An Al-10 at% Mg forging alloy contains widely spaced, uniform, spherical particles of the brittle Intermetallic, ?-Al₃ Mg₂, the mean diameter of which is 15 ?m. A heat treatment is desired for homogenization of the alloy to achieve a better forging response. If the alloy is annealed at 450 C, determine the time it would take for the particles of ?-Al₃ Mg₂ to totally dissolve into the Al-Mg 19 at % matrix, given that the diffusion coefficient, D, at 450C Mg mixing with Al in this alloy is 4.5 x

10( ? 10)cm²/s. The phase diagram is below.

How would the inclusion of (isotropic) interphase boundary energy affect this time

for dissolution?