Transcript MSE 201 LAB II: Part a Cold Rolling Copper Alloys

MSE 201 LAB II: Part a
Cold Rolling Copper Alloys
What is Cold Rolling?
• Deformation below the “recrystallization temperature”
COLD ROLLING
HOT ROLLING
Lab Overview
• 4 Alloys Rolled Today:
– Pure Copper
– 5% Zinc
– 10% Zinc
– 20% Zinc
• This is called “Alpha Brass”
– Solid solution of one phase (the alpha phase)
Why Add Zinc?
• Zinc hardens copper by “Solid Solution Hardening”.
Cu: Z=29
Zn: Z=30
(click to play)
Rolling Causes Deformation
• Deformed microstructure has many more
defects, thus it is harder.
(click to play)
Hardness, DPH
Goal: Hardness vs. % CW
Hardness, DPH vs. %CW
Increased
Solid Solution
Dislocation
Hardening
Density with
175
%CW 20% Zn DPH
125
10% Zn DPH
5% Zn DPH
75
Pure Cu DPH
25
0
20
40
%CW
60
How to Measure %CW?
• Percent Cold Work (%CW) is the
% Change in Cross-sectional Area.
%CW 
Af  Ao
Ao
*100
• Area of these samples = Width * Thickness.
Making It Easier
• Assume width doesn’t change.
%CW 

Af  Ao
Ao
wo *  t f  to 
wo * to
t final
*100 
w f * t f  wo * to
*100 
wo * to
t f  to
to
*100
 %Reduction 
 tinitial 1 

100


Using a Micrometer
Using a Micrometer (cont.)
Measuring to 0.001”
Using a Micrometer (cont.)
The Vernier Scale (0.0001”)
Lab Procedure
1.
2.
3.
4.
Measure initial thickness
Calculate target thickness values for each %CW
Measure initial width, hardness
Roll sample to reach the target thickness
(Set micrometer to target thickness for “pass-thru
test” to save time)
5. Measure “Actual Thickness”
6. Measure hardness
7. Reset micrometer and go to step 4
Notes on Hardness Measurement
• Start with HRF scale (60kgf load)
• If reading is >100 HRF, switch to HRB
(100kgf)
• If indent is visible on the back side of the
sample, use superficial scale
– HR30T for softer samples, or
– HR45T for harder samples
• Use “spot anvil” to negate curvature
Upon Completion of Rolling…
• Average hardness (HRF/HRB) and convert to DPH
• Make sure data sheet is completely filled out
• Write on your copper strip:
– Alloy (Pure, 5%, 10%, 20%)
– Class Time (1:25 or 3:25)
– Team members’ names
• Turn in to TA the following:
– Data sheet
– Copper strip
– Micrometer
NO
NO REPORT
REPORT DUE
DUE THIS
THIS TIME,
TIME,
BUT
BUT LAB
LAB MEETS
MEETS NEXT
NEXT WEEK
WEEK TO
TO FINISH
FINISH THE
THE EXPERIMENT!!!
EXPERIMENT!!!
Let’s Roll!