US2213198A - Age hardenable nickel alloys possessing hot workability - Google Patents

Description

Patented Sept. 3, 1940 PATENT OFFICE- AGE HARDENABLE meant. more POSSESSING HOT WOBKABILITY Clarence George Bieber and Mortimer Pierce Buck,

Huntington, W. Va., assignors to The International Nickel Company, Inc., New York, N. Y., a corporation of Delaware No Drawing. Application November 12, 1938, SerialNo. 240,012

9 Claims.

The present invention relates to age hardenable' nickel alloys and age hardened articles made thereof, andmore particularly to hot malleable age hardenable nickel alloys and improved age hardened articles made thereof.

It is well known thatalloys of nickel with carbon and magnesium can be hardened by heat treatment. These alloys have never-attained any degree of commercial importance because useful 10 increases in physical properties could not be ob- -tained within the composition range which was commercially ,hot malleable. This limited their possible use to casting purposes for which they were ill suited because of their inherent sluggish casting qualities. The necessity for rapid cooling further limited the size of castings to small articles and also tended to induce cracking in castings having irregular shapes and contours and changing from large cross sections to small cross sections and vice versa. Thus, in United States PatentNo. 1,986,585 granted on January 1, 1935,

to Wilhelm Kroll, it was asserted that nickel and nickel alloys were age hardenable when up to 10% of alkaline earth metal, including magne- 2Q sium and lithium,'was incorporated in the material, preferably in the presence of carbon. In the case of magnesium, it was preferred to maintain the element within the range of 0.8% lto 1.8% and the carbon within the range of 0.05% to 0.2%. 1 In actual practice on anindustrial scale, it was found that the alloys possessed certain shortcomings and were not commercially hot malleable. The alloys were also found to posesess a low burning" temperature, 1. e., a low temperature of incipient fusion, and were likewise found to be red short at temperatures slightly below the burning temperature.

Although many attempts were made to remedy the aforementioned shortcomings, none, as far capable of being carried into large scale, practical operations of an industrial character. We have discovered .that the prior art shortcomings can be avoided and that new and unexpected resultsycan be obtained by incorporating critical amounts of titanium in nickel containing critical amounts of magnesium and carbon.-

We have found that'nickel which contains controlled and critical amounts of carbon, magnesium and titanium, possesses improved hot malleability during processing'and improved properties after beingsubiected to age hardening.

It is'an object ofthe present invention to pro- 55 vide improved age hardened articles of manufacproved hardened articles of manufacture made as we are aware, was entirely successful when carried into practice commercially and none was then discovered that the carbon and magnesium ture made of nickel which is commercially hot malleable when controlled and critical. amounts of carbon, magnesium and titanium are incorporated in the nickel.

It is another object of the present invention 5 to provide improved age hardened articles of manufacture which possess improved mechanical properties and made of high nickel alloys which possess improved hot malleability and improved capability of being readily worked or drawn.

It is a further object of v the present invention to provide improved age-hardened articles of manufacture which possess high hardness, breaking strength, proportional limit, ductility, toughof nickel to which there have been added controlled and restricted amounts of carbon, magnesium, and titanium. We have discovered that a small, controlled amount'oftitanium in conjunction with ontrolled andrestricted amounts of carbon and cannot be successfully processed fromcommercial melts into malleable products. a We have furfor example about 0.2% v to about 0.75%, while the carbon content must be maintained within the range of about 0.15% to about 0.5% and the magnesium' content within therange of about [I 0.20% to about 0.45%. The high nickel alloys, 1. e., alloys preferably containing approximately 98% to 99% nickel, are rendered susceptible to age hardening by heat treatment when the material is quenched or rapidly cooled from temperatures between about 1850 F. and 2350 F. Preferably, a temperature of about 1950 to 2000 F. is employed. After this quench-anneal, the material now in a softened condition is readily rolled, forged, drawn, etc., in the cold condition without signs of cracking, etc. Hot worked material must be given a final quench from the softening range, preferably about 1950 to 2000 F., when the material is to be subsequently age hardened. The aging procedure is carried out at temperatures between about 750 F. and about 1200 F., preferably about 930 F., for periods of about one hour to about 24 hours or longer, but preferably about 16 hours. Breaking strength values have been developed by this treatment on material in the annealed condition without any preliminary cold work within the range of about 200,000 to 210,000 pounds per square inch and values of about 180,000 to 190,000 pounds per square inch can be readily obtained. The corresponding hardnesses vary from about 340 to about 400 Brinell hardness and about 38 to about 44 Rockwell C hardness.

