The compressive viscoplastic response of an A359/SiC_p metal-matrix composite and of the A359 aluminum alloy matrix

The mechanical behaviors of an A359/SiC_p metal-matrix composite and of the corresponding A359 cast aluminum alloy have been measured in compression over a wide range of strain rates (10^-4-10⁵ s^-1) using several different experimental techniques: servohydraulic testing, the compression Kolsky bar, and pressure-shear plate impact. Both the A359 matrix alloy and the A359/SiC_p composite show rate dependence of the flow stress in compression, with rate dependences that increase with increasing strain rate. The unreinforced A359 alloy shows strain hardening that is essentially independent of the strain rate, and similar in most respects to the behavior of wrought aluminum alloys such as 6061. The A359/SiC_p composite shows rate dependence similar to that of the unreinforced alloy, but also shows significantly less strain hardening than does the matrix alloy. This reduction in strain hardening appears to be a result of progressive particle fracture during these compressive deformations. Using the experimental data on the unreinforced A359 aluminum alloy as the input data for the matrix behavior, and accounting for particle shape and aspect ratio, an analytical model developed recently by the authors is used to estimate the mechanical response of the composite over the whole range of strain rates. The model is able to capture the rate dependence of the flow stress of the composite, and is able to provide a reasonable estimate of the flow stress of the composite material at small strains. However, because the model does not incorporate the particle damage that occurs in the composite, it is unable to predict the changed overall strain hardening of the composite material.