On the Precipitation Process in Aluminium-Zinc-Magnesium Alloys

Part I. Al–Al₂Zn₃Mg₃ System

抄録

When aluminium rich Al–Zn–Mg alloy containing 8 weight per cent zinc and 4 weight per cent magnesium is quenched from 450°C to the room temperature, a supersaturated solid solution is obtained, the breakdown of which on subsequent annealing at various temperatures has been studied by means of calorimetric and electrical resistance measurements and of X-ray photographs. The existing data have been incorporated with our new data to build up a more clear perspective as to the mechanism of precipitation. The existence of two separate processes has been confirmed, that is, the “Low Temperature-Aging” which is a stage of the formation of the Guinier-Preston zone and the “High Temperature-Aging” which involves the formation of the coherent precipitate and its transformation to the incoherent precipitate. This precipitation sequence is similar to those in the Al–Cu as well as in the Al–Ag binary alloys.