Four stage shearing of aa1xxx aluminum for improved strength and conductivity

Abstract

Systems, methods, and apparatuses are provided herein to thermomechanically process a workpiece to increase the strength in terms of hardness and the electrical conductivity of the workpiece. In some embodiments, a shear strain is induced in a workpiece at a temperature or within a range of temperatures, and the workpiece is rotated about its longitudinal axis. Then, another shear strain is induced in the workpiece. In various embodiments, four shear strains are induced in a workpiece, and the workpiece is rotated between shear strains. The shear strains, temperatures, and rotations contribute to the increase in density of dislocations, precipitation growth, and refinement of grain size. The result is a workpiece such as AA1xxx aluminum with an increase in hardness and electrical conductivity.

1 . A method of treating a workpiece to increase at least one of the strength and electrical conductivity of said workpiece, comprising:
 inducing a first shear strain in said workpiece while maintaining a temperature of said workpiece between approximately 20° C. and 50° C.;   rotating said workpiece about a longitudinal axis of said workpiece and inducing a second shear strain in said workpiece while maintaining said temperature of said workpiece between approximately 20° C. and 50° C.;   rotating said workpiece further about said longitudinal axis of said workpiece and inducing a third shear strain in said workpiece while maintaining said temperature of said workpiece between approximately 180° C. and 200° C.; and   rotating said workpiece further about said longitudinal axis of said workpiece and inducing a fourth shear strain in said workpiece while maintaining said temperature of said workpiece between approximately 110° C. and 130° C.   
     
     
         2 . The method of  claim 1 , wherein each shear strain is greater than 1.0. 
     
     
         3 . The method of  claim 1 , wherein said first shear strain, said second shear strain, said third shear strain, and said fourth shear strain have an accumulative magnitude greater than 4.0. 
     
     
         4 . The method of  claim 1 , wherein an off-diagonal shear component of a Green Strain tensor of said first shear strain, said second shear strain, said third shear strain, and said fourth shear strain is at least five times greater than any diagonal component of said Green Strain tensor. 
     
     
         5 . The method of  claim 1 , further comprising exposing said workpiece to temperatures between approximately 550° C. and 570° C. for between approximately 60 to 120 minutes and quenching said workpiece in water at between approximately 15° C. to 25° C. to form a solution-annealed workpiece. 
     
     
         6 . The method of  claim 5 , further comprising storing, after quenching, said workpiece between approximately 0° C. and −40° C. 
     
     
         7 . The method of  claim 1 , wherein said workpiece is an AA1xxx aluminum alloy. 
     
     
         8 . The method of  claim 1 , wherein each rotation about said longitudinal axis is by approximately 90 degrees. 
     
     
         9 . A system for treating a workpiece to increase the strength and electrical conductivity of said workpiece, comprising:
 a die having a first channel portion extending into a top surface of said die and having a second channel portion extending from said first channel portion to a side surface of said die;   a drive feature configured to move said workpiece into said first channel portion;   a heater configured to control a temperature of said workpiece; and   wherein said drive feature moves said workpiece into said first channel portion when said heater controls said temperature to a range between approximately 20° C. and 50° C.; and   wherein, in a subsequent action, said drive feature moves said workpiece, which has been rotated approximately 90 degrees about a longitudinal axis of said workpiece, into said first channel portion when said heater controls said temperature to a range between approximately 180° C. and 200° C.   
     
     
         10 . The system of  claim 9 , wherein said first channel portion and said second channel portion form a channel angle between approximately 90 degrees and 120 degrees. 
     
     
         11 . The system of  claim 9 , further comprising a quench bath, wherein said workpiece is quenched in said quench bath at between approximately 15° C. and 25° C. 
     
     
         12 . The system of  claim 9 , wherein said drive feature and said die induce a shear strain in said workpiece that is greater than 1.0. 
     
     
         13 . The system of  claim 9 , wherein, in a further subsequent action, said drive feature moves said workpiece, which has been rotated a further approximately 90 degrees about said longitudinal axis of said workpiece, into said first channel portion when said heater controls said temperature to a range between approximately 110° C. and 130° C. 
     
     
         14 . The system of  claim 9 , wherein said workpiece has a hardness between approximately 88HV0.2 to 94HV0.2 and an electrical conductivity of between approximately 62 and 63% IACS. 
     
     
         15 . A method of treating a workpiece to increase the strength and electrical conductivity of said workpiece, comprising:
 driving a workpiece into a channel of a die, wherein a temperature of said workpiece is in an initial temperature range;   rotating said workpiece by approximately 90 degrees about a longitudinal axis of said workpiece, and driving, within 60 minutes of said previous driving, said workpiece into said channel of said die, wherein said temperature of said workpiece is in said initial temperature range;   rotating said workpiece by a further approximately 90 degrees about said longitudinal axis of said workpiece, and driving, within 60 minutes of said previous driving, said workpiece into said channel of said die, wherein said temperature of said workpiece is in an intermediate temperature range, which is greater than said initial temperature range; and   rotating said workpiece by a further 90 approximately degrees about said longitudinal axis of said workpiece, and driving, within 60 minutes of said previous driving, said workpiece into said channel of said die, wherein said temperature of said workpiece is in a final temperature range, which is between said initial temperature range and said intermediate temperature range.   
     
     
         16 . The method of  claim 15 , further comprising:
 annealing said workpiece between approximately 60 to 120 minutes at between approximately 550° C. and 570° C.; and   quenching, after said annealing, said workpiece in a bath between approximately 15° C. and 25° C.   
     
     
         17 . The method of  claim 15 , wherein said initial temperature range is approximately 20° C. and 50° C., said intermediate temperature range is approximately 180° C. and 200° C., and said final temperature range is approximately 110° C. and 130° C. 
     
     
         18 . The method of  claim 15 , wherein said workpiece is one of a bar, a rod, a plate, a sheet, a strip, or a wire. 
     
     
         19 . The method of  claim 15 , wherein said channel comprises a first channel portion and a second channel portion, and said channel portions for a channel angle between approximately 90 degrees and 120 degrees. 
     
     
         20 . The method of  claim 15 , wherein said workpiece has a hardness between approximately 88HV0.2 to 94HV0.2 and an electrical conductivity of between approximately 62 and 63% IACS.