The deformation of two industrial alloys which exhibit superplasticity (Cu-9·5Al-4Fe and Cu-0·4Co-2·8Al-1·8Si) has been examined by subjecting thin circular diaphragms to one-sided hydrostatic pressure at elevated temperatures. The experimentally determined values of thinning factor (defined as the ratio of the actual thickness to the average thickness) for hemispherical domes show good agreement with theoretical predictions when the value of the strain-rate sensitivity is between 0·35 and 0·40. The various combinations of temperature, pressure, and forming time for optimum behaviour have been explored. An attempt has been made to correlate tensile data with the bulge-forming characteristics.
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