Showing papers by "Bhagwati Prasad Kashyap published in 1995"
TL;DR: In this article, tensile specimens of Type 316L stainless steel having grain sizes in the range 3.1-86.7 μm were deformed to 34% strain at temperatures 24, 400 and 700°C and strain rate 1 × 10−4s−1 to investigate the Hall-Petch (H-P) relationship, the nature of stress-strain curves and the substructure development.
Abstract: Tensile specimens of Type 316L stainless steel having grain sizes in the range 3.1–86.7 μm were deformed to 34% strain at temperatures 24, 400 and 700°C and strain rate 1 × 10−4s−1 to investigate the Hall-Petch (H-P) relationship, the nature of stress-strain curves and the substructure development. Upto ∼5% strain the H-P relationship exhibits bi-linearity whereas the single Hall-Petch relation is exhibited at larger strains. The presence of bi-linearity is explained by the back stress associated with the difference in the dislocation densities in the vicinity of grain boundary and in the grain interior. The log stress (σ)-log strain (e) plots depict three regimes and follow the relationship σ = Ken in each regime, but with varying magnitudes of the strength coefficient (K) and strain-hardening exponent (n).
187 citations
TL;DR: In this article, the authors investigated the possible mechanism controlling the appearance of serrations and their disappearance of the stress-strain curves in a modified 9Cr-1Mo steel in tempered martensitic condition, implying the occurrence of dynamic strain aging.
Abstract: During high temperature tensile testing of a modified 9Cr-1Mo steel in tempered martensitic condition, serrated plastic flow, implying the occurrence of dynamic strain aging, was observed. The serrated stress-strain curves were unique in the sense that the serrations appeared almost at the beginning of deformation and disappeared before the ultimate strengths were attained. Moreover, the strains to the disappearance of serrations varied systematically with the test temperature and strain-rate. A brief literature survey revealed that in studies on Nickel alloys and ferritic-martensitic steels, the disappearance of serrated flow was found to be a thermally activated process and that the phenomenon manifested in the higher temperature regime by either a progressively larger strains to the onset of serrations or a progressively smaller strain to the disappearance of serrations of the flow curve. However, it appears that the type of serrated flow curves observed in this study, has not yet been reported in any other ferritic-martensitic steels. It was thus felt necessary to carry out a detailed investigation of dynamic strain aging in this steel. In this paper, the possible mechanism controlling the appearance of serrations and their disappearance of the stress-strain curves are discussed.
14 citations