Methods of cold forming aluminum lithium alloys
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.
1. A method comprising:
prior to solution heat treatment, cold forming an unrecrystallized extruded aluminum-lithium product into a second product form;
(i) wherein the unrecrystallized extruded aluminum-lithium product comprises from 0.2-5.0 wt. % Li;
(ii) wherein the unrecrystallized extruded aluminum-lithium product is predominately unrecrystallized;
(iii) wherein the cold forming comprising initiating the cold forming when the unrecrystallized extruded aluminum-lithium product has a temperature of not greater than 400° F.;
(iv) wherein the cold forming comprises plastically deforming the unrecrystallized extruded aluminum-lithium product, wherein the plastically deforming comprises at least one of:
(A) non-uniformly deforming the unrecrystallized extruded aluminum-lithium product, wherein, due to the non-uniform deforming, a first portion of the second product form realizes a first strain amount and a second portion of the second product form realizes a second strain amount, wherein the first strain amount is at least 1% different than the second strain amount; and
(B) applying curvature to the unrecrystallized extruded aluminum-lithium product, wherein the second product form comprises at least one arcuate surface;
(v) wherein the second product form is predominately unrecrystallized.
2. The method of claim 1 , wherein, prior to the cold forming step, the method comprises:
heating the unrecrystallized extruded aluminum-lithium product to a treatment temperature, wherein the treatment temperature is at least 750° F.; and then
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.
3. The method of claim 2 , comprising:
second heating the second product form to a second treatment temperature, wherein the second treatment temperature is at least 750° F.;
second cooling the second product form from the second treatment temperature to a second post-treatment temperature;
second cold forming the second product form into another product form, wherein the another product form is predominately unrecrystallized.
4. The method of claim 3 , wherein the second product form is an intermediate product form, wherein the another product form is a final product form, and 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./minute.
5. The method of claim 2 , wherein the treatment temperature is below a solidus temperature of the unrecrystallized extruded aluminum-lithium product.
6. The method of claim 2 , wherein the treatment temperature is from 85° F. below a solidus temperature of the unrecrystallized extruded aluminum-lithium product to 15° F. below a solidus temperature of the unrecrystallized extruded aluminum-lithium product.
7. The method of claim 2 , wherein the heating comprises heating the unrecrystallized extruded aluminum-lithium product from a pretreatment temperature to the treatment temperature at a heating rate of at least 1° F. per minute.
8. The method of claim 2 , wherein the heating comprises heating the unrecrystallized extruded aluminum-lithium product from a pretreatment temperature to the treatment temperature at a heating rate of not greater than 100° F. per minute.
9. The method of claim 2 , 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.
10. The method of claim 2 , wherein the cooling 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./minute.
11. The method of claim 2 , wherein the treatment temperature is at least 800° F.
12. 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 2.0-5.0 wt. % Cu, 0.2-2.0 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.
13. The method of claim 1 , wherein the unrecrystallized extruded aluminum-lithium product is at least 60% unrecrystallized.
14. The method of claim 13 , wherein the second product form is at least 60% unrecrystallized.
15. The method of claim 1 , wherein the cold forming comprising including from 3% to 20% strain in the second product form.
16. The method of claim 1 , wherein the cold forming comprises initiating the cold forming when the unrecrystallized extruded aluminum-lithium product has a temperature of not greater than 300° F.
17. The method of claim 1 , wherein the cold forming comprises initiating the cold forming when the unrecrystallized extruded aluminum-lithium product is at ambient temperature.
18. The method of claim 1 , wherein the cold forming is stretch forming.