Docsity
Docsity

Prepare for your exams
Prepare for your exams

Study with the several resources on Docsity


Earn points to download
Earn points to download

Earn points by helping other students or get them with a premium plan


Guidelines and tips
Guidelines and tips

5 Questions of Phase Transformation in Material Processing - Exam 2 | MATL 6300, Exams of Materials science

Material Type: Exam; Professor: Kim; Class: PHASE TRANSFORMATIONS IN MATERIAL PROCESSING; Subject: Materials Engineering; University: Auburn University - Main Campus; Term: Spring 2010;

Typology: Exams

2012/2013

Uploaded on 03/16/2013

dixiedigger88
dixiedigger88 🇺🇸

11 documents

1 / 9

Toggle sidebar

This page cannot be seen from the preview

Don't miss anything!

bg1
Page 1 of 6
MATL 5300/6300/6306 Spring 2010
Exam #2
Time Allowed 75 min
Name
PLEASE READ THE FOLLOWING BEFORE STARTING
Please answer all questions in the space provided.
No credit will be given for irrelevant answers, so please READ THE QUESTIONS with care!
Credit is given for method as well as for solutions so it is essential that you CLEARLY show how
your answers were derived.
Put labels and units properly.
c
JD
x
=−
2
2
cc
D
tx
=
2
(,) exp 4
Sx
Cxt
D
t
Dt
π
⎛⎞
=⎜⎟
⎝⎠
2
(,) exp 4
4
Sx
Cxt
D
t
Dt
π
⎛⎞
=⎜⎟
⎝⎠
= Dt
x
erfCtxC s2
1),(
+= Dt
x
erfCCCtxC IsI 2
1)(),(
+= Dt
x
erf
C
txC 2
1
2
),( 0 exp
o
Q
DD RT
⎛⎞
=−
⎜⎟
⎝⎠
8.314 / 1.987 /
R
JmolK calmolK==ii
The error function table.
z erf(z) z erf(z) z erf(z) z erf(z)
pf3
pf4
pf5
pf8
pf9

Partial preview of the text

Download 5 Questions of Phase Transformation in Material Processing - Exam 2 | MATL 6300 and more Exams Materials science in PDF only on Docsity!

MATL 5300/6300/6306 Spring 2010

Exam #

Time Allowed 75 min

Name

PLEASE READ THE FOLLOWING BEFORE STARTING

  • Please answer all questions in the space provided.
  • No credit will be given for irrelevant answers, so please READ THE QUESTIONS with care!
  • Credit is given for method as well as for solutions so it is essential that you CLEARLY show how

your answers were derived.

  • Put labels and units properly.

c J D x

2

2

c c D t x

2

( , ) exp 4

S x C x t

π Dt Dt

2

( , ) exp 4 4

S x C x t

π Dt Dt

Dt

x C xt Cs erf 2

Dt

x C xt CI Cs CI erf 2

Dt

x erf

C

C xt 2

0

o exp

Q

D D

RT

R = 8.314 J / mol K i =1.987 cal / mol K i

The error function table.

z erf(z) z erf(z) z erf(z) z erf(z)


  1. Explain using diagrams, words, and equations how you could determine D as a function of

temperature. Be as specific as possible with your answer.


(b) At which places on the bar does the concentration change most as a function of time at

temperature? At which places on the bar does the concentration not change?

(c) What is the final composition of the bar, once homogenization is complete? Prove your answer.


(d) If the temperature were increased from 600 to 700 K, by what factor would the time required to

achieve the same level of homogenization be changed? Give a numerical answer? Note that the

activation energy for diffusion of C in the plain C steel = 60 Kcal/mole.


(b) Plot the nitrogen concentration gradient at a time of 15 hours for a temperature of 600 oC.

(c) For what times at 800 oC will your solutions be valid?


  1. Grain boundary diffusion is faster than bulk diffusion at temperatures < 0.7 – 0.8 T (^) m (where Tm

is the absolute melting point of the material).

(a) Why is grain boundary (GB) diffusion not faster than bulk diffusion at higher fractions of Tm?

Explain briefly.

(b) Explain the effect of grain size on the diffusion through grain boundary and bulk (use the plot for

the explanation).