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.

Claims

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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the disclosure and together with the Summary given above and the Detailed Description of the drawings given below, serve to explain the principles of these embodiments. In certain instances, details that are not necessary for an understanding of the disclosure or that render other details difficult to perceive may have been omitted. It should be understood, of course, that the disclosure is not necessarily limited to the particular embodiments illustrated herein. Additionally, it should be understood that the drawings are not necessarily to scale.

[0026] FIG. 1A is a cross-sectional front elevation view of a pressing system according to an embodiment of the present disclosure;

[0027] FIG. 1B is a cross-sectional front elevation view of another pressing system according to an embodiment of the present disclosure;

[0028] FIG. 2 is a perspective view of a workpiece according to an embodiment of the present disclosure; and

[0029] FIG. 3 is a flow chart for a multi-stage shearing process according to an embodiment of the present disclosure.

[0030] Similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a letter that distinguishes among the similar components. If only the first reference label is used, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

[0031] A list of the various components shown in the drawings and associated numbering is provided herein:

TABLE-US-00001 Number Component 10 Pressing System 12 Die 14 First Channel Portion 16 Second Channel Portion 18 Channel Angle 20 Workpiece 22 Plunger 24 Force 26 Heater 28 Quench Bath 30 Longitudinal Axis 32 Rotation Angle 34 Annealing Workpiece 36 Quenching Workpiece 38 Inducing Shear Strain in Workpiece 40 Rotating Workpiece 42 Inducing Shear Strain in Workpiece 44 Rotating Workpiece 46 Inducing Shear Strain in Workpiece 48 Rotating Workpiece 50 Inducing Shear Strain in Workpiece

DETAILED DESCRIPTION

[0032] The present disclosure has significant benefits across a broad spectrum of endeavors. It is the Applicant's intent that this specification and the claims appended hereto be accorded a breadth in keeping with the scope and spirit of the disclosure being disclosed despite what might appear to be limiting language imposed by the requirements of referring to the specific examples disclosed. To acquaint persons skilled in the pertinent arts most closely related to the present disclosure, a preferred embodiment that illustrates the best mode now contemplated for putting the disclosure into practice is described herein by, and with reference to, the annexed drawings that form a part of the specification. The exemplary embodiment is described in detail without attempting to describe all of the various forms and modifications in which the disclosure might be embodied. As such, the embodiments described herein are illustrative, and as will become apparent to those skilled in the arts, may be modified in numerous ways within the scope and spirit of the disclosure.

[0033] Although the following text sets forth a detailed description of numerous different embodiments, it should be understood that the detailed description is to be construed as exemplary only and does not describe every possible embodiment since describing every possible embodiment would be impractical, if not impossible. Numerous alternative embodiments could be implemented, using either current technology or technology developed after the filing date of this patent, which would still fall within the scope of the claims. To the extent that any term recited in the claims at the end of this patent is referred to in this patent in a manner consistent with a single meaning, that is done for sake of clarity only so as to not confuse the reader, and it is not intended that such claim term by limited, by implication or otherwise, to that single meaning.

[0034] Various embodiments of the present disclosure are described herein and as depicted in the drawings. It is expressly understood that although the figures depict inducing shear strain and controlling the temperature of a workpiece and related systems, the present disclosure is not limited to these embodiments.

[0035] Now referring to FIG. 1A, a cross-sectional, front elevation view of a pressing system 10 is provided. In this embodiment, the pressing system 10 includes a die 12, which can be part of continuous equal channel angular pressing (C-ECAP). The die 12 and a plunger 22 work together to induce a shear strain in a workpiece 20. Specifically, the die 12 comprises a first channel portion 14 that extends into a top surface of the die 12 and comprises a second channel portion 16 that extends from the first channel portion 14 to a side surface of the die 12. The channel portions 14, 16 are joined at an intersection and thus provide a channel through which to process the workpiece 20. As the plunger 22 drives the workpiece 20 through the first channel portion 14 with a force 24, the workpiece 20 moves into the intersection where the workpiece 20 is redirected and forced through the second channel portion 16, which induces a shear strain in the workpiece 20. As described in further detail below, the shear strain alters the microstructure of the workpiece 20 to increase the strength in terms of hardness and electrical conductivity of the workpiece 20. It will be appreciated that while a plunger 22 is depicted in the figures, a generic drive feature can move the workpiece 20. The drive feature can include a plunger, a rotating wheel, a translating block, or any other feature that moves the workpiece 20 with a force.

