THE RELATION BETWEEN THE BULK AND RIBBON ZR55NI25AL20 METALLIC GLASSES

The planar-flow-casting technique and quenching in flowing water were used to produce the glassy Zr55Ni25Al20 ribbon and bulk samples. The t hermodynamic states of these two types of samples were compared using differential scanning calorimetry and analysis of the structural relax ation kinetics. The relaxation enthalpy is 3 times larger and the glas s transition temperature is higher by 67.5 K in the case of the ribbon sample. These differences were theoretically confirmed by a kinetic m odel and were caused by the different quenching rates for the ribbon a nd bulk samples, namely 10(5) and 10(2) K s(-1), respectively. X-ray a nalysis has shown, that the main difference between the studied glassy structures consists in the different degree of the short-range order in the samples. (C) 1997 Elsevier Science S.A.