A study on flow stress of Al-SiC composites deformed in a large range of strain

The strain induced changes in the flow stress behaviour of Al-SiC composites have been studied in a large strain range oblained by cold rolling and uniaxial tension. • • The marked hardening effect of SiC observed at small strains decreases with strain and vanishes at medium and large strains.

Three strain stages can be defined: < ~ 0.03, 0.03−0.2 and > 0.2. The workhardening rate of the composites in these three stages is respectively greater than, equal to and lower than that in the unreinforced aluminium. • • The great difference in the hardening behaviour of composites due to the variations in the shape and volume concentration of SiC is also reduced with increasing strain.

The whisker composites, which exhibit higher hardening as compared to the particulate composites at small strains, suffer a greater loss of hardening effect as strain increases. This finally leads to flow stress saturation and softening in 2% SiCw and 10% SiCw composite, respectively. • • During cold rolling many of the voids caused by the fracture of SiC are healed by metal flow and the void formation at the interface is largely suppressed. • • The behaviour of composites prestrained to large strains is essentially determined by the work-hardening limitation of the aluminium matrix and independent of the parameters of SiC.

The work-hardening and tensile elongation of the prestrained Al-10% SiCw can be practically recovered by annealing.