US2666698A - Alloys of titanium containing aluminum and iron - Google Patents

Description

Patented Jan. 19, 1954 ALLOYS F TITANIUM CONTAINING ALUMINUM AND IRON Robert H. Dickinson and Lee S. Busch, Indianapolis, Ind., assignors, by mesne assignments,

to Mallory-Sharon Titanium Corporation, Indianapolis, Ind., a corporation of Delaware No Drawing. Application July 24, 1951, Serial No. 238,392

2 Claims. (01. 75-177) This invention relates to titanium base alloy and more particularly to ductile wrought alloys of titanium, aluminum and iron. 7

It is an object of the present invention to pro vide strong ductile alloys of titanium.

It is another object of the present invention to provide ductile wrought alloys of titanium, aluminum and iron which have good resistance to oxidation and high hardness at elevated temperatures, as well as tensile properties improved over the metal titanium alone.

A further object of the present invention is to provide ternary alloys of titanium, aluminum and iron and to which may be added the element silicon to form a quaternary alloy. It is, therefore, an object of the present invention to provide alloys of titanium, aluminum and iron to which may be added the element silicon providing a new quaternary alloy of titanium, aluminum, iron and silicon.

Another object of the present invention is to provide strong ductile alloys of titanium, alumi-' num and iron to which the elements carbon or silicon may be added to form additional alloys of titanium, aluminum, iron, carbon, and/or alloys of titanium, aluminum, iron, carbon and silicon.

Another object of the present invention is to provide methods for forming ductile alloys of titanium containing predominantly aluminum and iron and to which may be added the elements silicon and/or carbon to form quaternary or quintenary alloys having as a prime base therefor the elements titanium, aluminum and iron. v

It is also within the contemplation of the invention to provide means for making titanium base alloys containing aluminum, iron and titanium of improved physical properties on a practical and industrial scale at low cost.-

It has been discovered that aluminum and iron form strong ductileternary alloys within titanium. It has also been found that carbon may be added to the aforesaid ternary alloy containing aluminum, titanium and iron and by such addition the properties of the alloy may be materially afiected. If carbon is added to the ternary alloy of titanium, aluminum and iron,

it has been found that the range of carbon introduced therein may be from 0.25% to 0.75%

thereof. Below this range, the beneficial eifects of the carbon, it has been found, decrease materially, while above this range the elongation of the alloy to which the carbon has been added is reduced appreciably.

Thus, in accordance with the results obtained Ultimate tensile strength (p. s. i.) 146,000

Proportional limit (p. s. i.) 112,000 Elongation (per cent in 2") 13.3 Reduction in area (per cent) 39.7 Modulus of elasticity (p. s. i.) 18 10 Electrical resistivity (ohm-cm.) v 138x10- For comparison, unalloyed titanium had the following properties when containing the same impurities as the alloy above:

Ultimate tensile strength (p. s. i.) 87,000 Proportional limit (p. s. i.) 53,000 Elongation (per cent in 2") 16 Modulus of elasticity (p. s. i.) l6 10 Electrical resistivity (ohm-cm.) x10- It is to be noted, the basic alloy of the present invention is a ternary alloy of aluminum, iron and titanium. The ternary alloy thus formed is significantly improved over the binary alloys of aluminum and titanium and iron and titanium. The former binary alloy, it has been found,are difiicult to hot work. For example, when the aluminum content is greater than 2.5% in such a binary alloy, it is very diificult to hot work. On the other hand, alloys consisting of titanium and iron are very quench hardenable and it is diflicult to prevent cracking during forming operations.

When the alloy of titanium, iron and aluminum is provided, however, entirely unexpected results result. This is readily observable from a comparison of properties as disclosed in the alloys containing (1) titanium, aluminum and carbon; (2) titanium, iron and carbon; as compared to (3) ternary alloy of aluminum, iron, titanium, plus the addition of carbon:

Elongation (per cent in 2") 0 Electrical resistivity (ohm-cm.) 10- Forgeability Bad (2) Composition iron. 0.41% carbon. Balance titanium. Ultimate. tensile strength (p. s. i.) 155,000

Balance titanium. Ultimate tensile strength (p. s. 1).. 161,500

Proportional limit (p. s. i.) 120,000 Elongation (per cent in 2") 10.9 Electrical resistivity (ohm-cm.) 139 10- Forgeability Good It is noted that the tensile strength, proportional limit and elongation have thus been materially increased by the combination of aluminum and iron in titanium with the addition of the carbon thereto. As shown above, the tensile strength and elongation characteristics of titanium aluminum or titanium iron alloys has been increased by forming a ternary alloy of titanium, aluminum and iron. It may be seen, also, by referring to the table below, that the tensile strength and elongation of such ternary alloys formed by the combination of aluminum and iron with titanium depends upon the amount of aluminum and iron which is present in the ternary alloy. After experimentation, it was found that the characteristics of tensile strength and elongation are dependent upon the amount of aluminum and iron present, as follows:

Ultimate Percent Percent Tensile Aluminum I strength pc 2 (p. s. i.)

