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A search for the villari reversal effect in nickel
A SEARCH
FOR THE VILLARI EFFECT IN NICKEL.
REVERSAL
BY
S. R. WILLIAMS, Department
of Physics,
Ph.D.
Amherst
College.
IT IS a well-substantiated fact that a longitudinal pull applied to a bar of iron increases the magnetic induction when a weak magnetic field is applied, but decreases the flux in a strong field. FIG. I.
Magnetization
of annealed
iron
under
various
amounts
of longitudinal
pull.
The intensity of magnetization for an iron rod as it is magnetized, with and without a tension of 6 kilograms, is shown in the two curves of Fig. I, taken from Ewing’s book.’ The point of intsrsection of the two curves, P’, is called the “ Villari reversal point.” I,t is the point where the effect of a tension is reversed. Some years ago a series of polemical papers ’ discussed the question as to whether a similar effect could be found in nickel The arguments were left more or less unanswered or not. 843
S.
[J. F. I.
R. WILLIAMS.
because various mechanical and heat treatments may give a wide range of magnetostrictive effects, and it is barely possible that those finding the effect actually had some specimens which showed the reversal. Later it was shown 3 that if any extraneous magnetic fields were present these could give rise to Villari reversal FIG. 2.
~KROSCOPL Relation between y. cold reduction and the
various
degrees
HARDNESS of hardness
attained
by cold rolling.
points and, furthermore, when these extraneous fields were removed the Villari reversal points also disappeared in the speciEven this evidence against the possibility of mens being tested. a Villari reversal point in nickel was weak because only one kind of nickel was used. of a series of eleven In a recent study 4 of the hardness nickel strips by magnetic methods, it was possible to study the
June, igq.1
THE
VILLAKI
REVERSAL EFFECT.
845
Joule magnetostrictive effect in varieties of nickel where variations were produced by cold rolling to successive thicknesses or to different degrees of hardness. It has been shown .i that the Villari effect is the reciprocal of the Joule magnet,ostrictive effect. If a substance has its magnetic induction ‘decreased due to a tension, then that substance will shorten for those fields for which the magnetic induction FIG. 3.
Effect
of annealing
at 304’ C. for one hour.
decreased due to a tension. Similarly a rod will lengthen for those magnetic fields in which tension increases the flux. The principle Consequently if a of Le Chatelier holds in these phenomena. substance shows a Villari reversal effect, it will also show a reversal of sign in the change of length as the field is increased effect is, from zero to higher values. The Joule magnetostrictive therefore, a sensitive means of indirectly studying the presence This was the means or absence of the Villari reversal effect. the method for measuring the changes employed in this paper; in length as the field was varied has been described elsewhere.’ If nickel shows a Villari reversal effect like iron, then it will first lengthen for weak magnetic fields and shorten for strong. Twenty-two strips of nickel were studied in this work, there VOL. 203. No. 1z18-40
[J. F. I.
S. R. WILLIAMS.
846
being two samples for each degree of hardness. No initial lengthening occurred as the magnetic field was increased from Shorten&g only occwred for all field zero to larger values. stre*zgths ztp to a mlzie of 1200 gauss. This absence of the Villa& reverml isa the Gckcl ships with eleven diflerent ~hysicnl conditions ilr good evidence that the Villari rwersal poi& thus far reported for ltickel zperc fictitious. Through the courtesy of the International Nickel Company, FIG. 4. Q
IeXIO’QcM
Decreasing
the
thickness
of
a nickel
strip. 93 per cent.. change in length.
affects
tremendously
the
magnetic
eleven strips of nickel were furnished which had been rolled to This cold working of the nickel gave as successive thicknesses. Fig. 2 shows many degrees of hardness as there were reductions. the relation between the per cent. cold reduction and the various The nickel was in the form of bars, 4.8 cm. degrees of hardness. wide and 0.61 cm. thick, which were then rolled to the successive degrees of thickness and hardness as shown in Fig. 2. Due to the size of the strips as rolled it was possible to cut from the centre of each strip, longitudinally, two parallel strips 0.9 cm. wide. This gave a chance to check results for each degree of cold reduc-
June, rsr.1
THE \~IILARI REVERSAL EFFECT.
