Abstract: A method of forming metal articles comprises placing a pair of sheet members 1, 2 or superplastically deformable material in opposed, spaced apart relationship, (conveniently by means of a reinforced member 3), heating them to the temperature range within which superplastic deformation can take place, and urging portions of the sheets toward each other until they lie one against the other thereby to effect bonding. The bonding is preferably by means of diffusion bonding.

Abstract: Two face-to-face metal sheets, one or each of which is superplastically deformable, are subjected to a bonding and pressure deformation process in which the sheets are bonded together at a series of spaced positions thereon and the areas of the or each superplastically deformable sheet between these positions move away from the other sheet so that there is formed a series of cavities between the sheets, the sides of neighboring cavities being substantially adjacent to one another over substantial parts of their areas. These sides of the cavities, which are preferably substantially rectangular may come directly into contact with one another and be diffusion bonded together either directly or via reinforcing members.