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

The mechanical behaviors of an A359/SiCp metal-matrix composite and of the corresponding A359 cast aluminum alloy have been measured in compression ov er a wide range of strain rates (10(-4)-10(5) s(-1)) using several differen t experimental techniques: servohydraulic testing, the compression Kolsky b ar, and pressure-shear plate impact. Both the A359 matrix alloy and the A35 9/SiCp composite show rate dependence of the flow stress in compression, wi th rate dependences that increase with increasing strain rate. The unreinfo rced A359 alloy shows strain hardening that is essentially independent of t he strain rate, and similar in most respects to the behavior of wrought alu minum alloys such as 6061. The A359/SiCp composite shows rate dependence si milar to that of the unreinforced alloy, but also shows significantly less strain hardening than does the matrix alloy. This reduction in strain harde ning appears to be a result of progressive particle fracture during these c ompressive deformations. Using the experimental data on the unreinforced A3 59 aluminum alloy as the input data for the matrix behavior, and accounting for particle shape and aspect ratio, an analytical model developed recentl y by the authors is used to estimate the mechanical response of the composi te over the whole range of strain rates. The model is able to capture the r ate 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 dama ge that occurs in the composite, it is unable to predict the changed overal l strain hardening of the composite material. (C) 2000 Elsevier Science Ltd . All rights reserved.