An Investigation of the Alloy System of Aluminium, Copper, and Zinc

Abstract

In conclusion, the present .experiments are summarized as follows: (I) L5 alloy was quenched at various temperatures, and the phenomena of ageing were observed. The influence of quenching was marked in the alloy quenched at higher temperature, and hardening was found to be marked in the alloy containing less amount of copper. Also hardening was found to take place in two steps. (2) The effect of tempering at 150°-200° C. was observed to result in softening of the alloys, but hardness and tensile strength were somewhat improved by tempering at 200°-300° C. The effect of tempering was marked in the alloy containing 3 per cent of copper than that of less content of copper. (3) Quenching was carried out of 4 series of alloys whose content of copper varied from o 7 to 4.6 per cent , and whose content of zinc varied from 4 to 20 per cent. A complicated relation was found to exist between age-hardening and composition of alloys. (4) Thermal expansion of quenched specimens were measured, and the irregular change of expansion was found not to be the direct indication of hardening due to tempering or ageing. (5) Age-hardening was considered to be due to the spontaneous crystallization of solute phase or phases in a super-cooled solid solution. As the mechanism of hardening it was also considered that the separation of the second phase or phases accompanying with the disintegration of solvent lattices gave rise to hardening on one side, and on the other, internal strain produced in crystals, owing to the rapid change of lattice construction.