material shows superplastic forming capability in the solution treatment temperature range 500 u00b0 to 545 u00b0 c and at strain rates used commercially sample 5 has the lowest overall superplastic capability thus solution treating prior to lower temperature heat treatment is not preferred sample 3 has the better superplastic capability particularly at the higher strain rates and higher test temperatures fig4 shows the cavitation observed in optimised route material compared to that found in the same alloy processed using route 1 above a significant reduction in cavitation is found in the optimum route material fig5 a 6 6a 7 7a and 8 8a compare the grain structure observed during superplastic forming of optimised route material compared to material processed via route 1 the optimised route material develops a fine grain structure necessary forgood superplastic performance and low flow stress at a much earlier stage of straining transmission electron microscopy has been carried out on material in the as rolled final anneal state and in undeformed regions of samples held atthe forming temperature prior to straining we have found that in material processed according to the optimum route of the present invention has an unrecrystallised grain structure with a uniform structure whereas route 1 material is unrecrystallised grain structure with a non uniform structure in an undeformed region the optimum route is recovered whereas the route 1 material is un recrystallised thus it can be stated that in the prior art route 2 the essential is that a fine grain statically recrystallised structure is produced during processing and prior to superplastic deformation it is not practicable toproduce the fine grain structure in.