Methods of cold forming aluminum lithium alloys

Abstract

New methods of making cold formed, extruded aluminum lithium alloys, and unrecrystallized products made therefrom are disclosed. A method may include one or more of heating an unrecrystallized extruded aluminum-lithium product to a treatment temperature, cooling the unrecrystallized extruded aluminum-lithium product from the treatment temperature to a post-treatment temperature, and cold forming the unrecrystallized extruded aluminum-lithium product into a second product form. Due to the unique processing conditions of the method, the second product form may wholly or partially retain the unrecrystallized microstructure.

What is claimed is: 
     
         1 . A method comprising:
 (a) prior to solution heat treatment, heating an unrecrystallized extruded aluminum-lithium product to a treatment temperature, wherein the treatment temperature is at least 750° F. but below a solidus temperature of the unrecrystallized extruded aluminum-lithium product;
 (i) wherein the heating comprises heating the unrecrystallized extruded aluminum-lithium product from a pretreatment temperature to the treatment temperature at a heating rate of from 10° F. per minute to not greater than 100° F. per minute; and 
 (ii) wherein the heating comprises holding the unrecrystallized extruded aluminum-lithium product at the treatment temperature for a period of time sufficient to dissolve a predominate amount of precipitate phase particles but without recrystallizing the unrecrystallized extruded aluminum-lithium product; and 
   (b) cooling the unrecrystallized extruded aluminum-lithium product from the treatment temperature to a post-treatment temperature and at a cooling rate of not greater than 500° F./minute.   
     
     
         2 . The method of  claim 1  comprising, after the cooling step (b), solution heat treating the unrecrystallized extruded aluminum-lithium product. 
     
     
         3 . The method of  claim 1 , wherein the treatment temperature is from 85° F. to 15° F. below the solidus temperature of the unrecrystallized extruded aluminum-lithium product. 
     
     
         4 . The method of  claim 3 , wherein the heating comprises heating the unrecrystallized extruded aluminum-lithium product from the pretreatment temperature to the treatment temperature at a heating rate of at least 1° F. per minute. 
     
     
         5 . The method of  claim 1 , wherein the holding time is at least 5 minutes. 
     
     
         6 . The method of  claim 5 , wherein the holding time is not greater than 10 hours. 
     
     
         7 . The method of  claim 1 , wherein the cooling step (b) comprises cooling the unrecrystallized extruded aluminum-lithium product from the treatment temperature to the post-treatment temperature at a cooling rate of not greater than 400° F. per minute. 
     
     
         8 . The method of  claim 7 , wherein the cooling step (b) comprises cooling the unrecrystallized extruded aluminum-lithium product from the treatment temperature to the post-treatment temperature at a cooling rate of at least 1° F. per minute. 
     
     
         9 . The method of  claim 1 , wherein the cooling step (b) comprises air cooling the unrecrystallized extruded aluminum-lithium product. 
     
     
         10 . The method of  claim 1  comprising, after the cooling step (b), cold forming the unrecrystallized extruded aluminum-lithium product thereby realizing a second product form, wherein the second product form is predominately unrecrystallized. 
     
     
         11 . The method of  claim 10 , wherein the treatment temperature is a first treatment temperature, the post-treatment temperature is a first post-treatment temperature, and the cold forming step is a first cold forming step, wherein after the first cold forming step, the method comprises:
 heating the second product form to a second treatment temperature, wherein the second treatment temperature is at least 750° F.;   cooling the second product form from the second treatment temperature to a second post-treatment temperature; and   cold forming the second product form, thereby realizing a third product form, wherein the third product form is predominately unrecrystallized.   
     
     
         12 . The method of  claim 11 , wherein the second cooling comprises cooling the second product form from the second treatment temperature to the second post-treatment temperature at a rate of at least 1000° F. per minute. 
     
     
         13 . The method of  claim 11 , wherein the second treatment temperature is below the solidus temperature of the unrecrystallized extruded aluminum-lithium product. 
     
     
         14 . The method of  claim 11 , wherein the third product form comprises precipitate phase particles, and wherein the precipitate phase particles realize a D50 of not greater 0.50 μm. 
     
     
         15 . The method of  claim 14 , wherein the precipitate phase particles realize a D90 of not greater 2.0 μm. 
     
     
         16 . The method of  claim 14 , wherein the precipitate phase particles realize a D10 of not greater 0.125 μm. 
     
     
         17 . The method of  claim 1 , wherein the unrecrystallized extruded aluminum-lithium product is a 2xxx-Li product, and wherein the 2xxx-Li product comprises from 2.0 to 5.0 wt. % Cu, from 0.2 to 2.0 wt. % Li, up to 1.5 wt. % Mg, up to 1.0 wt. % Ag, up to 1.0 wt. % Mn, up to 1.5 wt. % Zn, up to 0.25 wt. % each of Zr, Ti, Sc, and Hf, the balance being aluminum, optional incidental elements and impurities. 
     
     
         18 . The method of  claim 17 , wherein the 2xxx-Li product is a 2×55 aluminum alloy product. 
     
     
         19 . The method of  claim 1 , wherein the treatment temperature is at least 800° F. 
     
     
         20 . The method of  claim 1 , wherein the unrecrystallized extruded aluminum-lithium product is at least 60% unrecrystallized.