Mechanical Properties of Nickel

Some of the mechanical properties of nickel were noted by the early workers. J. B. Richter observed that nickel is hard and susceptible of a high polish, it is very ductile, and may be hammered, either hot or cold, into plates 1/100th in. thick, or drawn into wires 1/54in. in diam. In more recent times it has been rolled into sheets 0.0008 in. in thickness, and drawn into wires of 0.0004 in. in diam. O. W. Ellis studied the malleability. According to L. Thompson, the malleability of purified nickel is so great that it can be rolled out nearly to the thickness of tinfoil. R. Tupputi said that nickel wears down a file rapidly, and when bent, it becomes hot, and shows an indented fracture. Its malleability is diminished by dissolved carbon or manganese. C. Brunner, and O. L. Erdmann emphasized the brittleness of the nickel which they prepared, and added that when broken by repeated hammering it may exhibit a lustrous, coarse-grained fracture. H. St. C. Deville showed that the metal can be forged without undue oxidation, and the wires are nearly 15 times as tough as iron wires of equal thickness.

T. Fleitmann found that additions of zinc or magnesium augment the toughness and malleability of nickel, and several other metals - Cd, Sn, Pb, Mn, and Fe - can be alloyed with nickel without impairing its working properties. W. C. Roberts- Austen added that the effect of 0.001 part of magnesium is marked. H. Wedding observed that manganese favoured the tensile properties of nickel; and J. Garnier found that 0.003 part of phosphorus enhances the working properties of nickel. H. Wedding, and G. von Selve and F. Lotter added that the cracking and poor working properties of some varieties of nickel are due to the presence of oxygen as nickelous oxide, and this can be overcome by adding deoxidizing agents - e.g., manganese, magnesium, etc. - to the molten metal.

Commercial nickel is not always malleable, and this is satisfactory when the metal is required for making alloys, but for making rods, wires, sheets, etc., malleability is an essential quality. If the metal be cast without magnesium, it is weak, and not malleable hot or cold, and a section of the casting is often honeycombed with blow-holes; cast with the magnesium - malleable nickel, previously described - the nickel is sound, homogeneous, and strong; it can be worked hot or cold; and in this malleable state it can be forged, rolled, cast, drawn into wire, spun, and otherwise worked. D. H. Browne and J. F. Thompson recommended 1200° for hot-rolling, and added that a temp, much in excess of this produces a condition approaching red-shortness; and that annealing begins at about 750°, full softness being attained at 900° - the temp, recommended for annealing. G. E. Gardam and D. J. MacNaughtan found that annealing electrodeposited nickel reduces the tensile strength.

According to J. B. Richter, and L. Thompson, nickel can be welded like iron, but C. D. Tourte succeeded in welding the metal only imperfectly. D. H. Browne and J. F. Thompson observed that nickel cannot be welded in the ordinary sense, viz. heating in a blacksmith's forge and hammering to a solid weld as with wrought iron. This is due to the absence of a proper flux to dissolve and remove the nickel oxide produced by heating. If the operation be conducted in a reducing atmosphere, nickel readily welds. Nickel can also be welded by means of the oxyacetylene flame, by electric spot-welding, or by butt-welding, where the two pieces form the electrodes and are pushed together so as to extrude the oxide from the weld. In this way it is possible to weld nickel wire to iron to form tips or points for sparkplugs, etc. F. Sauerwald and E. Jaenichen studied the adhesion between surfaces of the metal.

Young's Modulus for Small Stresses.

