A new Fe-based metallic glass with composition Fe 76 B 12 Si 9 Y 3 (at. %) is found to have extra... more A new Fe-based metallic glass with composition Fe 76 B 12 Si 9 Y 3 (at. %) is found to have extraordinary degradation efficiency towards methyl orange (MO, C14H14N3SO3) in strong acidic and near neutral environments compared to crystalline zero-valent iron (ZVI) powders and other Fe-based metallic glasses. The influence of temperature (294–328 K) on the degradation reaction rate was measured using ball-milled metallic glass powders revealing a low thermal activation energy barrier of 22.6 kJ/mol. The excellent properties are mainly attributed to the heterogeneous structure consisting of local Fe-rich and Fe-poor atomic clusters, rather than the large specific surface and strong residual stress in the powders. The metallic glass powders can sustain almost unchanged degradation efficiency after 13 cycles at room temperature, while a drop in degradation efficiency with further cycles is attributed to visible surface oxidation. Triple quadrupole mass spectrometry analysis conducted during the reaction was used to elucidate the underlying degradation mechanism. The present findings may provide a new, highly efficient and low cost commercial method for azo dye wastewater treatment. Azo dyes represent about one-half of the dyes used in the textile industry. It has been reported that about 20% of dyestuff is discharged directly into the environment by textile factories 1,2. However, azo dyes are very difficult to decompose and often result in the pollution of water and irrevocable environmental problems 3. New and effective treatment methods are needed for degrading azo dyes in order to reduce, or preferably eliminate, the amount of toxic and/or carcinogenic azo dye in wastewater. Traditional azo dye wastewater treatment methods usually filter or separate the organic chemicals through physical methods rather than decomposing the azo dye 4. However, these methods cannot sufficiently eliminate azo dyes and their environmental impacts. Furthermore, the chemical and biological methods currently available are often more expensive and display even lower efficiency 5,6 , so their applications are largely restricted. The removal of pollutants in water by means of a reduction reaction using zero-valent metals has been developed recently as a new treatment technology. The most commonly used metal is zero-valent iron, which exhibits low cost, simple operation, and high efficiency 7–9. However, ZVI is easily oxidized (rust) and its degradation efficiency decays rapidly. Recently, Fe-based amorphous powders and metallic glass composites have been developed that demonstrate higher efficiency in the degradation of azo dyes and other organic contaminants compared to conventional iron powders 10–12. Metallic glasses have attracted considerable attention over the past three decades due to their unique physical, mechanical and chemical properties 13,14. In particular, their good chemical and catalytic properties have been highlighted due to the far-from-equilibrium structures and high-energy states of the metallic glasses 15–18. A long-range disordered atomic configuration gives metallic glasses a complex atomic and electronic structure, which is distinct from their crystalline counterparts and can contribute to excellent chemical and catalytic properties 18. A shortcoming for using metallic glasses in applications requiring components with large physical dimensions are the size restrictions imposed by the glass formation ability 13. However, for functional applications, such as dye degradation, powder samples can be prepared easily and there is little concern about any processing restrictions. While there has also been interest in using Mg-based metallic glass and metallic glass composite powders for degrading azo dyes 19–21 , Fe-based metallic glasses represent a lower cost alternative and are thus most attractive for commercialization. Furthermore, in comparison to commercially pure ZVI, Fe-based metallic glasses
Bulk metallic glasses (BMGs) can exhibit excellent combinations of strength and fracture toughnes... more Bulk metallic glasses (BMGs) can exhibit excellent combinations of strength and fracture toughness that cannot be achieved by traditional metals, making them attractive for load bearing, mechanical engineering applications. Furthermore, recent research on BMGs has shown that many early perceived shortcomings, such as apparent brittleness or poor fatigue resistance, are not as big of a problem as once thought. The purpose of this paper is to review some of the unique mechanical characteristics of BMGs along with some of the strategies that may be used to improve or exploit their characteristics so that BMGs may be used as structural materials in engineering applications.
Bulk metallic glasses (BMGs) have been reported to have large variability in mode I fracture toug... more Bulk metallic glasses (BMGs) have been reported to have large variability in mode I fracture toughness. In this study, alternating soft and hard regions were created in a Zr52.5Ti5Cu18Ni14.5Al10 (at%) BMG via mechanical imprinting at room temperature. While only 50% of as-cast samples demonstrated plastic deformation during mode I fracture tests, 100% of imprinted samples demonstrated measurable plasticity and the scatter in measured mode I fracture toughness was significantly reduced. Mechanical treatments show promise for improving the fracture reliability of BMGs.
