Materials for engineering, 3rd Edition - (Malestrom)

Problems
Chapter 1
1. Distinguish between the following types of bonding in solids:
van der Waals bonds
covalent bonds
ionic bonds
metallic bonds.
Name four materials in which each of these types of bonding occur.
2. Show that differentiation of equation [1.4] leads to equation [1.5]. Obtain
an expression for the value of ∆G* (Fig. 1.4), which is the activation free
energy for the formation of a nucleus of critical size (r c ). By substituting
equation [1.3] into your expression, derive an equation which describes
the dependence of the value of ∆G* upon the degree of supercooling.
Can your derived equations enable you to predict qualitatively the
observed relative grain sizes of metal objects formed by casting the molten
metal (a) into a cold metal mould of large wall thickness and (b) into a
preheated sand mould?
Estimate the critical nucleus size and the free energy of formation of
the critical nucleus of solid tin at 473 K given the following data:
Melting point of tin = 505 K
Solid liquid interfacial energy = 0.1 J m –2
Latent heat of solidification = 4 × 10 5 kJ m –3 .
[Answer: 7.9 nm]
3. Discuss the appropriate metallographic techniques for the following studies:
(a) determination of the grain size of the sand-cast bronze marine propeller
blade,
(b) determination of the grain size of a mild sheet plate,
(c) examination of a fatigue fracture surface, and
(d) the identification of a precipitated phase in a tempered steel.
4. During the solidification of an alloy, it is assumed that there is complete
mixing in the liquid and no mixing in the solid (i.e. ‘cored’ crystals are
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