M. F. Angell found that the elasticity of nickel is greatly reduced by quenching, but it can be increased to its original value by annealing at a high temp. The elastic modulus, or Young's modulus, was found by M. Cantone to be 22,790 kgrms. per sq. mm.; G. S. Meyer gave 21,680 kgrms. per sq. mm.; H. J. Tapsell and J. Bradley, E. Griineisen, 0. Faust and G. Tammann, J. Galibourg, A. Wassmuth, K. F. Slotte, and W. Meissner, 20,000 to 22,000 kgms. per sq. mm.; and W. Voigt, 20,300 kgrms. per sq. mm. G. Searle gave 23,950 kgrms. per sq. mm. for the drawn metal, and C. Schaefer, 23,544 kgrms. per sq. mm. W. Sutherland noted that the recorded results gave the average value 22,400 kgrms. per sq. mm. H. Tomlinson gave 2271×10⁶ grms. per sq. cm. for hard-drawn wire, and 2175 ×10⁶ grms. per sq. cm. for annealed wire. A. L. Kimball and D. E. Lovell gave 21×10¹¹ dynes per sq. cm. for the cold-rolled metal; and K. Honda and T. Tanaka, 1.930×10¹² dynes per sq. cm. D. K. Froman's results for Young's modulus with small stresses are summarized in Fig. L. C. Tyte observed that nickel, like other metals examined, shows a deviation from Hooke's law over the whole experimental range examined; the actual deviation was found to vary with the heat treatment, and cold working.

The Effect of Temperature on the Elastic Modulus of Nickel.

W. Widder discussed the effect of temp, on the elastic constants, and gave E=E₂₀{1-0.0006983(θ - 20)}. A. Mallock gave 1.12 for the ratio of Young's modulus at - 273° to its value at 0°. C. Schaefer observed that for temp, between 20° and - 186°, the modulus increased 2463 kgrms. per sq. mm. per 100° difference of temp. K. R. Koch and C. Dannecker found that the elastic modulus of nickel has a minimum near 100°, a maximum near 300°, another minimum near 1200°, and a maximum near 1250°, indicating a second transformation temp, besides that between 300° and 400° - Fig. J. Zacharias found Young's modulus decreases about 13 per cent, for annealed nickel between 20° and 200°; there is then an increase of about 6 per cent, up to the Curie point; and above the Curie point there is a linear decrease. The results of K. R. Koch and C. Dannecker, and E. P. Harrison, in kgrms. per sq. mm., are, for the torsion and Young's moduli:

	20°	27.5°	96°	110°	200°	300°	400°	600°	1000°	1300°
Torsion.	-	7,300	-	6,430	6,860	1,390	7,120	6,080	3,730	2,480
Young's	22,000	-	21,300	-	-	-	15,700	-	-	-

The Effect of Cold-work, and of the Temperature of Annealing on the Elastic Modulus of Nickel

E. P. Harrison represented the effect of temp, on the elastic modulus, E, of nickel by E=E₀(1 – 0.000286θ – 0.0000008465θ²), where E₀=22,200 kgrms. per sq. mm. up to 300°. Above 325°, the modulus decreases rather more rapidly, reaching a minimum just below 400°; it then remains nearly constant to 425°, above which a rapid decrease occurs. Above 425°, some structural change occurs in which Hooke's law does not apply, for small loads then produce a permanent stretch which does not recover with time. This temp, is near to that at which critical points occur in the magnetism, thermoelectricity, electrical resistance, and thermal expansion. As with steel, the elastic after-effect increases with temp. Loading above a certain value, and subsequently unloading, is followed by a recovery of length, but not of elasticity. K. Honda and T. Terada gave for the elastic modulus of purified nickel 1.708×10¹² dynes per sq. cm. for a load of 1599 grms. per sq. mm., and 1.902×10¹² dynes per sq. cm. for a load of 10,480 grms. per sq. mm.; and for commercial nickel, 1.818×10¹² dynes per sq. cm. for a load of 1376 grms. per sq. mm., and 2.212×10¹² dynes per sq. cm. for a load of 9023 grms. per sq. mm. T. Kawai studied the effect of cold-work on Young's modulus. Gr. W. Pierce studied the subject. T. Kawai examined the effect of cold-work on Young's modulus - vide iron - and found that with the given maximum stress in stretching, kgrms. per sq. mm. (dotted curve, Fig.), the corresponding modulus of elasticity, kgrms. per sq. cm. × 10^-4, were as shown in Fig.. The effect of annealing the cold-worked metal at different temp, is also shown in the same diagram, Fig. 6. A. Ancelle studied the subject. M. F. Sayre investigated the elastic after-effect. G. A. Tomlinson discussed the relations between the elastic and cohesive forces; A. L. Bernoulli, J. Kleiber, and A. H. Stuart, the relations between the elastic forces and the sp. ht.; A. Mallock, the relation between the temp, coeff. of the elastic modulus and the m.p.; and A. Press, E. Griineisen, S. Ratnowsky, and J. P. Andrews, the relation between the coeff. of thermal expansion, the at. vol., and the elastic constants. B. Bogitch studied the effect of the mode of preparation of nickel on its physical properties. E. C. Thompson and W. E. W. Millington observed that a specimen of nickel for which the elastic limit was 5570 kgrms. per sq. cm. showed slip-bands under a stress of 788 kgrms. per sq. cm.

