The effects of SiC particle volume fraction on the microstructure and hot workability of SiCp/AA 2024 composites

The hot workability of AA 2024 composites reinforced with different volume fractions (5, 10, 15, 20, and 30 vol%) of SiCp was investigated within the temperature range 320-500 degrees C at a strain-rate of 1.0 s(-1). Dynamic recrystallization (DRX) or dynamic recovery (DRV) of the composites was stu died from the flow curves and deformed microstructures. The effect of the S iCp volume fraction on the critical strain for the onset of DRX was analyze d from the relationship between the work-hardening rate and effective strai n during hot deformation. The addition of the SiCp to an AA 2024 matrix all oy increased the dislocation density, resulting in a high flow stress and a low critical strain for the DRX of the composites. Upon increasing the SiC p volume fraction, the flow stress and the temperature showing the highest failure strain increased. Also, the difference in flow stress amongst the c omposites decreased with increasing deformation temperature. This result ha s been discussed in relation to dislocation density and stacking fault in t he matrix of the composites. (C) 1999 Elsevier Science S.A. All rights rese rved.