Transcript Investigating Thermodynamics and Phase Equilibrium In

Investigation of Phase Equilibrium In
Magnesium Alloys through Diffusion
Couples
Team H:
Sloan Dantzler -Reading High School
Alan Dorsinville -Reading High School
Vanay Joynes -Lankenau High School
Khadija Washington -Bishop McDevitt HS
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• Introduction
– Purpose
– Hypothesis
– Mg-Ca-Zn alloy
• Procedure
– Diffusion Couple Experiment
– Methods
• Data
– Microstructure
– Discussion
• Conclusion/Future Work
2
• Our goal is to prove Mg, Ca and Zn can be
fused together to create a stable phase under
certain conditions.
• What we learned:
– Why magnesium alloys are important
– Thermodynamics
– Gibbs Free Energy
– Phase Diagrams
– Diffusion Couple Experiment
3
WHY?
• Mg alloys are:
– Light, Low Density
– Strong
4
• Calcium addition
– Improve oxidation resistance
– Improve creep resistance
• Zinc addition
– Increase hardness
5
• Thermodynamics is the relationship between
heat and the ability for mechanical energy or
work to be done.
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The less free Gibbs
energy a phase has,
the more stable it
is.
Vapor
Water
G
Ice
T (°C)
7
Phase Diagram: Isothermal Section
• A340
graph
℃showing all the phases of a substance under
different conditions
• It shows us:
– All the phases whether stable,metastable or unstable.
– The number of phases
– Each phase’s composition
Carl and Liu (2004)
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The purpose of our experiment is to prove a
magnesium alloy (Ca2Mg5Zn13) at the predicted
circumstances
Our hypothesis is to prove that a stable
magnesium alloy does exist at 340℃
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• Is the action of putting two materials together
in close contact so they may diffuse into each
other
• The area of contact, where the diffusion took
place, is where the alloy will form.
MgCa
Alloy
Zn
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Step 1:Polishing Our Samples
Mg-30% Ca
Zn
We polished our samples for
smooth surfaces. The better
the polishing, the better the
results.
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Step 2:Diffusion Couple
First we put our samples in the clamp.
Then we put them in the furnace at
340 ℃ .
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Step 3:Quenching
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Step 4:Mounting & Cutting Sample
14
Step 5:Polishing and Etching for
Characterization
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Step 6: Etch and Examine
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Results
• After nine days at 340 C, only one of our
samples diffused.
• Reasons of error
– Clamp was not tight enough
– Oxidation
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MgCa
200 μm
Diffused Layer
Crack
Zn
Zn
Defects
100 μm
MgCa
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Summary
• At the moment, our hypothesis is unjustified
• Future Work
– Determine and recognize phases/Characterization
– Possibly finer polishing or longer time frame
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Magnesium
Alloy
Gibbs Free
Energy
Phase Diagram
Diffusion
Couple
Experiment
Thermodynamics
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We would like to thank:
• SEEMS Faculty
• Dr. Zi-Kui Liu
• Mr. Sunghoon Lee
• Ms. Jody Markley
• Mr. Derek James
• Mr. Joshua Harper
• UBMS Staff
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