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Zn-22Al-2Cu Alloy Phase Transformations at Different Homogenizing Temperatures
Héctor Javier Dorantes-Rosales,Víctor Manuel López-Hirata,Ramón Esquivel-González,Jorge Luis González-Velazquez,Joel Moreno-Palmerin,Antonio Torres-Castillo 대한금속·재료학회 2012 METALS AND MATERIALS International Vol.18 No.3
The effect of the homogenizing temperature on phase transformations and hardening behavior was studied in a Zn-22Al-2Cu (wt%) alloy homogenized for 7 days at 315, 350, and 390°C. The homogenized alloy was subsequently quenched and aged naturally at room temperature or artificially at 200°C for different time periods. The β phase was unstable at room temperature and it decomposed through the β→α+ηreaction during natural aging. An increase in the homogenizing temperature caused a decrease in the kinet-ics of the decomposition of the β phase in the alloy. Natural aging also caused an increase in the hardness due to the formation of nanometric grains with α and η phases and the presence of an intermetallic εphase. This result agrees with the time exponents (n) between 1.5 and 2.6, which were obtained using the Johnson-Mehl-Avrami-Kolmogorov equation for the decomposition of the β phase. The transformed frac-tion curves exhibited the fastest and slowest growth kinetics of the â phase decomposition at homogeniz-ing temperatures of 350 and 390°C, respectively. The artificial aging induced the formation of equilibrium phases and began a decrease in hardness due to the coarsening process of the equilibrium α, η, and τ'phases.