In addition. to the alloys thus formed by the combination, of aluminum, iron and titanium to form av ternary alloy, the alloy may be. modified by an. addition of up to 1% silicon to form a new quaternary alloy or a live element alloy consisting of titanium, aluminum, iron, silicon and carbon.

The addition of silicon to any one of the. ternary alloys of aluminum, iron and titanium was found to generally improve the tensile strength and proportional limit thereof. It wasalso found that silicon. does not affect the hot workability of. these alloys.

A. preferred alloy, as shown below, had the following properties:

Composition:

3% aluminum. 1% iron. 0.5% silicon. Balance titanium. Ultimate tensile strength (p. s. i.)' 161,800

Proportional limit (p. s. i.) 147,000 Elongation (per cent. in. 2") 10.9 Modulus of elasticity (p. s. i.) 18 10fi Electrical resistivity (ohm-cm.) 1 18x10 The alloys are made in an inert atmosphere, typified by argon or helium, provided the alloy is melted or sintered. The alloys can also be made in a vacuum environment. If the alloys are melted, the crucible can be graphite or a highly refractory oxide, preferably thoria 0r stabilized zirconia or carbides of. tungsten and boron. If the alloys-are arc-melted, in which case an inert atmosphere or vacuum must still be used, the crucible can be water cooled copper. Powder metallurgy methods can also be used. The tensile properties 01 the alloys, herein described, will vary according to the method used, but are better than the unalloyed titanium in every case.

The subject alloys are not modified appreciably by heat treatments. Quenching from l000 C. does, however, increase the strength and embrittle the alloys. The hardness of the alloys is not increased by quenching but does increase when heated at 500 C. for 4 hours after quenching after 1 hour at 900 C. It was found that a heat treatment of 5 hours at 700 (3., followed byfurnace cooling, did not afiect the ultimate tensile strength of a 5% aluminum-5% iron-titanium alloy, but it did increase the proportional limit from 144,000 p. s. i. to 162,000 p. s. i. and decreased the elongation from 7.0% to 6.2% in 2".

The forming of alloys containing aluminum and iron is done by forging to the desired shape at a metal temperature not to exceed 1200 C. The normal forging temperature of 950 C. does 1 not cause excessive oxidation.

An alloy containing approximately 2% aluminum and 2% iron was hot rolled at 800 C. The alloy was cold rolled to 37% reduction in area and annealed. The properties of this sheet 3, were:

Cold Hot Rcllcd Rolled and.

Annealed Ultimate Tensile Strength (p. s i) 161, 500 133, 000 Propcrt onal Limit (p. s. i.) 105,000 108. 000 Elongation (percent in 2) 10.2 14. 4

2. A titanium base alloy consisting of 0.75%

to 6% aluminum, 0.75% to 7% iron, 0.25% to 0.75% carbon, 0.25% to 1% silicon, the rest being essentially all titanium.

ROBERT H. DICKINSON. LEE S. BUSCH.

References; Cited in the file of. this patent UNITED STATES PATENTS Number Name Date 2,575,962 Jaffiee et a1 Nov. 20, 1951 OTHER REFERENCES Product Engineering, November 1949, page 148.

Journal of Metals, March 485-487, 492, 498, 504, 5 14 and 539.

Titanium? Report of- Symposium, December 16, 1948, sponsored by Ofiice of Naval Research, pages 73-75 and 132-134.

1950, pages

Claims (2)

1. TITANIUM ALLOYS CONSISTING OF FROM 0.75% TO 6% ALUMINUM, 0.75% TO 7% IRON, FROM 0.25% TO 1% SILICON, THE REST BEING ESSENTIALLY ALL TITANIUM.

2. A TITANIUM BASE ALLOY CONSISTING OF 0.75% TO 6% ALUMINUM, 0.75% TO 7% IRON, 0.25% TO 0.75% CARBON, 0.25% TO 1% SILICON, THE REST BEING ESSENTIALLY ALL TITANIUM.