Ambient to high temperature fracture toughness and fatigue-crack propagation behavior in a Mo–12Si–8.5B (at.%) intermetallic

Choe, Heeman; Chen, D.; Schneibel, J.H.; Ritchie, Robert O.

doi:10.1016/s0966-9795(01)00008-5

Cited by 127 publications

(95 citation statements)

References 42 publications

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“…In this regard, the increase in fracture resistance exhibited by the "medium" alloy at 1300°C, consistent with other Mo-Si-B alloys [8,9], is a highly desirable property. Observations of crack profiles (Fig.…”

Section: Discussion (1) Toughening Mechanismssupporting

confidence: 81%

“…MPa√m [8,9], i.e., they showed only marginal improvements in toughness over monolithic silicides. Additionally, the fracture toughness appeared to improve at higher temperatures; specifically the "medium" alloy displayed a 50% rise in peak toughness from 10 to 15 MPa√m on increasing the temperature from 25° to 1300°C.…”

Section: (1) Fracture Toughnessmentioning

confidence: 99%

“…In previous reports [8,9], we have described alloys containing (α-) molybdenum particles surrounded by the hard but brittle Mo 3 Si and Mo 5 SiB 2 (T2) intermetallic phases, which display definitive, but still small, improvements in toughness relative to monolithic silicides. Clearly, the key to achieving high fracture resistance in these materials is in making more effective use of the relatively ductile molybdenum phase, not unlike nickel-base (γ/γ′) superalloys, where high fracture toughnesses are obtained with a similarly high fraction of intermetallic (γ′) precipitates.…”

Section: Introductionmentioning

confidence: 96%

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Fracture and fatigue resistance of Mo–Si–B alloys for ultrahigh-temperature structural applications

2004

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Section: Discussion (1) Toughening Mechanismssupporting

confidence: 81%

Section: (1) Fracture Toughnessmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

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Fracture and fatigue resistance of Mo–Si–B alloys for ultrahigh-temperature structural applications

2004

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“…The mechanical properties of this class of alloys have also been studied [11][12][13][14][15][16][17][18][19][20][21][22][23]. The Mo3Si and T2 intermetallic phases retain high strengths up to 1400°C [13][14][15][16], but are extremely brittle, with room temperature fracture toughness values on the order of 3 MPa-√m [13].…”

Section: Introductionmentioning

confidence: 99%

“…The Mo3Si and T2 intermetallic phases retain high strengths up to 1400°C [13][14][15][16], but are extremely brittle, with room temperature fracture toughness values on the order of 3 MPa-√m [13]. Substantial improvements in the room temperature fracture toughness are obtained, to values as high as 10 MPa, in three phase α-Mo+Mo3Si+T2 compositions, wherein the α-Mo provides ductile phase toughening by plastic stretching and crack trapping [18,19]. Further increases (to ~15 MPa √m) have also been made possible using novel vacuum annealing and powder metallurgical processing to produce microstructures with continuous α-Mo layers surrounding the intermetallic phases [21].…”

Section: Introductionmentioning

confidence: 99%

Processing, Microstructure and Creep Behavior of Mo-Si-B-Based Intermetallic Alloys for Very High Temperature Structural Applications

Vasudevan¹

2008

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This research project is concerned with developing a fundamental understanding of the effects of processing and microstructure on the creep behavior of refractory intermetallic alloys based on the Mo-Si-B system. In the first part of this project, the compression creep behavior of a Mo-8.9Si-7.71B (in at.%) alloy, at 1100 and 1200°C was studied, whereas in the second part of the project, the constant strain rate compression behavior at 1200, 1300 and 1400°C of a nominally Mo-20Si-10B (in at.%) alloy, processed such as to yield five different α-Mo volume fractions ranging from 5 to 46%, was studied. In order to determine the deformation and damage mechanisms and rationalize the creep/high temperature deformation data and parameters, the microstructure of both undeformed and deformed samples was characterized in detail using x-ray diffraction, scanning electron microscopy (SEM) with back scattered electron imaging (BSE) and energy dispersive x-ray spectroscopy (EDS), electron back scattered diffraction (EBSD)/orientation electron microscopy in the SEM and transmission electron microscopy (TEM). The microstructure of both alloys was three-phase, being composed of α-Mo, Mo3Si and T2-Mo5SiB2 phases. The values of stress exponents and activation energies, and their dependence on microstructure were determined. The data suggested the operation of both dislocation as well as diffusional mechanisms, depending on alloy, test temperature, stress level and microstructure. Microstructural observations of post-crept/deformed samples indicated the presence of many voids in the α-Mo grains and few cracks in the intermetallic particles and along their interfaces with the α-Mo matrix. TEM observations revealed the presence of recrystallized α-Mo grains and sub-grain boundaries composed of dislocation arrays within the grains (in Mo-8.9Si-7.71B) or fine sub-grains with a high density of b = ½<111> dislocations (in Mo-20Si-10B), which are consistent with the values of the respective stress exponents and activation energies that were obtained and provide confirmatory evidence for the operation of diffusional (former alloy) or dislocation (latter alloy) creep mechanisms. In contrast, the intermetallic phases contained very few dislocations, but many cracks. The relative contributions of the α-Mo and the intermetallic particles to the overall deformation process, including their individual and collective dependence on temperature and strain rate are discussed in light of the present results and those from previous reports.iii

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Mo‐Si‐B Alloys for Ultrahigh‐Temperature Structural Applications

Lemberg¹,

Ritchie²

2012

Advanced Materials

253

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A continuing quest in science is the development of materials capable of operating structurally at ever-increasing temperatures. Indeed, the development of gas-turbine engines for aircraft/aerospace, which has had a seminal impact on our ability to travel, has been controlled by the availability of materials capable of withstanding the higher-temperature hostile environments encountered in these engines. Nickel-base superalloys, particularly as single crystals, represent a crowning achievement here as they can operate in the combustors at ~1100 °C, with hot spots of ~1200 °C. As this represents ~90% of their melting temperature, if higher-temperature engines are ever to be a reality, alternative materials must be utilized. One such class of materials is Mo-Si-B alloys; they have higher density but could operate several hundred degrees hotter. Here we describe the processing and structure versus mechanical properties of Mo-Si-B alloys and further document ways to optimize their nano/microstructures to achieve an appropriate balance of properties to realistically compete with Ni-alloys for elevated-temperature structural applications.

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Ambient to high temperature fracture toughness and fatigue-crack propagation behavior in a Mo–12Si–8.5B (at.%) intermetallic

Cited by 127 publications

References 42 publications

Fracture and fatigue resistance of Mo–Si–B alloys for ultrahigh-temperature structural applications

Fracture and fatigue resistance of Mo–Si–B alloys for ultrahigh-temperature structural applications

Processing, Microstructure and Creep Behavior of Mo-Si-B-Based Intermetallic Alloys for Very High Temperature Structural Applications

Mo‐Si‐B Alloys for Ultrahigh‐Temperature Structural Applications

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