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Ductile phase toughening of MoSi2 effect of reinforcement morphology
Int. J. Fatigue Vol. 17, No. 6, pp. 447-452, 1995 Elsevier Science Limited. Printed in Great Britain 0142-1123/95/$10.00
Fatigue Abstracts This section contains abstracts of selected articles, technical reports, dissertations and patents concerned with fatigue. It is prepared in collaboration with Materials Information, a joint service of The Institute of Materials and ASM International. Readers wishing to obtain the full text of articles abstracted here should contact either: The Institute of Materials, 1 Carlton House Terrace, London SWlY 5DB, UK, or: ASM International, Metals Park, OH 44073, USA (not International Journal of Fatigue). The fees charged for photocopying articles are £7.00 for the first ten pages and £3.00 per additional ten pages (UK office), or $10.00 for the first ten pages and $4.00 per additional ten pages (US office).
Distribution of fatigue microcracks in an aluminum-matrix silicon carbide whisker composite. Chen, E.Y., Lawson, L. and Menhii, M. Scr. Metall. Mater. (15 March 1994) 30 (6), 737-742
Ductile phase toughening of MoSi2 effect of reinforcement morphology. Chen, L.-C., Bahtishi, N., Lederich, R. and Soboyejo, W. Proc. Conf. lntermetallic Matrix Composites 111, San Francisco, CA, USA, 4-6 April 1994, pp. 183-188
Discontinuously reinforced MMCs have excellent mechanical properties but often fail in fatigue without the presence of a stable fatal crack. Rather, it appears that microcracks join up shortly before fracture, leading to catastrophic failure. Since the density of microcracks in MMCs is greater than in conventional materials, the nature of this phenomenon must be understood in order to be able to predict service lives in fatigue applications. Histograms of the microcrack length distribution of surface microcracks in an A12124-SiCw composite were plotted as a function of fatigue cycles. By fitting the data to commonly used distribution factors, it was found that the Weibull distribution gave the best fit. This is because it fits the tail of the distribution and is useful in estimating the weakest flaw or shortest time to failure. Graphs, photomicrographs. 18 ref.
The effects of ductile reinforcement morphology on the mechanical behaviour of MoSi2 reinforced with 20 vol.% niobium are presented. While all the composites exhibit improved fracture toughness relative to the monolithic MoSi2, the most significant improvement is obtained in the composite with laminate reinforcement, followed by coarse fibre, fine fibre and particulate reinforcements. Bend strength measurements indicate a ductile-brittle transition temperature of approx. 1250 °C, and highlight the attractive properties of laminate-reinforced composites. Preliminary studies of room-temperature fatigue crack growth in particular reinforced composites show a stable fatigue crack growth, which is not achieved in monolithic MoSi2. Possible ways of achieving a better combination of mechanical properties are also discussed. Photomicrographs, graphs, 18 ref. Fracture and fatigue resistance of Ag/Ta-coated SCS-6/Ti3AI composites. Chiu, H.-P. and Yang, J.-M. Proc. Conf. lntermetallic Matrix Composites 111, San Francisco, CA, USA, 4-6 April 1994, pp. 153-158
Fatigue and fracture of nickel aluminide composites. Ramasundaram, P., Bowman, R. and Soboyejo, W. Proc. Conf. lntermetaUic Matrix Composites 111, San Francisco, CA, USA, 4-6 April 1994, pp. 225-230
The effect of an Ag/Ta coating on the fracture resistance of a notched SCS6 fibre-reinforced Ti3AI matrix composite under both static and fatigue loading was investigated. The crack propagation patterns and damage mechanisms under various loading conditions were characterized and compared with the uncoated composite counterparts. The results show that the Ag/Tacoated composites exhibit typical mode I failure patterns under both static and fatigue loading, while mixed mode I and II failure patterns were observed in the uncoated SCS-6/Ti-25-10 composite. Localized interfacial debonding, matrix cracking and fibre fracture in the crack wake were the responsible damage mechanisms for the Ag/Ta-coated SCS-6/Ti-25-10 composite. Extensive interfacial debonding, crack splitting and branching, however, were found to be the dominant mechanisms in the uncoated SCS-6/Ti-25-10 composite. Photomicrographs, graphs, 9 ref.
The results of preliminary investigations of the room-temperature fatigue and fracture mechanisms in model NiAI composites are presented. The composite systems studied include NiAl reinforced with: ductile second-phase particles (molybdenum); ductile fibres (Mo); brittle second-phase particles (zirconia partially stabilized with yttria); and brittle fibres + particles (AI203+ zirconia). Mechanisms of fatigue crack growth in heat-treated specimens of the fibrereinforced composites are also elucidated. The investigations indicate that both ductile and brittle reinforcements can enhance the toughness of NiAl significantly, and the ductile-phase particulate reinforcement may even contribute to room-temperature ductility in the composite. Photomicrographs, 8 ref.
