Investigation of Phase Equilibrium In Magnesium Alloys through Diffusion Couples Team H: Sloan Dantzler -Reading High School Alan Dorsinville -Reading High School VanayJoynes -Lankenau High School Khadija Washington -Bishop McDevitt HS
Outline • Introduction • Purpose • Hypothesis • Mg-Ca-Zn alloy • Procedure • Diffusion Couple Experiment • Methods • Data • Microstructure • Discussion • Conclusion/Future Work
Introduction • 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
Magnesium Alloys WHY? • Mg alloys are: • Light, Low Density • Strong
Contributed Properties • Calcium addition • Improve oxidation resistance • Improve creep resistance • Zinc addition • Increase hardness
Thermodynamics • Thermodynamics is the relationship between heat and the ability for mechanical energy or work to be done.
Gibbs Free Energy The less free Gibbs energy a phase has, the more stable it is. Vapor Water G Ice T (°C)
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 340 ℃ Carl and Liu (2004)
Purpose The purpose of our experiment is to prove a magnesium alloy (Ca2Mg5Zn13) at the predicted circumstances Hypothesis Our hypothesis is to prove that a stable magnesium alloy does exist at 340℃
MgCa Alloy Zn Diffusion Couple Experiment • 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.
Step 1:Polishing Our Samples Mg-30% Ca Zn We polished our samples for smooth surfaces. The better the polishing, the better the results.
Step 2:Diffusion Couple First we put our samples in the clamp. Then we put them in the furnace at 340 ℃ .
Results • After nine days at 340 C, only one of our samples diffused. • Reasons of error • Clamp was not tight enough • Oxidation
MgCa 200 μm Diffused Layer Crack Zn Zn Microscope Results Defects 100 μm MgCa
Summary • At the moment, our hypothesis is unjustified • Future Work • Determine and recognize phases/Characterization • Possibly finer polishing or longer time frame
Acknowledgements 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 Thank You Any Questions?