847
tion expressed in per cent. The strips as finally used were 0.9 cm. wide and 58 cm. long with thicknesses as left by rolling. Table I gives the chemical analysis of the nickel from which the strips were rolled. TABLE I. Copper
.....................................
Nickel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Iron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sulphur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .._.... Silicon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carbon
..................................... Manganese . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
0.16
98.88 0.56 0.008 0.06 o.og 0.23
The two sets of strips were numbered:
A,,A2,A3,A4............A11 and B,,B,,B,,B,........... .Bll, respectively.
The subscripts refer to the sample numbers as given in Fig. 2. In the cutting and shaping of these strips great care was taken not to‘ raise the temperature of the strip more than ten or fifteen degrees centigrade, in order that as little change as possible would be produced in the physical properties of the strips. The changes in length were first measured as rolled. After annealing at 304” C. for an hour to take out local strains, the changes in length of the strips were again measured. This annealing process affected the Joule magnetostrictive effect a little as shown in Fig. 3. Fig. 4 shows how the change in length progressed in the strips A, and A,, as the field increased from zero up to about 1200 gauss. Curves for the other strips are not shown, since from A, to A,,, inclusive, they are practically the same as A,,.The values for A,, are shown because this strip had the highest hardness The similarity of the curves for the Joule effect, after number. the second reduction, is shown in Fig. 5, where the values are Whatever the taken for the field strength of 58.88 gauss. machinery whereby the change in length occurs, it is all reduced to the same phase after the second reduction. Fig. 5 also shows how reproducible the results are. The circles show the values of the changes in length for the A series of strips and the square dots are those for the B series. Attention is called to the close agreement between the two sets of readings. It is unfortunate that, in controversies of the sort indicated in
s.
848
R.
[J.
WILLIAMS.
F. I.
this paper, others did not have an opportunity for checking the results of those finding the Villari reversal or -Ace zlersn. Thus far the evidence seems to support the conclusion that in FIG. 5.
The
machinery
for magnetic
change duction.
the tension-magnetization reversal points.
in length is reduced to the same In all cases. H = 58.88 gauss.
curves
of nickel
phase
there
after
are
the second
no
re-
Villari
BIBLIOGRAPHY. ’ EWING
: “Magnetic
Induction in Iron, Etc.,” p. 198, 1900. 3d Ed. d. Wurzb. ph_vs.-med. Ges., II Mirz, 1893; ’ HEYDWEILLER, A. : Sitzmgsber. Phil. Mug., 3.5, p. 469, 1893; Beibl., 17, p. 1095, 1893; Ann. d. Phys., 52, P. 462, 1894. MEYER, S.: Ann. d. Phys.. 59, pp. 134 and 142, 1896. HONDA, K., and SHIMIZU, S.: Am. d. Phys., 14, p. 791, 1904; Phys.
Zeits.,
5, P. 254, 1904. HEYDWEILLER,A.: Am. d. Phys., 15, p. 415, 1904; Phys. .&its., 5, p. 255, 1904. HONDA, K., and SHI~UZU, S.: Ann. d. Phys., 15, p. 855, 1904; Phys. Zeits., 5, P. 631, 1904. a WILLIAMS, S. R.: Phgs. Rev., IO, p. 135, 1917. ‘WILLIAMS, S. R.: Trans. A. S. S. T., 1926. of Dynamics ‘THOMSON, J. J.: “Applications 41-59, 1888 ’ WILLIAILIS, S. R.
to
Phys.
and
Chem.,”
: Phys. Rev., 32, p. 281, 1911 ; J. 0. S. A., 7, 1011, 1923.
pp.
