Illustrate, with the aid of a diagram, substitutional AND interstitial strengthening mechanisms in metal alloys.

a) On the atomic level, what causes strain hardening?   b) Explain the difference between engineering stress and true stress. Under tension, which one is greater, and why?

c) What mechanism of creep can be prevented using a single crystal part? Justify your answer using suitable examples or references.

Using the isothermal transformation diagram for a 0.45 wt% C steel alloy (Animated Figure 10.40), determine the approximate percentages of the microconstituents that form the final microstructure of a small specimen that has been subjected to the following time- temperature treatments. In each case assume that the specimen begins at 845°C (1550°F), and that it has been held at this temperature long enough to have achieved a complete and homogeneous austenitic structure.

Explain the following, using dislocation theory: metal strengthening by: (a) grain size (b) solid solution strengthening  (c) strain hardening (d) quenching in cold water following heating close to melting pt ( hint: Nv = Nexp(-Qv/kT)

The flow stress of a coarse-grained dilute copper alloy increased from 2 to 55 MPa when the dislocation density was increased from a low value of 10 cm via cold working to a modest value of 100 cm2. Calculate the flow stress for this alloy when heavy cold working introduces a dislocation density of 10¹2 cm². An equation similar to the Hall-Petch equation has been proposed for dislocations, and is: Tflow To ka Paisl where Tflow is the flow stress (i.e., the force per unit area necessary to get plastic deformation), pdisi is the dislocation density (the dislocation line length per unit volume), and To and ka are constants for a given material. The easiest way to solve this problem is to put values into this equation twice, subtract one expression from the other, and solve for ka. Then enter your value of ka into either original equation to determine To. Keep track of units, and then solve the problem stated above.

a) Sketch and label tensile stress-strain curves for a typical BCC and FCC metal and explain the salient differences from a slip system perspective Explain the Fick’s two laws of diffusion and discuss their common uses. What atomic factors govern the extent of solid solubility?

When a cold-worked metal is heat-treated below its melting point over a period of time, which of the following phenomena occur? (This question has more than one correct answer) a. Strength is increased b. Dislocation density decreases c. Grain size increases d. Internal lattice strains decrease e. Ductility is reduced

What is slip deformation? Why does it only occur in metal and not in ionic solids?

(c) Explain the reason of FCC metals are often recommended for use at low temperatures, particularly when any sudden loading of the part is expected.