Mode I fracture tests were conducted on both as-cast and cold-rolled Zr-Cu-Ni-Al-Nb bulk metallic... more Mode I fracture tests were conducted on both as-cast and cold-rolled Zr-Cu-Ni-Al-Nb bulk metallic glass (BMG) single edge notch bend samples. The results show a 54% improved fracture toughness (KJ = 55.2 vs. 85.0 MPa√m) is obtained by cold rolling to ~2.5% true strain. The precrack patterns and fractography were also analyzed to evaluate the influence of cold rolling on the fracture process and also the validity of the mode I fracture toughness results. Cold rolling was found to promote numerous shear bands along the main crack, crack bifurcation, and a tortuous crack path, all of which are thought to contribute to the improved toughness. The influence of various precrack morphologies on the fracture toughness results are discussed. It was found that it is difficult to produce perfect standardized precracks in BMGs with heterogeneous glassy structures induced by cold rolling and this issue needs further evaluation if fracture toughness testing standards for BMGs are to be established.
Mo-Si-B silicides consisting of the phases -Mo (Mo solid solution), MoSi, and MoSiB have melting ... more Mo-Si-B silicides consisting of the phases -Mo (Mo solid solution), MoSi, and MoSiB have melting points on the order of 2000 C and have potential as ultra-high temperature structural materials. Mo-Si-B alloys can be processed such that the -Mo is present in the form of isolated particles in a silicide matrix, or as a continuous matrix 'cementing' individual silicide particles together. The latter microstructure is similar to that of WC-Co hard metals. This paper focuses on the relationship between the topology as well as scale of the microstructure of Mo-MoSi-MoSiB alloys, and their creep strength and fracture toughness. For example, the creep strength of Mo-Si-B alloys is improved by reducing the -Mo volume fraction and by making the -Mo phase discontinuous. The fracture toughness is improved by increasing the -Mo volume fraction and by making the -Mo phase continuous. Room temperature stress intensity factors as high as 21 MPa m¹² were obtained. The room temperature frac...
ABSTRACT The fatigue crack growth behavior of a Zr44Ti11Ni10Cu10Be25 bulk metallic glass (BMG) wa... more ABSTRACT The fatigue crack growth behavior of a Zr44Ti11Ni10Cu10Be25 bulk metallic glass (BMG) was measured in an inert dry N2 environment. When compared to results measured in ambient air, the present results showed a higher fatigue threshold and lower crack growth rates in the near-threshold region. Such results reveal that there is a significant effect of ambient air in accelerating fatigue crack growth for this BMG.
Early studies suggested there was a severe problem with the fatigue resistance of some bulk metal... more Early studies suggested there was a severe problem with the fatigue resistance of some bulk metallic glasses (BMGs) and BMG matrix composites, while more recent studies begin to demonstrate a wide variety of fatigue behaviors may be possible for both fully amorphous BMGs and their composites. However, in order to truly understand and control the fatigue behavior of these materials, the role of such factors as thermomechanical processing, the corresponding glass structure, environment, and defects must be understood. Additionally, it is important to understand how these factors relate to the mechanisms of fatigue. This article reviews the current understanding in this regard, and identifies some of the challenges for the future development of fatigue-resistant BMG-based materials.
Gamma-based TiAl intermetallic alloys have received considerable attention recently as candidate ... more Gamma-based TiAl intermetallic alloys have received considerable attention recently as candidate materials for high-temperature aerospace applications. Two classes of microstructure have been prominent in the two-phase (γ + αâ) alloys: a lamellar structure consisting of lamellar colonies containing alternating γ and αâ grains. In general, duplex structures display better elongation and strength, whereas lamellar structures show better toughness and fatigue
Two major mechanisms that could potentially be responsible for toughening in mineralized tissues,... more Two major mechanisms that could potentially be responsible for toughening in mineralized tissues, such as bone and dentin, have been identified—microcracking and crack bridging. While evidence has been reported for both mechanisms, there has been no consensus thus far on which mechanism plays the dominant role in toughening these materials. In the present study, we seek to present definitive experimental evidence supporting crack bridging, rather than microcracking, as the most significant mechanism of toughening in cortical bone and dentin. In vitro fracture toughness experiments were conducted to measure the variation of the fracture resistance with crack extension (resistance- curve (R-curve) behavior) for both materials with special attention paid to changes in the sample compliance. Because these two toughening mechanisms induce opposite effects on the sample compliance, such experiments allow for the definitive determination of the dominant toughening mechanism, which in the p...
