Effect of aluminum particles on the fracture toughness of a 7093/SiC/15p composite

The effects of Al-particles on the toughness of a discontinuously reinforced aluminum (DRA) alloy composite were studied in this investigation. A powder metallurgically processed ‘control’ DRA consisting of 7093/SiC/15p (10 μm) was selected as the base material. The remaining DRAs contained aluminum particles of different size, volume fraction and composition, that were blended with the base DRA, and powder metallurgically processed and extruded; they are termed as ‘bean’ materials. The modulus, yield strength, and work hardening rate of the bean materials with Al-alloy particles were quite insensitive to the distribution of the SiC particles. On the other hand, the strain to failure was most strongly influenced by the presence of pure-Al and Al-alloy particles, and is explained based on the local SiC particle volume fraction. Fracture toughness calculations show that the ASTM E-561 procedure is more appropriate for DRA materials, that exhibit small scale yielding conditions, than ASTM E-813 and E-1152 procedures. The bean materials exhibited improved crack growth toughnesses over the control DRA, and in some cases the initiation toughness was also increased. The toughening mechanisms are discussed.