J. R. Benton gave 0.33 for Poissan's ratio; and A. Wassmuth, K. F. Slotte, and W. Meissner gave 0.30. H. Rolnick calculated Poissan's ratio, ω, from ω=0.5-1/6Ek, where E denotes Young's modulus such that E=20.2×l0^-1 c.g.s. units, and k is the compressibility, 0.542 c.g.s. units, consequently ω= 0.318. E. Gruneisen observed 0.31.

According to W. Gowland, the tensile strength of wrought nickel is 42.4 tons per sq. in. W. B. Parker gave 40 to 45 tons per sq. in. for the maximum stress of commercial nickel, and for purified nickel, 18 to 20 tons per sq. in.; the proportional limit for the commercial metal is 18 to 20 tons per sq. in., and for the purified metal, 6 to 10 tons per sq. in.; the elongation in 8 in. is 4.5 to 2 per cent, for the commercial metal, and 8 to 15 per cent, for the purified metal. H. Copaux gave 18,000 lbs. per sq. in. for the tensile strength of nickel - vide cobalt; L. Jordan and W. H. Swanger, 46,400 lbs. per sq. in. for 99.94 per cent, nickel; and W. von Selve, 42 kgrms. per sq. mm. and an elongation of 32 per cent, for the metal annealed after rolling. D. H. Browne and J. F. Thompson gave for samples of commercial, malleable nickel: yield-point, when cold-rolled, 90,000 to 110,000, and, when annealed, 20,000 to 30,000 lbs. per sq. in.; tensile strength, when cold-rolled, 100,000 to 120,000, and, when annealed, 60,000 to 90,000 lbs. per sq. in.; elongation in 2 in., when cold-rolled, 15 to 20, and, when annealed, 40 to 50 per cent.; and the reduction of area, when cold-rolled, 40 to 50, and, when annealed, 45 to 55 per cent.

R. A. Hadfield found for the tensile properties expressed in tons per sq. in. to be:

	Elastic limit	Tensile strength	% Elongation in 2 inches	% Reduction of area	Fracture
Cast bar unannealed	11	16.25	4.50	9.76	Granular
Forged bar unannealed	14	32.20	45.50	57.04	Fibrous, silky
Forged bar annealed	7	31.25	54.00	52.50	Fibrous, silky

J. Kollmann gave 38.9 tons per sq. in. for the tenacity of nickel containing 0.05 per cent, of magnesium. Observations were made by H. J. Coe, M. Combe, S. Erk, H. J. French and W. A. Tucker, C. E. Guillaume, T. Kawai, R. Koch and R. Dieterle, P. D. Merica and R. G. Waltenberg, H. F. Moore and T. M. Jasper, W. A. Mudge and L. W. Luff, C. E. Ransley and C. J. Smithells, and A. Schulz.

