Diffusion, twinning, fatigue, acoustic emission, and aging can be studied using readily available materials and the household oven. Each experiment can be expanded to a more extensive investigation of the properties of the material investigated, as well as other materials, and offers an opportunity for the student to learn about the relationship between engineering, science, society, and politics

Spiegel, F. Xavier

English

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FIVE EXPERIMENTS IN mTERIALS SCIENCE FOR LESS T $ l a > , O O  
F. Xavier Spiegel 
Loyola College, Baltimore, Maryland 
KEY WORDS 
Diffusion, Twinning, Fatigue, Acoustic Emission, Ageting. 
ABSTRACT 
Diffusion, Twinning, Fatigue, Acoustic Emission and Ageing 
can be studied using readily available materials and the h.ousehold 
oven. Each experiment can be expanded to a more extensive 
investigation of the properties of the material investigated, as 
well as other materials, and offers an opportunity for the student 
to learn about the relationship between engineering, science, 
society and politics. 
INTRODUCTION 
Simple experiments with everyday items can be used to 
familiarize students with the importance of materials and some of 
the properties which they possess. The following experiments have 
been performed by the author for over eight years with enthusiastic 
response by audiences of all ages. 
EQUIPMENT AE3D SUPPLIES 
1) Aluminum nails, 
2) United States Pennies, 
3) Metal Paper Clips. 
THE ALUMINUM NAIL 
Aluminum nails are age hardened to disperse the silicon and 
harden the aluminum. If an aluminum nail is re-heated to 600 F for 
one hour it will soften and can be bent by hand. This brief 
experiment demonstrates the movement of atoms in a material, This 
migration of atoms in a material is diffusion. In the age-hardened 
state the silicon atoms are finely dispersed, whereas in the re- 
heated or over-aged material the silicon atoms coalesce into larger 
particles and no longer strengthen the aluminum to a useful 
hardened state.' 
THE UNITED STATES P E m P  
The U.S. penny has an interesting history; the pennies minted 
since 1982 are electroplated zinc. The present composition is 97,6% 
https://ntrs.nasa.gov/search.jsp?R=19920021040 2020-03-17T11:25:23+00:00Z
zinc and 2 , 4 %  copper. The copper can easily be scratched from the 
surface of t h e  coin to reveal the zinc. Before 1982 the penny was 
35% copper and 5% zinc or 95% copper, 2,5% zinc and 2 , 5 %  tin, 
~xcept :for 1943 when the penny was zinc coated on steellO2r 3 1  4 f  
Bn interesting experiment can be performed on all of the 
p e n ~ l i a s  except the 1943 version by placing them in an oven at 
350--400 F for about an hour or so. The surface of the penny will 
sequi r le  a heat tint that makes the coin appear golden. This heat 
t i n - i  can easily be removed by normal wear or by polishing, 
The pennies minted since 1982  exhibit another interesting 
2roperty when heat treated. If this penny is heated at 700 P for 
3ne hour the zinc grains will become large and can easily be 
twinned by biting on the penny or by bending it. An acoustic 
ern iss io l~  will be heard when the penny is deformed. This experiment 
c l e a r l y  demonstrates diffusion and grain growth, as the Bsas foundf8 
?enny will not twin because the grains are so small. Diffusion is 
causing the grain growth of the zinc and the deformation is causing 
the twinning. The twinning is causing the crackling noise heard 
1~~7herj the penwy is deformed. This crackling is called acoustic 
emission and is being extensively researched for NDE 
purpostes. 1 9 . 3 9 4 1 5  
THE PAPER CLIP 
An ordinary metal paper clip can readily be used to 
4emo~s t : r a t e  fatigue. A fatigue failure arises from the cyclic 
laadirlg of a material at relatively small loads.' If a paper clip 
As opened so that it appears as an elongated BgSBt and is repeatedly 
ben.5 bzck and forth it will break, clearly demonstrating the 
-3he:neme:aon of fatigue, If the broken paper clip is quickly moved to 
zhe lower portion of the upper lip the paper clip appears warm, a 
result of internal friction, If the color of the region around the 
fracturro is examined a discoloration will be observed, and if the 
t e x t u r e  is observed the area around the fracture will be noticeably 
roughened, 
CONCLUSIONS 
As previously mentioned, these demonstrations have met with 
m e 5  si~1c:cess and the author" experience has been that many in the 
audj-ences have demonstrated them to others and frequently called 
the autlaor for more information or other experiments, Each of these 
experimc2nts can be expanded to be quantitative, and include other 
naterials, variation of heat treatments, different loading 
eechnlhq~~es and perhaps observations of different properties, It is 
r h e  author" opinion that the equipment need not be complex and in 
fact should not be complex to interest students in the study of 
n a t e r i a  ks, 
ACKNOWLEDGMENTS 
The author wishes to thank Miss Margaret Davis, engineering 
student at Loyola College, for duplicating these experiments and 
eomenting on their worth. I also wish to thank Mr, John Ross, 
friend and colleague, for his continued interest, advice a:nd moral 
support in my endeavor to understand metals. I also thank my wife 
Mary for typing this manuscript. 
REFERENCES 
11, William 0. Fellers, Materials Science, Testing, and Properties 
for Technicians, Prentice Hall 1990. 
2 ,  Wagner, H.J., Hall, A.M., The New Coinage, Journal of Metals, 
March 1966, pp. 301-307. 
3. French, Charles F., 1991 American Guide to U.S. Coins, Simon 
& Schuster Inc., 1990. 
4. Junge, Ewald, World Coin Encyclopedia, William Morrow & 
Colrlpany Inc. , 1984. 
5. Yeoman, R. S., Current Coins of the World, 8th Edition, Western 
Pukalishing, Co. Inc., 1988. 


Five experiments in materials science for less than $10.00

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