Effects of SiC particulate size on dynamic compressive properties in 7075-T6 Al-SiCp composites

Abstract

Quasi-static and dynamic compressive properties of 7075-T6 Al matrix composites reinforced with SiC(p)s (size; 10 mu m, 30 mu m, and bimodal (10 + 30) mu m), i.e., 10S, 30S, and BS composites, respectively, were investigated in relation with fracture mechanisms. SiC(p)s were homogeneously distributed without SiCp agglomeration, pores, or cracks, and their volume fractions were 49.5 vol%, 54.1 vol%, and 56.5 vol% in the 30S, 10S, and BS specimens, respectively. Compressive properties could be explained by a rule of mixtures based on SiCp volume fraction and by three major fracture phenomena including deformation of Al matrix, cracking of SiC(p)s, and interfacial debonding between SiCp and Al. As the SiCp size decreased, crack initiation sites changed from SiC(p)s themselves to SiCp/Al interfaces, which mainly affected the compressive strength. In the BS composite, coarse SiC(p)s additionally worked for the strengthening by increasing the total reinforcement fraction, and the three fracture phenomena were well homogenized, thereby leading to the highest strain energy density as well as the best combination of strength and strain.