Quantification of particle distribution effects on fatigue in an Al–SiCp composite

A detailed experimental investigation has been carried out into the effects of particle distribution and morphology on the smooth specimen fatigue behaviour in a powder-processed 2124-based Al–18.7 vol.% silicon carbide particulate (SiCp) composite with a nominal reinforcement particle size of 6.5 μm. Experimental results are reported on the development of fatigue damage in the moderate to high cycle regime, highlighting the role of short crack growth behaviour and the limited initiation life in the materials tested. A methodology is presented for quantitatively analysing the effects of reinforcement spatial distribution and morphology on short crack growth using previously reported finite-body tessellation techniques. Tessellation analysis of the composite has demonstrated that direct crack–tip interactions with the reinforcement particles occurred preferentially in small particle/low volume fraction regions, with further analysis suggesting a controlling influence of particle size on crack path behaviour. In addition, multiple linear regressions of the tessellation data identify a combined influence on growth rates in the ‘discontinuous’ regime of reinforcement clustering and reinforcement morphology (orientation and/or aspect ratio). Results are discussed in relation to known short crack growth mechanics and the microstructural and micromechanical characteristics of particle-reinforced systems.