A new Fe-based metallic glass with composition Fe 76 B 12 Si 9 Y 3 (at. %) is found to have extra... more A new Fe-based metallic glass with composition Fe 76 B 12 Si 9 Y 3 (at. %) is found to have extraordinary degradation efficiency towards methyl orange (MO, C14H14N3SO3) in strong acidic and near neutral environments compared to crystalline zero-valent iron (ZVI) powders and other Fe-based metallic glasses. The influence of temperature (294–328 K) on the degradation reaction rate was measured using ball-milled metallic glass powders revealing a low thermal activation energy barrier of 22.6 kJ/mol. The excellent properties are mainly attributed to the heterogeneous structure consisting of local Fe-rich and Fe-poor atomic clusters, rather than the large specific surface and strong residual stress in the powders. The metallic glass powders can sustain almost unchanged degradation efficiency after 13 cycles at room temperature, while a drop in degradation efficiency with further cycles is attributed to visible surface oxidation. Triple quadrupole mass spectrometry analysis conducted during the reaction was used to elucidate the underlying degradation mechanism. The present findings may provide a new, highly efficient and low cost commercial method for azo dye wastewater treatment. Azo dyes represent about one-half of the dyes used in the textile industry. It has been reported that about 20% of dyestuff is discharged directly into the environment by textile factories 1,2. However, azo dyes are very difficult to decompose and often result in the pollution of water and irrevocable environmental problems 3. New and effective treatment methods are needed for degrading azo dyes in order to reduce, or preferably eliminate, the amount of toxic and/or carcinogenic azo dye in wastewater. Traditional azo dye wastewater treatment methods usually filter or separate the organic chemicals through physical methods rather than decomposing the azo dye 4. However, these methods cannot sufficiently eliminate azo dyes and their environmental impacts. Furthermore, the chemical and biological methods currently available are often more expensive and display even lower efficiency 5,6 , so their applications are largely restricted. The removal of pollutants in water by means of a reduction reaction using zero-valent metals has been developed recently as a new treatment technology. The most commonly used metal is zero-valent iron, which exhibits low cost, simple operation, and high efficiency 7–9. However, ZVI is easily oxidized (rust) and its degradation efficiency decays rapidly. Recently, Fe-based amorphous powders and metallic glass composites have been developed that demonstrate higher efficiency in the degradation of azo dyes and other organic contaminants compared to conventional iron powders 10–12. Metallic glasses have attracted considerable attention over the past three decades due to their unique physical, mechanical and chemical properties 13,14. In particular, their good chemical and catalytic properties have been highlighted due to the far-from-equilibrium structures and high-energy states of the metallic glasses 15–18. A long-range disordered atomic configuration gives metallic glasses a complex atomic and electronic structure, which is distinct from their crystalline counterparts and can contribute to excellent chemical and catalytic properties 18. A shortcoming for using metallic glasses in applications requiring components with large physical dimensions are the size restrictions imposed by the glass formation ability 13. However, for functional applications, such as dye degradation, powder samples can be prepared easily and there is little concern about any processing restrictions. While there has also been interest in using Mg-based metallic glass and metallic glass composite powders for degrading azo dyes 19–21 , Fe-based metallic glasses represent a lower cost alternative and are thus most attractive for commercialization. Furthermore, in comparison to commercially pure ZVI, Fe-based metallic glasses
Bulk metallic glasses (BMGs) can exhibit excellent combinations of strength and fracture toughnes... more Bulk metallic glasses (BMGs) can exhibit excellent combinations of strength and fracture toughness that cannot be achieved by traditional metals, making them attractive for load bearing, mechanical engineering applications. Furthermore, recent research on BMGs has shown that many early perceived shortcomings, such as apparent brittleness or poor fatigue resistance, are not as big of a problem as once thought. The purpose of this paper is to review some of the unique mechanical characteristics of BMGs along with some of the strategies that may be used to improve or exploit their characteristics so that BMGs may be used as structural materials in engineering applications.
Bulk metallic glasses (BMGs) have been reported to have large variability in mode I fracture toug... more Bulk metallic glasses (BMGs) have been reported to have large variability in mode I fracture toughness. In this study, alternating soft and hard regions were created in a Zr52.5Ti5Cu18Ni14.5Al10 (at%) BMG via mechanical imprinting at room temperature. While only 50% of as-cast samples demonstrated plastic deformation during mode I fracture tests, 100% of imprinted samples demonstrated measurable plasticity and the scatter in measured mode I fracture toughness was significantly reduced. Mechanical treatments show promise for improving the fracture reliability of BMGs.
