Solidification Processing and Fracture Behavior of RuAl-Based Alloys

2004 ◽  
Vol 842 ◽  
Author(s):  
Todd Reynolds ◽  
David Johnson
Keyword(s):  
Solid Solution ◽  
Fracture Toughness ◽  
Fracture Behavior ◽  
Room Temperature ◽  
Volume Fraction ◽  
Solidification Processing ◽  
Ductile Phase

ABSTRACTAlloys of RuAl-Ru were processed using various solidification methods, and the fracture behavior was examined. The fracture toughness values for RuAl-hcp(Ru, Mo) and RuAl-hcp(Ru, Cr) alloys ranged from 23 to 38 MPa√m, while the volume fraction of RuAl ranged from 22 to 56 percent. Increasing the volume fraction of RuAl resulted in a decrease in fracture toughness. The hcp solid solution was shown to be the more ductile phase with a fracture toughness approaching 68 MPa?m, while the B2 solid solution (RuAl) was found to have a fracture toughness less than 13 MPa√m. An alloy of Ru-7Al-38Cr (at.%) that consisted of a hcp matrix with RuAl precipitates had the highest room temperature toughness and the greatest hardness.

Effect of Ternary Alloying Elements on Microstructure and Mechanical Property of Nb-Si Based Refractory Intermetallic Alloy

2005 ◽  
Vol 486-487 ◽  
pp. 342-345 ◽  
Author(s):  
Won Yong Kim ◽  
Han Sol Kim ◽  
Shae K. Kim ◽  
Tae Yeub Ra ◽  
Mok Soon Kim
Keyword(s):  
Mechanical Property ◽  
Solid Solution ◽  
Fracture Toughness ◽  
Yield Strength ◽  
Room Temperature ◽  
Volume Fraction ◽  
Alloying Elements ◽  
Fracture Toughness Test ◽  
Ternary Alloying ◽  
Microstructure And Mechanical Property

Microstructure and mechanical property at room temperature and at 1773 K of Nb-Si based refractory intermetallic alloys were investigated in terms of compression and fracture toughness test. Mo and V were chosen as ternary alloying elements because of their high melting points, atomic sizes smaller than Nb. Both ternary alloying elements were found to have a significant role in modifying the microstructure from dispersed structure to eutectic-like structure in Nb solid solution/Nb5Si3 intermetallic composites. The 0.2% offset yield strength at room temperature increased with increasing content of ternary elements in Nb solid solution and volume fraction of Nb5Si3. At 1773 K, Mo addition has a positive role in increasing the yield strength. On the other hand, V addition has a role in decreasing the yield strength. The fracture toughness of ternary alloys was superior to binary alloys. Details will be discussed in correlation with ternary alloying, volume fraction of constituent phase, and the microstructure.

Unusual fracture behavior of nanoporous polymeric thin-films

2005 ◽  
Vol 880 ◽  
Author(s):  
Andrew V. Kearney ◽  
Reinhold H. Dauskardt ◽  
Carol E. Mohler ◽  
Michael E. Mills
Keyword(s):  
Fracture Toughness ◽  
Pore Size ◽  
Fracture Resistance ◽  
Fracture Behavior ◽  
Volume Fraction ◽  
Porous Solids ◽  
Void Size ◽  
Polymeric Thin Films ◽  
Arylene Ether ◽  
Ductile Polymer

AbstractWe present surprising evidence that the fracture resistance of porous forms of poly(arylene) ether (PAE) films exhibit increasing fracture resistance with increasing porosity. Such behavior is in stark contrast to the fracture toughness of porous solids, which typically decrease markedly with increasing porosity. A fracture mechanics based model is presented to rationalize the increase in fracture toughness of the voided polymer film and explain the behavior in terms of the pore size and volume fraction. It is shown that a certain dependence of pore size and volume fraction is required to increase rather than decrease the fracture resistance. The research has implications for the optimum void size and volume fraction needed to enhance the fracture resistance of porous ductile polymer films.

