Abstract: Improved superplastic aluminum alloys are formulated to contain less than 0.05 weight percent each of iron and silicon based on the total weight of the superplastic aluminum alloy. Advantageously these two elements are present at levels of 0.03 weight percent or below, preferably 0.01 weight percent or below. Advantageous superplastic forming properties are achieved with these low iron, low silicon alloys. Further advantageous superplastic forming properties are achieved by subjecting aluminum alloys to a thermomechanical treatment followed by a rapid recrystallization-anneal treatment as, for instance, a recrystallization-anneal treatment utilizing a molten salt bath. When these formulations and processes are practiced alone, in combination with each other or together with cavitation supression improvements in superplastic forming of component parts are achieved.

Abstract: A method for improving mechanical properties of superplastically formed alloy by healing the cavities formed as result of a superplastic forming process is disclosed. The alloy, such as an aluminum alloy, is superplastically formed and is then placed in an autoclave and hot isostatically pressed at a pressure ranging from about 10,000 psi to 30,000 psi for a time and temperature sufficient to heal cavities.

Abstract: Disclosed is a method of forming metallic materials exhibiting the phenomenon of superplasticity, particularly high strength aluminum alloys, by the technique of superplastic forming by focing an alloy blank into a die cavity using opposing fluid pressures, the pressure on the die side of the blank initially balancing the pressure on the opposite blank side, the die side pressure being reduced as the other pressure is maintained constant or increased to deform the blank at a combined high pressure whereby precision molding occurs as the blank engages the die intimately and cavitation in the blank is reduced or alleviated.

Abstract: The use of a sequentially applied warm working/cold working procedure in the conventional steps of preparing heat treatable superplastic alloys yields material which demonstrates substantially equiaxed fine grain structure and improved superplastic forming characteristics.

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 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.