Issues in potential IMC application for aerospace structures. Ward, C.H. and Culbertson, A.S. Proc. Conf. lntermetallic Matrix Composites 1ll, San Francisco, CA, USA, 4-6 April 1994, pp. 3-11
Thermal fatigue of MoSi2 particulate and short fiber composites. Kush, M.T., Holmes, J.W. and Gibala, R. Proc. Conf. lntermetallic Matrix Composites 111, San Francisco, CA USA, 4-6 April 1994, pp. 189-194
Intermetallic matrix composites (IMCs) are intended for applications involving higher temperatures and stresses than conventional metallic matrix composites. Consequently, environmental effects, thermomechanical fatigue, interfaeial thermodynamic stability, creep resistance, processing and cost are only a few of the obstacles to introduction in real products. The primary goal of current IMC development efforts is to provide revolutionary materials for components that are enabling technologies in advanced demonstrator gas turbine engines. As compared with production applications, the hurdles for entry into demonstrator engine programmes are not as high, owing to the limited operating time and the small number of parts to be produced. This paper examines the barriers to the introduction of IMCs in the context of application to production aerospace structures. 20 ref.
Induction heating of disk-shaped specimens was used to compare and contrast the thermal fatigue behaviour of MoSi2 and MoSi2-based composites. Specimens were subjected to 5 s heating and cooling cycles between temperature limits of 700 and 1200 °C. The monolithic material and an MoSi2-10 vol.% TiC composite exhibited poor thermal shock resistance and could not be thermally cycled according to this temperature-time profile. A 30 vol.% TiC composite exhibited much better thermal shock and thermal fatigue resistance as compared with the monolithic material, but exhibited undesirable oxidation. MoSi2-10 and 30 vol.% SiC particulate composites exhibited excellent thermal shock and thermal fatigue resistance compared with that of the monolithic material. An MoSi2-10 vol.% SiC whisker composite did not show improved thermal fatigue resistance, owing to the initial processsing defects present in the material. The monolithic material and the 10 vol.% TiC composite were also subjected to 30 s heating and cooling cycles between temperature limits of 700 and 1200 °(2. Both of these materials exhibited better thermal fatigue resistance at this temperature-time profile, but the 10 vol.% TiC composite also exhibited undesirable oxidation. The fatigue results are discussed with reference to the initial microstructure of the specimens and the stress-strain history of the specimens, which was obtained by a thermoelastic finite element analysis. Graphs, photomicrographs, 8 ref.
Inordinate failures of rotating biological contractor (RBC) drive shafts in wastewater treatment plant service worldwide. Ross, B., Lange, C. and Barrett, R. Int. J. Pressure Vessels Piping (1994) 59 (1-3), 197-209 The rotating biological contactor (RBC) concept for wastewater treatment plants was first patented at the turn of the century but not implemented in commercial practice until the 1960s. The actual equipment designed, built and operated during an almost two-decade period experienced exceptionally
447
Fatigue Abstracts This section contains abstracts of selected articles, technical reports, dissertations and patents concerned with fatigue. It is prepared in collaboration with Materials Information, a joint service of The Institute of Materials and ASM International. Readers wishing to obtain the full text of articles abstracted here should contact either: The Institute of Materials, 1 Carlton House Terrace, London SWlY 5DB, UK, or: ASM International, Metals Park, OH 44073, USA (not International Journal of Fatigue). The fees charged for photocopying articles are £7.00 for the first ten pages and £3.00 per additional ten pages (UK office), or $10.00 for the first ten pages and $4.00 per additional ten pages (US office).
Distribution of fatigue microcracks in an aluminum-matrix silicon carbide whisker composite. Chen, E.Y., Lawson, L. and Menhii, M. Scr. Metall. Mater. (15 March 1994) 30 (6), 737-742
Ductile phase toughening of MoSi2 effect of reinforcement morphology. Chen, L.-C., Bahtishi, N., Lederich, R. and Soboyejo, W. Proc. Conf. lntermetallic Matrix Composites 111, San Francisco, CA, USA, 4-6 April 1994, pp. 183-188
Discontinuously reinforced MMCs have excellent mechanical properties but often fail in fatigue without the presence of a stable fatal crack. Rather, it appears that microcracks join up shortly before fracture, leading to catastrophic failure. Since the density of microcracks in MMCs is greater than in conventional materials, the nature of this phenomenon must be understood in order to be able to predict service lives in fatigue applications. Histograms of the microcrack length distribution of surface microcracks in an A12124-SiCw composite were plotted as a function of fatigue cycles. By fitting the data to commonly used distribution factors, it was found that the Weibull distribution gave the best fit. This is because it fits the tail of the distribution and is useful in estimating the weakest flaw or shortest time to failure. Graphs, photomicrographs. 18 ref.
