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 1

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. 6

T (°C) Ice Water Vapor The less free Gibbs energy a phase has, the more stable it is. G 7

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 ℃ 8

The purpose of our experiment is to prove a magnesium alloy (Ca 2 Mg 5 Zn 13 ) at the predicted circumstances Our hypothesis is to prove that a stable magnesium alloy does exist at 340 ℃ 9

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 10

Step 1:Polishing Our Samples We polished our samples for smooth surfaces. The better the polishing, the better the results. Mg-30% Ca Zn 11

Step 2:Diffusion Couple First we put our samples in the clamp. Then we put them in the furnace at 340 ℃. 12

Step 3:Quenching 13

Step 4:Mounting & Cutting Sample 14

Step 5:Polishing and Etching for Characterization 15

Step 6: Etch and Examine 16

Results After nine days at 340 C, only one of our samples diffused. Reasons of error – Clamp was not tight enough – Oxidation 17

Diffused Layer Crack Defects 200 μm 100 μm MgCa Zn 18 MgCa Zn

Summary At the moment, our hypothesis is unjustified Future Work – Determine and recognize phases/Characterization – Possibly finer polishing or longer time frame 19

Magnesium Alloy Diffusion Couple Experiment Thermodynamics Phase Diagram Gibbs Free Energy 20

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 21