Patent Publication Number: US-2018037019-A1

Title: Controlled grain size structures

Description:
BACKGROUND 
     1. Field 
     The present disclosure relates to structures, more specifically to controlled grain size structures. 
     2. Description of Related Art 
     Metals with grain sizes below 1 micron, for example, are known to have strength, hardness, and fatigue endurance limits superior to coarser grain (i.e., greater than 1 micron) metals. These property enhancements stem from the Hall-Petch grain size strengthening effect whereby smaller grains results in higher strength. Challenges exist in synthesizing useful components that extract benefit from submicron grain metal. 
     Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved structures and methods for making such structures. The present disclosure provides a solution for this need. 
     SUMMARY 
     A structure includes a first substrate and a variable grain layer disposed on or formed into the first substrate. The variable grain layer includes a first grain portion having a first grain size and second grain portion having a second grain size. The first grain size is smaller than the second grain size. 
     The first grain size can be submicron. In certain embodiments, the second grain size can be 1 micron or greater. The substrate can include a sheet shape and/or any other suitable shape. The variable grain layer can be made of and/or can include metal, for example. 
     In certain embodiments, the variable grain layer can include a thickness greater than or equal to the substrate, or any other suitable thickness. A second substrate can be disposed on the variable grain layer opposite the first substrate to form a sandwich structure. 
     An aperture can be defined through the first substrate, the variable grain layer, and the second substrate at the first grain portion. The aperture can be configured to receive a fastener, for example. 
     The second substrate can be compression bonded (e.g., roll bonded) to the variable grain layer or bonded in any other suitable manner. The first grain portion and the second grain portion can be defined in strips. 
     In accordance with at least one aspect of this disclosure, a method for forming a structure having variable grain sizes includes creating a first grain portion having a first grain size on a first substrate and creating a second grain portion having a second grain size on the first substrate. The first grain size is smaller than the second grain size and the first grain portion and the second grain portion form at least part of a variable grain layer. 
     Creating a first grain portion can include masking a portion of the first substrate and allowing the first grain portion to deposit on the substrate where there is no masking. Creating the second grain portion can include masking the first grain portion and allowing a second grain portion to deposit on the substrate where there is no masking. Creating the first and/or second grain layer can include at least one of vapor deposition, electroplating, chemical plating, mechanical working of the surface of the substrate, or disposing a preformed variable grain layer. 
     The method can include disposing a second substrate on the variable grain layer to form a sandwich structure. The method can include bonding the second substrate to the variable grain layer. 
     Bonding can include roll bonding the sandwich structure in a roller system. The method can include controlling grain size as a function of one or more rolling parameters of the roller system. The one or more rolling parameters can include at least one of heating, cooling, compression, or speed. 
     These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, embodiments thereof will be described in detail herein below with reference to certain figures, wherein: 
         FIG. 1  is a perspective view of an embodiment of a structure in accordance with this disclosure, shown having a variable grain layer disposed on a substrate; 
         FIG. 2  is a perspective, partially sectional view of  FIG. 1 , shown having a second substrate disposed on the variable grain layer to form a sandwich structure, and an aperture defined through the sandwich structure at a first grain portion of the variable grain layer. 
         FIG. 3  is a cross-sectional view of the embodiment of  FIG. 2 ; and 
         FIG. 4  is a schematic flow view of an embodiment of a method in accordance with this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, an illustrative view of an embodiment of a structure in accordance with the disclosure is shown in  FIG. 1  and is designated generally by reference character  100 . Other embodiments and/or aspects of this disclosure are shown in  FIGS. 2-4 . The systems and methods described herein can be used to provide structures having beneficial material properties. 
     Referring to  FIG. 1 , a structure  100  includes a first substrate  101  and a variable grain layer  103  disposed on or formed into the first substrate  101 . The substrate  101  can include a sheet shape and/or any other suitable shape. The substrate can include a metal (e.g., stainless steel) and can have any suitable grain size (e.g., coarse such as greater than 1 micron). 
