Development of unique cross-lamellar microstructure, resulting in the drastic increase in fracture toughness in Cr/Ir-codoped (Mo 0.85 Nb 0.15 )Si 2 crystals
“…Figure 1(a–d) describe the crystal orientation maps of the precipitated C11 b phases analyzed by the electron backscatter diffraction in a scanning electron microscope (SEM-EBSD) in the annealed two-phase crystals 26 . The black parts and the colored grains represent the C40-matrix-phase and precipitated C11 b -phase grains, respectively.…”
Section: Resultsmentioning
confidence: 99%
“…As a result, three C11 b -phase variants - variant 1 (V1), variant 2 (V2), and variant 3 (V3) – produced from the C40 single crystals are denoted as follows:Figure 1Microstructure variations depending on the added element. ( a – d ) Crystal orientation maps of the constituent C11 b phases in the FZ-grown crystals annealed at 1400 °C for 168 h examined by SEM-EBSD, according to the previous study 26 . ( a ) Nonadded (Mo 0.85 Nb 0.15 )Si 2 ternary crystal, ( b ) 1 at.% Cr-added crystal, ( c ) 1 at.% Ir-added crystal, ( d ) 0.5 at.% Cr and 0.5 at.% Ir-coadded crystals.…”
Section: Resultsmentioning
confidence: 99%
“…( a – d ) Crystal orientation maps of the constituent C11 b phases in the FZ-grown crystals annealed at 1400 °C for 168 h examined by SEM-EBSD, according to the previous study 26 . ( a ) Nonadded (Mo 0.85 Nb 0.15 )Si 2 ternary crystal, ( b ) 1 at.% Cr-added crystal, ( c ) 1 at.% Ir-added crystal, ( d ) 0.5 at.% Cr and 0.5 at.% Ir-coadded crystals.…”
Section: Resultsmentioning
confidence: 99%
“…In the research process, we found the novel development of the unique “cross-lamellar microstructure” in the Cr/Ir-codoped crystal, as the details are described later. Development of such microstructure was never reported until now, and it was found to result in a drastic increase in fracture toughness 26 . However, the variation in creep properties at high-temperatures around 1400 °C, which is more essential for realizing the practical application of this crystal as an UHT material, remains unknown.…”
Section: Introductionmentioning
confidence: 91%
“…For their practical application, we have proposed two-phase crystals in which different disilicides with properties that complement each other are combined. A combination of C11 b phase (such as MoSi 2 ) and C40 phase (such as NbSi 2 ) with considerable ductility and superior high-temperature strength by controlling the loading orientation, respectively, is considered the most promising candidate 8–26 . In Nakano et al .…”
A (Mo0.85Nb0.15)Si2 crystal with an oriented, lamellar, C40/C11b two-phase microstructure is a promising ultrahigh-temperature (UHT) structural material, but its low room-temperature fracture toughness and low high-temperature strength prevent its practical application. As a possibility to overcome these problems, we first found a development of unique “cross-lamellar microstructure”, by the cooping of Cr and Ir. The cross-lamellar microstructure consists of a rod-like C11b-phase grains that extend along a direction perpendicular to the lamellar interface in addition to the C40/C11b fine lamellae. In this study, the effectiveness of the cross-lamellar microstructure for improving the high-temperature creep deformation property, being the most essential for UHT materials, was examined by using the oriented crystals. The creep rate significantly reduced along a loading orientation parallel to the lamellar interface. Furthermore, the degradation in creep strength for other loading orientation that is not parallel to the lamellar interface, which has been a serious problem up to now, was also suppressed. The results demonstrated that the simultaneous improvement of high-temperature creep strength and room temperature fracture toughness can be first accomplished by the development of unique cross-lamellar microstructure, which opens a potential avenue for the development of novel UHT materials as alternatives to existing Ni-based superalloys.
“…Figure 1(a–d) describe the crystal orientation maps of the precipitated C11 b phases analyzed by the electron backscatter diffraction in a scanning electron microscope (SEM-EBSD) in the annealed two-phase crystals 26 . The black parts and the colored grains represent the C40-matrix-phase and precipitated C11 b -phase grains, respectively.…”
Section: Resultsmentioning
confidence: 99%
“…As a result, three C11 b -phase variants - variant 1 (V1), variant 2 (V2), and variant 3 (V3) – produced from the C40 single crystals are denoted as follows:Figure 1Microstructure variations depending on the added element. ( a – d ) Crystal orientation maps of the constituent C11 b phases in the FZ-grown crystals annealed at 1400 °C for 168 h examined by SEM-EBSD, according to the previous study 26 . ( a ) Nonadded (Mo 0.85 Nb 0.15 )Si 2 ternary crystal, ( b ) 1 at.% Cr-added crystal, ( c ) 1 at.% Ir-added crystal, ( d ) 0.5 at.% Cr and 0.5 at.% Ir-coadded crystals.…”
Section: Resultsmentioning
confidence: 99%
“…( a – d ) Crystal orientation maps of the constituent C11 b phases in the FZ-grown crystals annealed at 1400 °C for 168 h examined by SEM-EBSD, according to the previous study 26 . ( a ) Nonadded (Mo 0.85 Nb 0.15 )Si 2 ternary crystal, ( b ) 1 at.% Cr-added crystal, ( c ) 1 at.% Ir-added crystal, ( d ) 0.5 at.% Cr and 0.5 at.% Ir-coadded crystals.…”
Section: Resultsmentioning
confidence: 99%
“…In the research process, we found the novel development of the unique “cross-lamellar microstructure” in the Cr/Ir-codoped crystal, as the details are described later. Development of such microstructure was never reported until now, and it was found to result in a drastic increase in fracture toughness 26 . However, the variation in creep properties at high-temperatures around 1400 °C, which is more essential for realizing the practical application of this crystal as an UHT material, remains unknown.…”
Section: Introductionmentioning
confidence: 91%
“…For their practical application, we have proposed two-phase crystals in which different disilicides with properties that complement each other are combined. A combination of C11 b phase (such as MoSi 2 ) and C40 phase (such as NbSi 2 ) with considerable ductility and superior high-temperature strength by controlling the loading orientation, respectively, is considered the most promising candidate 8–26 . In Nakano et al .…”
A (Mo0.85Nb0.15)Si2 crystal with an oriented, lamellar, C40/C11b two-phase microstructure is a promising ultrahigh-temperature (UHT) structural material, but its low room-temperature fracture toughness and low high-temperature strength prevent its practical application. As a possibility to overcome these problems, we first found a development of unique “cross-lamellar microstructure”, by the cooping of Cr and Ir. The cross-lamellar microstructure consists of a rod-like C11b-phase grains that extend along a direction perpendicular to the lamellar interface in addition to the C40/C11b fine lamellae. In this study, the effectiveness of the cross-lamellar microstructure for improving the high-temperature creep deformation property, being the most essential for UHT materials, was examined by using the oriented crystals. The creep rate significantly reduced along a loading orientation parallel to the lamellar interface. Furthermore, the degradation in creep strength for other loading orientation that is not parallel to the lamellar interface, which has been a serious problem up to now, was also suppressed. The results demonstrated that the simultaneous improvement of high-temperature creep strength and room temperature fracture toughness can be first accomplished by the development of unique cross-lamellar microstructure, which opens a potential avenue for the development of novel UHT materials as alternatives to existing Ni-based superalloys.
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