HOT DEFORMATION, DYNAMIC RECOVERY, AND RECRYSTALLIZATION BEHAVIOR OF ALUMINUM 6061-SICP COMPOSITE

Hot working and microstructural behaviour of a 15 vol.-%SiC particle r einforced Al 6061 composite is discussed in this paper. The average si ze of the SiC particles is 18 mu m. The hot torsion test temperatures range from 200 to 500 degrees C with strains rates of 0.1, 1.0, and 4 s(-1). The equivalent stress versus strain curves show that the Al 606 1-SiCp composite has great strengthening behaviour compared with the A l-Mg-Si bulk alloy below 500 degrees C. It is mainly due to the high d islocation density from differential thermal contraction between Sic(p ) and the matrix during cooling and to geometrical constraints around SiC particles during the plastic deformation. The logarithmic maximum stress and reciprocal temperature relationship is non-linear in the te mperature range 200-500 degrees C which indicates a complex mechanism. Transmission electron microscopy confirms that the dislocation densit y is increased and subgrain size is decreased with an increase in stra in rate and decrease of the test temperature. Transmission electron mi croscopy reveals that a number of grains in the matrix of approximatel y 2-3 mu m are highly misoriented, indicating that dynamic recrystalli sation occurred during deformation. Highly misoriented 200-600 nm crys tallites have also been found at various test temperatures. These are dynamic recrystallisation nuclei. The dynamic recrystallised grains nu cleate both in the Al matrix between the SiC particles and at the SiCp /matrix interfaces. Experimental investigations are performed to exami ne a strain hardening model. The distribution of dynamic recrystallise d grains in metal matrix composites fits the computer simulation resul ts well. (C) 1994 The Institute of Materials.