EFFECT OF HEAT OF MIXING ON FORMATION AND STABILITY OF Zr-BASE METALLIC GLASSES

The glassy alloys, Zr_(1-x)M_x (M=Fe, Co, Ni, Cu and Pd) and Cu_(67.5)Ti_(32.5), were prepared by the melt spinning technique. Their critical tangential speed of the glassy state formation was determined to be 31 m/s by means of changing the tangential speed of rotator. Their structure in a glassy state of all alloy tested has been confirmed by X-ray diffraction analysis. Their thermal behaviour was examined by differential scanning calorimetry (DSC) under different heating rates. An exothermic peak in DSC tracing was presented for glassy alloys Fe_(24)Zr_(76) and Ni_(24)Zr_(76), but two or three peaks for Co_(21)Zr_(79), Pd_(24.5)Zr_(75.5), Cu_(45)Zr_(55) and Cu_(67.5)Ti_(32.5). The activation energies for crystallization of these aUoys were evaluated by the Kissinger's method. Furthermore, the effect of heat of mixing on the formation and stability of these binary glassy alloys has been discussed after calculation used the Miedema's model.