Titanium aluminide alloys

Abstract

Alloys based on titanium aluminides, such as γ (TiAl) which may be made through the use of casting or powder metallurgical processes and heat treatments. The alloys contain titanium, 38 to 46 atom % aluminum, and 5 to 10 atom % niobium, and they contain composite lamella structures with B19 phase and β phase there in a volume ratio of the B19 phase to β phase 0.05:1 and 20:1.

What is claimed is: 
     
         1 . An alloy comprising titanium, 38 to 46 at % aluminum, and 5 to 10 at % niobium, and comprising composite lamella that contain a B19 phase and a β phase in a volume ratio of B19:13 of 0.05:1 to 20:1. 
     
     
         2 . The alloy of  claim 1 , comprising/containing 38 to 42 at % aluminum. 
     
     
         3 . The alloy of  claim 1 , comprising 38.5 to 42.5 at % aluminum, and 0.5 to 5 at % chromium. 
     
     
         4 . The alloy of  claim 1 , comprising 39 to 43 at % aluminum, and 0.5 to 5 at % zirconium. 
     
     
         5 . The alloy of  claim 1 , comprising 41 to 45 at % aluminum, and 0.5 to 5 at % tantalum. 
     
     
         6 . The alloy of  claim 1 , comprising 41 to 45 at % aluminum, and 0.1 to 1 at % lanthanum, scandium or yttrium. 
     
     
         7 . The alloy of  claim 1 , comprising 41 to 45 at % aluminum, and 0.5 to 5 at % vanadium. 
     
     
         8 . The alloy of  claim 1 , comprising 41 to 44.5 at % aluminum, and 0.5 to 5 at % iron or molybdenum. 
     
     
         9 . The alloy of  claim 1 , comprising 41 to 46 at % aluminum, and 0.5 to 5 at % tungsten. 
     
     
         10 . The alloy of  claim 1 , comprising 41 to 46 at % aluminum, and 0.5 to 5 at % manganese. 
     
     
         11 . The alloy of  claim 1 , comprising 0.1 to 1 at % boron, or 0.1 to 1 at % carbon, or both 0.1 to 1 at % boron and 0.1 to 1 at % carbon. 
     
     
         12 . The alloy of  claim 1 , the alloy containing composite lamella structures that include B19 phase and β phase in a volume ratio between 0.2:1 and 5:1. 
     
     
         13 . The alloy of  claim 1 , the alloy containing composite lamella structures that include B19 phase and β phase in a volume ratio between 1:3 and 3:1. 
     
     
         14 . The alloy of  claim 1 , the alloy containing composite lamella structures that include B19 phase and β phase in a volume ratio between 0.75:1 and 1.25:1. 
     
     
         15 . The alloy of  claim 1 , the alloy containing composite lamella structures and type γ TiAl lamella structures. 
     
     
         16 . The alloy of  claim 15 , comprising composite lamella structures surrounded by type γ TiAl lamella structures. 
     
     
         17 . The alloy of  claim 1 , the alloy containing more than 10 volume percent composite lamella structures, based on the volume of the alloy. 
     
     
         18 . The alloy of  claim 1 , wherein the composite lamella structures include a α 2 -Ti 3 Al phase. 
     
     
         19 . The alloy of  claim 18 , wherein the alloy contains  20  volume percent α 2 -Ti 3 Al phase or less, by volume of the alloy. 
     
     
         20 . A method for the production of an alloy, comprising:
 providing a composition that comprises titanium, 38 to 46 at % aluminum, and 5 to 10 at % niobium;   subjecting the composition to a casting or powder metallurgical technique to produce an intermediate product; and   subjecting the intermediate product to a heat treatment, the heat treatment comprising heating the intermediate product at a temperature above 900° C. for more than sixty minutes, and cooling the intermediate product at a rate of more than 0.5° C. per minute.   
     
     
         21 . The method of  claim 20  wherein the heat treatment comprises heating the intermediate product at a temperature above 1000° C. 
     
     
         22 . The method of  claim 20  wherein the heat treatment comprises heating the intermediate product at a temperature between 1000° C. and 1200° C. 
     
     
         23 . The method of  claim 20  wherein the heat treatment comprises heating the intermediate product at said temperature above 900° C. for more than 90 minutes. 
     
     
         24 . The method of  claim 20  wherein the heat treatment comprises heating the intermediate product at a temperature above 1000° C. for more than 90 minutes. 
     
     
         25 . The method of  claim 20 , comprising cooling the intermediate product at a rate of 1° C. per minute to 20° C. per minute. 
     
     
         26 . The method of  claim 20 , comprising cooling the intermediate product at a rate of 1° C. per minute to 10° C. per minute. 
     
     
         27 . An alloy made by the method of  claim 20 . 
     
     
         28 . A component comprising the alloy of  claim 1 .