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Showing papers by "Bhagwati Prasad Kashyap published in 1999"


Journal ArticleDOI
TL;DR: In this paper, the influence of prior tensile deformation on the magnetic Barkhausen emission (MBE) and the hysteresis curve has been studied in 0.2% carbon steel and 2.25Cr-1Mo steel under different tempered conditions.

42 citations


Journal ArticleDOI
TL;DR: In this paper, the authors performed tensile tests on specimens in quenched and tempered and thermally aged conditions over a wide temperature range (300-873 K) to assess the occurrence of serrated flow, a manifestation of dynamic strain aging (DSA), in 9Cr-1Mo ferritic steel, with an emphasis on the influence of prior thermal aging on serrated yielding.
Abstract: Tensile tests were performed on specimens in quenched and tempered and thermally aged conditions over a wide temperature range (300–873 K) to assess the occurrence of serrated flow, a manifestation of dynamic strain aging (DSA), in 9Cr–1Mo ferritic steel, with an emphasis on the influence of prior thermal aging on serrated yielding. The alloy exhibited jerky/serrated flow in the load–elongation curves at intermediate temperatures. Types A, B, and C serrations were observed, depending on the test temperature and applied strain rate. The apparent activation energy of 83 kJ mol-1 measured for serrated flow suggests that diffusion of an interstitial solute such as carbon is responsible for dynamic strain aging in 9Cr–1Mo steel. Prior thermal aging at 793 K for 5000 h and at 873 K for 1000 and 5000 h resulted in a significant decrease in the height of serrations, i.e. the magnitude of the stress drop, as well as an increase in the critical strain for the onset of serrations. Both of these observations ...

38 citations


Journal ArticleDOI
TL;DR: In this paper, the influence of thermal aging on room temperature tensile properties of the forging remained similar to that reported for thin section 9Cr-1Mo steel, whereas the reduction in area exhibited a decrease in the value with increasing thermal ageing.

34 citations


Journal ArticleDOI
TL;DR: In this article, a Zr-2.5 wt% Nb pressure tube alloy was deformed at strain rates (e ) of 3.2 × 10−4−2 s−1 and test temperatures (T) of 625-800°C to investigate the nature of stress-strain curves and the optimum condition for superplasticity.

13 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the effect of cold working on the stress (σ)-strain rate (έ) behavior over a strain rate range of ∼2 × 10−5 to 5 × 10 −3 s−1 and a temperature range of 625 to 700 °C.
Abstract: Zr-2.5 wt% Nb alloy sheet, obtained by unfolding and straightening a pressure tube, was further cold rolled upto 39% reduction in thickness to investigate the effect of cold working on the stress (σ)-strain rate (έ) behaviour over a strain rate range of ∼2 × 10−5 to 5 × 10−3 s−1 and a temperature range of 625 to 700 °C. Irrespective of the amount of rolling, the log σ vs log έ plots exhibit superplastic behaviour with strain rate sensitivity index, m, as high as 0.8, which decreases to 0.2 at higher strain rates. On the other hand, the activation energy for deformation, Q, increases from 171.1 kJ/mol for superplastic deformation to 249 kJ/mol in Region III. The tendency for improved superplasticity (m) is seen upon cold working by 22% or more at the test temperatures 675 and 700 °C.

6 citations