An analysis of hot formability of the 6061+20% Al2O3 composite by means of different stability criteria

The hot workability of a 6061 alloy reinforced with 20% Al2O3 particulate was investigated by means of torsion and compression tests in the temperature range between 350 and 500 °C. Different stability criteria were used to identify the ‘processing window’. Gegelʹs approach, based on the use of the Liapunov function, resulted in instability areas larger than those identified with the other criteria. The conventional approach of the maximisation of the strain-rate sensitivity and the criterion based on Zieglerʹs plastic flow theory, in its more general form, valid for any type of stress vs. strain-rate curve, gave substantially similar indications for the determination of the processing window.