# Using data in Table 5.2, calculate the self-diffusivity for iron in bcc iron at 900ºC.

Problem 5.17 (p.150)
Using data in Table 5.2, calculate the self-diffusivity for iron in bcc iron at 900ºC.
Table 5.2
Diffusivity Data for a Number of Metallic Systemsa

Solute Solvent D0 (m2/s) Q (kJ/mol) Q (kcal/mol)
Carbon Fcc iron 20 x 10-6 142 34.0
Carbon Bcc iron 220 x 10-6 122 29.3
Iron Fcc iron 22 x 10-6 268 64.0
Iron Bcc iron 200 x 10-6 240 57.5
Nickel Fcc iron 77 x 10-6 280 67.0
Manganese Fcc iron 35 x 10-6 282 67.5
Zinc Copper 34 x 10-6 191 45.6
Copper Aluminum 15 x 10-6 126 30.2
Copper Copper 20 x 10-6 197 47.1
Silver Silver 40 x 10-6 184 44.1
Carbon Hcp titanium 511 x x 10-6 182 43.5
Problem 5.24 (p.150)
Diffusion length, ?, is a popular term in characterizing the production of semiconductors by the controlled diffusion of impurities into a high- purity material. The value of ? is taken as 2vDt, where ? represents the extent of diffusion for an impurity with a diffusion coefficient, D, over a period of time, t. Calculate the diffusion length for B in Ge for a total diffusion time of 30 minutes at a temperature of (a) 800ºC and (b) 900ºC.

Problem 5.25 (p.150)
A differential nitrogen pressure exists across a 2 mm thick steel furnace wall. After some time, steady-state diffusion of the nitrogen is established across the wall. Given that the nitrogen concentration on the high pressure surface of the wall is 2kg/m3 and on the low pressure surface is 0.2 kg/m3, calculate the flow of nitrogen through the wall ( in kg/m2.h) if the diffusion coefficient for nitrogen in this steel is 1.0 x 10-10 m2/s at the furnace operating temperature.
Problem 9.3 (p.300)
Calculate the degrees of freedom for a 50:50 copper- nickel alloy at (a) 1,400ºC, where it exists as a single, liquid phase; (b) 1,300 ºC, where it exists as a two-phase mixture of liquid and solid solutions; and (c) 1,200 ºC, where it exists as a single, solid- solution phase. Assume a constant pressure of 1 atm above the alloy in each case.
Problem 9.17 Important! The answer in the back of the book is wrong! (p.300)
Calculate the amount of each phase present in 1 kg of a 50 wt % Ni-50 wt % Cu alloy at (a) 1,400 ºC, (b) 1,300 ºC, (c) 1,200 ºC (see figure 9.9)

Problem 9.21 (p.300)
Calculate the amount of each phase present in 50 kg of a brass with composition 35 wt % Zn-65 wt % Cu at (a) 1,000 ºC, (b) 900 ºC, (c) 800 ºC, (d) 700 ºC (e) 100 ºC, (f) 0 ºC. (see figure 9.28)

Problem 10.10 (p.342)
A eutectoid steel is (i) quenched instantaneously to 500 ºC, (ii) held for 5 seconds, (iii) quenched instantaneously to room temperature, (iv) reheated to 300 ºC for 1 hour, and (v) cooled to room temperature. What is the final microstructure? (b) A carbon steel with 1.13 wt% C is given exactly the same heat treatment described in part (a). What is the resulting microstructure in this case?

Problem 10.27 (p.343)
Quenching a bar of 4140 steel at 700 ºC into a stirred water bath produces an instantaneous quench rate at the surface of 100 ºC/s. Use Jominy test data to predict the surface hardness resulting from this quench. (Note: The quench described is not in the Jominy configuration. Nonetheless, Jominy data provide general information on hardness as a function of quench rate.)

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