Development of Tough and Strong Cubic Titanium Trialuminides

2000 ◽  
Vol 646 ◽  
Author(s):  
Robert A. Varin ◽  
Les Zbroniec ◽  
Zhi Gang Wang
Keyword(s):  
Fracture Toughness ◽  
Fracture Behavior ◽  
Room Temperature ◽  
Fold Increase ◽  
Strength Increase ◽  
Solid Solution Strengthening ◽  
Boron Doped ◽  
Temperature Fracture ◽  
Solution Strengthening ◽  
B Doping

ABSTRACTIn this work, the recent breakthroughs in the understanding of the fracture behavior and fracture toughness of L12-ordered titanium trialuminides are described and discussed. First, it is shown that, as opposed to many other intermetallics and specifically those with an L12 crystal structure, the fracture toughness of L12 titanium trialuminides is insensitive to testing in various environments such as air, water, argon, oxygen and vacuum (∼1.3×10–5 Pa). Second, it is reported here that by increasing the concentration of Ti combined with boron (B) doping, the room temperature fracture toughness of a Mn-stabilized titanium trialuminide can be improved by 100% from ∼4 MPam1/2 to ∼8 MPam1/2 and by 150–250% at 1000°C to ∼(10–12) MPam1/2 with a simultaneous suppression of intergranular fracture (IGF) to ∼(40–50%). Almost three fold increase in yield strength to ∼550 MPa is attained at room temperature for high Ti, boron-doped trialuminides. Both Vickers microhardness and strength increase linearly with increasing concentration of (Ti+B) indicating a classical solid solution strengthening response.

On the Mechanisms of Ductility Enhancement in β+γ′- Ni70Al30 and β+(γ+γ)-Ni50Fe30Al20In Situ Composites

1992 ◽  
Vol 273 ◽  
Author(s):  
A. Misra ◽  
R. D. Noebe ◽  
R. Gibala
Keyword(s):  
Room Temperature ◽  
Volume Fraction ◽  
Tensile Ductility ◽  
Nominal Composition ◽  
Substantial Portion ◽  
Directionally Solidified ◽  
Ductile Phase ◽  
Room Temperature Ductility ◽  
Slip Transfer ◽  
Slip Traces

ABSTRACTDuctile phase reinforcement is an attractive approach for improving room temperature ductility and toughness of intermetallics. Two alloys of nominal composition (at.%) Ni70Al30 and Ni50Fe30Al20 were directionally solidified to produce quasi-lamellar microstructures. Both alloys exhibit ∼10% tensile ductility at 300 K when the ductile phase is continuous, while the Ni70Al30 alloy has a tensile ductility of ∼4% when the γ′ phase is discontinuous. Observations of slip traces and dislocation substructures indicate that a substantial portion of the ductility enhancement is a result of slip transfer from the ductile phase to the brittle matrix. The details of slip transfer in the two model materials and the effect of the volume fraction and morphology of the ductile phase on the ductility enhancement in the composite are discussed.

Mechanical Properties of SiC/FexSiy Composites

2011 ◽  
Vol 236-238 ◽  
pp. 1523-1527 ◽  
Author(s):  
Xiao Meng Zhang ◽  
Shu Feng Ye ◽  
Li Hua Xu ◽  
Peng Qian ◽  
Lian Qi Wei ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
Flexural Strength ◽  
Fracture Behavior ◽  
Room Temperature ◽  
Sintering Temperature ◽  
Raw Material ◽  
Reaction Sintering ◽  
Sintering Process ◽  
Scanning Electron

The SiC/FexSiycomposites were synthesized by reaction sintering process with iron tailings as raw material and carbon as reductant. The room and high temperature flexural strengths and fracture toughness of composites were studied in this paper. Fracture surfaces were observed by means of a scanning electron microscope (SEM). The results showed that the room temperature flexural strength of SiC/FexSiycomposites changed along with the different contents of FexSiyand sintering temperature. The flexural strength of composites reaches the maximum at 900°C. The correlation between flexural strength and temperature is consistent with curveⅠ.The fracture toughness of composites is related to the content of FexSiy. The fracture behavior of composites is mainly transcrystalline in room temperature and intercrystalline in high temperature.