In carrying the present invention into practice, it is preferred to incorporate in nickel the essential elements, carbon, magnesium and titanium, approximately within the ranges given in Table I.

When nickel is said to constitute the balance or when we say that the balance is substantially all nickel, we include within the expressions nickel plus cobalt and also minor constituents and impurities such as copper, manganese, iron, silicon, sulf r, ,etc. Thus, an alloy might contain 0.2% copper, 0.25% manganese, 0.6% iron, 0.3% silicon, 0.02% sulfur, etc., in which case the actual nickel plus cobalt content could be as low as about 96.5% when the maximum amount of essential elements is also present. It is preferred to maintain the nickel plus cobalt content somewhat higher, e. g., about 98.5%.

Cobalt may be present as an incidental element usually associated with nickel, for example, in small amounts less than about one to two percent such as 0.4%. However, we do not desire to be restricted to these particular amounts of cobalt. On the contrary, cobalt may be present in such amounts as occur in commercial nickels as an incidental element, or in amounts not substantially affecting the properties of the nickel alloy. While it is preferred to maintain the composi-. tion within the ranges specified in TableI, satisfactory results are obtained when any two of the essential elements are held approximately near or within the ranges specified in Table I, and the third element is present in amounts approaching the maximum or minimum amounts specified hereinbefor'e. Table II gives the composition and properties of some materials containing approximately the maximum amounts or the minimum amounts of each of the essential elements, the other two essential elements in each example being present in approximately average or preferred amounts.

Table II Per- Per- Perccnt Ductility o cleingt ceTnt PercentNi B.H. N. g ,o

Dewar 0. 15 0. 34 0.44 250 1200 to 2350 0. 45 0. 32 0. 27 321 1600 to 2300 0.30 0. 22 0. 25 277 1400 to 2350 0. 30 0.42 0. 25 375 1600 to 2150 0.29 0.32 0.14 331 1400 to 2350 0.23 0.29 1.04 do 350 1400 to 2150 B. H. N.=l3rincll hardness after heat treatment.

Ductility range, F.=ronge of good but ductility in T.

