A first report on fracture toughness ofbcc iron alloys as influenced by solutes: opposite effects of silicon and cobalt

Srinivas, M.; Malakondaiah, G.; Rao, P. Rama

doi:10.1007/bf02744570

Cited by 7 publications

(2 citation statements)

References 17 publications

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“…It should be noted that there are contradictory results on the Co effect on hardening in ferrite. Cobalt addition was experimentally found to result in alloy softening [23,24], while no solid solution softening was observed in Fe-3 at.% Co between 77 and 295 K [25]. According to [26], neither softening nor hardening due to Co solute addition occurs at any temperature.…”

Section: Introductionmentioning

confidence: 94%

First principle study of cobalt impurity in bcc Fe with Cu precipitates

et al. 2012

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The addition of cobalt was experimentally observed to increase the strength and impact toughness of Cu precipitation hardened steel. In order to understand the mechanism of this strengthening, we studied the effect of cobalt in the bulks and surfaces of bcc Fe and bcc Cu, as well as at the Fe/Cu interface by ab initio density-functional approach. We investigated the cobalt distribution between the Fe matrix and Cu precipitate, and found that cobalt is rejected from the core of the Cu particle. The calculated elastic constants and stacking fault energies show that cobalt does not produce any solid solution softening or hardening in bcc Fe. However, cobalt segregated in the interfacial region increases the cleavage fracture energies and cleavage stress of the Fe/Co/Cu interface. The compressive stress, which arises near the interface due to strong Fe-Co bonds, may serve as a barrier for dislocation motion through the interface resulting in additional hardening.

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Section: Introductionmentioning

confidence: 94%

First principle study of cobalt impurity in bcc Fe with Cu precipitates

et al. 2012

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“…Specimen configurations used for Jlc testing are given in table 1. O ther experim ental details are reported elsewhere (Srinivas et al 1987(Srinivas et al , 1988. M icrosegregation in Armco iron and F e -5 Co alloy was studied in an ims 4F secondary ion mass spectroscope equipped w ith a prim ary beam mass filter and a caesium m icrobeam source.…”

Section: Methodsmentioning

confidence: 99%

Influence of solute additions on the fracture behaviour of Armco iron

Srinivas

Malakondaiah

Rao

1994

Proc. R. Soc. Lond. A

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The influence of solutes, namely cobalt, molybdenum, nickel and silicon, on the deformation and fracture behaviour of Armco iron has been studied. The J -integral method was used for the measurement of ductile initiation fracture toughness J IC . Although cobalt is seen to enhance significantly J IC of the starting material (Armco iron), molybdenum, nickel and silicon are observed to have a deleterious effect. The increase in J IC with cobalt addition can be understood in terms of the enhanced strain hardening exponent, which is known to have a bearing on the plastic zone size around the crack tip and on micromechanisms of crack initiation. The large decrease in J IC with silicon and higher molybdenum concentration is explained on the basis of a change in fracture mode from ductile to cleavage as a result of stress concentration ahead of the crack tip reaching the cleavage fracture stress. The loss in fracture toughness with nickel addition is attributed to sulphur segregation at grain boundaries which results in pockets of intergranular fracture. Cobalt addition leads to alloy softening. Through secondary ion mass spectroscopy (SIMS), experimental evidence has been obtained for the first time for the suggestion that the ‘scavenging’ of interstitials leads to alloy softening. It was observed through yield stress dependence on grain size that the Hall–Petch constants σ 0 and k y substantiate SIMS observations.

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