The cyclic fatigue and fracture behavior of ceramic-particle-reinforced tool steel metal-matrix composite

Abstract

In this paper, the cyclic stress response characteristics, cyclic strain resistance and fracture behavior of powder-metallurgy-processed tool steel discontinuously reinforced with titanium carbide particulates is examined. The test specimens were cycled using tension-compression loading under total strain control. The metal-matrix composite material exhibited initial hardening with cyclic straining, followed by stability for most of the fatigue life. Micro-mechanisms contributing to strengthening or hardening of the composite matrix during cyclic straining are highlighted, and the rational for the observed cyclic stress response is ascribed to concurrent and competing influences of an increase in dislocation-dislocation interaction, dislocation multiplication and dislocation-particle interactions. Fracture of the composite was brittle both on the macroscopic and microscopic levels. The cyclic fracture process is rationalized on the basis of competing influences of composite microstructural effects, plastic-strain amplitude and concomitant response stress.