Calorimetric study of solid-state amorphization reaction of rod-milled Al xTa 1- x alloy powders

Abstract

In the present study, Al x Ta 1- x ( x=0.67, 0.50 and 0.33) alloy powders have been prepared by mechanical alloying (MA) from pure powders of aluminium and tantalum using the rod-milling technique. Depending on the MA time and the aluminium content ( x), various thermal properties of amorphization and crystallization are observed. The results can be summarized as follows: (1) At the intermediate stage of milling, heating the alloy powders to 700 K leads to the formation of an amorphous phase by the solid-state reaction. (2) The amorphization process occurs slowly in Al-rich alloy powders ( x=0.67); however, in Ta-rich alloy powders, the amorphization process is fast. (3) The stability of the amorphous alloy powders presented by the crystallization temperature, T x , increases as the aluminium content decreases. (4) The plot of the amorphous volume fraction vs. the MA time proves that the rate of the amorphization depends on one factor, i.e. the tantalum content in the alloy powders. It shows clearly that the rate of amorphization increases as this factor increases.