THE CYCLIC FATIGUE AND FRACTURE-BEHAVIOR OF A TITANIUM-ALLOY METAL-MATRIX COMPOSITE

The results of a study designed to improve our understanding of the lo w-cycle fatigue, high-cycle fatigue properties, cyclic stress response characteristics and cyclic fracture behavior of a discontinuously-rei nforced Ti-6Al-4V alloy are presented. The Ti-6Al-4V/TiB composite spe cimens were cyclically deformed at an ambient temperature (27 degrees C), over a range of cyclic strain amplitudes, using fully-reversed ten sion-compression loading under total strain amplitude control. The tit anium alloy metal matrix composite exhibited softening to failure at a ll cyclic strain amplitudes, The degree of softening was observed to b e greater at the higher cyclic strain amplitudes than at corresponding lower strain amplitudes. Stress-controlled high-cycle fatigue charact eristics were also established at both ambient and elevated temperatur es. The intrinsic mechanisms and micromechanisms controlling the cycli c stress response characteristics, cyclic stress-strain response, cycl ic strain resistance, low-cycle fatigue and high-cycle fatigue lives a re highlighted and the rationale for observed behavior is discussed. T he cyclic fracture behavior of the composite is discussed in light of concurrent and mutually interactive influences of composite microstruc tural effects, cyclic strain amplitude, concomitant response stress, c yclic ductility and test temperature.