P. Ludwik, and W. del Regno observed that the tensile strength of nickel gradually falls as the temp, rises until it attains a value of 48.5 kgrms. per sq. mm. at 400°, and it then falls nine times more rapidly to 35.8 kgrms. per sq. mm. at 500°. The break near 400° corresponds with breaks also found in the rigidity, resistance, thermo-electric power, and emissive power. F. Robin found that the maximum brittleness occurred at 300 to 350°; I. M. Bregowsky and L. W. Spring gave for the tensile strength, and yield point in lbs. per sq. in. at different temp.:

	21°	149°	232°	315°	399°	460°	482°	499°	538°
Tensile strength	38,000	40,900	36,700	35,900	36,600	28,500	27,800	31,900	16,800
Yield point	23,800	25,100	25,100	22,900	22,600	-	14,200	-	-

and A. le Chatelier gave for the tensile strength, T kgrms., and the elongation, E per cent., of a wire at different temp.:

	15°	100°	150°	200°	250°	300°	350°	400°	460°
T	55.2	55.2	55.1	55.0	54.0	51.0	46.0	37.0	30.4
E	16	16	16	17	20	21.5	23	21	15

The fall in the tensile strength and the corresponding drop in the elongation and reduction of area have been attributed to an allotropic change corresponding with the change in magnetic properties. This does not agree with observations on the space-lattice, and Z. Jeffries and R. S. Archer attribute the effect to a spontaneous hardening of the metal, such as occurred with the samples tested by W. P. Sykes for Brinell's hardness. The hardening is attributed to the spontaneous healing of slip-planes formed during deformation. In W. P. Sykes' tests, nickel wires freshly cold-drawn from 0.090 in. to 0.025 in. diameter, were placed in a muffle for heat treatment, or kept in liquid air until tested for the tensile strength, in lbs. per sq. in. - the object of the liquid air treatment was to prevent self-hardening which is known to occur in iron, but very slowly at low temp.:

	Tested after 15 min. in liquid air	250° (45 min. after drawing)			250° (2 hrs. after drawing)		275°
Time heating		1	5	20	5	15	5	20	30
Tensile strength × 10-3	125.75	126	128	130	128	130.5	130.5	132	131

The Tensile Strength of Nickel at Different Temperatures.

W. P. Sykes' curves, Fig., discussed by Z. Jeffries and R. S. Archer, for the tensile strength of annealed and cold-drawn nickel show the tendency of the metal to decrease in strength with a rise of temp. The break in the annealed wire between 200° and 300° has just been discussed. The discontinuity with the cold-drawn wire is less apparent. Annealing occurs rapidly between 600° and 800°. The elongation curves for the same wires are shown in Fig. Below the temp, of recrystallization of the annealed wire, there is a general tendency to increasing elongation with decrease of temp. This is interrupted at 200° to 400°, and the minimum in the elongation at 200° corresponds with the horizontal portion of the tensile strength curve. The slight drop in the elongation on cooling from room temp, to the temp, of liquid air is attributed to the beginning of low temp, brittleness. It is probable that at some intermediate temp, the elongation will be higher than at any point on the curve.

The Elongation-Temperature Curves of Nickel

The elongation of cold-drawn wire increases continuously as it is cooled from 200° down to the temp, of liquid air. There is no drop in elongation at low temp., and this corresponds with the general observation that cold-drawn metals remain ductile at lower temp, than do annealed metals. The rise in elongation in the cold-drawn wire above 400° is due to annealing. The elongation curves, Fig., refer to wire reduced the same amount (61 per cent.) at room temp, and at 400°, respectively.

The Effect of Annealing on the Tensile Properties of Commercial Nickel.

The elongation of the latter is higher in agreement with the general observation that the effect of cold-work is greater the lower is the temp, at which it is effected. There is a distinct minimum in elongation at 300° corresponding with the horizontal zone in the tensile strength curve for annealed nickel. The minimum in the elongation, Fig., is attributed, in part at least, to a blue-heat phenomenon. Observations on the effect of temp. on the tensile properties of nickel were made by B. Bogitch, A. le Chatelier, P. Chevenard, E. W. Colbeck and W. E. MacGillivray, F. A. Fahrenwald, P. Goerens and P. Mailander, L. Guillet and J. Cournot, W. J. de Haas and R. Hadfield, D. H. Ingall, K. R. Koch and R. Dieterle, W. Lode, P. Ludwik, W. del Regno, F. Sauerwald and co-workers, W. P. Sykes, H. J. Tapsell and J. Bradley, and C. Upthegrove and A. E. White.

