Intrinsic intergranular brittleness of molybdenum

Brosse, J.B.; Fillit, R.Y.; Biscondi, M.

doi:10.1016/0036-9748(81)90038-7

Cited by 109 publications

(35 citation statements)

References 7 publications

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“…15 Additionally, it is believed that the HAGBs of molybdenum are intrinsically weak. 7,8,32 The DBTT of the L-T oriented sample is lower, which can be correlated with the premature occurrence of delamination cracks causing an increase in toughness. This phenomenon seems to be mainly influenced by the orientation of the crack plane independent of the crack propagation direction.…”

Section: T-l and L-t Orientationmentioning

confidence: 97%

“…6,11,12 On the other hand, it is believed that the embrittlement is an intrinsic property of molybdenum. 7,8,32 Intergranular fractures occur more often in microstructures with many random high-angle grain boundaries. Lowangle and special boundaries, such as sigma grain boundaries, seem to cause transgranular fractures.…”

Section: Recrystallized Molybdenum In the Charpy Impact Testmentioning

confidence: 99%

“…However, controlling grain size, grain shape, grain boundary character, alloying content, and stress state seem to be key approaches to influencing the DBTT of molybdenum. [4][5][6][7][8][9] Nevertheless, recrystallization annealing of the as-deformed and stress-relieved condition of molybdenum leads to a significant increase of the DBTT and even more to intergranular embrittlement, which is believed to be caused by the larger grain size and segregation enrichments at the grain boundaries. [4][5][6][10][11][12][13] Recent atom probe investigations revealed phosphor, nitrogen and oxygen impurities at the grain boundaries of technically pure molybdenum 14,15 of which especially segregated oxygen is assumed to promote intergranular failure.…”

Section: Introductionmentioning

confidence: 99%

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Fracture Behavior and Delamination Toughening of Molybdenum in Charpy Impact Tests

Babinsky

Primig

Knabl

et al. 2016

JOM

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This study combines advanced characterization techniques with conventional Charpy impact tests to relate the mechanical properties to the microstructure of technically pure molybdenum, especially regarding its toughness. V-notched samples with different orientations were prepared from a rolled molybdenum plate in stress-relieved and recrystallized condition. The ductile-tobrittle transition-temperature was analyzed in terms of the delamination behavior influenced by the microstructure. A pronounced increase of toughness was found for specific oriented samples, which can be explained by macroscopic delamination. Elongated grains led to enhanced delamination in Charpy impact tests with variations for different orientations. In general, delamination occurs as a result of brittle fracture; however, an increase in toughness in the Charpy impact test can be provoked. This mechanism is called thin sheet toughening or delamination toughening. Electron backscatter diffraction measurements were performed to get a deeper knowledge about crack propagation and delamination behavior in the rolled plate. Recrystallization shifts the transition region to significantly higher temperatures, which is explained by the globular grain shape as well as grain boundary segregation. The occurrence of delamination is discussed, taking texture, grain shape and segregation effects into account.

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Section: T-l and L-t Orientationmentioning

confidence: 97%

Section: Recrystallized Molybdenum In the Charpy Impact Testmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fracture Behavior and Delamination Toughening of Molybdenum in Charpy Impact Tests

Babinsky

Primig

Knabl

et al. 2016

JOM

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“…[16][17][18][19] It is likely that the propensity to cavity nucleation at triple junctions can vary depending on the grain boundary connectivity, because individual grain boundaries have an inherent resistance to boundary fracture depending on their character. [20][21][22][23] Lowangle and AE boundaries show higher resistance to fracture than random boundary. Bollmann classified triple junctions into two types; one where the Burgers vectors of grain boundary dislocations on three boundaries are balanced (Iline) and the other where the Burgers vectors are not balanced (U-line) at the junction.…”