We have found that accurate control of the essential elements is of great importance for the production of the malleable material required in the processing of the hardened articles contemplated by the present invention, especially in the hot condition. If the carbon content is much below 0.2% the maximum mechanical properties are sharply-reduced. When the carbon content is above 0.3% both hot malleability and cold malleability are sacrificed. Magnesium should preferably be present within the range of about 0.3% to 0.4% to develop best properties. If present in quantities below 0.20% substantially no response to heat treatment is obtained while quantities of the order of 0.20% to 0.25% render material slightly responsive to heat treatment. Very little increase in mechanical properties is obtained by. increasing the magnesium content above the 0.4% limit of the preferred range, while quantities above this percentage result in a sharp de crease in hot ductility. Higher magnesium contents narrow the hot malleable range both by decreasing the burning temperature, i. e., the upper limit of temperature to which the material may safely be heated, and by increasing the red short range at low red heats. Nickel containing carbon, magnesium and titanium, within the ranges contemplated by the present invention, is commercially malleable and permits the material to be processed into wrought products. In addition, the mechanical properties are markedly increased and the heat treatment is rendered less difificult. Alloys free from titanium usually have a low burning temperature of about 1950 F. and cannot be hot worked above this temperature without'rupturing. Due to their low burning temperature these alloys cannot be heated to high enough temperatures to make them soft enough for forging, etc., without burning them. In addition to their low burning temperatures the titanium-free alloys are also red short at temperatures below about 1900" F. These two conditions leave the titanium-free alloys substantially no hot working range as hot working must be carried out below the burning temperature and above the red short range. From a commercial point of view this has been an extremely serious handicap due to the fact that it is very difficult or practically impossible to complete hot working operations with the standard mill equipment entirely within the very limited hot working range of the titanium-free alloys. Thus, an alloy containing 1.34% magnesium, 0.20% carbon and 98.38% nickel was too hot short, even on laboratory scale operations, to permit forging. Another containing 1.08% ma nesium, 0.14% carbon and 97.93% nickel likewise possessed poor malleability and could not be forged without cracking. Nickel which contains etc., within the temperature range of about 1300 F. to about 2300 F., without any tendency to crack or corner check during hot working. A very satisfactory alloy in accordance with the present invention contains about 0.24% carbon, about 0.35% magnesium, about 0.45% titanium, the balance substantially nickel.

The markedly improved malleability of the titanium-containing high, nickel alloy permits commercial processing into a wide variety of cold or hot worked shapes by rolling, forging. drawing, etc. Hot ,bend tests, indicative of hot malleability, reveal that the titanium-free nickel-carbon-magnesium material has very poor ma1leability at practically all hot working temperatures,

i. e., fromabout 1100 F; to about 2300 F., while titanium-containing material when made in accordance with the present invention possesses good malleability over the hot working range.- For example, hot bend tests conducted at temperatures of 1300 F. to 2300 F. showed that a titanium-free material possessed poor malleabil- I ity at all temperatures except in a very narrow range around 1900 F., while a titanium-containing material had good malleability at all temperatures from 1400 F. to 2300" F. and had fair malleability at 1300" F. Y The titanium-free material possesses such a limited degree of hot malleabil:

ity that even by using very small reductions fre-- quent reheatings and a great deal of. overhauling and care, only 'a few, limited, simple products can be made on a laboratory scale at great expense'of time, labonietc. The titanium-free material cannot be used for processing on an industrial scale in commercialpractice.

The addition of titanium in critical amounts inconiuncti'on withcritical amounts of carbon and magnesium overcomes these defects and results in a product which can readily be processed into any of the shapes which are commercially available in steel or other wrought products. The addition of titanium increases the mechanical properties to a point where they exceed the strength and hardness 'of any other readily malleable, nonferrous heat-treatable alloy, The advantageous use of titanium is demonstrated in Tables m and IV. Table III gives the composition of a titanium-free alloy v(alloy A) and a similar titanium-containing alloy ("alloy B) while Table IV is illustrative of the mechani cal properties developed by these two alloys after square inch N.-Brinell hardness number.

' factory results.

Alloy B had a wide hot malleable rahge extending from about 1300" F. to about 2300 F., whereas alloyA could only be hot worked over a narrow range of high temperatures, to wit: about 1800 F. to about 2100 1}.

possessed by our nickel-carbon-magnesium-titanium alloys permits heating the material to a high working temperature, for example, about 2200" F., and hot working down to substantially any-desired temperature or, any temperature which the equipment is capable of handling. In practice, the standard hot working equipment is capable of handling metal having atemperature as low as about. 1200 F. or lower. The titaniumfree material because of its low burning temperature and high 'red short" range has practically no hot working range. In industrial practice great care must be exercised to maintain a finishing temperature within a safe zone above the-red short range. This practice leaves substantially-no-commercial hot working range for the titanium-free material. Commercial hot working operations on titanium-free material, if attempted, would in most instances be carried into the red short range thereby resulting in a finished product which would develop numerous seams, cracks, splits, fissures, corner checks, etc.,

and which would usually have to be rejected'as unsatisfactory. These prior shortcomingsand difficulties have been eliminated in the present invention and the final products have been found to be very satisfactory and commercially free from the dimculties noted hereinbefore.