O. Schwarz observed for the effect of rolling, expressed as a percentage reduction, on the tensile strength, expressed in kgrms. per sq. mm.

Reduction	0	6.0	9.1	20.8	39.5	60.2	80.0	88.0 per cent.
Tenacity	43.6	45.1	46.6	54.4	65.2	77.0	84.5	95.1

L. Guillet and co-workers, and M. Weidig observed that annealing the metal at 400° to 800°, and then cooling it in air, reduced its tensile strength, expressed in tons per sq. in.:

	Original metal	Annealed at
		400°	600°	800°
Tensile strength	48.0	47.9	40.1	34.5
Elongation	3.5	11.0	11.5	32.5

L. Guillet examined the effect of annealing on the tensile strength of hard-drawn nickel wires. In all cases the temp, of complete annealing corresponded with a rapid fall in the maximum strength and elastic limit, and a rapid increase in the elongation, and it was practically independent of the amount of cold work. The tensile strength, elastic limit, and elongation of hardened nickel are not affected by heating the metal to a temp, below 400°; a slight deflection occurred at about 400°, and a marked alteration between 700° and 750°. The temp, of complete annealing for nickel is between 700° and 750°. L. Guillet also concluded that the effect of time on the annealing process is relatively small. W. B. Price and P. Davidson represented the effect of annealing on the tensile properties of commercial, cold- rolled nickel by the curves, Fig. The tests were made with and across the grain. The annealing range is between 600° to 800°. Commercially, the metal is annealed at about 900°. No difference has been noticed in quick or slow cooling from the annealing temp.

Notched-bar Strength and Hardness of Nickel.

J. Galibourg, and A. Ancelle studied the effect of ageing on the cold-worked metal at 15°, at 175° to 180°, and at 225° to 235°; J. McNeil, the effect of the casting temp.; F. C. Lea, the effect of hydrogen - see iron; P. D. Merica and R. G. Waltenberg, the effect of impurities - vide infra, the alloys of nickel; and G. Tammann, the effect of cold-work.

F. Sauerwald and T. Sperling studied the notched-bar test, and the results are summarized in Fig. There is a minimum near 380°, and a maximum near 450°, and these singular points also occur in the hardness curve. A. Jacquerod and H. Mugeli observed the bending elasticity of drawn nickel to be 22,100 kgrms. per sq. mm. at 0°, and of annealed nickel, 20,400 kgrms. per sq. mm. The temp, coeff. between 0° and 100° are, respectively, 0.0003108 and 0.001056. J. Cournot and M. S. Silva found that the creep-stress of nickel is about twice that of steel at temp, between 500° and 700°. P. L. Irwin, H. J. Gough and D. G. Sop with, G. A. Hankins, H. F. Moore and T. M. Jasper, and J. M. Lessels studied the fatigue and corrosion fatigue strength of nickel. D. J. McAdam obtained data for some static tests, and also for the endurance limit of nickel under cyclic stresses - rotating and alternating torsion.

The Fatigue and Corrosion-Fatigue of Nickel.

The simultaneous action of corrosion and fatigue - corrosion-fatigue - may cause failure at stresses far below the ordinary endurance limit - vide the corrosion of iron. The results of the tests are represented in the form of graphs of the stress, and the logarithm of the numbers of cycles for failure. The specimens were simultaneously exposed to the action of fatigue and corrosion in air (fatigue curve), fresh, carbonate water, and salt water having about one-third the saline content of sea- water, and stresses alternating at 1450 revs, per minute, gave the results for corrosion-fatigue indicated in Fig. O. Behrens studied the subject.

