Abstract: A method is set forth of forming a hollow structure having a varying mass distribution. Two sheets of a diffusion bondable and superplastic formable material are formed with one flat surface and an opposite surface contoured to have a selected mass distribution. A stop-off material is applied between selected non-peripheral portions of each of the flat surfaces whereat diffusion bonding is to be prevented and superplastic forming is to be required. An intermediate flat core sheet may also be present. The flat surfaces are positioned in abutting relation to each other or to the intermediate flat core sheet. The sheets are subjected to diffusion bonding conditions. The sheets are superplastically formed to expand them apart against a die. The invention also provides a method of preinflating contoured sheets prior to superplastically forming them to avoid truss core rupture. Hollow aircraft engine components are formed by the methods.

Abstract: A fluidized bed of solid particulate material cools a heated workpiece through a temperature range critical to strength property determination. Upon immersion into the fluidized bed container the bed is allowed to collapse around the workpiece forming a universal fixture which firmly supports the workpiece for the remainder of the cooling, allowing cooling to be completed at a slower rate to prevent or minimize distortion caused from differential thermal contractions.

Abstract: A method is set forth for forming a unitary structure having a plurality of deformable foils having first and second sides stacked one upon another with the first sides facing in one direction and the second sides in an opposite direction, each of the foils having an undulating cross-section, adjacent of the foils having their undulations orthogonal to one another and every other one of the foils having parallel orientations. The method comprises positioning a first plurality of parallel rods against the first side of a respective one of the foils and positioning a second plurality of parallel rods against the second side of the same foil with the rods of the second plurality of rods between and parallel to the rods of the first plurality of rods. Thereafter the aforementioned steps are repeated with each next adjacent foil having the rods defining the undulating cross-section thereof at a non-zero angle to the rods of the next adjacent foil.

Abstract: Process for producing metallic structures such as T-cap structures of a metal capable of diffusion bonding and superplastic forming, which comprises inserting at least two metal workpieces, for example, a titanium alloy, preferably in the form of sheets or diaphragms, in contact with each other in a tooling apparatus, and providing a space or cavity, e.g., of triangular shape, in the tooling above and below the workpieces along an area thereof. A sharp ridge is provided in the tooling at one end of the cavity to pinch off the workpieces at that point. The workpieces are diffusion bonded at preselected contacting areas thereof. The unbonded areas of the workpieces are then expanded by superplastic forming into contact with a wall of the tooling cavity, forming a hollow, e.g., triangular, cross-sectional shape.

Abstract: An improvement to an apparatus for and method of making structures from at least one workpiece is disclosed. The prior art apparatus and method comprised a pair of dies which were clamped about the periphery of the at least one workpiece creating a gap therebetween. A pair of non-inflatable platens were then used to apply a force against the pair of dies further clamping the workpiece in place. The die assembly and workpiece were then heated to forming temperatures and thereafter the workpiece was formed within the pair of dies by fluid under pressure. Typically the forming was Superplastic Forming or Superplastic Forming/Diffusion Bonding. The improvement to the apparatus and method comprises providing an inflatable platen between one of the dies and one of the non-inflatable platens, adapted to regulate the force applied by said pair of dies to said at least one workpiece.

Abstract: An improvement to an apparatus for and method of making structures from at least one workpiece is disclosed. The prior art apparatus and method comprised a pair of dies which were clamped about the periphery of the at least one workpiece creating a gap therebetween. A pair of non-inflatable platens were then used to apply a force against the pair of dies further clamping the workpiece in place. The die assembly and workpiece were then heated to forming temperatures and thereafter the workpiece was formed within the pair of dies by fluid under pressure. Typically the forming was Superplastic Forming or Superplastic Forming/Diffusion Bonding. The improvement to the apparatus and method comprises producing an inflatable platen mounted between one of the dies and one of the non-inflatable platens, adapted to regulate the force applied by said pair of dies to said at least one workpiece.

Abstract: A method for fabricating superplastically formed/diffusion bonded structures wherein metal blanks of a titanium alloy are joined at selected areas by diffusion bonding and expanded superplastically to form a desired sandwich or integrally stiffened structure. In such method, the metal blanks are treated in selected areas with a "stopoff" material to prevent bonding at those areas during diffusion bonding and to permit forming or shaping at the same areas during superplastic forming. An improved stopoff compound is provided for this purpose, in the form of yttria of relatively coarse particle size, coarser than 5 microns, in a suitable volatilizable vehicle. Such stopoff compound is inert to reactive metals such as titanium at the high diffusion bonding temperatures, and permits relatively low breakthrough pressure-time product during superplastic forming, thereby preventing excessive strain or rupture of the metal through non-superplastic deformation.

Abstract: An improvement to the method of making a structure by superplastic forming, wherein portions of a preform are expanded, in the superplastic condition, against a forming member, is disclosed. The improvement comprises the step, prior to expanding the preform, of providing a lower coefficient of friction between the portions of the preform to be expanded and the forming member than which exists between the portions of the preform where expansion is intended to be minimal and the forming member. The two values of coefficient of friction are obtained by applying first and second release coatings to the portions of the preform to be expanded and those where expansion is to be minimal respectively, with the first release coating having a coefficient of friction less than the second release coating. Alternately, the first and second release coatings can be applied to the forming member. The preferred first and second release coatings are boron nitride and yttria respectively.

Abstract: A method is provided for controlling the strain rate during superplastic forming of a blank of material into a part. The method produces a part in a minimum time by deforming the material under suitable-optimum superplastic conditions. A relationship is determined between time and the pressure required to form the blank against the configured surface of a die at a strain rate which causes the blank to flow superplastically. The blank is positioned in the die and held at a temperature at which the material exhibits superplasticity. Pressure is applied to the blank in accordance with the previously determined relationship between time and pressure until the part is formed.

Abstract: A method for fabricating superplastically formed/diffusion bonded structures wherein metal blanks of a titanium alloy are joined at selected areas by diffusion bonding and expanded superplastically to form a desired sandwich or integrally stiffened structure. In such method, the metal blanks are treated in selected areas with a "stopoff" material to prevent bonding at those areas during diffusion bonding and to permit forming or shaping at the same areas during superplastic forming. An improved stopoff compound is provided for this purpose, in the form of yttria of relatively coarse particle size, coarser than 5 microns, in a suitable volatilizable vehicle. Such stopoff compound is inert to reactive metals such as titanium at the high diffusion bonding temperatures, and permits relatively low breakthrough pressure-time product during superplastic forming, thereby preventing excessive strain or rupture of the metal through non-superplastic deformation.