Influence of Second-Phase Dispersions on Shear Instability and Fracture Toughness of Ultrahigh Strength 4340 Steel.

摘要

The resistance to shear instability and subsequent flow localization in ultrahigh strength (UHS) steels is dependent upon second-phase particle dispersions and the matrix strain hardening. The effect of the interparticle spacing (lambda) to the geometric mean particle radius (R) ratio on the shear instability strain of UHS 4340 steel is discussed. Experimental results indicate a linear relationship exists between shear instability strain and this lambda/R ratio. Microvoid nucleation softening associated with second-phase particles appears to be the dominant destabilizing event leading to fracture. Strain rate and hydrostatic compression effects are also discussed. Ordnance steel, High strength alloys, Fracture (mechanics), Toughness, Dispersion relations, Shear tests, Shear properties, Plastic deformation. (jes)