Dislocation character and operative slip systems in α-Nb5Si3 tested at 1673K

Sekido, Nobuaki; Miura, Seiji; Yamabe‐Mitarai, Yoko; Kimura, Yuichi; Mishima, Yoshinao

doi:10.1016/j.intermet.2009.12.010

Cited by 16 publications

(10 citation statements)

References 28 publications

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“…The material exhibits brittle behavior when B/G b 1.75, and vice versa, a material demonstrates ductile when B/G N 1.75. From Table 2, the calculated B/G ratio of Nb 5 Si 3 (1.54) is lower than 1.75, implying that it exhibits intrinsic brittle behavior, which is consistent with the experimental result [27][28][29]. It is clear that the calculated B/G ratio of Nb -va1 , Nb -va2 and Si -va2 is lower than 1.75, but the calculated B/G ratio is gradually close to 1.75.…”

Section: Mechanical Propertiessupporting

confidence: 85%

Vacancy induced brittle-to-ductile transition of Nb5Si3 alloy from first-principles

et al. 2015

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Section: Mechanical Propertiessupporting

confidence: 85%

Vacancy induced brittle-to-ductile transition of Nb5Si3 alloy from first-principles

et al. 2015

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“…However, mechanical properties of monolithic α-Nb 5 Si 3 have remained largely unknown, mainly because of the difficulty in single crystal preparation due to the β-α polymorphic transformation. There is only one report on plastic deformation behaviors of α-Nb 5 Si 3 studied with Nb-Nb 5 Si 3 two-phase polycrystalline alloys with Ti addition [ 8 ]. Two types of dislocations having the Burgers vectors of <100> and 1/2 < 111> were observed by transmission electron microscopy (TEM) in α-Nb 5 Si 3 in Ti-alloyed Nb-Nb 5 Si 3 two-phase alloys deformed at 1400°C.…”

Section: Introductionmentioning

confidence: 99%

“…Two types of dislocations having the Burgers vectors of <100> and 1/2 < 111> were observed by transmission electron microscopy (TEM) in α-Nb 5 Si 3 in Ti-alloyed Nb-Nb 5 Si 3 two-phase alloys deformed at 1400°C. Three slip systems, {0 1}<111>, {100}<010> and {001}<010> were inferred to be operative in α-Nb 5 Si 3 based on trace analysis of dislocation line vectors in the TEM [ 8 ]. In view of the fact that significant dislocation climb occurs at high temperatures during and after mechanical testing, however, slip system identification with the trace analysis method in the TEM has its own limitation for the accuracy.…”

Section: Introductionmentioning

confidence: 99%

“…Nb 5 Si 3 crystalizes into two polymorphs; α-Nb 5 Si 3 , a low temperature form with the tetragonal D8 l structure (tI32, space group: I4/mcm, a = 0.657 nm, c = 1.1884 nm [7]) and β-Nb 5 Si 3 , a high temperature form with the D8 m structure (tI32, space group: I4/mcm, a = 1.0026 nm, c = 0.50717 nm [7]), with polymorphic transition occurring approximately at 1700 °C. It is α-Nb 5 Si 3 that has been There is only one report on plastic deformation behaviors of α-Nb 5 Si 3 studied with Nb-Nb 5 Si 3 two-phase polycrystalline alloys with Ti addition [8]. Two types of dislocations having the Burgers vectors of <100> and 1/2<111> were observed by transmission electron microscopy (TEM) in α-Nb 5 Si 3 in Ti-alloyed Nb-Nb 5 Si 3 two-phase alloys deformed at 1400 °C.…”

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confidence: 99%

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Micropillar compression deformation of single crystals of α-Nb₅Si₃ with the tetragonal D8_l structure

Kishida

Maruyama

Fukuyama

et al. 2020

Science and Technology of Advanced Materials

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“…This is due not only to their higher melting temperatures, but also to their excellent high-temperature strength, room-temperature fracture toughness, and low densities [3][4][5][6]. According to recent studies, with respect to the hot workability of the alloys, it is rather laborious and impractical to produce their components and parts via forging methods because of the formation of cracks during hot deformation [7,8]. Investment casting has naturally become the ultimate forming process for this alloy.…”

