On the stability and crystallisation of bulk amorphous Mg-Cu-Y-Al alloys

Amorphous (Mg1-yAly)(60)Cu30Y10 alloys (with y between 0 and 7 at.%) have been prepared by casting the melt into a Cu mold. Differential scanning calorimetry is used to determine the crystallisation and the glass transition temperatures as functions of sample composition and heating rates. The supercooled liquid region (DeltaT = T-x - T-g) is found to become smaller with substitution of Mg with Al. The glass forming ability is also found to decrease with the addition of Al. The dependence of the crystallisation and glass transition temperatures are fitted to a Kissinger or a Vogel-Fulcher-Tammann type of expression. Combined with the cooling history of the samples the critical cooling rate is deduced to be 70 +/- 20 Ks(-1). (C) 2001 Elsevier Science B.V. All rights reserved.