Near-beta titanium alloy heat treated casting

Abstract

A heat treatment for a near-beta titanium alloy as well as a near-beta titanium alloy casting to provide a heat treated, refined Widmanstätten microstructure comprising primary alpha phase and secondary alpha phase precipitated in a beta phase matrix. The heat treatment produces a hardness that corresponds to a desirable combination of tensile strength and ductility and of the heat treated near beta-titanium alloy casting.

1 . A heat treated near-beta titanium alloy casting having a Widmanstätten microstructure comprising primary alpha phase and secondary alpha phase precipitated in a beta phase matrix.  
   
   
       2 . A heat treated titanium alloy casting comprising, in weight percent, about 4.4 to about 5.7% Al, about 4.0 to about 5.5% Mo, about 4.0 to about 5.5% V, about 2.5 to about 3.5% Cr, about 0.3 to about 0.5% Fe, and balance essentially titanium, having a Widmanstätten microstructure comprising primary alpha phase and secondary alpha phase precipitated in a beta phase matrix and having a Vickers hardness of about 375 to about 385 measured using a 300 gram load.  
   
   
       3 . A method of heat treating a near-beta titanium alloy, comprising subjecting the alloy to a solution heat treatment above an alpha/beta transformation temperature followed by a cooling to a temperature that is at least 400 degrees F. below the alpha/beta transformation temperature and aging at an aging temperature to form a Widmanstätten microstructure comprising primary alpha phase and secondary alpha phase precipitated in a beta phase matrix.  
   
   
       4 . The method of  claim 3  including hot isostatically pressing the casting prior to heat treating.  
   
   
       5 . A method of heat treating a titanium alloy casting comprising, in weight percent, about 4.4 to about 5.7% Al, about 4.0 to about 5.5% Mo, about 4.0 to about 5.5% V, about 2.5 to about 3.5% Cr, about 0.3 to about 0.5% Fe, and balance essentially titanium, comprising subjecting the casting to a solution heat treatment above an alpha/beta transformation temperature followed by a cooling at rate of 100 to 500 degrees F. to a temperature of about 1000 to 1200 degrees F. and aging at an aging temperature to provide a Widmanstätten microstructure comprising primary alpha phase and secondary alpha phase precipitated in a beta phase matrix.  
   
   
       6 . The method of  claim 5  including hot isostatically pressing the casting prior to heat treating.  
   
   
       7 . The method of  claim 5  conducted to produce a Vickers hardness of about 375 to 385 measured using a 300 gram load.  
   
   
       8 . The method of  claim 5  wherein the solution treatment is conducted at about 1620 degrees F. for a time followed by cooling at a rate of about 300 degrees F./hour to about 1000 to about 1200 degrees F. and aging at an aging temperature of about 1000 to about 1200 degrees F. for a time to produce a Vickers hardness of about 380.