CONTROLLED GRAIN SIZE STRUCTURES

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.

BACKGROUND

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.

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 inFIG. 1and is designated generally by reference character100. Other embodiments and/or aspects of this disclosure are shown inFIGS. 2-4. The systems and methods described herein can be used to provide structures having beneficial material properties.

Referring toFIG. 1, a structure100includes a first substrate101and a variable grain layer103disposed on or formed into the first substrate101. The substrate101can 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 layer103can include one or more first grain portions103ahaving a first grain size and one or more second grain portions103bhaving a second grain size. The first grain size is smaller than the second grain size. The variable grain layer103can include a metal material, for example. Any other suitable material is contemplated herein.

In certain embodiments, the variable grain layer103can be deposited on the substrate101. In certain embodiments, the variable grain layer103is formed from the first substrate101and/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 layer103can include a thickness greater than or equal to the substrate101. However, any other suitable thickness (e.g., less than the substrate101) is contemplated herein.

Referring toFIGS. 2 and 3, a second substrate205can be disposed on the variable grain layer103opposite the first substrate101to form a sandwich structure as shown. In certain embodiments, the second substrate205can be the same material and/or dimensions (e.g., shape and/or size) as the first substrate101. Any other suitable dimensions and/or material is contemplated herein.

As shown inFIGS. 2 and 3, an aperture207can be defined through the first substrate101, the variable grain layer103, and the second substrate205at the first grain portion103a. The aperture207can be configured to receive a fastener (e.g., a bolt), for example.

The first and/or second substrate101,205can be compression bonded (e.g., roll bonded) to the variable grain layer103, and/or bonded in any other suitable manner. As shown inFIGS. 1-3, the first grain portion103aand the second grain portion103bcan be defined in strips. Any other suitable shape for the first and second grain portions103a,103bis contemplated herein.

Referring additionally toFIG. 4, in accordance with at least one aspect of this disclosure, a method for forming a structure100having variable grain sizes includes creating a first grain portion103ahaving a first grain size on a first substrate101and creating a second grain portion103bhaving a second grain size on the first substrate101. 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 layer103. Creating the first and/or second grain layer103a,103bcan 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 layer103on the first substrate103.

Creating a first grain portion103acan include masking a portion of the first substrate101and allowing the first grain portion103ato deposit on the substrate101where there is no masking. Similarly, creating the second grain portion103bcan include masking the first grain portion103aand allowing a second grain portion103ato deposit on the substrate101where there is no masking.

The method can include disposing a second substrate207on the variable grain layer to form a sandwich structure. The method can include bonding the second substrate205to the variable grain layer103.

Bonding can include roll bonding the sandwich structure in a roller system400as shown inFIG. 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 system400. 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 structure100can 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.