Nickel containingcarbon, magnesium and titanium in the amounts contemplated by the present invention may be hardened by rapid cooling, preferably from atemperature of 1950 F.

or slightly higher, followed by a draw, prefer-- I ably at about 850 F. to 950 R, for about romeo twenty-four hours. The tensile strength can rial is in the soft condition following the 1950 F. quench and may then be cold fabricated. Such operations as bending, rolling, drawing, forging and machining are readily accomplished. After the final machining or fabricating operation the material should preferably be hardened by heat treatingat a. temperature of about 850 F. to 950 F. for about 16 hours when mardmum properties .a.re to be developed although shorter periods, e. g., four hours, often produce satis- Due to the low hardening temperature, little, if any, .distorticn or discoloration of fabricated parts occurs during hardening. A

-- drawing or hardening temperature of about 930 F. is preferred'when starting with soft or when the Rockwell C hardness of material which has been. quenched but has not been heat treated is respectively under 25, between 25 and 35, and over 35, the corresponding heat treating or hardening temperatures are preferably about 930 to 950 F., about 905.F., and about 850 to 880 F. Thus, it willb'e observed that preferably thehardening temperature is roughly inversely proportional to the amount orextent of cold ,rdeformation received by the alloys prior to hardening heat treatment. Thus, hot rolled orannealed material is preferably heat treated at.930 F. for 16 hours. After the "draw the 1 material becomes very hard-and diflicult to fabricate and also becomes diincult to machine in most cases as the hardness ordinarily exceeds about 300 Brinell. Such operations are generally performed before hardening. In case the longer drawing period of 16 hours is considered uneconomical, a shorter period of 6 hours at 1000" F. may be employed. This will develop about 80% to 90% of the best properties obtained by the longer period at about 930 F. Somewhat lower mechanical properties may be developed by heat treating at 1100 F. for 3 hours or at 1200 F. for one hour. The higher heat treating temperatures develop somewhat. lower mechanical properties. Following the holding period at heat treating temperatures the material does not require slow cooling and may be rapidly furnace cooled, air cooled or quenched, if so desired. L

The preliminary high temperature treatment and cooling from about 1950 F..appears to be critical in obtaining the most satisfactory combinations of desired properties. The material should be left in the furnace only long enough to obtain uniform heating at the desired temperature and then immediately withdrawn and rapidly cooled, e. g., quenched in water. Since rapid removal of heat is necessary, best results are obtained on the lighter sections. In treating smaller sections air cooling may be sufliciently rapid to render the material responsive-to hardening by heat treatment, i. e., rapid air cooling is equivalent to a quench in small-sections. An important feature of the quench treatment" is that the material should be cooled sufficiently rapidly through the temperature range of approximately 1950 F. to below approximately 930 F. This cooling may be effected by any convenient method such as water or air cooling or by conduction from contact with a cold hearth as in the case of a continuous strip annealing furnace. Material may also be cooled by a combination of two or more of the convenient methods. For example, a rod may be withdrawn from a furnace preferably above 1950 F. and cooled for about 200 F. or 300 F. in air followed by water quenching. The material will develop good properties on subsequent aging provided that the interval in coolihg from approximately 1950 F. to approximately 930 F. is not too great. Satisfactory results are obtained when the cooling through the critical range takes place in less soaking at about 1950 F. results in a coarse.

grain and very poor ductility. Full and best response to heat treatment has not been obtained by quenching from temperatures below about 1830 F. The optimum quenching temperature for reducing the best combination of strength and ductility is about 1950 F. to 2000 Material quenched from these temperatures develops good response to heat treatment combined with of rods and heavy flat articles. The introduction of about 5 to 10% of hydrocarbon gas to nitrogen or hydrogen atmospheres will prevent decarbonizatlon. 1n furnaces using atmospheres of cracked (partially burned) city or natural gas the mixtures should be adjusted so as to be extremely rich, 1. e., adjusted almost to the point where carbon is deposited on the metal. Vv'henever fabrication involves a series of operations with intermediate anneals, these are preferably carried out at about 1400 F. to 1900" F. except the final quench anneal which is preferably done from about 1950 F.

