Generation of high strength metal through formation of nanocrystalline structure by laser peening

Abstract

A method of processing a metal piece comprises a number of steps. One step comprises directing a laser beam onto the metal piece for laser peening the metal piece. Another step comprises causing relative movement between the laser beam and the metal piece. Another step comprises providing a tamping material between the laser beam and the metal piece. Another step comprises continuing the laser peening to induce rapid strain and substantial strain in the metal piece and inducing the formation of nanocrystalline structure in the metal piece.

1 . A method of processing a metal piece, comprising the steps of: 
 directing a laser beam onto the metal piece for laser peening the metal piece,    causing relative movement between said laser beam and the metal piece,    providing between said laser beam and the metal piece a tamping material that is essentially transparent to the laser beam, and    continuing said laser peening to induce rapid strain and substantial strain in the metal piece and inducing the formation of nanocrystalline structure in the metal piece.    
     
     
         2 . The method of processing a metal piece of  claim 1  wherein said laser peening is accomplished with said laser producing nanosecond pulse duration and controllable high peak pressure sufficient to induce rapid strain and substantial strain in the metal piece and induce the formation of nanocrystalline structure.  
     
     
         3 . The method of processing a metal piece of  claim 1  wherein said laser beam has pulse duration in the range of several hundred picoseconds to 10 s of nanoseconds and controllable high peak pressure sufficient to induce rapid strain and substantial strain in the metal piece and induce the formation of nanocrystalline structure.  
     
     
         4 . The method of processing a metal piece of  claim 1  wherein said laser beam provides an output of approximately 20 J per pulse at 18 to 25 ns pulse duration directed onto the surface of the metal piece at an irradiance of approximately 200 J/cm2 and a power density of approximately 10 GW/cm2.  
     
     
         5 . The method of processing metal of  claim 1  wherein said step of continuing said laser peening comprises applying multiple layers of laser peening to the metal piece.  
     
     
         6 . The method of processing metal of  claim 1  wherein said step of causing relative movement between said laser beam and the metal piece comprises moving said laser beam over the metal piece.  
     
     
         7 . The method of processing metal of  claim 1  wherein said step of causing relative movement between said laser beam and the metal piece comprises moving the metal piece relative to said laser beam.  
     
     
         8 . The method of processing metal of  claim 1  wherein said steps of directing a laser beam onto the metal piece and continuing said laser peening comprise applying peening to metal plate.  
     
     
         9 . The method of processing metal of  claim 1  wherein said steps of directing a laser beam onto the metal piece and continuing said laser peening comprise applying peening to metal sheet.  
     
     
         10 . The method of processing metal of  claim 1  wherein said laser beam is directed onto the metal piece at a point of the laser beam incidence and said step of providing a tamping material between said laser beam and the metal piece comprises applying a tampering material that exhibit the electro-strictive effect, are transparent to the laser light, and have a low SBS gain coefficient between said laser beam and the metal piece.  
     
     
         11 . The method of processing metal of  claim 1  wherein said laser beam is directed onto the metal piece at a point of the laser beam incidence and said step of providing a tamping material between said laser beam and the metal piece comprises applying a laminar stream of water to the metal piece at the point of the laser beam incidence.  
     
     
         12 . The method of processing metal of  claim 1  wherein said step of providing an ablation material between said laser beam and the metal piece comprises covering the metal piece an ablation/absorption layer.  
     
     
         13 . A method of processing a metal piece, comprising the steps of: 
 directing a laser beam onto the metal piece for laser peening the metal piece,    causing relative movement between said laser beam and the metal piece,    providing an ablative/insulating material adhered to or in intimate contact with the metal piece between said laser beam and the metal piece,    providing a tamping material that is essentially transparent to the laser beam, and    continuing said laser peening to induce rapid strain and substantial strain in the metal piece and inducing the formation of nanocrystalline structure in the metal piece.    
     
     
         14 . The method of processing a metal piece of  claim 13  wherein said laser peening is accomplished with said laser producing nanosecond pulse duration and controllable high peak pressure sufficient to induce rapid strain and substantial strain in the metal piece and induce the formation of nanocrystalline structure.  
     
     
         15 . The method of processing a metal piece of  claim 13  wherein said laser beam has pulse duration in the range of several hundred picoseconds to 10 s of nanoseconds and controllable high peak pressure sufficient to induce rapid strain and substantial strain in the metal piece and induce the formation of nanocrystalline structure.  
     
     
         16 . The method of processing a metal piece of  claim 13  wherein said laser beam provides an output of approximately 20 J per pulse at 18 to 25 ns pulse duration directed onto the surface of the metal piece at an irradiance of approximately 200 J/cm2 and a power density of approximately 10 GW/cm2.  
     
     
         17 . The method of processing metal of  claim 13  wherein said step of continuing said laser peening comprises applying multiple layers of laser peening to the metal piece.  
     
     
         18 . The method of processing metal of  claim 13  wherein said step of causing relative movement between said laser beam and the metal piece comprises moving said laser beam over the metal piece.  
     
     
         19 . The method of processing metal of  claim 13  wherein said step of causing relative movement between said laser beam and the metal piece comprises moving the metal piece relative to said laser beam.  
     
     
         20 . The method of processing metal of  claim 13  wherein said steps of directing a laser beam onto the metal piece and continuing said laser peening comprise applying peening to metal plate.  
     
     
         21 . The method of processing metal of  claim 13  wherein said steps of directing a laser beam onto the metal piece and continuing said laser peening comprise applying peening to metal sheet.  
     
     
         22 . The method of processing metal of  claim 13  wherein said laser beam is directed onto the metal piece at a point of the laser beam incidence and said step of providing a tamping material between said laser beam and the metal piece comprises applying a laminar stream of water to the metal piece at the point of the laser beam incidence.  
     
     
         23 . The method of processing metal of  claim 13  wherein said step of providing an ablation material between said laser beam and the metal piece comprises covering the metal piece an ablation/absorption layer.  
     
     
         24 . The method of processing metal of  claim 13  wherein said step of providing a ablation/insulation material between said laser beam and the metal piece comprises covering at least a portion of the metal piece with PVC tape.  
     
     
         25 . The method of processing metal of  claim 13  wherein said step of providing a ablative material between said laser beam and the metal piece comprises covering at least a portion of the metal piece with aluminum tape.  
     
     
         26 . The method of processing metal of  claim 13  wherein said step of providing an ablative material between said laser beam and the metal piece comprises covering at least a portion of the metal piece with paint.