C. Schaefer gave 9518 kgrms. per sq. mm. for the torsion modulus, or the rigidity of nickel; W. Voigt gave 7820 kgrms. per sq. mm.; and E. Gruneisen, A. Wassmuth, K. F. Slotte, and W. Meissner gave 7800 kgrms. per sq. mm. H. Tomlinson obtained 723×10⁶ grms. per sq. cm. for tlie rigidity of hard-drawn and annealed nickel wires. K. Honda and T. Tanaka gave 7.50×10¹¹ dynes per sq. cm. for the rigidity of nickel; and B. Gutenberg and H. Schlechtweg obtained 8×10¹¹ dynes per sq. cm. K. Iokibe and S. Sakai found the rigidity of wires of length 27.2 cm., and diameter 0.326 mm., to be

	27°	58°	127°	208°	330°	402°	490°	572°
Rigidity ×10-11	7.23	7.21	7.09	6.95	6.68	6.31	5.38	4.29

The Effect of Cold-Work on the Rigidity Modulus of Nickel.

The results are plotted in Fig. The diminution of the rigidity with rise of temp, is relatively small in the ferromagnetic region up to 400°, but above that temp, the decrease is rapid. W. del Regno noted a break in the rigidity-temperature curve near 400°. W. Voigt said that the temp, coeff. of the torsion modulus, in percentages between 20° and - 186°, is - 3-18. Observations were made by T. Gnesotto and L. A. Alberti, T. Kawai, C. E. Guye and H. Schapper, S. Higuchi, K. Honda and S. Konno, T. Kikuta, G. Subrahmanian, and H. J. Tapsell and J. Bradley. P. W. Bridgman found that with an increase in press, up to 10,000 kgrms. per sq. cm., the rigidity modulus increases 1.84 per cent. W. Lode discussed the rate of flow under the influence of press, and of tension.

The Rigidity and Logarithmic Decrement of Nickel at different Temperature.

T. Kawai measured the effect of cold-working on the rigidity of nickel, and obtained the results summarized in Fig. for the metal annealed at 15° and at 100°. K. R. Koch and C. Dannecker's, and E. P. Harrison's results are indicated above, and those of D. J. McAdam, below. T. Lonsdale studied the changes in the dimensions of nickel produced by torsion, and he found that if e denotes the elongation of nickel wire as a percentage of the initial length; T, the twist in turns per cm.; t, the initial torsion in kgrms. per sq. cm.; and D, the diameter in cm., then e=DT(5.8 + 0.023t). L. di Lazzaro observed that when torsional and tensile stresses are simultaneously applied to nickel, the modulus of torsion is diminished, and restored when the tension is released. C. Schaefer observed that the relation between the torsion modulus and the m.p. is the same as that observed between the hardness and the m.p.; and D. Schenk studied the effect of torsional oscillations on the rigidity of nickel.

H. Tomlinson gave 0.002005 for the logarithmic decrement (base 10), λ, of a torsionally-oscillating, hard-drawn nickel wire, and for the annealed wire, 0.000852. K. Iokibe and S. Sakai measured the logarithmic decrement of nickel wires at different temp., and for wires with the moment of inertia 33,358 grms. per sq. cm., length 27.2 cm., and diameter 0.326 mm., they found

	22°	72°	115°	205°	239°	338°	492°	546°
λ×105	160	147	151	180	163	262	2730	4130

The results are plotted in Fig. For ordinary temp., and up to 80°, the logarithmic decrement decreases; then increases to a maximum at 160°; decreases slightly to 250°, and then increases rapidly. The existence of the maximum is a resultant of the increasing effect due to temp., and the decreasing effect due to the magnetic transformation of nickel. J. Cournot and M. S. Silva, and M. Ishimoto also studied the internal viscosity of nickel; and T. Gnesotto and L. A. Alberti, and K. Honda and S. Konno, the rigidity and viscosity at the Curie point.