Method of consolidating precipitation-hardenable alloys to form consolidated articles with ultra-fine grain microstructures

Abstract

A method by which consolidated articles can be produced from nanocrystalline materials to have mechanical properties that can be improved through thermal treatment. The method entails machining a body to produce polycrystalline chips having nanocrystalline microstructures, and then consolidating the chips to form a consolidated article having mechanical properties that exceed that of the body from which the chips were formed. In particular, consolidation of nanocrystalline chips formed by machining a supersaturated solid-solution body causes precipitation of a fine dispersion of precipitates in the consolidated article, with the potential for certain properties to even improve during consolidation or subsequent thermal treatment of the consolidated article.

1 . A method of producing a consolidated article, the method comprising the steps of: 
 forming a supersaturated solid-solution body;    machining the body to produce polycrystalline chips having nanocrystalline microstructures; and    consolidating the chips at an elevated temperature to form the consolidated article and cause precipitation of precipitates dispersed in the consolidated article.    
     
     
         2 . A method according to  claim 1 , wherein the elevated temperature is held for a sufficient duration to cause annealing of the consolidated article.  
     
     
         3 . A method according to  claim 1 , further comprising the step of annealing the consolidated article following the consolidation step.  
     
     
         4 . A method according to  claim 1 , wherein the hardness of the chips increases during the consolidation step.  
     
     
         5 . A method according to  claim 1 , wherein the body is formed of an age-hardenable alloy chosen from the group consisting of age-hardening steels, nickel-based precipitation-strengthened superalloys, and precipitation-strengthened aluminum alloys.  
     
     
         6 . A method according to  claim 1 , wherein the chips have maximum grain sizes in a range of about 30 to 500 nm prior to the consolidation step.  
     
     
         7 . A method according to  claim 6 , wherein the grain sizes of the chips are substantially retained in the consolidated article following the consolidation step.  
     
     
         8 . A method according to  claim 1 , wherein the chips undergo strain deformation during the machining step characterized by a shear strain of about 0.5 to about 10.  
     
     
         9 . A method according to  claim 1 , wherein the chips undergo strain deformation during the machining step characterized by a strain rate of up to 10 6  per second.  
     
     
         10 . A method of producing a consolidated article, the method comprising the steps of: 
 forming a supersaturated solid-solution body;    machining the body to achieve a shear strain of about 0.5 to about 10 and produce polycrystalline chips consisting essentially of nanocrystalline microstructures; and    consolidating the chips at an elevated temperature to form the consolidated article and cause precipitation of precipitates dispersed in the consolidated article, the precipitates being formed in an amount sufficient to substantially prevent grain coarsening and strength loss in the chips.    
     
     
         11 . A method according to  claim 10 , wherein the elevated temperature is held for a sufficient duration to cause annealing of the consolidated article.  
     
     
         12 . A method according to  claim 10 , further comprising the step of annealing the consolidated article following the consolidation step.  
     
     
         13 . A method according to  claim 10 , wherein the body is formed of an age-hardenable alloy chosen from the group consisting of age-hardening steels, nickel-based precipitation-strengthened superalloys, and precipitation-strengthened aluminum alloys.  
     
     
         14 . A method according to  claim 10 , wherein the chips have maximum grain sizes in a range of about 30 to 500 nm prior to the consolidation step.  
     
     
         15 . A method according to  claim 10 , wherein the chips have maximum grain sizes in a range of about 30 to 500 nm in the consolidated article following the consolidation step.  
     
     
         16 . A method according to  claim 10 , wherein the chips undergo strain deformation during the machining step characterized by a strain rate of up to 10 6  per second.