US2675309A - Titanium base alloys with aluminum and manganese - Google Patents

Description

Patented Apr. 13, 1954 UNITED STATES AT OFF ICE TITANIUM BASE ALLOYS WITH ALUMINUM AND MANGANESE vam'a No Drawing. Application December '3, 1949, Serial No. 131,044

This invention relates to titanium base alloys, and more specifically to a ternary alloy of titanium with aluminum and manganese.

The binary alloys of titanium and aluminum show improved physical properties as compared with titanium itself but the improvement in strength at accepted ductility levels is of moderate proportions, with the result that the structural uses of such alloys are limited. The binary alloys of titanium with up to about 13% manganese show greatly improved strength and particularly in the region of 6% to 13% manganese content a very favorable ratio of strength to ductility. However, the characteristics of these alloys are such that their optimum properties are best developed by a processing associated with rolling or drawing, thus they are useful chiefly in the form of rod, wire or sheet.

The present invention comprises the discovery that the concurrent use of manganese and aluminum in titanium-base alloys is productive of properties which render the alloys more universally useful than either the binary alloy of titanium and aluminum or the binary alloy of titanium and manganese.

An outstanding difficulty in titanium metallurgy is the tendency of titanium and its alloys, when in the liquid phase, to dissolve or combine with refractory container materials, both melting crucibles and casting molds. Carbon crucibles and molds have been quite useful in handling molten titanium and its alloys, but difficulties are too frequently encountered, especially with the alloys rich in manganese, iron or chromium, in that the reaction rate between melt and crucible or mold is increased by the presence of the alloy constituent. Instances have been noted, particularly with manganese alloys, and with the mold preheated for outgassing and to minimize cold shuts (cast shuts), that the melt continues to react with the mold even after removal from the hot zone of the furnace. This has not been encountered with manganese alloys containing at least 1% aluminum, and molds can frequently be re-used a number of times, the wetting and sticking tendency apparently having been reduced considerably. Cleaner and more easily scarfed and machined ingot surfaces result. In addition, there has been shown less tendency toward alloy segregation with the ternary than with the binary alloy.

Excellent results have been secured with alloys containing as little as 2% of aluminum with 2% of manganese, and as little as 1% aluminum with about 7% manganese, balance in each alloy sub- 6 Claims. Cl. "315-177) '2 stantially all commercial titanium. While the total alloy metal content may be as high as 10%, a total of about 8% is preferred, this alloy content being divided between manganese and aluminum in proportions varying from about 1% aluminum and 7% manganese to about 6% aluminum and 2% manganese.

Typical alloys and their properties in the warm rolled and stabilized condition are as follows:

Composition k 0 2 Elong- Bend (Balance 10 HS Ultimate ation Radius Titanium) Hardness Ofiset in T 201 51, 000 76, 000 21 0. 8 7Mu 1A1..- 319 132, 200 148, 500 17 2. 2 6MB 2A] 340 149, 500 161, 000 16 3. 0 5Mn 3A1 34.5 142, 000 163, 500 13 3. 4 4Mn 4A1 336 154, 500 166, 800 12 5 3Mn 5A1 349 162, 100 176, 400 10 4. 8 2Mn 6A1 .1 353 165, 400 176, 200 9 5. 8

It is in the as-forged condition that the alloys of this invention exhibit the most distinctive properties as compared with other titanium-base alloys, particularly binary titanium-manganese alloys. For example, an alloy containing 5% aluminum and 2% manganese, balance substantially all commercial titanium, forged at a temperature of 16-50 F., shows a yield strength of 140,000 p. s. i. and. an elongation of 21%. An alloy of 4% aluminum and 4% manganese, bal-' ance substantially all commercial titanium, rough forged at 1600 F., and finish forged a, 1500 F'., has a yield strength of 147,000 p. s. i., and an elongation of 18%-an extraordinary combination of strength and ductility as compared with forgings of the binary analogues. These alloys thus have a universal adaptability which is lacking in other titanium-base alloys, being highly useful both as forgings and as rolled sheet or drawn wire. In sheet, some truly extraordinary properties have been secured. An alloy containing 3.94 manganese, 5.54. aluminum, balance commercial titanium, rolled at 650 C., annealed for 16 hours at 550 C., cold-rolled 10%, and stress-relieved for one hour at 400 0., showed a yield strength of over 190,000 p. s. i., an ultimate strength of about 220,000 p. s. i., an elongation in of 5%, and a cross-bend ductility of 4.3T. (Bend ductility is measured. as the radius to which the specimen can be bent at an angle of without cracking, the radius being expressed as a multiple of the specimen thickness.)

The alloys of this invention are susceptible to embrittlement by an excess of carbon or nitrogen.

While the quantities of carbon, oxygen and nitrogen normally present in high quality commercial titanium can be tolerated, the nitrogen content should not exceed about 0.1% and the carbon content should not exceed about 0.25%.

What is claimed is:

1. A titanium base alloy consisting essentially of 1 to 7% manganese, 2 to 6% aluminum, up to 0.25% carbon, balance titanium, and characterized in being ductile and forgeable and in having a tensile strength substantially in excess of the unalloyed titanium base metal.

2. A titanium base alloy consisting essentially of 2 to 7% manganese, 1 to 6% aluminum, up to 0.25% carbon, balance titanium, and characterized in being ductile and .forgeable and in having a tensile strength substantially in excess of the unalloyed titanium base metal.

3. An alloy consisting of about: 1 to 7% man- ;up to 0.1% nitrogen, balance titanium.

4. An alloy consisting of about: 2. to 7% manganese, 1 to 6% aluminum, up to 0.25% carbon, up to 0.1% nitrogen, balance titanium.

5. An alloy consisting of about: 1 to 7% manganese, 2 to 6% aluminum, balance titanium.

6. An alloy consisting of about: 2 to 7% manganese, 1 to 6% aluminum, balance titanium.

References Cited in the file of this patent Zeitschrift fiir Metallkunde, vol. 29 (1937), page 190.

Titanium ProjectNavy Dept, Bureau of Aeronautics-Navy Contract No. NOa(s) 8698, The Manufacture of Ductile Titanium and Titanium Alloys, Report No. 14, pages 6 and '7 (May-11, 1948), Final Report No. 17, pages 151-155 (Sept. 1, 1948).

Metallurgia, April 1949, page 304.

Product Engineering, November 1949, page 149.

Claims (2)

1. 3. AN ALLOY CONSISTING OF ABOUT: 1 TO 7% MANGANESE, 2 TO 6% ALUMINUM UP TO 0.25% CARBON UP TO 0.1% NITROGEN, BALANCE TITANIUM.
2. 4. AN ALLOY CONSISTING OF ABOUT: 2 TO 7% MANGANESE, 1 TO 6% ALUMINUM, UP TO 0.25% CARBON, UP TO 0.1% NITROGEN, BALANCE TITANIUM.