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Investigation of Phase Equilibrium In Magnesium Alloys through Diffusion Couples
Team H:Sloan Dantzler -Reading High SchoolAlan Dorsinville -Reading High SchoolVanay 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
Outline
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• 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
Introduction
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WHY?• Mg alloys are:– Light, Low Density– Strong
Magnesium Alloys
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• Calcium addition– Improve oxidation resistance – Improve creep resistance
• Zinc addition– Increase hardness
Contributed Properties
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• Thermodynamics is the relationship between heat and the ability for mechanical energy or work to be done.
Thermodynamics
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T (°C)
Ice
Water
Vapor
Gibbs Free Energy
The less free Gibbs energy a phase has, the more stable it is.G
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Phase Diagram: Isothermal Section
• A 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)
340 ℃
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Purpose
Hypothesis
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.
DIFFUSION COUPLE EXPERIMENT
MgCa Alloy Zn
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Step 1:Polishing Our Samples
We polished our samples for smooth surfaces. The better the polishing, the better the results.
Mg-30% Ca
Zn
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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
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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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MicroscopeResults
Diffused Layer
Crack
Defects
200 μm
100 μm
MgCa
Zn
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MgCa
Zn
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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MagnesiumAlloy
Diffusion Couple
Experiment
ThermodynamicsPhase Diagram
Gibbs Free Energy
What We Learned
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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
Acknowledgements
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Thank You
Any Questions?
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