemental Co and Sn powder mixtures of nominal compositions Co-15at.%Sn, Co-50at.%Sn and Co-60at.%Sn were milled for 720 ks in a conventional ball mill. Structure and phase transformations in the milled powders were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). XRD and TEM analyses showed that as-milled Co-15at.%Sn, Co-35at.%Sn and Co-50at.%Sn powder mixtures were partially amorphozed, presenting also small crystals of a nanometer order size. No partial amorphization took place in the Co-60at.%Sn mixture milled for 720 ks. DSC analyses showed that the crystallization temperature of partially amorphized alloys varied from 500 to 580 K, with an activation energy of crystallization of about 70 kJ mol^-1. These results agree well with the values determined for CoSn amorphous alloy films produced by vapor quenching.