The effect of Sn addition on the crystallization and thermal stability of Cu–Zr–Ti metallic glasses

Abstract

This paper describes the effect of Sn addition on the thermal and structural behaviour of (Cu60Zr25Ti15)100−xSnx (x=0, 1, 2, 3 and 4) alloys. Expansion of the amorphous phase causing larger inter-atomic distances is observed with increasing Sn content. The glass transition temperature (Tg) and the onset of the first crystallization temperature (Tx) shifts to higher temperatures for alloys with increased Sn content. These, together with the increase in the activation energy of the 1st crystallization peak obtained from Kissinger analysis indicate the enhanced thermal stability of the alloys with increasing Sn content. Sn addition also widened super cooled liquid region of the alloys. TEM and XRD studies show nucleation of nano crystals associated with the first exothermic events. The size of the nano crystals increased from 6 to 20nm when the Sn content varied from 0 to 4at.%. A plausible explanation is invoked for the increase in the size of nano crystals with increase in Sn content. Irrespective of the Sn content all the alloys transform to Cu51Zr14 crystalline phase after the second exothermic peak.Glass transition temperature of the alloys varies with heating rate following Lasocka’s relationship; using the relationship, the theoretical limits of the low temperature range of the glass transformation region, i.e. for the heating rate β=1, of these alloys are also estimated.