The Initiation and Propagation of Dynamic Abnormal Grain Growth in Molybdenum

Noell, Philip; Worthington, Daniel L.; Taleff, Eric M.

doi:10.1007/s11661-015-3188-6

Cited by 9 publications

(16 citation statements)

References 20 publications

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“…Powder-metallurgy techniques were used to fabricate the Mo sheet material. This material meets the ASTM B 386, Grade 361 specification for commercially-pure Mo [26] and is the same sheet material designated as Mo PMB in a previous study by Noell et al [12]. This sheet material was rolled to the as-received thickness of 0.76 mm, and the final rolling direction was used as a reference for the orientations of tensile test specimens.…”

Section: Methodsmentioning

confidence: 99%

“…In extreme cases, abnormal grains can consume the entire microstructure to produce a uniformly coarse grain size or even a single crystal [2][3][4][5][6][7]. AGG is thus of interest for producing single crystals in the solid state, a capability demonstrated in the laboratory for molybdenum (Mo) [8][9][10][11][12][13][14] and tantalum (Ta) [15]. For grain-oriented silicon steels, AGG is desired and necessary to produce the coarse, highly-textured microstructures required for optimal performance in electrical transformers [16].…”

Section: Introductionmentioning

confidence: 99%

“…DAGG is a recently discovered phenomenon that produces AGG at lower temperatures than does SAGG. For the case of commercial-purity Mo sheet materials, DAGG was observed at approximately 1773 K (1500 • C) and has been repeatedly produced at 1923 K (1650 • C) [10][11][12]. SAGG, however, has only been observed in Mo at temperatures of 2073 K (1800 • C) and higher [8,24].…”

Section: Introductionmentioning

confidence: 99%

“…Prior investigations demonstrated the importance of grain-boundary curvature and concurrent plastic deformation in the growth of abnormal grains by DAGG [10][11][12][13][14][15]. Grain-boundary curvature was demonstrated to supply the most important driving force for DAGG in Mo, and concurrent deformation is thought to primarily increase boundary mobility during DAGG [11][12][13]. However, the critical strains required for DAGG initiation indicate that significant dislocation substructure likely forms within the interiors of deformed grains prior to DAGG [25].…”

Section: Introductionmentioning

confidence: 99%

“…To avoid the complications produced by normal grain growth, this study uses a commercialpurity Mo sheet material that resists normal grain growth at temperatures up to 2073 K (1800 • C) [11,12]. This facilitates meaningful comparisons between tests at different temperatures and after different annealing times.…”

Section: Introductionmentioning

confidence: 99%

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Growth of preexisting abnormal grains in molybdenum under static and dynamic conditions

Noell

Worthington

Taleff

2017

Materials Science and Engineering: A

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This investigation compares the growth rates of preexisting abnormal grains under both static and dynamic conditions. Abnormal grains several millimeters in length were produced in two commercial-purity molybdenum (Mo) materials by tensile straining at temperatures from 1923 to 2073 K (1650 to 1800 • C). This process is termed dynamic abnormal grain growth (DAGG) because it produces abnormal grains during concurrent plastic straining. DAGG creates abnormal grains at much lower temperatures than does static abnormal grain growth (SAGG). Abnormal grains created through DAGG were characterized with their surrounding microstructures and were then subjected to annealing treatments. Only one-third of the preexisting abnormal grains subsequently grew by SAGG. Among these, SAGG occurred only in those specimens that required the largest strains to initiate DAGG when creating the abnormal grain(s). The rates of boundary migration observed for SAGG were approximately two orders of magnitude slower than those for DAGG. When DAGG in one specimen was interrupted by extended static annealing, it did not recur when straining resumed. The dislocation substructure developed during hot deformation, which includes subgrains typical of five-power creep, is critically important to both DAGG and SAGG of preexisting abnormal grains under the conditions examined.

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Section: Methodsmentioning

confidence: 99%