e99mtm - Engineering 45 The Structure and Properties of...

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Engineering 45 The Structure and Properties of Materials Midterm Examination April 2, 1999 Problem 1: (a) Almost all of the elements that crystallize in the hexagonal close-packed structure are metallic conductors. Why would you expect this? (b) There are at least a couple of elements that crystallize in the hexagonal close- packed structure and are electrical insulators. How can this be? (c) How is the α -ZnS structure related to the HCP? Problem 2: A binary system of atoms A and B has the complex phase diagram drawn below. Only the single-phase fields are labelled; the shaded areas are two-phase fields. (a) A possible state of the system is indicated by the dot on the left-hand side of the diagram. Give the phases present, estimate the compositions of the phases, and estimate their fractions when the system is at equilibrium in the state shown by the dot. (b) Let a liquid with the composition indicated by the vertical line on the left of the phase diagram be cooled slowly enough to preserve equilibrium. Describe the
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This note was uploaded on 04/05/2011 for the course ENGIN 45 taught by Professor Devine during the Spring '07 term at Berkeley.

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e99mtm - Engineering 45 The Structure and Properties of...

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