Thermal stability of the αZn-Mg₂Zn₁₁ and αZn-βAl eutectics obtained by Bridgman growth

The thermal stability of rod-like αZn-Mg₂Zn₁₁ and lamellar αZn-βAl eutectics obtained by Bridgman growth of Zn-3.1 wt% Mg and Zn-5 wt% Al has been studied for soaking times up to 10 h at 300 and 350°C, respectively. Two-dimensional coarsening resulted for αZn-Mg₂Zn₁₁ grown at 0.5 and 1 mm s^-1 while fault migration was operative for lamellar αZn-βAl grown at 0.1 and 1 mm s^-1. Hardness decreased with increased soaking time according to a Hall Petch relationship with mean interphase spacing and the values H₀ and k_Y accord well with the values obtained from the Hall Petch relationship for H_V of as-solidified αZn-Mg₂Zn₁₁ and αZn-βAl with eutectic interphase spacing, respectively.