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Serrated yielding in 9Cr–1Mo ferritic steel
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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 ...read more
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Mechanics of Progressive Collapse: Learning from World Trade Center and Building Demolitions
Zdenek P. Bazant,Mathieu Verdure +1 more
TL;DR: In this article, a dynamic one-dimensional continuum model of progressive collapse is developed, in which two phases are distinguished by a nonlinear second-order differential equation for the propagation of the crushing front of a compacted block of accreting mass.
Journal ArticleDOI
Influence of strain rate and temperature on serrated flow in 9Cr–1Mo ferritic steel
TL;DR: In this article, the authors examined serrated flow behavior in 9Cr-1Mo ferritic steel with different types of serrations, namely type A, B and C serrations at intermediate temperatures, and found that serrations were strongly dependent on temperature and applied strain rate.
Journal ArticleDOI
Dynamic strain ageing, deformation, and fracture behavior of modified 9Cr–1Mo steel
Preeti Verma,G. Sudhakar Rao,P. Chellapandi,G.S. Mahobia,Kausik Chattopadhyay,N.C. Santhi Srinivas,Vakil Singh +6 more
Abstract: Tensile behavior of modified 9Cr–1Mo steel was studied over the temperature range from room temperature (RT) to 600 °C at three strain rates 10 −5 , 10 −4 and 10 −3 s −1 Serrated plastic flow was observed from 250 to 350 °C at strain rate of 10 −4 s −1 , signifying occurrence of dynamic strain ageing (DSA) Characteristic features of DSA such as plateau/peak in yield and tensile strength, minima in ductility, negative strain rate sensitivity, and peak in internal friction were also observed Activation energy for DSA was found equivalent to that for diffusion of nitrogen, hence nitrogen was considered to cause DSA Dislocation substructure in the region of DSA revealed dislocation debris, kinks, bowing of dislocations and high density of dislocations Irrespective of temperature from 200 to 450 °C there was formation of dislocation cell structure; however, cell size in the region of DSA was smallest Fractographic analysis showed rosette type fracture at RT resulting from longitudinal splitting It was associated with decohesion of interface of carbide particles and prior austenite grain boundaries Non uniform and shallow dimples were observed in fibrous zones in the region of DSA Contours of dual shear lip zone were observed at elevated temperatures from 200 to 450 °C
Journal ArticleDOI
Isothermal and thermomechanical fatigue studies on a modified 9Cr–1Mo ferritic martensitic steel
TL;DR: In-phase and out-of-phase thermomechanical fatigue (TMF) tests were carried out on a modified 9Cr-1Mo ferritic martensitic steel under a mechanical strain control mode employing a strain amplitude of ± 0.4%.
Journal ArticleDOI
Dynamic Strain Aging Phenomena and Tensile Response of Medium-Mn TRIP Steel
TL;DR: In this article, three medium manganese steels were studied in both the hot band and batch annealed after cold working conditions, and three distinct DSA mechanisms were identified: one related to manganous ordering in stacking faults associated with e-martensite and austenite interface, with activation energies for the onset and termination of DSA being 145 and 277 kJ/mol.
References
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Journal ArticleDOI
Serrated plastic flow
TL;DR: In this paper, the authors present an assessment of the current understanding of the phenomenon of serrated plastic flow, which manifests itself as serrations, load drops, jerkiness or other discontinuities in the stress-strain curves obtained in constant extension rate tensile tests, and as sudden bursts of strain in constant loading rate tests and in constant load (stress) creep tests (the so called staircase creep).
Journal ArticleDOI
Serrated flow in a ferritic stainless steel
Erwin Pink,Adolfo Grinberg +1 more
TL;DR: In this article, the authors analyzed the Portevin-Le Chatelier effect by measuring the stress drop Δσ and found no agreement between the theory and the experimental results for a ferritic stainless steel.
Journal ArticleDOI
Repeated yielding in tin bronze alloys
TL;DR: In this paper, the index m in Van Bueren's (1955) equation C v = B ∊m, which relates the concentration of vacancies (C v) in a strained metal to the instantaneous plastic strain (∊), was evaluated in solid solutions of 1.7 at.% tin in copper.
Journal ArticleDOI
The effects of strain-ageing due to interstitial solutes on the mechanical properties of metals
TL;DR: In this paper, the effects of strain-ageing by interstitial solutes on the mechanical properties of metals are investigated. But the present review is limited to recent work on the effects on the structural properties of steel.
Journal ArticleDOI
Serrated flow in gold-indium alloys
TL;DR: In this paper, the characteristics of serrated flow in gold-indium solid solution alloys are studied over a range of strain rates and temperatures. But the authors focus on two types of serrations, the general Type A locking serrations and the Type C unlocking serrations.
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