Section: Introductionmentioning

confidence: 99%

Re-Melting Nb–Si-Based Ultrahigh-Temperature Alloys in Ceramic Mold Shells

Yin

Guo

2019

Metals

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In furnaces with different heating elements, Nb-Si based ultrahigh-temperature alloy rods were re-melted in pure yttria mold shells and zirconia face-coat mold shells at 1850 • C for 30 min. The results evidenced that in the furnace with a tungsten heating element, the microstructure of the re-melted alloy became coarser, and the composition varied depending on the type of mold shell. Although the interface reaction layer between the re-melted alloy and the zirconia face-coat mold shell was much thicker, the deformability of the mold shell and the sand burning phenomenon of the alloy inside it were improved and ameliorated, respectively. However, after being re-melted in the furnace with a graphite heating element, the misrun phenomenon occurred in both specimens. Both re-melted alloys inside the mold shells were divided by a gap into an internal and an external part, with totally different microstructures and compositions. No reaction layer emerged at the interface between the re-melted alloy and the mold shells. Instead, infiltration zones arose in the mold shells adjacent to the interface.Metals 2019, 9, 721 2 of 15 coating in mold shells for investment casting of active and refractory metals. Especially, yttria has been successfully applied in the preparation of directionally solidified Nb-Si based ultrahigh-temperature alloys with a single orientation structure and high mechanical properties. As an example, Guo and Guo [11] performed integrally directional solidification of Nb-Si based ultrahigh-temperature alloys, in which yttria was employed as crucible material. Ma et al. [12] technically studied the interface interactions between Nb-Si-based ultrahigh-temperature alloys and pure yttria mold shells and found only a 5 to 15 µm-thick reaction layer composed of HfO 2 and Y 2 O 3 formed at the metal-mold shell interface. This further confirms that yttria is relatively inert to this alloy and is a qualified material for the mold shell during investment casting of this alloy. However, yttria is inclined to be hydrated with water, which leads to a significant loss of the life period of the as-prepared slurries as a result of gelatinization [13]. This ineluctably increases the overall technical costs of investment casting. On the contrary, it is not an issue for slurries filled by zirconia. However, in view of the substitution reaction between ZrO 2 and Hf, the application of zirconia on re-melting Nb-Si-based ultrahigh-temperature alloys is scarce. Nevertheless, the addition of Hf is becoming unnecessary, considering the impact of this element on the alloy, as reported recently [14]. It can be predicted that the content of Hf is likely to be reduced or replaced completely by other elements in the modified alloy. Hence, zirconia is also a potential mold shell material with practical application in confectioning this alloy.Besides the mold shell problems to be solved, the issues of the filling capability, microstructure homogeneity, element segregation, casting defects, and sand burning should all be evaluated fo...

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Dislocation character and operative slip systems in α-Nb5Si3 tested at 1673K

Cited by 16 publications

References 28 publications

Vacancy induced brittle-to-ductile transition of Nb5Si3 alloy from first-principles

Vacancy induced brittle-to-ductile transition of Nb5Si3 alloy from first-principles

Micropillar compression deformation of single crystals of α-Nb₅Si₃ with the tetragonal D8_l structure

Re-Melting Nb–Si-Based Ultrahigh-Temperature Alloys in Ceramic Mold Shells

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Dislocation character and operative slip systems in α-Nb5Si3 tested at 1673K

Cited by 16 publications

References 28 publications

Vacancy induced brittle-to-ductile transition of Nb5Si3 alloy from first-principles

Vacancy induced brittle-to-ductile transition of Nb5Si3 alloy from first-principles

Micropillar compression deformation of single crystals of α-Nb5Si3 with the tetragonal D8l structure

Re-Melting Nb–Si-Based Ultrahigh-Temperature Alloys in Ceramic Mold Shells

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Micropillar compression deformation of single crystals of α-Nb₅Si₃ with the tetragonal D8_l structure