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Recitation 3 O

This document contains 6 questions about imperfections in solids, including: 1) Calculating the activation energy for vacancy formation in aluminum given equilibrium vacancy numbers at a temperature. 2) Identifying which elements would form different types of solid solutions with copper based on properties like atomic radius and electronegativity. 3) Calculating the weight percent composition of an alloy with 5 atomic % copper and 95 atomic % platinum. 4) Determining the crystal structure of a hypothetical alloy given the weight percentages and properties of its constituent metals. 5) Predicting whether the surface energy of a (100) plane or (110) plane would be greater for a body-centered cubic single crystal

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77 views2 pages

Recitation 3 O

This document contains 6 questions about imperfections in solids, including: 1) Calculating the activation energy for vacancy formation in aluminum given equilibrium vacancy numbers at a temperature. 2) Identifying which elements would form different types of solid solutions with copper based on properties like atomic radius and electronegativity. 3) Calculating the weight percent composition of an alloy with 5 atomic % copper and 95 atomic % platinum. 4) Determining the crystal structure of a hypothetical alloy given the weight percentages and properties of its constituent metals. 5) Predicting whether the surface energy of a (100) plane or (110) plane would be greater for a body-centered cubic single crystal

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Para Dise
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MSE 225-INTRODUCTION TO MATERIAL SCIENCE

RECITATION 3-IMPERFECTIONS IN SOLIDS

Q.1. Calculate the activation energy for vacancy formation in aluminum, given that the
23 -3
equilibrium number of vacancies at 500°C (773 K) is 7.55x10 m . The atomic weight and
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density (at 500°C) for aluminum are, respectively, 26.98 g/mol and 2.62 g/cm .

Q.2. Atomic radius, crystal structure, electronegativity, and the most common valence are tabulated in the
following table for several elements; for those that are nonmetals, only atomic radii are indicated.
Which of these elements would you expect to form the following with copper (Cu):
(a) A substitutional solid solution having complete solubility
(b) A substitutional solid solution of incomplete solubility
(c) An interstitial solid solution

Q.3. Calculate the composition, in weight percent, of an alloy that consists of 5 at. % Cu and 95 at.% Pt?

Q4. Some hypothetical alloy is composed of 25 wt.% of metal A and 75 wt% of metal B. If the densities of
metals A and B are 6.17 and 8.00 g/cm3, respectively, whereas their respective atomic weights are 171.3
and 162.0 g/mol, determine whether the crystal structure for this alloy is simple cubic, face-centered cubic,
or body-centered cubic. Assume a unit cell edge length of 0.332 nm.
Q.5. For a BCC single crystal, would you expect the surface energy for a (100) plane to be greater or less
than that for a (110) plane? Why?

Q.6. The grain boundary energy of a small-angle grain boundary is less than for a high-angle one. Why is
this so?

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