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Thermal dilation of copper
Physica XVI, no 10
THERMAL
October 1950
DILATION
OF COPPER
by D. S. E P P E L S H E I M E R and R. R. PENMAN Department of metallurgical engineering Missouri School of mines and metallurgy Rolla, Missouri
Synopsis The prediction t h a t certain cubic metals m ay not be precisely cubic t h r o u g h o u t a range of t e m p e r a t u r e below their melting points led to t h e present investigation. Pure copper was chosen as the cubic metal to e x a m i n e for anisotropy in its thermal dilation, and the (024) and the (331) planes were chosen in the lattice. Temperatures for ex am i n at i o n ranged between 18°-770°C, using a 19-cm high-temperature powder camera by U n i c a m of Cambridge, England. Plotting the lattice constant vs. temperature, the t h er m al dilation of pure copper was found to be isotropic t h r o u g h o u t the t e m p e r a t u r e range investigated.
It has been previously shown that certain cubic metals may not be precisely cubic through a range of temperatures below their melting points. K o c h a n o v s k a 1), found a decided anisotropy in the thermal dilation of iron in the temperature range 22-366°C using the (013) and (I 12) planes and the well-known back reflection technique. The present investigators chose copper as their cubic metal to examine for anisotropy, using the planes (024) an (331). A 19-cm high-temperature-vacuum camera (Unicam) of the Bradley-Jay design, and incorporating the recommendations for such a camera as suggested b y W. L. B r a g g 2), was used in this investigation. Temperatures for examination ranged between 18-770°C. Two PtP t / R h thermocouples were used to measure the temperature around the specimen, one thermocouple being near the base of the si~ecimen in the heating zone, and another couple at the top of the specimen in the heating zone. When equilibrium was established between the two couples, there could never be a thermal gradient greater than 4- ! o, between them. The couples were checked b y a U. S. Bureau of 792 - -
793
THERMAL DILATION OF COPPER
Standards P t - P t / R h thermocouple, and were found to be accurate. The copper used in this examination was 99.999 +, and was produced by the National Research Corporation, Cambridge, Mass. Specimens for each examination were prepared by swaging down to 0.050 inches, annealed at 200 ° for 4 hours in cast iron chips and further reduced down by etching in concentrated H N Q . Copper radiation was used, and the quadratic form of B r a g g's law was applied: a o = ½~(h 2 +
k2 +/2)I;2/sin 0
TABLE I
T e m p . °C 18
Data Value ao in .A.
Value ao in ./~
(024) 3.60,59 =
(331 ) 3.61
3.60,66 =
3.61
250 450
3.6194 = 3.62 3.6321 = 3 . 6 3
3.6210 = 3.62 3.6304 = 3.63
770
3.6507 =
3.6498 =
3.65
3.65
In view of the fact that no attempts were made to correct the 800X- (024)
PLANE
O- (3 700-
600-
o
0
500-
400o. I--
300-
200"
I00-
0
m
3.60
3161
3.'62 LATTICE
Fig. 1. T e m p e r a t u r e
3!63
31,4
~.e8
(.~ONSTANlr "~1.0 "
°C vs. l a t t i c e c o n s t a n t " a 0 " A ° for c o p p e r .
794
THERMAL
DILATION OF COPPER
above data, the lattice constants were accurate to only two decimals. From the data, it is readily observed that the lattice constants are the same for each set of planes and no anisotropy exists throughout the range of temperature investigated. See Figure 1. The thermal expansion and lattice spacing of copper had previously been done by H u m e - R o t h e r y and A n d r e w s 3 ) , and the data do not correspond precisely to their data and it was not the purpose of this investigation to correlate their data. No attempt was made to correct the lattice constants for errors due to eccentricity, film shrinkage, absorption in the specimen, or operator errors. All such errors would be incorporated in each film and would be approximately the same for each line being compared on individual films. A direct reading temperature indicator was used for convenience, in lieu of a potentiometer. While not as accurate as a potentiometer, it gave a constant temperature reading which was desired and achieved. The lines on the film were clear and distinct with no indication of fuzziness, indicating that the temperature was constant in the furnace ± 5 °. From the data presented, and plot of the data, it can be seen that copper does not appear to exhibit any anisotropy in its thermal dilation, and is precisely cubic throughout the temperature range investigated. R e c e i v e d 1-7-50.
REFERENCES 1) K o e h a n o v s k a, A., I n v e s t i g a t i o n of T h e r m a l D i l a t i o n of Cubit' .Mt'tals, P h y s i c a 15 (1949) 191-196. 2) B r a d l e y , A.J., Bragg, W . L . and S y k e s , C., Researches into tlle S t r u c t u r e s of Alloys, J o u r n a l of the Iron a n d Steel I n s t i t u t e , No 1, 141 (1740) 75. 3) H u m e - R o t h e r v, W. a n d A n d r e w s , K.W.,Tht'LatticeSpacingandThermal E x p a n s i o n of Copper, J o u r n a l of the I n s t i t u t e of Metals, 63, pt. 2, (1942) 19.