     The variable grain layer  103  can include one or more first grain portions  103   a  having a first grain size and one or more second grain portions  103   b  having a second grain size. The first grain size is smaller than the second grain size. The variable grain layer  103  can include a metal material, for example. Any other suitable material is contemplated herein. 
     In certain embodiments, the variable grain layer  103  can be deposited on the substrate  101 . In certain embodiments, the variable grain layer  103  is formed from the first substrate  101  and/or forms a separate layer. 
     In certain embodiments, the first grain size can be submicron. In certain embodiments, the second grain size can be 1 micron or greater. 
     In certain embodiments, the variable grain layer  103  can include a thickness greater than or equal to the substrate  101 . However, any other suitable thickness (e.g., less than the substrate  101 ) is contemplated herein. 
     Referring to  FIGS. 2 and 3 , a second substrate  205  can be disposed on the variable grain layer  103  opposite the first substrate  101  to form a sandwich structure as shown. In certain embodiments, the second substrate  205  can be the same material and/or dimensions (e.g., shape and/or size) as the first substrate  101 . Any other suitable dimensions and/or material is contemplated herein. 
     As shown in  FIGS. 2 and 3 , an aperture  207  can be defined through the first substrate  101 , the variable grain layer  103 , and the second substrate  205  at the first grain portion  103   a . The aperture  207  can be configured to receive a fastener (e.g., a bolt), for example. 
     The first and/or second substrate  101 ,  205  can be compression bonded (e.g., roll bonded) to the variable grain layer  103 , and/or bonded in any other suitable manner. As shown in  FIGS. 1-3 , the first grain portion  103   a  and the second grain portion  103   b  can be defined in strips. Any other suitable shape for the first and second grain portions  103   a ,  103   b  is contemplated herein. 
     Referring additionally to  FIG. 4 , in accordance with at least one aspect of this disclosure, a method for forming a structure  100  having variable grain sizes includes creating a first grain portion  103   a  having a first grain size on a first substrate  101  and creating a second grain portion  103   b  having a second grain size on the first substrate  101 . As described above, the first grain size can be smaller than the second grain size and the first grain portion and the second grain portion can form at least part of a variable grain layer  103 . Creating the first and/or second grain layer  103   a ,  103   b  can include at least one of vapor deposition, electroplating (e.g., electro-chemical plating), chemical plating, mechanical working of the surface of the substrate, or disposing a preformed variable grain layer  103  on the first substrate  103 . 
     Creating a first grain portion  103   a  can include masking a portion of the first substrate  101  and allowing the first grain portion  103   a  to deposit on the substrate  101  where there is no masking. Similarly, creating the second grain portion  103   b  can include masking the first grain portion  103   a  and allowing a second grain portion  103   a  to deposit on the substrate  101  where there is no masking. 
     The method can include disposing a second substrate  207  on the variable grain layer to form a sandwich structure. The method can include bonding the second substrate  205  to the variable grain layer  103 . 
     Bonding can include roll bonding the sandwich structure in a roller system  400  as shown in  FIG. 4 . Any other suitable bonding means is contemplated herein. 
     The method can include controlling grain size as a function of one or more rolling parameters of the roller system  400 . The one or more rolling parameters can include at least one of temperature (heating and/or cooling), compression load, thickness reduction level, or speed, for example. The structure  100  can be machined for any suitable use after bonding, for example. As described above, in certain embodiments, a graded grain structure can be achieved with a hybrid manufacturing approach that combines bottom up synthesis of small grain metal on a substrate formed into a sandwich panel with roll bonding. 
     Embodiments as described above can harness strong submicron grain metal, for example, to create components with improved mechanical performance. The strong submicron grain metal can be strategically incorporated into regions of the structure where high stress develops during use of the structure, for example. Embodiments of this disclosure enable components to achieve improvements in fatigue resistance, strength, lifetime, and more that are afforded by submicron metal. 
     The methods and systems of the present disclosure, as described above and shown in the drawings, provide for structures with superior properties. While the apparatus and methods of the subject disclosure have been shown and described with reference to embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the spirit and scope of the subject disclosure.