Hot deformation,dynamic recovery,and recrystallisation behaviour of aluminium 6061–SiC p composite

Hot working and microstructural behaviour of a 15 vol.-%SiC particle reinforced Al 6061 composite is discussed in this paper. The average size of the SiC particles is 18 μm. The hot torsion test temperatures range from 200 to 500°C with strain rates of 0·1, 1·0, and 4 s⁻¹. The equivalent stress versus strain curves show that the Al 6061–SiC_p composite has great strengthening behaviour compared with the Al–Mg–Si bulk alloy below 500°C. It is mainly due to the high dislocation density from differential thermal contraction between SiC_p and the matrix during cooling and to geometrical constraints around SiC particles during theplastic deformation. The logarithmic maximum stress and reciprocal temperature relationship is non-linear in the temperature range 200–500°C which indicates a complex mechanism. Transmission electron microscopy confirms that the dislocation densityis increased and subgrain size is decreased with an increase in strain rate and decrease of the test temperature. Transmissionelectron microscopy reveals that a number of grains in the matrix of approximately 2–3 μm are highly misoriented, indicatingthat dynamic recrystallisation occurred during deformation. Highly misoriented 200–600 nm crystallites have also beenfound atvarious test temperatures. These are dynamic recrystallisation nuclei. The dynamic recrystallised grains nucleate both in the Almatrix between the SiC particles and at the SiC_p/matrix interfaces. Experimental investigations are performed to examine astrain hardening model. The distribution of dynamic recrystallised grains in metal matrix composites fits the computer simulationresults well.

MST/2095