FOR THE VILLARI EFFECT IN NICKEL.
REVERSAL
BY
S. R. WILLIAMS, Department
of Physics,
Ph.D.
Amherst
College.
IT IS a well-substantiated fact that a longitudinal pull applied to a bar of iron increases the magnetic induction when a weak magnetic field is applied, but decreases the flux in a strong field. FIG. I.
Magnetization
of annealed
iron
under
various
amounts
of longitudinal
pull.
The intensity of magnetization for an iron rod as it is magnetized, with and without a tension of 6 kilograms, is shown in the two curves of Fig. I, taken from Ewing’s book.’ The point of intsrsection of the two curves, P’, is called the “ Villari reversal point.” I,t is the point where the effect of a tension is reversed. Some years ago a series of polemical papers ’ discussed the question as to whether a similar effect could be found in nickel The arguments were left more or less unanswered or not. 843
S.
[J. F. I.
R. WILLIAMS.
because various mechanical and heat treatments may give a wide range of magnetostrictive effects, and it is barely possible that those finding the effect actually had some specimens which showed the reversal. Later it was shown 3 that if any extraneous magnetic fields were present these could give rise to Villari reversal FIG. 2.
~KROSCOPL Relation between y. cold reduction and the
various
degrees
HARDNESS of hardness
attained
by cold rolling.
points and, furthermore, when these extraneous fields were removed the Villari reversal points also disappeared in the speciEven this evidence against the possibility of mens being tested. a Villari reversal point in nickel was weak because only one kind of nickel was used. of a series of eleven In a recent study 4 of the hardness nickel strips by magnetic methods, it was possible to study the
June, igq.1
THE
VILLAKI
REVERSAL EFFECT.
845
Joule magnetostrictive effect in varieties of nickel where variations were produced by cold rolling to successive thicknesses or to different degrees of hardness. It has been shown .i that the Villari effect is the reciprocal of the Joule magnet,ostrictive effect. If a substance has its magnetic induction ‘decreased due to a tension, then that substance will shorten for those fields for which the magnetic induction FIG. 3.
Effect
of annealing
at 304’ C. for one hour.
decreased due to a tension. Similarly a rod will lengthen for those magnetic fields in which tension increases the flux. The principle Consequently if a of Le Chatelier holds in these phenomena. substance shows a Villari reversal effect, it will also show a reversal of sign in the change of length as the field is increased effect is, from zero to higher values. The Joule magnetostrictive therefore, a sensitive means of indirectly studying the presence This was the means or absence of the Villari reversal effect. the method for measuring the changes employed in this paper; in length as the field was varied has been described elsewhere.’ If nickel shows a Villari reversal effect like iron, then it will first lengthen for weak magnetic fields and shorten for strong. Twenty-two strips of nickel were studied in this work, there VOL. 203. No. 1z18-40
[J. F. I.
S. R. WILLIAMS.
846
being two samples for each degree of hardness. No initial lengthening occurred as the magnetic field was increased from Shorten&g only occwred for all field zero to larger values. stre*zgths ztp to a mlzie of 1200 gauss. This absence of the Villa& reverml isa the Gckcl ships with eleven diflerent ~hysicnl conditions ilr good evidence that the Villari rwersal poi& thus far reported for ltickel zperc fictitious. Through the courtesy of the International Nickel Company, FIG. 4. Q
IeXIO’QcM
Decreasing
the
thickness
of
a nickel
strip. 93 per cent.. change in length.
affects
tremendously
the
magnetic
eleven strips of nickel were furnished which had been rolled to This cold working of the nickel gave as successive thicknesses. Fig. 2 shows many degrees of hardness as there were reductions. the relation between the per cent. cold reduction and the various The nickel was in the form of bars, 4.8 cm. degrees of hardness. wide and 0.61 cm. thick, which were then rolled to the successive degrees of thickness and hardness as shown in Fig. 2. Due to the size of the strips as rolled it was possible to cut from the centre of each strip, longitudinally, two parallel strips 0.9 cm. wide. This gave a chance to check results for each degree of cold reduc-
June, rsr.1
THE \~IILARI REVERSAL EFFECT.