The effects of ductile reinforcement morphology on the mechanical behaviour of MoSi2 reinforced with 20 vol.% niobium are presented. While all the composites exhibit improved fracture toughness relative to the monolithic MoSi2, the most significant improvement is obtained in the composite with laminate reinforcement, followed by coarse fibre, fine fibre and particulate reinforcements. Bend strength measurements indicate a ductile-brittle transition temperature of approx. 1250 °C, and highlight the attractive properties of laminate-reinforced composites. Preliminary studies of room-temperature fatigue crack growth in particular reinforced composites show a stable fatigue crack growth, which is not achieved in monolithic MoSi2. Possible ways of achieving a better combination of mechanical properties are also discussed. Photomicrographs, graphs, 18 ref. Fracture and fatigue resistance of Ag/Ta-coated SCS-6/Ti3AI composites. Chiu, H.-P. and Yang, J.-M. Proc. Conf. lntermetallic Matrix Composites 111, San Francisco, CA, USA, 4-6 April 1994, pp. 153-158
Fatigue and fracture of nickel aluminide composites. Ramasundaram, P., Bowman, R. and Soboyejo, W. Proc. Conf. lntermetaUic Matrix Composites 111, San Francisco, CA, USA, 4-6 April 1994, pp. 225-230
The effect of an Ag/Ta coating on the fracture resistance of a notched SCS6 fibre-reinforced Ti3AI matrix composite under both static and fatigue loading was investigated. The crack propagation patterns and damage mechanisms under various loading conditions were characterized and compared with the uncoated composite counterparts. The results show that the Ag/Tacoated composites exhibit typical mode I failure patterns under both static and fatigue loading, while mixed mode I and II failure patterns were observed in the uncoated SCS-6/Ti-25-10 composite. Localized interfacial debonding, matrix cracking and fibre fracture in the crack wake were the responsible damage mechanisms for the Ag/Ta-coated SCS-6/Ti-25-10 composite. Extensive interfacial debonding, crack splitting and branching, however, were found to be the dominant mechanisms in the uncoated SCS-6/Ti-25-10 composite. Photomicrographs, graphs, 9 ref.
The results of preliminary investigations of the room-temperature fatigue and fracture mechanisms in model NiAI composites are presented. The composite systems studied include NiAl reinforced with: ductile second-phase particles (molybdenum); ductile fibres (Mo); brittle second-phase particles (zirconia partially stabilized with yttria); and brittle fibres + particles (AI203+ zirconia). Mechanisms of fatigue crack growth in heat-treated specimens of the fibrereinforced composites are also elucidated. The investigations indicate that both ductile and brittle reinforcements can enhance the toughness of NiAl significantly, and the ductile-phase particulate reinforcement may even contribute to room-temperature ductility in the composite. Photomicrographs, 8 ref.
Issues in potential IMC application for aerospace structures. Ward, C.H. and Culbertson, A.S. Proc. Conf. lntermetallic Matrix Composites 1ll, San Francisco, CA, USA, 4-6 April 1994, pp. 3-11
Thermal fatigue of MoSi2 particulate and short fiber composites. Kush, M.T., Holmes, J.W. and Gibala, R. Proc. Conf. lntermetallic Matrix Composites 111, San Francisco, CA USA, 4-6 April 1994, pp. 189-194
Intermetallic matrix composites (IMCs) are intended for applications involving higher temperatures and stresses than conventional metallic matrix composites. Consequently, environmental effects, thermomechanical fatigue, interfaeial thermodynamic stability, creep resistance, processing and cost are only a few of the obstacles to introduction in real products. The primary goal of current IMC development efforts is to provide revolutionary materials for components that are enabling technologies in advanced demonstrator gas turbine engines. As compared with production applications, the hurdles for entry into demonstrator engine programmes are not as high, owing to the limited operating time and the small number of parts to be produced. This paper examines the barriers to the introduction of IMCs in the context of application to production aerospace structures. 20 ref.
Induction heating of disk-shaped specimens was used to compare and contrast the thermal fatigue behaviour of MoSi2 and MoSi2-based composites. Specimens were subjected to 5 s heating and cooling cycles between temperature limits of 700 and 1200 °C. The monolithic material and an MoSi2-10 vol.% TiC composite exhibited poor thermal shock resistance and could not be thermally cycled according to this temperature-time profile. A 30 vol.% TiC composite exhibited much better thermal shock and thermal fatigue resistance as compared with the monolithic material, but exhibited undesirable oxidation. MoSi2-10 and 30 vol.% SiC particulate composites exhibited excellent thermal shock and thermal fatigue resistance compared with that of the monolithic material. An MoSi2-10 vol.% SiC whisker composite did not show improved thermal fatigue resistance, owing to the initial processsing defects present in the material. The monolithic material and the 10 vol.% TiC composite were also subjected to 30 s heating and cooling cycles between temperature limits of 700 and 1200 °(2. Both of these materials exhibited better thermal fatigue resistance at this temperature-time profile, but the 10 vol.% TiC composite also exhibited undesirable oxidation. The fatigue results are discussed with reference to the initial microstructure of the specimens and the stress-strain history of the specimens, which was obtained by a thermoelastic finite element analysis. Graphs, photomicrographs, 8 ref.
Inordinate failures of rotating biological contractor (RBC) drive shafts in wastewater treatment plant service worldwide. Ross, B., Lange, C. and Barrett, R. Int. J. Pressure Vessels Piping (1994) 59 (1-3), 197-209 The rotating biological contactor (RBC) concept for wastewater treatment plants was first patented at the turn of the century but not implemented in commercial practice until the 1960s. The actual equipment designed, built and operated during an almost two-decade period experienced exceptionally
447