Glass-forming ability of Pr-(Cu,Ni)-Al alloys in eutectic system

Abstract

A eutectic point in Pr-rich Pr-(Cu,Ni)-Al alloys was experimentally determined by measuring the solidus temperature (Tm) and liquidus temperature (Tl). It was found that Pr68(Cu0.5Ni0.5)25Al7 (at.%) is at the eutectic composition in the pseudoternary Pr-(Cu0.5Ni0.5)-Al alloys. The alloy Pr68(Cu0.5Ni0.5)25Al7 exhibits better glass-forming ability (GFA) than the ternary eutectic alloy Pr68Cu25Al7. However, the best GFA was obtained at an off-eutectic composition (Pr54[Cu0.5Ni0.5]30Al6) in the Pr-(Cu0.5Ni0.5)-Al alloys, which can be formed in fully amorphous rods with diameter of 1.5 mm by copper mold casting. Moreover, the glass-transition temperature Tg increases quickly (from 367 to 522 K) with the increasing of the Al content (from 3 to 27 at.%). The deviation of the best GFA composition from the eutectic point [Pr68(Cu0.5Ni0.5)25Al7] was explained in terms of the asymmetric coupled eutectic zone, the competition between growth of crystalline phase and formation of amorphous, and the higher glass-transition temperature Tg on the hypereutectic side.