Section: Introductionmentioning

confidence: 98%

Grain Boundary Microstructure-Controlled Superplasticity in Al-Li-Cu-Mg-Zr Alloy

et al. 2003

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Grain boundary microstructure-controlled superplasticity in an Al-Li alloy is discussed on the basis of OIM observations using the specimens with different grain boundary microstructures. The specimens having the homogeneous {110} textured grains with a high frequency of low-angle boundaries showed superplasticity, whereas the specimen having a heterogeneous and randomly oriented grains with a high frequency of random boundaries did not yield superplasticity. Cavities were preferentially formed at the triple junctions where two or three random boundaries interconnected. From those results, the optimum grain boundary microstructure for superplasticity is discussed in connection with the relationship between grain boundary character distribution (GBCD) and triple junction character distribution. The strain rate change tests were carried out during deformation in order to rejuvenate initially introduced optimal grain boundary microstructure. The superplasticity can be improved by the strain rate change test resulting in an increase of the frequency of low angle boundaries at the early work softening stage of deformation.

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“…Brosse et al (2) investigated symmetrical <100> and <110> tilt bicrystals by four-point bending test at room temperature. The fracture strength decreased with increasing misorientation angle orientation.…”

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confidence: 99%

Intergranular Fracture in BCC Metals

Kimura

1988

Trans. JIM

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The intergranular fracture (IGF) in high purity molybdenum and high purity iron are discussed together with the effects of interstitial and substitutional solutes on it.Recrystallized molybdenum is inherently susceptible to IGF. Purification does not improve it. Grain boundary segregation of carbon increases the grain boundary cohesion of general boundaries and that of oxygen decreases it.IGF occurs in recrystallized commercial high purity iron about 99.995% pure, but does not in specially prepared iron of about 99.999% or better purity. Segregation of oxygen decreases the boundary cohesion, but the effect is much smaller than usually believed. Segregation of carbon increases the grain boundary cohesion and reduces IGF caused by segregation of other impurities, such as hydrogen, phosphorus and sulfur. Molybdenum and chromium reduce IGF caused by the segregation of phosphorus as far as the alloy is in the solid solution. These elements interact with phosphorus to reduce the detrimental effect of phosphorus and also increase the boundary cohesion of iron. Nickel also reduces IGF, but the reduction is caused by the solid solution softening due to nickel.Also discussed are the chemical state of the segregated phosphorus and the dependence of the phosphorus segregation on the grain boundary character. (Received May 9, 1988) Keywords: intergranular fracture, high purity iron, high purity molybdenum, effect of carbon and oxygen, iron-phosphorus-molybdenum alloys, iron-phosphorus-chromium alloys, iron-phosphorus-nickel alloysThe intergranular fracture (IGF) is not rare in BCC metals and alloys, and causes serious technical probelems. Phosphorus and sulfur are common impurities in iron and steel and are known to embrittle them severely. In most cases IGF is caused by the segregation of impurities to grain boundaries. IGF caused by an impurity is promoted or suppressed by other kinds of impurities and alloying elements. An example is the temper-embrittlement in low alloy steels; when low alloy steels with high strength are heated at temperatures between 770 and 870K after quenching and tempering, impurities (typically phosphorus) segregate to grain boundaries and cause IGF. On the other hand, if a plain carbon steel containing a similar amount of phosphorus is subjected to the same heat treatment, no temper-embrittlement is observed. Thus, in the discussion of IGF due to impurity segregation, we have to consider not only the impurity directly responsible for the IGF, but also other impurities and alloying elements. Furthermore, effects of one kind of solute on a specific impurity may be modified by other kinds of solutes. Hence, we have to employ high purity materials with controlled compositions to investigate the behavior of a specific impurity and the effects of a specific solute without interference from other solutes.The grain boundary segregation is measured fairly accurately with Auger electron spectroscopy (AES); specimens are fractured and the revealed surface is analyzed under an ultra high vacuum without bei...

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Intrinsic intergranular brittleness of molybdenum

Cited by 109 publications

References 7 publications

Fracture Behavior and Delamination Toughening of Molybdenum in Charpy Impact Tests

Fracture Behavior and Delamination Toughening of Molybdenum in Charpy Impact Tests

Grain Boundary Microstructure-Controlled Superplasticity in Al-Li-Cu-Mg-Zr Alloy

Intergranular Fracture in BCC Metals

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