CYCLIC STRAIN RESISTANCE AND FRACTURE-BEHAVIOR OF AL2O3-PARTICULATE-REINFORCED 2014-ALUMINUM-ALLOY METAL-MATRIX COMPOSITES

A study has been made to understand the low-cycle fatigue properties and cyclic fracture characteristics of 2014 aluminium alloy discontinuously reinforced with varying amounts of Al2O3 particulates. The 2014/Al2O3 composite specimens were cyclically deformed over a range of cyclic strain amplitudes, using tension-compression loading under total strain-amplitude control. The 2014/Al2O3 composites exhibited softening at all cyclic plastic strain amplitudes and for different volume fractions of the discontinuous particulate reinforcement in the ductile metal matrix. The softening effect was greater at the higher cyclic strain amplitudes, and increased with test temperature. The intrinsic micromechanisms controlling the stress response characteristics during fully reversed cyclic straining are highlighted and the rationale for the observed softening behaviour is discussed. The cyclic strain resistance and resultant low-cycle fatigue life of the composites improved with increase in test temperature. The improvement was noteworthy at low cyclic plastic strain amplitudes and resultant long fatigue life. The kinetics governing the cyclic fracture process are discussed in the light of composite microstructural effects, cyclic plastic strain amplitude, concomitant response stress and test temperature.