High Efficient Recovery of Pure Aluminum from Al–Sn and Al–Ni Alloys by Rheorefining Process

Abstract

An investigation was made on the rheorefining process of Al-Sn and Al-Ni alloys in order to reproduce efficiently high-purity metallic materials. The load applied to the Al-Ni and Al-Sn alloy ingots during rheorefining increased rapidly and subsequently changed with repeating of its alternate increase and decrease like a sawtooth. The height of the ingot during the rheorefining reduced with increasing load and reduced slightly with decreasing load. The chemical composition of an initial composition Al-50%Sn alloy ingot rheorefined by pressurizing the ingot for 72 ks at a plunger speed of 2.8 x 10 -4 mm/s was 98% Al and less than 0.01% Sn. Thus, a large amount of tin could be almost completely removed from the alloy ingot, although a small amount of eutectic was formed by chemical reaction with the steel filter. In the rheorefining by pressurizing Al-Ni alloy ingots for 72 ks at a plunger speed of 2.8 x10 -4 mm/s, the nickel in the alloy ingots with initial compositions of Al-2%Ni, Al-1%Ni, Al-0.5%Ni and Al-0.2%Ni was also removed effectively. It was known in the rheorefined Al-Ni alloy ingot with the initial content of 0.5%Ni that the amount of exuded filtrate increased and the nickel content decreased with an increase in isothermal rheorefining temperature. It was observed in the microstructure of the rheorefined Al-Ni alloys having initial contents of 0.2 to 2 mass%Ni that the fraction of eutectic decreased with a decrease in initial nickel content of the alloy ingots. It was found that the slow rheorefining for 72 ks at a plunger speed of 2.8 x 10 -4 mm/s was superior to the fast rheorefining for 7.2 ks at a plunger speed of 2.8 x 10 -9 mm/s in order to remove impurities from the Al-Sn alloy ingot.