THERMAL
October 1950
DILATION
OF COPPER
by D. S. E P P E L S H E I M E R and R. R. PENMAN Department of metallurgical engineering Missouri School of mines and metallurgy Rolla, Missouri
Synopsis The prediction t h a t certain cubic metals m ay not be precisely cubic t h r o u g h o u t a range of t e m p e r a t u r e below their melting points led to t h e present investigation. Pure copper was chosen as the cubic metal to e x a m i n e for anisotropy in its thermal dilation, and the (024) and the (331) planes were chosen in the lattice. Temperatures for ex am i n at i o n ranged between 18°-770°C, using a 19-cm high-temperature powder camera by U n i c a m of Cambridge, England. Plotting the lattice constant vs. temperature, the t h er m al dilation of pure copper was found to be isotropic t h r o u g h o u t the t e m p e r a t u r e range investigated.
It has been previously shown that certain cubic metals may not be precisely cubic through a range of temperatures below their melting points. K o c h a n o v s k a 1), found a decided anisotropy in the thermal dilation of iron in the temperature range 22-366°C using the (013) and (I 12) planes and the well-known back reflection technique. The present investigators chose copper as their cubic metal to examine for anisotropy, using the planes (024) an (331). A 19-cm high-temperature-vacuum camera (Unicam) of the Bradley-Jay design, and incorporating the recommendations for such a camera as suggested b y W. L. B r a g g 2), was used in this investigation. Temperatures for examination ranged between 18-770°C. Two PtP t / R h thermocouples were used to measure the temperature around the specimen, one thermocouple being near the base of the si~ecimen in the heating zone, and another couple at the top of the specimen in the heating zone. When equilibrium was established between the two couples, there could never be a thermal gradient greater than 4- ! o, between them. The couples were checked b y a U. S. Bureau of 792 - -
793
THERMAL DILATION OF COPPER
Standards P t - P t / R h thermocouple, and were found to be accurate. The copper used in this examination was 99.999 +, and was produced by the National Research Corporation, Cambridge, Mass. Specimens for each examination were prepared by swaging down to 0.050 inches, annealed at 200 ° for 4 hours in cast iron chips and further reduced down by etching in concentrated H N Q . Copper radiation was used, and the quadratic form of B r a g g's law was applied: a o = ½~(h 2 +
k2 +/2)I;2/sin 0
TABLE I
T e m p . °C 18
Data Value ao in .A.
Value ao in ./~
(024) 3.60,59 =
(331 ) 3.61
3.60,66 =
3.61
250 450
3.6194 = 3.62 3.6321 = 3 . 6 3
3.6210 = 3.62 3.6304 = 3.63
770
3.6507 =
3.6498 =
3.65
3.65
In view of the fact that no attempts were made to correct the 800X- (024)
PLANE
O- (3 700-
600-
o
0
500-
400o. I--
300-
200"
I00-
0
m
3.60
3161
3.'62 LATTICE
Fig. 1. T e m p e r a t u r e
3!63
31,4
~.e8
(.~ONSTANlr "~1.0 "
°C vs. l a t t i c e c o n s t a n t " a 0 " A ° for c o p p e r .
794
THERMAL
DILATION OF COPPER
above data, the lattice constants were accurate to only two decimals. From the data, it is readily observed that the lattice constants are the same for each set of planes and no anisotropy exists throughout the range of temperature investigated. See Figure 1. The thermal expansion and lattice spacing of copper had previously been done by H u m e - R o t h e r y and A n d r e w s 3 ) , and the data do not correspond precisely to their data and it was not the purpose of this investigation to correlate their data. No attempt was made to correct the lattice constants for errors due to eccentricity, film shrinkage, absorption in the specimen, or operator errors. All such errors would be incorporated in each film and would be approximately the same for each line being compared on individual films. A direct reading temperature indicator was used for convenience, in lieu of a potentiometer. While not as accurate as a potentiometer, it gave a constant temperature reading which was desired and achieved. The lines on the film were clear and distinct with no indication of fuzziness, indicating that the temperature was constant in the furnace ± 5 °. From the data presented, and plot of the data, it can be seen that copper does not appear to exhibit any anisotropy in its thermal dilation, and is precisely cubic throughout the temperature range investigated. R e c e i v e d 1-7-50.
REFERENCES 1) K o e h a n o v s k a, A., I n v e s t i g a t i o n of T h e r m a l D i l a t i o n of Cubit' .Mt'tals, P h y s i c a 15 (1949) 191-196. 2) B r a d l e y , A.J., Bragg, W . L . and S y k e s , C., Researches into tlle S t r u c t u r e s of Alloys, J o u r n a l of the Iron a n d Steel I n s t i t u t e , No 1, 141 (1740) 75. 3) H u m e - R o t h e r v, W. a n d A n d r e w s , K.W.,Tht'LatticeSpacingandThermal E x p a n s i o n of Copper, J o u r n a l of the I n s t i t u t e of Metals, 63, pt. 2, (1942) 19.