Characterization Of The Fracture Behavior Of Fine Grained High Strength Low Alloy Hsla Steels And Iron Base Alloys Under Low Temperature And Mechanical Environments

This paper discusses the use of different fractographic techniques to characterize the fracture morphology of high-strength low-alloy (HSLA) steels with a variety of fine-grained microstructures and iron-base alloys strengthened by intermetallic precipitates in order to understand the various fracture mechanisms controlling their fracture resistance under low-temperature and mechanical environments. The fractographic techniques that have been used are conventional techniques, scanning electron fractography, sectioning techniques, and a newly developed chemical polishing method in conjunction with the Nomarski interphase contrast technique. The mechanical tests that have been used are tensile, notched-tensile, instrumented impact testing with precracked Charpy V-notch specimens, low-cycle fatigue, and high-cycle fatigue. A comprehensive characterization of the fracture morphology of the HSLA steels developed for arctic applications has resulted. Important features of the fracture (such as "splitting," striations, ductile tearing, quasi-cleavage, microvoid coalescence, unit fracture path, persistent slip bands) have been identified and related to the mechanical behavior of the materials.