Method for preparing ultrafine-grained metallic foil

Abstract

Coarse-grained titanium and ultrafine-grained (UFG) titanium billets were processed into titanium foil cold rolling and intermediate annealing. The foil produced from the UFG titanium billet exhibits a homogeneous nanostructure. By contrast, foil produced by cold rolling the coarse-grained titanium billet exhibits a heterogeneous structure with both nanostructured and coarser-grained regions. The foil produced from UFG billets has higher strength, higher ductility, and exhibits uniform deformation over a larger strain range at room temperature than foil produced from coarse-grained billets.

1 . A method for preparing ultrafine-grained metal foil, comprising: 
 (a) preparing an ultrafine-grained metal billet having a thickness;    (b) cold rolling the ultrafine-grained billet until the thickness of the billet is reduced by at least at least 40%;    (c) annealing the cold rolled billet of step (b);    (d) cold rolling the annealed billet of step (c) until the thickness of the billet is reduced by at least 70%;    (e) annealing the billet of step (d); and    (f) cold rolling the annealed billet of step (e) until the thickness of the billet is reduced by at least another 70%;    (g) annealing the billet of step (f); and    (h) cold rolling the annealed billet of step (f) to produce ultrafine-grained metal foil.    
     
     
         2 . The method of  claim 1 , wherein the step of preparing an ultrafine-grained metal billet comprises subjecting a coarse-grained metal billet to equal channel angular extrusion.  
     
     
         3 . The method of  claim 2 , where the step of preparing an ultrafine-grained metal billet comprises subjecting a coarse-grained metal billet to from one to twelve passes through an equal channel angular extrusion die.  
     
     
         4 . The method of  claim 2 , wherein the step preparing an ultrafine-grained billet comprises subjecting a coarse-grained billet to from two to eight passes through an equal channel angular extrusion die and rotating the billet by an angle of zero degrees, 90 degrees or 180 degrees between successive passes through the equal channel extrusion die.  
     
     
         5 . The method of  claim 1 , wherein step (c) comprises annealing at a temperature from about 100° C. to about 500° C.  
     
     
         6 . The method of  claim 1 , wherein the ultrafine-fine grained metal foil comprises metal selected from the group consisting of copper, nickel, aluminum, zinc, zirconium, tantalum, chromium, molybdenum, iron, cobalt, platinum, silver, gold, and alloys thereof.  
     
     
         7 . The method of  claim 1 , wherein the ultrafine-grained metal foil comprises ultrafine-grained titanium foil.  
     
     
         8 . The method of  claim 1 , wherein the ultrafine-grained metal foil comprises a thickness of no greater than 50 microns.  
     
     
         9 . The method of  claim 1 , wherein the ultrafine-grained metal foil comprises a thickness of no greater than 20 microns.  
     
     
         10 . A method for preparing ultrafine-grained titanium foil comprising preparing an ultrafine-grained metal billet having a thickness; thereafter cold rolling the ultrafine-grained billet until the thickness of the billet is reduced by about 75%; thereafter annealing the cold rolled billet at a temperature of about 350° C.; thereafter cold rolling the annealed billet again until the thickness of the billet is reduced by at least another 75%; annealing the billet again at a temperature of about 350° C.; thereafter cold rolling the billet again until the thickness is reduced by at least 75%; thereafter annealing the cold rolled billet again at a temperature of about 350° C.; and thereafter cold rolling the annealed billet to produce ultrafine-grained titanium foil.