[0036] FIGS. 1A and 1B show a channel angle 18 between the first channel portion 14 and the second channel portion 16. In FIG. 1A, the channel angle 18 is approximately 120 degrees. In some embodiments, this channel angle 18 is between approximately 100 and 140 degrees. In FIG. 1B, the channel angle 18 is approximately 90 degrees. In some embodiments, this channel angle 18 is between approximately 70 and 110 degrees. The different channel angles 18 induce different forces and strains in the workpiece 20 during processing.

[0037] Also shown in FIGS. 1A and 1B are a heater 26 and a quench bath 28. In various embodiments, the workpiece 20 and/or die 12 are a particular temperature or within a range of temperatures during different actions of the manufacturing process to contribute to key changes in the microstructure of the workpiece 20. The heater 26 controls the temperature of the workpiece 20 and/or die 12, and the heater 26 shown in FIGS. 1A and 1B is embedded in the die 12. However, it will be appreciated that the heater 26 can be positioned on or outside of the die 12 to control the temperature of the workpiece 20 and/or die 12. It will be further appreciated that the heater 26 can be any type of heater including, for example, a resistance heater, a fuel-burning heater, a heat pump, etc. The quench bath 28 can be filled with water or any other fluid, and as described below the quench bath 28 can be used during processing to reduce the temperature of the workpiece 20.

[0038] Now referring to FIG. 2, a perspective view of the workpiece 20 is provided. The workpiece 20 in this embodiment is a rod with a longitudinal axis 30. In various embodiments, the workpiece 20 is rotated about this longitudinal axis 30 between passes through the pressing system 10 to induce different shear strains, or shear strains in a different direction, on the workpiece 20. In some embodiments, the workpiece 20 is rotated approximately 90 degrees about the longitudinal axis 30 as shown by the rotation angle 32 in FIG. 2. The workpiece can be any material in any form including, but not limited to, a bar, a rod, a plate, a sheet, a strip, or a wire.

[0039] Now referring to FIG. 3, a flowchart of an exemplary manufacturing process is provided. It will be appreciated that the actions shown in FIG. 3 can be performed in any order, in series, and/or in parallel with a fewer or greater number of actions than those shown in FIG. 3. To begin, the workpiece can be supplied in an as is state or in a solution-annealed state. To generate the annealed solution state 34, the workpiece is placed in an environment with a temperature between approximately 550 C. to 570 C. for a time period between approximately 60 and 120 minutes. After annealing, the workpiece is quenched 36 in a bath down to room temperature between approximately 15 C. and 25 C. Once quenched, the workpiece can immediately proceed to the multi-stage shearing. However, if the workpiece will not immediately proceed to the multi-stage shearing, then the workpiece is stored between approximately 0 C. and 40 C. to preserve the microstructure of the workpiece.

[0040] Whether as is, annealed, or annealed-then stored, the workpiece is then subjected to multiple stages of shear strain. The embodiment in FIG. 3 has four stages or actions of shear strain.

[0041] However, it will be appreciated that various embodiments of the manufacturing process can include more or fewer stages. Moreover, the pressing system described above or other systems such as a high pressure compressive shear can induce the strain in the workpiece.

[0042] First, a shear strain is induced 38 in the workpiece at a temperature between approximately 20 C. and 50 C. This shear strain is greater than 1.0 and increases the density of dislocations in the workpiece and stores these dislocations. If delayed from further processing for at least 60 minutes, then the workpiece is stored between approximately 0 C. and 40 C.

