Method and apparatus for producing a refined grain structure

Abstract

The apparatus for operating on a workpiece includes a die defining first and second apertures and an interior therebetween. The first aperture and the interior of the die are structured to receive the workpiece. The interior of the die can be structured to shape the workpiece into a predetermined configuration. The apparatus includes at least one rotatable pin extending at least partially into the interior of the die. The pin is structured to at least partially stir the workpiece as the workpiece moves through the interior of the die to thereby refine the grain structure of the workpiece.

What is claimed is:  
     
         1 . A preform comprising a body having predetermined dimensions and wherein said body comprises a refined grain structure having a cross-section comprising a curvilinear configuration.  
     
     
         2 . A preform according to  claim 1  wherein said grain structure comprises grains having equiaxed shape.  
     
     
         3 . A preform according to  claim 1  wherein said grain structure comprises grains having a grain size of about 3 microns to about 5 microns.  
     
     
         4 . A preform according to  claim 1  wherein said body is formed of a material selected from the group consisting of aluminum, an aluminum alloy, titanium, a titanium alloy and a steel alloy.  
     
     
         5 . A preform according to  claim 1  wherein said body has an elongation of between about 15% and about 35%.  
     
     
         6 . A preform according to  claim 1  wherein said body has an elongation of greater than about 20%.  
     
     
         7 . A preform formed from a workpiece, the preform prepared by a process comprising the steps of: 
 moving the workpiece through a die; and    concurrently with said moving step, mixing the workpiece with at least one rotating pin to thereby refine the grain structure of the workpiece to thereby form a preform having a refined grain structure having a cross-section comprising a curvilinear configuration.    
     
     
         8 . A preform prepared by the process according to  claim 7  wherein said mixing step comprises: 
 individually rotating a plurality of pins in corresponding first directions; and  
 collectively rotating the plurality of pins in a second direction.  
 
     
     
         9 . A preform prepared by the process according to  claim 8  wherein the corresponding first directions are the same as the second direction.  
     
     
         10 . A preform prepared by the process according to  claim 8  wherein the corresponding first directions are opposite to the second direction.  
     
     
         11 . A preform prepared by the process according to  claim 8  wherein said first rotating step comprises individually rotating at least two of the plurality of friction stir pins in opposite directions.  
     
     
         12 . A preform prepared by the process according to  claim 7  further comprising precipitation hardening the workpiece prior to said moving step.  
     
     
         13 . A preform prepared by the process according to  claim 7  further comprising solution heat treating the workpiece at a predetermined temperature schedule after said mixing step.  
     
     
         14 . A preform prepared by the process according to  claim 13  further comprising precipitation heat treating the workpiece by aging at a second predetermined temperature schedule after said solution heat treating step.  
     
     
         15 . A preform prepared by the process according to  claim 7  further comprising heating the workpiece concurrently with said mixing step.  
     
     
         16 . A preform prepared by the process according to claim  27  further comprising heating at least one of the pin or the die concurrently with said mixing step.  
     
     
         17 . A preform prepared by the process according to  claim 16  wherein said heating step comprises heating the at least one of the pin or the die to a temperature between about 600° F. and about 1000° F.  
     
     
         18 . A preform prepared by the process according to  claim 7  further comprising cooling the die concurrently with said mixing step.  
     
     
         19 . A preform prepared by the process according to  claim 7  wherein the grain structure of the preform comprises grains having equiaxed shape.  
     
     
         20 . A preform prepared by the process according to  claim 7  wherein the grain structure of the preform comprises grains having a grain size of about 3 microns to about 5 microns.  
     
     
         21 . A preform prepared by the process according to  claim 7  wherein the preform comprises a body having an elongation of between about 15% and about 35%.  
     
     
         22 . A preform prepared by the process according to  claim 7  wherein the preform comprises a body having an elongation of greater than about 20%.