EMS 164- Homework 6 Solutions Problems 3.12, 3.13 and 3.20 in textbook. Q1. Assume a thin Mg layer has to be deposited on an Al substrate. Is it possible to develop a coherent interface? Explain. A coherent interface arises when two crystals match perfectly at the interface plane so that the two lattices are continuous across the interface. This can only be achieved if the crystals are oriented relative to each other in a specific way so that interfacial plane has the same atomic configuration in both phases. Al is fcc, Mg is hcp. These two crystal structures may have a common (matching) plane which is the (111) in fcc and (0001) in hcp. The common direction is  in fcc and  in hcp. Q2. Similar to Problem 3.11 in textbook, demonstrate that the Cu-rich GP zones in Al-Cu system are disc shaped. The zone misfit is defined as: δ= aβ-aα/ aα where the precipitate is the β phase. When |δ|<%5, strain energy effects are less important than the interfacial energy effects. In this
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