UNDERCOOLED LIQUID VISCOSITY AND GLASS-FORMATION OF A MG62CU26Y12 ALLOY

The glass forming ability of a Mg62Cu26Y12 alloy was delineated by the ories of crystallization kinetics. The viscosity of the molten Mg62Cu2 6Y12 alloy above its melting point was measured by using a rotational viscometer. The temperature dependence of the viscosity derived from t he free volume theory was extrapolated to the undercooled liquid regio n by the Fulcher-Vogel expression, i.e., eta = 5.78 x 10(-5) exp[7293. 6/(T - 255.6)] where eta is given in cP and T in K. Furthermore, the C -C-T curve was derived from the isothermal crystallization T-T-T curve which had been constructed based on the mechanism of homogeneous nucl eation and crystal growth, From such a curve, the critical cooling rat e required to form glassy state was derived to be 98 degrees C/s.