The effect of soaking times on the mechanical properties of rapidly solidified aluminium alloys

Abstract

The microcrystalline state of rapidly solidified alloys has been investigated by many experimentalists in the past ten years. Much attention has been given to the process variables of the rapid solidification process, to the microstructural effects on the obtained powder, splat or ribbon material, and to the constitutional effects, e.g. extended solid solubility and the presence of non-equilibrium crystalline phases [1]. In more recent years the consolidation process from the basic material into a solid testing material has also been the object of general interest [2]. As a logical step in the development of this material the last part of the production process, the thermomechanical treatment, should be optimized and adapted to the different properties of rapidly solidified material. Here we present some preliminary results of the optimization of the modified heat treatment of the aluminium alloy 2024 in the T4 condition, from which it becomes clear that a considerably shorter soaking time for solution heat treatment is desirable than in the case of the same conventional alloy. Tensile properties were used as the optimization criterion. Production of test material: smooth tensile test specimens with a reduced diameter of 5 mm were made out of bars of 8.4 mm diameter 2024 alloy, that were made by melt spinning, cold compaction and hot extrusion. The melt spinning equipment consisted of an electric resistance furnace with a capacity of 13 kg aluminium alloy and a rotating copper wheel (2000 rpm) with a diameter of 300ram. The furnace was filled with commercial 2024 alloy and the molten metal was ejected through a thermally isolated siphon with an orifice of 0.8 mm diameter onto the rotating wheel by an overpressure of argon to form rapidly solidified ribbons of 80#m thick and 1.5mm wide. The ribbons were compacted at room temperature, up to