DTIC ADA481924: Microstructural Evolution during the Dynamic pdf

DTIC ADA481924: Microstructural Evolution during the Dynamic

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We have characterized the propensity for adiabatic shear band formation (an associated microstructural evolution) under dynamic deformation conditions in an ultra-high strength (160 Ksi/I 1.1GPa) Fe-10 Ni-0.lC-Cr,Mo,V steel and demonstrated that this steel is highly prone to shear localization and failure. In the as-received condition, the steel has a lath martensite microstructure. During dynamic deformation, shear localization occurs and manifests by an optically visible shear band; the original microstructure is discemible within the band. With progression in severity of localization, there is evidence for a central region within the shear band composed of approx. 300 nm size equiaxed grains constituting austenite, with a low dislocation content, and heavily twinned ferrite. In the extreme situation, a crack chases the shear band, and examination of the resulting fracture surfaces provides evidence for the presence of a thin liquid film layer. We have also observed that lowering the Ni content in the alloy significantly and adding Cu to the alloy, enables improvements in resistance to shear localization, both in terms of initiation and propagation of the shear band

• Creator/s: Defense Technical Information Center
• Date: 5/19/2008
• Year: 2008
• Book Topics/Themes: DTIC Archive, Kumar, K S, BROWN UNIV PROVIDENCE RI DIV OF ENGINEERING, *HIGH STRENGTH ALLOYS, *MICROSTRUCTURE, *DEFORMATION, *STEEL, AUSTENITE, DISLOCATIONS, EVOLUTION(GENERAL), THINNESS, ADIABATIC CONDITIONS, MARTENSITE, SHEAR BANDS, FILMS, RESISTANCE, SHEAR PROPERTIES, FRACTURE(MECHANICS

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