eo0mtm - A B x a º L T(a Label the two-phase fields in the...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Engineering 45 The Structure and Properties of Materials Midterm Exam March 13, 2000 Problem 1: (a) Describe the ß-ZnS structure and show how it is related to the FCC structure. (b) The ß-ZnS structure is adopted by many covalently bonded compounds, like GaAs. Why would this structure be favored? [Ga has valence 3, As has valence 5.] (c) The ß-ZnS structure is also adopted by some ionic compounds, like AgI, while substitutionally ordered FCC structures, like Cu 3 Au are not. Why is ß-ZnS a suitable ionic structure while ordered FCC is not? Problem 2: (a) Draw an edge dislocation in a simple cubic crystal. (b) Show how the glide of that dislocation produces plastic deformation. (c) Explain why it is difficult for an edge dislocation to climb unless the temperature is high. Problem 3: A binary system of atoms A and B has the complex phase diagram drawn below.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: A B x a º L T (a) Label the two-phase fields in the diagram. (b) Let a liquid with the composition indicated by the vertical line on the phase diagram be cooled from the liquid slowly enough to preserve equilibrium. Describe the evolution of the system as it is cooled. Page 1 Engineering 45: Spring, 2000 Midterm Exam (c) Suppose that you are given the assignment of purifying a B-rich solution until it is almost pure B. How would you proceed? Problem 4: (a) Silica glass is a good thermal insulator, while Ag is not (have you ever drunk chilled wine from a silver goblet?). Why? (b) BCC sodium has a higher Debye temperature than HCP sodium. Which of the two phases is likely to be preferred at high temperature? Why? Page 2...
View Full Document

{[ snackBarMessage ]}

Page1 / 2

eo0mtm - A B x a º L T(a Label the two-phase fields in the...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online