Mode I fracture tests were conducted on both as-cast and cold-rolled Zr-Cu-Ni-Al-Nb bulk metallic... more Mode I fracture tests were conducted on both as-cast and cold-rolled Zr-Cu-Ni-Al-Nb bulk metallic glass (BMG) single edge notch bend samples. The results show a 54% improved fracture toughness (KJ = 55.2 vs. 85.0 MPa√m) is obtained by cold rolling to ~2.5% true strain. The precrack patterns and fractography were also analyzed to evaluate the influence of cold rolling on the fracture process and also the validity of the mode I fracture toughness results. Cold rolling was found to promote numerous shear bands along the main crack, crack bifurcation, and a tortuous crack path, all of which are thought to contribute to the improved toughness. The influence of various precrack morphologies on the fracture toughness results are discussed. It was found that it is difficult to produce perfect standardized precracks in BMGs with heterogeneous glassy structures induced by cold rolling and this issue needs further evaluation if fracture toughness testing standards for BMGs are to be established.
Mo-Si-B silicides consisting of the phases -Mo (Mo solid solution), MoSi, and MoSiB have melting ... more Mo-Si-B silicides consisting of the phases -Mo (Mo solid solution), MoSi, and MoSiB have melting points on the order of 2000 C and have potential as ultra-high temperature structural materials. Mo-Si-B alloys can be processed such that the -Mo is present in the form of isolated particles in a silicide matrix, or as a continuous matrix 'cementing' individual silicide particles together. The latter microstructure is similar to that of WC-Co hard metals. This paper focuses on the relationship between the topology as well as scale of the microstructure of Mo-MoSi-MoSiB alloys, and their creep strength and fracture toughness. For example, the creep strength of Mo-Si-B alloys is improved by reducing the -Mo volume fraction and by making the -Mo phase discontinuous. The fracture toughness is improved by increasing the -Mo volume fraction and by making the -Mo phase continuous. Room temperature stress intensity factors as high as 21 MPa m¹² were obtained. The room temperature frac...
ABSTRACT The fatigue crack growth behavior of a Zr44Ti11Ni10Cu10Be25 bulk metallic glass (BMG) wa... more ABSTRACT The fatigue crack growth behavior of a Zr44Ti11Ni10Cu10Be25 bulk metallic glass (BMG) was measured in an inert dry N2 environment. When compared to results measured in ambient air, the present results showed a higher fatigue threshold and lower crack growth rates in the near-threshold region. Such results reveal that there is a significant effect of ambient air in accelerating fatigue crack growth for this BMG.
Early studies suggested there was a severe problem with the fatigue resistance of some bulk metal... more Early studies suggested there was a severe problem with the fatigue resistance of some bulk metallic glasses (BMGs) and BMG matrix composites, while more recent studies begin to demonstrate a wide variety of fatigue behaviors may be possible for both fully amorphous BMGs and their composites. However, in order to truly understand and control the fatigue behavior of these materials, the role of such factors as thermomechanical processing, the corresponding glass structure, environment, and defects must be understood. Additionally, it is important to understand how these factors relate to the mechanisms of fatigue. This article reviews the current understanding in this regard, and identifies some of the challenges for the future development of fatigue-resistant BMG-based materials.
Gamma-based TiAl intermetallic alloys have received considerable attention recently as candidate ... more Gamma-based TiAl intermetallic alloys have received considerable attention recently as candidate materials for high-temperature aerospace applications. Two classes of microstructure have been prominent in the two-phase (γ + αâ) alloys: a lamellar structure consisting of lamellar colonies containing alternating γ and αâ grains. In general, duplex structures display better elongation and strength, whereas lamellar structures show better toughness and fatigue
Two major mechanisms that could potentially be responsible for toughening in mineralized tissues,... more Two major mechanisms that could potentially be responsible for toughening in mineralized tissues, such as bone and dentin, have been identified—microcracking and crack bridging. While evidence has been reported for both mechanisms, there has been no consensus thus far on which mechanism plays the dominant role in toughening these materials. In the present study, we seek to present definitive experimental evidence supporting crack bridging, rather than microcracking, as the most significant mechanism of toughening in cortical bone and dentin. In vitro fracture toughness experiments were conducted to measure the variation of the fracture resistance with crack extension (resistance- curve (R-curve) behavior) for both materials with special attention paid to changes in the sample compliance. Because these two toughening mechanisms induce opposite effects on the sample compliance, such experiments allow for the definitive determination of the dominant toughening mechanism, which in the p...
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Papers by Jamie J Kruzic