The Effects of Grain Size and Carbon Content on the Ductility of Recrystallized Molybdenum Wire

Aritomi, Noriyoshi; Tsuya, Kazuo

doi:10.2320/matertrans1960.13.32

Cited by 5 publications

(2 citation statements)

References 22 publications

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“…1954; Maringer & Schwope 1954). I t has been widely accepted th a t interstitial impurities are im portant in promoting recrystallization embrittlement (Olds & Rengstorff 1956;Belk 1959; Semchyshen & Barr 1966), although recent results have shown th a t carbon can have a beneficial effect (Tsuya & Aritomi 1968; Aritomi & Tsuya 1972). However, little work has been carried out with surface analysis techniques to positively identify segregated species at grain boundaries.…”

Section: Introductionmentioning

confidence: 99%

Grain boundary segregation and intergranular fracture in molybdenum

Kumar

Eyre

1980

Proc. R. Soc. Lond. A

141

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The refractory group VIA metals generally exhibit intergranular brittleness when they are in the recrystallized condition. This causes severe problems in their fabrication and places major limitations on their practical application. The phenomenon, generally referred to as recrystallization embrittlement, results in large increases in the ductile-to-brittle transition temperature and a change in fracture mode in the lower shelf regime from cleavage to intergranular with a significant decrease in ductility. The embrittlement is widely considered to be associated with interstitial impurities but there have been few systematic studies to elucidate their effects. The present paper reports results from a systematic study of segregation and intergranular embrittlement in binary molybdenum-oxygen and ternary molybdenum-oxygen-carbon alloys. The experiments were carried out on ‘bamboo’ specimens containing a series of identical single grain boundaries traversing their cross-sections. Measurements have been made of the activation energy for oxygen segregation to grain boundaries in the binary molybdenum-oxygen alloys. The influence of carbon additions on the level of oxygen segregation has also been determined. In addition, the influence of oxygen segregation on the energy to fracture has been studied and this has involved quantitative measurements of the work of fracture and the contribution made by plastic deformation. Results from metallographic studies are also presented, showing the effects of segregation on fracture surface topography and dislocation structures immediately adjacent to the fracture surfaces. In discussing the results we consider the thermodynamics of oxygen segregation to grain boundaries and the role played by carbon in inhibiting segregation. It is proposed that carbon either increases the effective solubility of oxygen in molybdenum or acts as a trap for oxygen atoms. In either case the effect is to reduce the driving force for segregation. We also consider the influence of segregation on the work of fracture and show that the reduction in oxygen segregation resulting from the addition of carbon produces small increases in fracture energy. This increases the local stress to propagate a crack sufficiently to promote plastic deformation which blunts the crack tip. The consequent change in geometry reduces the stress concentration at the crack tip, thereby resulting in a large increase in the applied fracture stress and the work to fracture.

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Section: Introductionmentioning

confidence: 99%

Grain boundary segregation and intergranular fracture in molybdenum

Kumar

Eyre

1980

Proc. R. Soc. Lond. A

141

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“…[1][2][3][4][5][6][7][8] A small amount of carbon can significantly enhance the fracture strength of pure molybdenum, and consequently, its ductility. The latter effect is characterized by the relative decreasing in the ductile-to-brittle transition temperature (DBTT).…”

Section: Introductionmentioning

confidence: 99%

Change of Mechanical Property and Fracture Mode of Molybdenum by Carbon Addition

Kadokura¹,

Hiraoka

Yamamoto³

et al. 2010

Mater. Trans.

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Commercially available specimens of pure molybdenum were immersed in a graphite-filled Ta container and heated at a relatively low temperature of 1373 and 1473 K for 1.2 to 18.0 ks. Changes in the yield and maximum strength were evaluated by a three-point bending test at a temperature between room temperature and liquid-nitrogen temperature. Then two parameters, critical stress (apparent intergranular fracture strength) and critical temperature (DBTT), were determined. Finally, the fracture mode was examined using SEM and the apparent transgranular fracture strength was estimated from the relationship between the critical stress and the fracture mode.Results are summarized as follows. (1) Both the critical stress and the critical temperature changed drastically with carbon addition and exhibited a peak value under optimum conditions: 1373 K-3.6 ks and 1473 K-1.2 ks. (2) The fracture mode changed from intergranular to transgranular after carbon addition. (3) The change in the critical stress as a function of the increase in carbon content in this work almost agrees with that in the previous work of Hiraoka et al. (4) The apparent transgranular fracture strength was unchanged (about 990 MPa) after carbon addition of 10 mass ppm or less. This value is almost equal with that before carbon addition. The apparent transgranular fracture strength was lowered after excess carbon addition.

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An electron microscope study of Mo2C precipitates in molybdenum—I. Crystallographic relationships

Kumar¹,

Eyre²

1978

Acta Metallurgica

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The Effects of Grain Size and Carbon Content on the Ductility of Recrystallized Molybdenum Wire

Cited by 5 publications

References 22 publications

Grain boundary segregation and intergranular fracture in molybdenum

Grain boundary segregation and intergranular fracture in molybdenum

Change of Mechanical Property and Fracture Mode of Molybdenum by Carbon Addition

An electron microscope study of Mo2C precipitates in molybdenum—I. Crystallographic relationships

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