Most of the strength and hardness developed by cold reduction or cold Work on material made in accordance with the present invention is retained during the low temperature hardening treatment so that further increased strength and hardness are obtained by cold working and then heat treating. Cold worked material can readily be heat treated without developing an oxide film. Without heat treatment, the material also possesses improved ability to harden by cold working alone. The greatest hardnesses, etc., are obtained when the hardening effect of heat treatment is superimposed on the hardening produced by cold reduction or cold work. For example, a quenched material possessing a tensile strength of about 100,000 pounds per square inch and a Brinell hardness of about 150 can after about 80% cold reduction possess a tensile strength of about 198,000 pounds per square inch and a Brinell hardness of about 375. After heat treating for about 6 hours at about 900 F., these properties would be further increased to about 245,000 to 250,000 pounds per square inch and about 485 Brinell. The same material without any cold reduction would, after the same heat treatment, possess a tensile strength of about 190,000 pounds per square inch and a Brinell hardness'of about '363.' Breaking strengths in excess of 200,000

pounds per square inch have been obtained by cold rolling or cold drawing annealed and quenched material 40% and then heat treating at about 900 F. An illustrative example of the composition and the properties of material made in accordance with the present invention and drawn to wire is given in Tables V and VI.

Table V 0 per- Mg Ti 2 Fe S per- Si per- Cupcr- Nipert per cent cent cent cent cm cent cent cent cent Table VI Condition Y. s. 'r. s.

Quench annealed from 2000 .3. 36.2 05.0 40.0 Quenchannealedlrom 2000 F. Aged 16 hrs. at 930 F 146.0 191.0 16.5 Quench annealed from 2000 drawn 80 177.5 108.0 2.0 Quench annealed from 2000" F' and cold drawn80%. Agcd8hrs.at900 F. 231.0 246.0 5.5

fiY.t.=yield strength in thousand pounds per square inch (0.2%

T. S.=tensile strength in thousand pounds per square inch. PercentEL=perccnt elongation in 2 inches.

The data given in Table V11 are typical examples of the average properties that can be readily developed in accordance with the present invention. It should be noted that'the properties that can be obtained depend on the size, amount and kind of hot and cold working, heat treatment, composition, etc., of the material and article.

5, to store a maximum amount of energy 'in a Table w:

Form 0! material Treatment '1. S. Y. P. El. .8. H. R. 0" IL- Oold drawn wire- Annealed condition 00-120 50-25 Do- Annealed condition heat treated i80-200 15-7 1 90- 5-32 80-45 As rolled cpndition 90-1 -65 50-25 160-225 0-10 0 As roiled condition heat treated. 160-180 120-140 20-10 300-350 38-41 Cold rolled strip Soit .t 75-90 D Soft heat treate 60-40 Do Hali hard 25-34 D Half hard heat treated- 83-42 Do- 80-40 180-230 15-5 86-46 Full hard Full hard heat treated '1. S.=tensile strength in thousand undsdper square inch.

Y. P.yicid point (0.2% offset) in t ousan pounds per square El.=elongation in 2 inches in percent. y

B. H.==Brinell hardness number (3,000 kg. load).

R. 0" H.=Rockwell "0 hardness. 'Rockwell "B" hardness.

' Table VIII shows some of the typical physical constantsof nickel which contains controlled and critical amounts of titanium, carbon, and magnesium in accordance with the present invention.