847
tion expressed in per cent. The strips as finally used were 0.9 cm. wide and 58 cm. long with thicknesses as left by rolling. Table I gives the chemical analysis of the nickel from which the strips were rolled. TABLE I. Copper
.....................................
Nickel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Iron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sulphur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .._.... Silicon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Carbon
..................................... Manganese . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
0.16
98.88 0.56 0.008 0.06 o.og 0.23
The two sets of strips were numbered:
A,,A2,A3,A4............A11 and B,,B,,B,,B,........... .Bll, respectively.
The subscripts refer to the sample numbers as given in Fig. 2. In the cutting and shaping of these strips great care was taken not to‘ raise the temperature of the strip more than ten or fifteen degrees centigrade, in order that as little change as possible would be produced in the physical properties of the strips. The changes in length were first measured as rolled. After annealing at 304” C. for an hour to take out local strains, the changes in length of the strips were again measured. This annealing process affected the Joule magnetostrictive effect a little as shown in Fig. 3. Fig. 4 shows how the change in length progressed in the strips A, and A,, as the field increased from zero up to about 1200 gauss. Curves for the other strips are not shown, since from A, to A,,, inclusive, they are practically the same as A,,.The values for A,, are shown because this strip had the highest hardness The similarity of the curves for the Joule effect, after number. the second reduction, is shown in Fig. 5, where the values are Whatever the taken for the field strength of 58.88 gauss. machinery whereby the change in length occurs, it is all reduced to the same phase after the second reduction. Fig. 5 also shows how reproducible the results are. The circles show the values of the changes in length for the A series of strips and the square dots are those for the B series. Attention is called to the close agreement between the two sets of readings. It is unfortunate that, in controversies of the sort indicated in
s.
848
R.
[J.
WILLIAMS.
F. I.
this paper, others did not have an opportunity for checking the results of those finding the Villari reversal or -Ace zlersn. Thus far the evidence seems to support the conclusion that in FIG. 5.
The
machinery
for magnetic
change duction.
the tension-magnetization reversal points.
in length is reduced to the same In all cases. H = 58.88 gauss.
curves
of nickel
phase
there
after
are
the second
no
re-
Villari
BIBLIOGRAPHY. ’ EWING
: “Magnetic
Induction in Iron, Etc.,” p. 198, 1900. 3d Ed. d. Wurzb. ph_vs.-med. Ges., II Mirz, 1893; ’ HEYDWEILLER, A. : Sitzmgsber. Phil. Mug., 3.5, p. 469, 1893; Beibl., 17, p. 1095, 1893; Ann. d. Phys., 52, P. 462, 1894. MEYER, S.: Ann. d. Phys.. 59, pp. 134 and 142, 1896. HONDA, K., and SHIMIZU, S.: Am. d. Phys., 14, p. 791, 1904; Phys.
Zeits.,
5, P. 254, 1904. HEYDWEILLER,A.: Am. d. Phys., 15, p. 415, 1904; Phys. .&its., 5, p. 255, 1904. HONDA, K., and SHI~UZU, S.: Ann. d. Phys., 15, p. 855, 1904; Phys. Zeits., 5, P. 631, 1904. a WILLIAMS, S. R.: Phgs. Rev., IO, p. 135, 1917. ‘WILLIAMS, S. R.: Trans. A. S. S. T., 1926. of Dynamics ‘THOMSON, J. J.: “Applications 41-59, 1888 ’ WILLIAILIS, S. R.
to
Phys.
and
Chem.,”
: Phys. Rev., 32, p. 281, 1911 ; J. 0. S. A., 7, 1011, 1923.
pp.