Effects of Oxygen, Nitrogen, and Carbon on The Ductility of Cast Molybdenum

Olds, L. E.; Rengstorff, G. W. P.

doi:10.1007/bf03377662

Cited by 31 publications

(6 citation statements)

References 2 publications

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“…The Mo-ZrC alloy showed a large elongation of 180 pct ties of Mo materials. [24,25,26] Therefore, the lower elongation at 1970 K and at 6.7 ϫ 10 Ϫ4 s Ϫ1 , however. It is suggested for Mo-ZrC is likely to be attributed to the higher interstithat the ZrC particles stabilized the fine-grained microtial contents.…”

Section: A Strengthening and Fracture Mechanisms At Room Temperaturementioning

confidence: 97%

The role of dispersed particles in strengthening and fracture mechanisms in a Mo-ZrC alloy processed by mechanical alloying

Takida¹,

Mabuchi

Nakamura

et al. 2000

Metall Mater Trans A

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The tensile properties of a ZrC particle-dispersed Mo, which was processed by spark plasma sintering with mechanically alloyed powder, were investigated at room temperature and at elevated temperatures of 1170 to 1970 K. The Mo-ZrC alloy showed much higher strength at room temperature than a fully recrystallized pure Mo. The high strength of Mo-ZrC is mainly attributed to a very small grain size (about 3 m). The main role of the ZrC particle is not to increase strength due to the particledislocation interaction, but to limit grain growth during sintering and to attain the very small grain size. The elongation at room temperature of Mo-ZrC was much lower than that of pure Mo. This is probably related to the higher interstitial contents. However, Mo-ZrC showed a large elongation of 180 pct at 1970 K and 6.7 ϫ 10 Ϫ4 s Ϫ1 . It was suggested that the ZrC particles stabilized the finegrained microstructure yet provided no cavitation sites at 1970 K; as a result, the large elongation was attained.

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Section: A Strengthening and Fracture Mechanisms At Room Temperaturementioning

confidence: 97%

The role of dispersed particles in strengthening and fracture mechanisms in a Mo-ZrC alloy processed by mechanical alloying

Takida¹,

Mabuchi

Nakamura

et al. 2000

Metall Mater Trans A

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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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“…Of the interstitials, the effect of oxygen is the most extreme, nitrogen being intermediate, and carbon the least. [6,7] By reducing the oxygen and nitrogen contents to less than one weight ppm, the tensile DBTT has been observed to be below -196°C (-320°F). [8J In addition to low oxygen, the atom ratio of carbon to oxygen has also been reported to effect the DBTT.…”

Section: (Ods)[2]mentioning

confidence: 99%

Mechanical properties of oxide dispersion strengthened (ODS) molybdenum alloys

Bianco¹,

Buckman²

1998

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Effects of Oxygen, Nitrogen, and Carbon on The Ductility of Cast Molybdenum

Cited by 31 publications

References 2 publications

The role of dispersed particles in strengthening and fracture mechanisms in a Mo-ZrC alloy processed by mechanical alloying

The role of dispersed particles in strengthening and fracture mechanisms in a Mo-ZrC alloy processed by mechanical alloying

Grain boundary segregation and intergranular fracture in molybdenum

Mechanical properties of oxide dispersion strengthened (ODS) molybdenum alloys

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