MSE 201 LAB II: Part a Cold Rolling Copper Alloys

What is Cold Rolling? Deformation below the “recrystallization temperature” Deformation below the “recrystallization temperature” COLD ROLLINGHOT ROLLING

Lab Overview 4 Alloys Rolled Today: 4 Alloys Rolled Today: –Pure Copper –5% Zinc –10% Zinc –20% Zinc This is called “Alpha Brass” This is called “Alpha Brass” –Solid solution of one phase (the alpha phase)

Why Add Zinc? Zinc hardens copper by “Solid Solution Hardening”. Zinc hardens copper by “Solid Solution Hardening”. (click to play) Cu: Z=29 Zn: Z=30

Rolling Causes Deformation Deformed microstructure has many more defects, thus it is harder. Deformed microstructure has many more defects, thus it is harder. (click to play)

Goal: Hardness vs. % CW Solid Solution Hardening Increased Dislocation Density with %CW

How to Measure %CW? Percent Cold Work (%CW) is the % Change in Cross-sectional Area. Percent Cold Work (%CW) is the % Change in Cross-sectional Area. Area of these samples = Width * Thickness. Area of these samples = Width * Thickness.

Making It Easier Assume width doesn’t change. Assume width doesn’t change.

Using a Micrometer

Using a Micrometer (cont.) Measuring to 0.001”

Using a Micrometer (cont.) The Vernier Scale (0.0001”)

Lab Procedure 1. Measure initial thickness 2. Calculate target thickness values for each %CW 3. Measure initial width, hardness 4. Roll sample to reach the target thickness (Set micrometer to target thickness for “pass-thru test” to save time) (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) Start with HRF scale (60kgf load) If reading is >100 HRF, switch to HRB (100kgf) If reading is >100 HRF, switch to HRB (100kgf) If indent is visible on the back side of the sample, use superficial scale 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 Use “spot anvil” to negate curvature

Upon Completion of Rolling… Average hardness (HRF/HRB) and convert to DPH Average hardness (HRF/HRB) and convert to DPH Make sure data sheet is completely filled out Make sure data sheet is completely filled out Write on your copper strip: 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: Turn in to TA the following: –Data sheet –Copper strip –Micrometer NO REPORT DUE THIS TIME, BUT LAB MEETS NEXT WEEK TO FINISH THE EXPERIMENT!!!

Let’s Roll!