Table VIII Melting point, "F 2590 'Density, pounds per cubic inch-.- 0.316 Specific gravity 8.75

Specific eat at 80 to 212 F 0.130 Coefl. linear expansion at 80 to 212 0 0000072 Therngal condiuctivity, at loo-212 F. in B. t. u./sq. ft.,

Magnetic attract Magnetic attract on at 200" Electrical resistivity at 320 ohms/circ. mil it The present invention provides age hardened articles of manufacture made of nickel containing controlled and critical amounts of titanium, carbon and magnesium, said nickel having improved hardnesses, tensile strength, etc. The invention also provides age hardened articles of manufacture which possess excellent corrosion resistance (similar to commercial nickel), and which possess the peculiar ability of protecting metal-sensitive products from the deleterious effects of other metallic elements. For example, hardened articles of manufacture made in accordance with the present invention combine the ability to protect caustic soda, viscose rayon, photographic iilm dope and emulsions, soap, etc., from harmful contamination by copper or iron with exceptional strength or hardness. A high tensile modulus of elasticity of about 31,000,000 pounds per square inch and a high torsional modulus of elasticity of about 11,000,000 pounds per square inch are important properties in connection with such hardened articles as coil springs, spring clips, etc.,

where a high degree of stiffness andthe ability limited space are important. These properties combined with high strength and corrosion resistance are particularly important for spring applications where-the metal is subjected to corrosive influences, e. g., in mines, etc. It is well known that even a slightamount of corrosion on the surface of. a spring results in early failure by fatigue and also results in a definite lossin. mechanical strength. The good electrical coninch.

and non-gelling properties whichpermit efllcient operation with the parts in close contact, e. g., with the housing. Cold chisels, etc., made by cold forging and heat treating develop Rockwell C hardnsses of about 4. to 47 and show no chipplug or spalling during use. Their non-sparking characteristics are particularly valuable where I the danger or fires, explosions,etc.', is great. The

lack of inclusions and other surface defects combined with the small close-grained structure of the material permits of obtaining'highly polished surfaces on those hardened articles where this is important, e. g., in plastic molding.

Turbine blades made from the materials contemplated by the present invention have given excellent results. The turbine blades combine the necessary high strength with the necessary hardness and necessary resistance to erosion and corrosion. Drop forging may be advantageously employed in producing turbine blades. Thus, the

1 material may be heated to a temperature'of about 2200 F. and drop forged to a finishing temperature of about 1800 F. to about 1500" F., e. g., about 31600 F. The drop forged material may then beair cooled from an appropriate temperature depending upon the degree of age hardening desired. Partial age hardening may often be suflicient. Air cooling may be used provided that Among the articles of manufacture contem- I plated by the present invention, mention is also made oi the following: springs, e. g., coil springs, flat springs, helical springs, garter springs on turbines, contact springs, etc.; clips, e. g., laundry clips, spring clips, etc. tools, e. g., chisels, blades,

diamond boring tools, scrapers, spatulas, non- Y sparking tools, etc.; structural shapes, e. g., sheets, plates, angles, tubes, wires, strip, rods, etc.; pump parts, e. g., screws and worms for screw pumps,

rotary pumps, etc.; wire products, e. g., nails, pins, fish hooks, fish line leaders, wire brushes, Fourdrinier screens, thread guides, etc.; strip products,

e. g., measuring devices such as rulers, calipers and the like, diaphragms for use in control valves and the like, shutters in shutter devices, reeds for musical instruments, etc.; shaping devices, e. g'.-,

dies, molding plates, rolls, etc.; machinery'parts,

e. g., gears, etc.; nozzle tips; spraying equipment; etc.

Although the present invention has been described in conjunction with preferred embodiments, it is-to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Variations and modifications apparent to those skilled in the art are considered to be within the purview and scope of the appended claims.