[0043] Next, the workpiece is rotated 40 by approximately 90 degrees about a longitudinal axis of the workpiece, and another shear strain is induced 42 in the workpiece at a temperature between approximately 20 C. and 50 C. This shear strain is greater than 1.0 and further increases and further stores dislocations in the workpiece. If delayed from further processing for at least 60 minutes, then the workpiece is stored between approximately 0 C. and 40 C.

[0044] Then, the workpiece is rotated 44 by approximately 90 degrees about a longitudinal axis of the workpiece, and another shear strain is induced 46 in the workpiece at a temperature between approximately 180 C. and 200 C. This shear strain is greater than 1.0 and enables some precipitate growth in the workpiece. If delayed from further processing for at least 60 minutes, then the workpiece is stored between approximately 0 C. and 40 C.

[0045] Finally, the workpiece is rotated 48 by approximately 90 degrees about a longitudinal axis of the workpiece, and another shear strain is induced 50 in the workpiece at a temperature between approximately 110 C. and 130 C. This shear strain is greater than 1.0 and refines the grain size in the workpiece and allows the dislocations to interact with the formed precipitates. In total, the accumulative magnitude of the total shear strain exceeds 4.0, and that off-diagonal shear component of the Green Strain tensor is at least five times greater than any diagonal component of the Green Strain tensor.

[0046] The temperatures ranges of the various stages can be expressed in relative terms. For instance, the first two stages have an initial temperature range. The third stage has an intermediate temperature range where the lower bounds of the intermediate temperature range is greater than the upper bounds of the initial temperature range. Lastly, the fourth stage has a final temperature range that is between the initial and intermediate temperature ranges. The upper bounds of the final temperature range is less than the lower bounds of the intermediate temperature range, and the lower bounds of the final temperature range is greater than the upper bounds of the initial temperature range. In some embodiments, there are four stages, but generally, the temperature ranges begin at the lowest, move to the highest, and then settle therebetween. The effect of the relative temperatures, and the progression of temperatures, on the microstructure of the workpiece is to create and store dislocations, initiate precipitate growth, and then cause the interaction between the dislocations and the precipitate growth.

[0047] The resulting workpiece or material has improved electrical conductivity and strength. In some embodiments, after having been processed according to the flowchart in FIG. 3, the resulting workpiece has an increased Vickers hardness, which corresponds to the strength of the workpiece. In some embodiments, for example for an AA1xxx aluminum alloy, the hardness increases from 32HV0.2+/0.44HV0.2 to 91HV0.2+/2.6HV0.2. Thus, in some embodiments, the hardness of the resulting workpiece can be described as being between approximately 88HV0.2 to 94HV0.2.

[0048] An aluminum workpiece prior to being processed as described with respect to FIG. 3 may have an electrical conductivity of 61.33% IACS. In various embodiments, an aluminum workpiece processed as described with respect to FIG. 3 may have an electrical conductivity of 62.63% IACS. Typically, any processing that substantially increases the strength of a workpiece, like that in FIG. 3, diminishes other characteristics of the workpiece such as electrical conductivity. Thus, any increase in electrical conductivity is desirable and an achievement. In some embodiments, the hardness increases but the electrical conductivity remains the same or even reduces. In this sense, the traditional tradeoff between strength in terms of hardness and electrical conductivity is defied.

[0049] The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limiting of the disclosure to the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments described and shown in the figures were chosen and described in order to best explain the principles of the disclosure, the practical application, and to enable those of ordinary skill in the art to understand the disclosure.

[0050] While various embodiments of the present disclosure have been described in detail, it is apparent that modifications and alterations of those embodiments will occur to those skilled in the art. Moreover, references made herein to the present disclosure or aspects thereof should be understood to mean certain embodiments of the present disclosure and should not necessarily be construed as limiting all embodiments to a particular description. It is to be expressly understood that such modifications and alterations are within the scope and spirit of the present disclosure, as set forth in the following claims.