The Aging Characteristics of Magnesium-4wt% Zinc Alloy

Abstract

The aging characteristics of a magnesium-4wt% zinc alloy were studied over a temperature range of 0°∼200°C by means of electrical resistivity and hardness measurements, the X-ray Debye-Scherrer method and electron-microscopic observations. From the kinematic point of view the aging sequences were analyzed using the C-curve obtained by plotting the logarithm of the incubation time as a function of the reciprocal of the absolute aging temperature. The results showed that the aging sequences varied with the three different temperature ranges, viz., above 110°, 110°∼60°C and below 60°C. The presence of the following three stages in the aging sequences above 110°C were also confirmed by X-ray analysis and electron microscopic observations; supersaturated solid solution→pre-β′→β′→β(MgZn). The apparent activation energy calculated from the slope of the linear part of the C-curve was about 29 kcal/mol for β′ precipitates and about 24 kcal/mol for pre-β′ precipitates. The aging sequences in the temperature ranges of 110°∼60°C and below 60°C may be characterized by the formation of G. P. zones.