We claim:

1. An age hardened article of manufacture possessing high mechanical properties, especially high tensile strength and high hardness, made of a worked nickel alloy which contains 0.2% to 0.3% carbon, 0.3% to 0.4% magnesium, 0.25% to 0.5% titanium, and at least 95% nickel; said nickel alloy possessing commercial hot malleability within the temperature range of about 1300 F. to about 2300 F., and said article having a hardness of at least about 300 Brinell hardness numbers.

2. A cold worked and age hardened article of manufacture possessing high mechanical properties and corrosion resisting properties made of a worked nickel alloy which contains. 0.2% to 0.3% carbon, 0.3% to 0.4% magnesium, 0.25% to 0.5% titanium, and the balance substantially all nickel; said nickel alloy being characterized by improved hot malleability'within the temperature range of about I300 F. to 2300 F., and said article being in the condition resulting from rapidly cooling said alloy from within the temperature range of about 1850 F. to about 2350 F., subsequently cold working said alloy, and heat treating the cold worked alloy at temperatures within the range of about 750 F. to about 1200 F. whereby the improved hardness of the ing and of subsequently aging.

3. A cold worked and age hardened article of manufacture possessing improved mechanical properties and made of a worked nickel alloy which contains 0.15% to. 0.5% carbon, 0.2% to 0.45% magnesium, more than 0.1% and less than 1% titanium, and the balance substantially all nickel; said nickel alloy being characterized by v I good hot malleability at least within the temperature range of about 1600 F. to 2150 F.; the improved hardness of said article being due to the composite effect of cold working and of subsequent aging.

4. An age hardened article of manufacture possessing improved mechanical properties and made of-a worked nickel-base-alloy which contains 0.15% to 0.5% carbon, 0.2% to 0.45% magnesium, more than 0.1% and less than 1% titanium, and the balance substantially all nickel; said nickel alloy being characterized by improved range of about 1600 F. to 2150 F., and said article having a hardness of at least about 250 Brinell hardness numbers.

article is due to the composite'effect of cold workhot malleability at least within the temperature aararee 95% nickel; said nickel alloy being character-.

ized by good commercial hot malleability at least within the temperature range of about 1600 F. to about 2150 F., and being age hardenable at least to hardnesses in excess of about 250 Brinell hardness byrapidly cooling from within the temperature range of about 1950 F. to about 2000 F. and subsequently heat treating within the temperature range of about 850 F. to about 950 F.

6. A process of hardening malleable nickelcarbon-magnesium-titanium alloys containing 0.2% to 0.3% carbon, 0.3% to 0.4% magnesium, 0.25% to 0.5% titanium, and the balance substantially all nickel, which comprises rapidly cooling said alloys from a temperature within the range of about 1950" F. to about 2000 F., thereafter subjecting said alloys to cold deformation, and subsequently hardening said alloys by heat treating at temperatures within the range of about 850 F. to about 950 F., the hardening temperature within said range being determined roughly inversely proportional to the amount of cold deformation received by said alloys prior to hardening heat treatment whereby hardened alloys of the aforesaid composition are obtained having improved hardnesses due to the composite effect of cold working and of subsequent aging.

7. A process of hardening malleable nickelcarbon-magnesium-titanium alloys containing 0.15% to 0.5% carbon, 0.2% to 0.45% magnesium, more than 0.1% and less than 1% titanium, and the balance substantially all nickel, which comprises rapidly cooling said alloys from a temperature within the range of about 1950 F. to about 2000 F., thereafter subjecting said alloys to cold deformation, and subsequently hardening said a1- loys by heat treating at temperatures within the range of about 850 F. to about 950 F. whereby hardened alloys of the aforesaid composition are obtained having improved hardnesses due to the composite efiect of cold working. and of subsequently aging.

8. As an article of manufacture, a. turbine blade constituted of a hot malleable, corrosion resistant, worked nickel alloy which contains 0.15% to 0.5% carbon, 0.2% to 0.45% magnesium, more than 0.1% and less than 1% titanium, and the balance substantially all nickel; said turbine