Titanium aluminide material resistant to molten aluminum

Abstract

A titanium aluminide alloy and tooling made therefrom for use in contact with molten aluminum and its alloys where the titanium aluminide alloy includes a rare earth element in an effective amount to prolong resistance to attack of the alloy and tooling by the molten aluminum and its alloys.

We claim  
     
         1 . A titanium aluminide alloy for use in contact with a molten material comprising aluminum, said titanium aluminide alloy including a rare earth element in an effective amount to prolong resistance to attack of said alloy by the molten material.  
     
     
         2 . The alloy of  claim 1  wherein the rare earth element comprises Y.  
     
     
         3 . The alloy of  claim 2  wherein said Y is present in an amount of about 1.5% to about 5.5% by weight of the alloy.  
     
     
         3 - 1 . The alloy of  claim 1  which comprises predominantly gamma TiAl.  
     
     
         4 . The alloy of  claim 1  that includes a surface oxide formed in-situ thereon.  
     
     
         5 . The alloy of  claim 4  wherein said surface oxide is formed in-situ by heating said alloy in an oxygen bearing atmosphere.  
     
     
         6 . The alloy of  claim 4  wherein said surface oxide is formed by cooling a hot casting comprising said alloy in air.  
     
     
         7 . The alloy of  claim 1  comprising TiAl that includes one or more additional alloying elements.  
     
     
         8 . Tooling for use in contact with molten material comprising aluminum, wherein said tooling comprises the titanium aluminide alloy of any one of claims  1 - 7 .  
     
     
         10 . A method of increasing the service life of a titanium aluminide alloy in contact with a molten material comprising aluminum, comprising including in the titanium aluminide alloy a rare earth element in an effective amount to prolong resistance to attack of the alloy by the molten material.  
     
     
         11 . The method of  claim 10  wherein said rare earth element is included in a predominantly gamma TiAl alloy.  
     
     
         12 . The method of  claim 10  wherein said rare earth element comprises Y included in an amount of about 1.5% to about 5.5% by weight of the alloy.  
     
     
         13 . The method of  claim 10  including forming a surface oxide in-situ on the alloy.  
     
     
         14 . The method of  claim 13  wherein the surface oxide is formed by cooling a hot casting comprising said alloy in air.  
     
     
         15 . The method of  claim 13  wherein the surface oxide is formed in-situ by heating said alloy in an oxygen bearing atmosphere.  
     
     
         16 . A method of prolonging resistance of a titanium aluminide alloy to a molten material comprising aluminum, comprising contacting the alloy for a time with said molten material, removing the alloy from the molten material, heating the alloy in an oxygen-bearing atmosphere at elevated superambient temperature to form a surface oxide thereon, and re-contacting the alloy having the surface film thereon in the molten material.  
     
     
         17 . The method of  claim 16  including prior to first contacting the alloy with the molten material, heating the alloy in an oxygen-bearing atmosphere at elevated temperature to form a surface oxide thereon.  
     
     
         18 . The method of  claim 16  including providing a rare earth element in the alloy.  
     
     
         19 . The method of  claim 18  wherein the rare earth element is provided in a predominantly gamma TiAl alloy.  
     
     
         20 . The method of  claim 18  wherein the rare earth element is Y.  
     
     
         21 . In a method of die casting a molten material comprising aluminum, wherein said molten material is introduced into a die from a shot sleeve using a plunger in the shot sleeve, the improvement comprising providing one or more of said die, shot sleeve, and plunger as a titanium aluminide alloy including a rare earth element in an effective amount to prolong resistance to attack of said one or more of said die, shot sleeve and plunger by the molten material.  
     
     
         22 . The method of  claim 21  wherein said titanium aluminide alloy includes Y.  
     
     
         23 . The method of  claim 22  wherein said Y is present in said alloy in an amount of about 1.5% to about 5.5% by weight of said alloy.  
     
     
         24 . The method of  claim 21  wherein a core element is disposed in the die and comprises said titanium aluminide alloy.