5xxx aluminum alloys and methods of making the same

Abstract

New 5xxx aluminum alloy sheet products and methods for making the same are disclosed. The new 5xxx aluminum alloy sheet products may realize a low yield point elongation (YPE) thereby facilitating reduction or elimination of Type A Lüdering (stretcher-strain lines). The new 5xxx aluminum alloy sheet products may be hot rolled into an intermediate gauge product, then cold rolled to a final gauge product, wherein no intermediate annealing occurs prior to or during the cold rolling, and then post cold roll annealing at a temperature and for a time sufficient to first realize a recovered but unrecrystallized microstructure, and then converting of at least some of the recovered but unrecrystallized microstructure to a recrystallized microstructure via a second annealing operation of the post cold roll annealing step.

What is claimed is: 
     
         1 . A method comprising:
 (a) hot rolling a 5xxx aluminum alloy to an intermediate gauge product;   (b) after the hot rolling step, conducting a cold rolling operation to achieve a final gauge product, wherein the cold rolling operation includes at least one cold rolling step, and wherein no intermediate annealing occurs prior to or during the cold rolling operation;   (c) after the cold rolling operation, post cold roll annealing the final gauge product, wherein the post cold roll annealing step (c) comprises:
 (i) first annealing at a first temperature for a first duration, wherein, due to the first annealing step, the final gauge product contains a recovered but unrecrystallized microstructure; and 
 (ii) after the first annealing step, applying a second annealing step to the final gauge product, thereby converting at least some of the recovered but unrecrystallized microstructure to a recrystallized microstructure. 
   
     
     
         2 . The method of  claim 1 , wherein the post cold roll annealing step comprises annealing the final gauge product at a temperature and for a time sufficient for the final gauge product to realize a YPE of not greater than 0.60%. 
     
     
         3 . The method of  claim 2 , wherein the final gauge product realizes at least one of:
 (A) an area weighted average grain size of not greater than 40 micrometers;   (B) a Brass texture amount of not greater than 14%; and   (C) an S texture amount of not greater than 19%.   
     
     
         4 . The method of  claim 3 , wherein, due to the second annealing step, the final gauge product realizes at least two of (A), (B) and (C). 
     
     
         5 . The method of  claim 1 , wherein the final gauge product realizes an area weighted average grain size of from 15 to 39 micrometers. 
     
     
         6 . The method of  claim 5 , wherein the final gauge product realizes a Brass texture amount of from 1% to 13%. 
     
     
         7 . The method of  claim 6 , wherein the final gauge product realizes an S texture amount of from 5% to 18%, or an S texture amount of not greater than 17%, or an S texture amount of not greater than 16%, or an S texture amount of not greater than 15%, or an S texture amount of not greater than 14%. 
     
     
         8 . The method of  claim 1 , wherein the second temperature is at least 25° F. higher than the first temperature;
 wherein the first duration is at least 30 minutes; 
 wherein the second duration is at least 1 second. 
 
     
     
         9 . The method of  claim 8 , wherein the first temperature is below a recrystallization temperature of the final gauge product, and wherein the second temperature is above the recrystallization temperature of the final gauge product. 
     
     
         10 . The method of  claim 9 , wherein the first temperature is from 350° F. to 500° F. 
     
     
         11 . The method of  claim 10 , wherein the first duration is from at least 1 hour to not greater than 10 days. 
     
     
         12 . The method of  claim 11 , wherein the second temperature is from greater than 500° F. to 900° F. 
     
     
         13 . The method of  claim 12 , wherein the second duration is from 5 seconds to 48 hours. 
     
     
         14 . The method of  claim 1 , wherein the cold rolling operation is accomplished with a single cold rolling pass. 
     
     
         15 . The method of  claim 1 , wherein the cold rolling operation is accomplished with multiple cold rolling passes. 
     
     
         16 . The method of  claim 1 , wherein the cold rolling operation comprises reducing a thickness of the intermediate gauge product by from 25% to 80%. 
     
     
         17 . The method of  claim 1 , wherein the hot rolling comprises hot rolling an ingot or a continuously cast strip of the 5xxx aluminum alloy. 
     
     
         18 . A 5xxx aluminum alloy sheet product comprising from 4.0 to 6.0 wt. % Mg and having a thickness of from 0.5 to 5.0 mm, wherein the 5xxx aluminum alloy sheet product is at least 60% recrystallized and realizes an YPE of not greater than 0.60%; wherein the 5xxx aluminum alloy sheet product realizes at least one of:
 (A) an area weighted average grain size of not greater than 40 micrometers;   (B) a Brass texture amount of not greater than 14%; and   (C) an S texture amount of not greater than 19%.   
     
     
         19 . The 5xxx aluminum alloy sheet product of  claim 18 , comprising:
 from 4.0 to 5.0 wt. % Mg   up to 0.50 wt. % Mn;   up to 0.75 wt. % Zn;   up to 0.35 wt. % Fe;   up to 0.20 wt. % Si;   up to 0.15 wt. % Cu;   up to 0.10 wt. % Cr;   up to 0.10 wt. % Ti;   the balance being aluminum, optional incidental elements and impurities.   
     
     
         20 . The 5xxx aluminum alloy sheet product of  claim 19 , wherein the 5xxx aluminum alloy includes at least 0.25 wt. % Zn, or at least 0.30 wt. % Zn, or at least 0.35 wt. % Zn, or at least 0.40 wt. % Zn, or at least 0.45 wt. % Zn, or at least 0.50 wt. % Zn.