Material Having Ultrafine Grained Structure and Method of Fabricating Thereof

Abstract

In the present invention, there is provided a fabrication method of a material having an ultrafine grained structure characterized by including a step of providing a metal or an alloy having a stacking fault energy no greater than 50 mJ/mm 2 and a step of introducing deformation twins having a twin interval no greater than 200 nm into structures of the metal or the alloy by processing the metal or the alloy. Further, according to this method, a material having an ultrafine grained structure characterized in that twins are included in a crystal structure and the twins have a twin interval no greater than 200 nm.

1 . A material comprising: an ultrafine grained structure including a metal or an alloy that has a stacking fault energy no greater than 50 mJ/mm 2 , wherein structures that predominantly exist in the material have twins included in a crystal structure, wherein the twins have a twin interval no greater than 100 nm. 
   
   
       2 . A material comprising: an ultrafine grained structure including a metal or an alloy that has a stacking fault energy no greater than 50 mJ/mm 2 , wherein structures that are predominant in the material have recrystallized grains, wherein twin boundaries having a crystal grain size ranging from 20 nm to 600 nm predominantly exist in the recrystallized grains. 
   
   
       3 . A fabrication method of the material having an ultrafine grained structure as claimed in  claim 1  comprising the steps of:
 providing a metal or an alloy having a stacking fault energy no greater than 50 mJ/mm 2 ; and   introducing deformation twins having a twin interval no greater than 100 nm into structures of the metal or the alloy by processing the metal or the alloy.   
   
   
       4 . The method as claimed in  claim 3 , wherein the step of introducing the deformation twins includes a step of performing a multidirectional forging process on the metal or the alloy at a temperature no greater than room temperature. 
   
   
       5 . The method as claimed in  claim 4 , wherein the step of performing the multidirectional forming process includes a step of performing a forging process on the metal or the alloy at a strain rate no less than 1×10 −4 /s. 
   
   
       6 . The method as claimed in  claim 4 , wherein the temperature no greater than room temperature is no greater than an absolute temperature of 223 K. 
   
   
       7 . The method as claimed in  claim 4 , further comprising a step of performing an annealing process on the multidirectional-forged metal or alloy. 
   
   
       8 . The method as claimed in  claim 3 , wherein the step of introducing the deformation twins includes a step of performing a rolling process on the metal or the alloy at a temperature no greater than room temperature. 
   
   
       9 . The method as claimed in  claim 8 , further comprising a step of performing an annealing process on the rolled metal or alloy. 
   
   
       10 . (canceled) 
   
   
       11 . The method as claimed in  claim 8 , wherein the step of performing the rolling process includes a step of rolling the metal or the alloy at a rolling rate no less than 5×10 −1  cm/s. 
   
   
       12 . The method as claimed in  claim 8 , wherein the step of performing the rolling process includes a step of rolling the metal or the alloy so that a final draft becomes no less than 20%. 
   
   
       13 . The method as claimed in  claim 8 , wherein the step of performing the rolling process includes a step of performing a rolling process on the metal or the alloy at a temperature no greater than an absolute temperature of 223 K. 
   
   
       14 . A material having an ultrafine grained structure comprising:
 structures predominantly existing in a single grain, the structures including   a first packet having a group of layered twins oriented substantially in a first direction, and   a second packet including at least one of the twins inside the first packet that has a group of layered twins oriented substantially in a second direction,   wherein the first and second directions form an angle other than 60 degrees.   
   
   
       15 . The material having an ultrafine grained structure as claimed in  claim 14 , wherein the structures include
 a first structure, the first structure including the first packet having a group of layered twins oriented substantially in the first direction and the second packet including at least one of the twins inside the first packet that has a group of layered twins oriented substantially in the second direction,   a second structure including recrystallized grains of the first packet, and   a third structure including recrystallized grains formed of a plurality of layered twins arranged substantially in the same direction,   wherein the first, second, and third structures predominantly exist in the single crystal grain.   
   
   
       16 . (canceled) 
   
   
       17 . The method as claim as claimed in  claim 7 , wherein the step of performing the annealing process includes a step of performing an annealing process on the metal or the alloy at a temperature no greater than 0.5×Tm, wherein Tm is a melting point of the metal or the alloy. 
   
   
       18 . The method as claim as claimed in  claim 9 , wherein the step of performing the annealing process includes a step of performing an annealing process on the metal or the alloy at a temperature no greater than 0.5×Tm, wherein Tm is a melting point of the metal or the alloy. 
   
   
       19 . The material having an ultrafine grained structure as claimed in  claim 14 , wherein the material is brass. 
   
   
       20 . The material having an ultrafine grained structure as claimed in  claim 15 , wherein the material is brass.