Microstructure and Mechanical Properties of Sm1-xSrxCo0.2Fe0.8O3

2000 ◽  
Vol 15 (7) ◽  
pp. 1505-1513 ◽  
Author(s):  
Y-S. Chou ◽  
J. W. Stevenson ◽  
T. R. Armstrong ◽  
J. S. Hardy ◽  
K. Hasinska ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Fracture Behavior ◽  
Room Temperature ◽  
Indentation Fracture ◽  
Flexure Strength ◽  
Indentation Toughness ◽  
Indentation Fracture Toughness ◽  
Microhardness Indentation ◽  
Biaxial Flexure

The room temperature mechanical properties of a mixed conducting perovskite Sm1?xSrxCo0.2Fe0.8O3 (x = 0.2 to 0.8) were examined. Density, crystal phase, and microstructure were characterized. It was found that the grain size increased abruptly with increasing Sr content. Mechanical properties of elastic modulus, microhardness, indentation fracture toughness, and biaxial flexure strength were measured. Young's modulus of 180–193 GPa and shear modulus of 70–75 GPa were determined. The biaxial flexure strength was found to decrease with increasing Sr content from ∼70 to ∼20 MPa. The drop in strength was due to the occurrence of extensive cracking. Indentation toughness showed a similar trend to the strength in that it decreased with increasing Sr content from ∼1.1 to ∼0.7 MPa m1/2. In addition, fractography was used to characterize the fracture behavior in these materials.

Effects of Hydride Morphology and Test Temperature on Fracture Toughness of Zr-2.5Nb Pressure Tube Material

2009 ◽  
Author(s):  
Jun Cui ◽  
Gordon K. Shek
Keyword(s):  
Fracture Toughness ◽  
Test Temperature ◽  
Fracture Behavior ◽  
Room Temperature ◽  
Fracture Initiation ◽  
Compact Tension ◽  
Pressure Tube ◽  
Primary Coolant ◽  
Tube Section ◽  
Pressure Tubes

CANDU® reactor uses Zr-2.5Nb alloy pressure tubes as the primary coolant containment. Fracture toughness properties of the pressure tubes are required for evaluation of fracture initiation and leak-before-break. This paper presents an experimental study on the effects of hydride morphology and test temperature on axial fracture toughness of a cold-worked, unirradiated Zr-2.5Nb pressure tube. Compact tension specimens were prepared from one tube section which contained as-received hydrogen concentration and another section which was electrolytically hydrided to 70 ppm hydrogen. Reoriented hydrides were formed in the hydrided tube section in ten thermal cycles under an applied tensile hoop stress of 160 MPa. The hydride morphologies were characterized by a parameter referred to as the hydride continuity coefficient (HCC), which provided a measure of the extent to which the hydrides were reoriented with respect to the applied stress direction. Partially reoriented hydrides with HCC between 0.3–0.4 were formed under the stress and temperature cycles used to precipitate the hydrides. J-R curves were generated to characterize the fracture behavior of the specimens tested at five different temperatures: 25°C (room temperature), 100°C, 150°C, 200°C and 250°C. Test results indicate that, for the as-received specimens, the fracture toughness is relatively high at room temperature and not significantly affected by the test temperature between room temperature and 250°C. For the 70 ppm hydrided specimens containing partially reoriented hydrides, the fracture toughness is significantly lower than that of the as-received specimens at room temperature. At 100°C, the fracture toughness is higher than that at room temperature but the average value is still lower than that of the as-received specimens. The specimens exhibit either brittle or ductile fracture behavior with a sharp transition to an upper-shelf toughness value. At 150°C, the specimens achieve an upper-shelf toughness level. Between 150°C and 250°C, the fracture toughness is similar to that of the as-received specimens and not affected by the reoriented hydrides.

Microstructures and Properties of Ds in-Situ Composites of Nb-Ti-Si Alloys

1994 ◽  
Vol 364 ◽  
Author(s):  
B. P. Bewlay ◽  
M. R. Jackson ◽  
W. J. Reeder ◽  
H. A. Lipsitt
Keyword(s):  
Mechanical Properties ◽  
Solid Solution ◽  
Fracture Toughness ◽  
Room Temperature ◽  
In Situ Composites ◽  
Environmental Resistance ◽  
High Temperature Mechanical Properties ◽  
Three Phase ◽  
Temperature Fracture

AbstractIn-situ composites based on binary Nb-Si alloys and consisting of a Nb solid solution with Nb3Si or Nb5Si3 have shown a promising combination of low temperature and high temperature mechanical properties. The environmental resistance and room temperature fracture toughness of these composites can be further enhanced by additions such as Ti, Hf, Cr, and Al. In the present study, ternary Nb-Ti-Si alloys were prepared by directional solidification to generate aligned two and three phase composites containing a Nb solid solution with Nb3Si and/or Nb5Si3. The present paper will describe microstructures, phase equilibria and fracture toughness of these composites. The improvement in the room temperature fracture toughness over binary Nb-Nb5Si3 composites is discussed.

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