MATERIALS LABORATORY

Lab: Phase Diagrams

THE LAB:
• Construction of a phase diagram utilizing cooling curve data for a molten binary alloy.

THE SAMPLES:

Tin-lead alloys of the following weight percent compositions:

• 30%Sn-70%Pb
• 50%Sn-50%Pb
• 63%Sn-37%Pb
• 70%Sn-30%Pb
• 90%Sn-10%Pb

Fig. 1. Phase diagram lab set-up

THE EQUIPMENT:

• Safety Glasses
• Stopwatch/timer
• Steel crucible
• Hot plate
• Thermocouple with calibrated digital display

THE PROCEDURE:

1. Wear safety glasses and ensure all lab participants are wearing safety glasses prior to beginning the Phase Diagram Experiment.

2. Assign members of your team to the following:

o Monitor the stopwatch and announce the ten-second intervals.
o Monitor the thermocouple and announce the temperature reading.
o Record the temperature reading with respect to the time.

3. Heat the sample to a temperature above 500 °F at which the alloy reaches the molten liquid state, and then turn off the hot plate.

4. Once the temperature reaches 500oF, record the temperature of the sample at ten- second intervals, as the specimen cools.

5. Continue this process until the thermocouple temperature falls below 190 ° F when the alloy reaches the solidified state.

6. Plot the cooling curve data as temperature (^oC) as a function of time (minutes) using Microsoft Excel.

THE REPORT:

Your Company is interested in the Pb-Sn alloy system as a possible solder material. Your Boss would like you to check the eutectic composition and temperature of the Sn-Pb system. Therefore, to accomplish this assignment you must conduct the following:

• Determine the cooling curve for the 90 Sn-10 Pb alloy.

The report (no more than five pages), should include (but not limited to) the following:

• A detailed drawing/photograph illustrating the experimental setup.

• A plot of your cooling curve experimental data (Temperature (in °C) as a function of time (in minutes), identify on the plot both the liquidus temperature and the eutectic temperature.

• Your actual experimental data should be included in an appendix.

• A plot of the complete phase diagram (also provided electronically).

• Your conclusion as to what is the eutectic composition and temperature of this system.

• Also comment on and discuss any difference between experimental and published data if any.

Your report should fully conform to the format and organization as given in the

REPORTS & TECHNICAL WRITING DOCUMENT provided on blackboard.

Attachment:- Temerature vs time table.pdf