Abstract: A superplastic forming (SPF) method using a self-contained die obviates the need for external containment bands or rings. The method and die are particularly advantageous for use in forming generally planar parts but may also be used to form parts of a more cylindrical shape. The die includes two or more die segments, each of which is unitarily formed from a suitable material such as graphite or ceramic. Each die segment has a unitarily formed connecting portion for interlocking it to another die segment. The connection portion may be a tab having a bore through which a pin may be extended to interlock the die segments. The die may swing open and closed in a hinged manner or be completely separable. In accordance with the method, a gas-tight preform assembly made of a metal such as titanium alloy is placed in the die. The die and preform assembly are heated in a vacuum furnace. Gas is injected into the preform assembly, expanding it to conform to the shape of the interior of the die.