Investigation of Phase Equilibrium In Magnesium Alloys through Diffusion Couples

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27 Οκτ 2013 (πριν από 3 χρόνια και 10 μήνες)

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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


I
t 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
μ
m

100
μ
m

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