Investigation of the superplastic behaviour in 10 and 20% AL2O3 particle reinforced 6061 AL composites

The torsional stress-strain curves of 10 and 20% Al2O3 particle reinforced 6061 Al composites were studied. Low constant now stress and high ductility were found at/above 500 degrees C temperature at strain rates of 0.1-5 s(-1). TEM investigations revealed that there are dynamically recrystallized grains in some high strain regions of the matrix. This suggested an investigation of superplastic behaviour of the composites in torsion tests at 500, 540 and 570 degrees C by means of strain rate change tests between 0.001 and 0.5 s(-1). The strain-rate sensitivity (m) has been calculated at 500, 540 and 570 degrees C: for the 10% Al2O3 reinforced composite, the average m values are 0.19, 0.30 and 0.33 respectively, and are 0.18, 0.25 and 0.26 respectively for the 20% Al2O3 reinforced composite. Studies of the mechanical behaviour and of the microstructures of both indicate that superplasticity may occur to a degree in both composites during high temperature deformation.