Macro -, micro - and re-entrant shape forming of sheets of alloy Ti - 6A1 - 4V

Experiments involving macro-,micro- and re-entrant shape forming in superplastic Ti-6A1-4V alloy sheets of initial thickness 1.6 mm are described. Macroforming followed by microforming into grooves of different geometry as well as re-entrant shape cum micro-forming could be completed successfully. The rate of forming into a wider groove was greater than into a narrower groove but microforming and the filling of corner radii of grooves required considerably more pressure and time than macroforming. For the chosen geometries, at the end of the macroforming stage there was a significant thickness gradient which led to a highly non-uniform thickness distribution after microforming. The effects of the geometry of the dies and the changes in the experimental conditions have also been discussed. © 1990.