A method for superplastic deformation, as well as a three-dimensional of superplastic a shaped article

摘要

The present invention provides a method of superplastically forming at least two sheets of superplastically formable material to form a three dimensional article, the sheets being joined together along diffusion bonds (12) to form discrete cells (16) and wherein at least one gas path (18) is provided through the bond between cells; the method involves heating the sheets to a temperature at which they exhibit superplastic properties and injecting a gas between the sheets to expand the cells, the gas paths (18) allowing the injected gas to pas from cell to cell. According to the invention, the edges of the gas paths are locally heated (22), e.g. by laser heat treatment, to cause a change in the microstructure of the sheets in the heat-treated edge areas, which reduces the flow resistance of the edges under superplastic forming conditions as compared with the rest of the sheets and thereby reduces the propensity of the diffusion bonds (12) bordering the gas transfer holes to peel apart under the forces of the inert gas exerted on the sheets at the gas transfer paths (18).