Fracture Mechanisms in NiAlCr Eutectic Composites

1992 ◽  
Vol 273 ◽  
Author(s):  
Keh-Minn Chang
Keyword(s):  
Fracture Toughness ◽  
Fracture Resistance ◽  
Fracture Behavior ◽  
Room Temperature ◽  
Ternary Systems ◽  
Fracture Mechanisms ◽  
Fracture Properties ◽  
Intermetallic Matrix ◽  
Binary Eutectic ◽  
Ternary Eutectics

ABSTRACTSelected eutectic compositions in Ni-Al-Cr ternary systems were processed by directional solidification (DS) with various growth rates. Fracture toughness tests were performed at room temperature and 400 °C; fracture surfaces of broken specimens were examined using SEM to investigate fracture behavior of each alloy. The alignment of eutectic phases was found to play an important role in composite toughening for the intermetallic matrix. Binary eutectic composites consisting of bcc α-Cr and B2 β-NiAl phases with a directional, well-aligned structure showed improved fracture properties over NiAl single crystals. Ternary eutectics, which contain an fcc γ-Ni phase, offered an excellent fracture resistance at room temperature.

TiAl Intermetallics for Aerospace Applications: Fracture Resistance and Cracking Mechanisms

2009 ◽  
Author(s):  
Amar N. Kumar ◽  
Amiya Nayak ◽  
Alka Srivastava ◽  
Udit K. Roy ◽  
Prakash C. Patnaik
Keyword(s):  
Fracture Toughness ◽  
Crack Growth ◽  
Fracture Resistance ◽  
Room Temperature ◽  
Lamellar Microstructure ◽  
Crack Size ◽  
Crack Growth Resistance ◽  
Size Analysis ◽  
Fracture Mechanisms ◽  
Cracking Mechanisms

Research on TiAl aluminides has been undertaken to further advance the understanding of deformation and fracture mechanisms, vis-a`-vis the heat treatment effects on microstructure, fracture resistance and cracking mechanisms. Two TiAl grades considered comprise of Al-Nb-Mn-Cr-Bal Ti with two different microstructures, namely duplex and lamellar types. The size of colonies in fully lamellar structure also varied widely from 50 micron to 700 microns. Fracture toughness and crack growth resistance are studied under three point bend loading of SEN specimens at room temperature and at higher temperatures (700 °C and 900°C). The fracture resistance behavior for the intermetallics is studied following two methods, namely fracture toughness and crack growth resistance curves (KI vs. Δa). An appreciable improvement (around 50 percent) at 700°C is observed as compared to room temperature data. The crack size analysis is done by elastic compliance method and a normalized compliance curve (NCC) with a power law function for the aluminides is obtained irrespective of temperature. The mechanism of crack initiation as well as crack growth in different microstructures of the alloy is looked into to get an insight of the deformation and cracking process. In lamellar microstructure, colony boundaries appear to be the most preferred path for the crack growth, while multiple cracking mechanisms is observed in duplex structure.

scholarly journals Fracture Behavior of Bio-Inspired Functionally Graded Soft–Hard Composites Made by Multi-Material 3D Printing: The Case of Colinear Cracks

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2735 ◽  
Author(s):  
Mirzaali ◽  
Nava ◽  
Gunashekar ◽  
Nouri-Goushki ◽  
Doubrovski ◽  
...  
Keyword(s):  
3D Printing ◽  
Transition Zone ◽  
Digital Image ◽  
Fracture Resistance ◽  
Fracture Behavior ◽  
Functionally Graded ◽  
Image Correlation ◽  
High Tech ◽  
Fracture Properties ◽  
Gradient Function

The functional gradient is a concept often occurring in nature. This concept can be implemented in the design and fabrication of advanced materials with specific functionalities and properties. Functionally graded materials (FGMs) can effectively eliminate the interface problems in extremely hard–soft connections, and, thus, have numerous and diverse applications in high-tech industries, such as those in biomedical and aerospace fields. Here, using voxel-based multi-material additive manufacturing (AM, = 3D printing) techniques, which works on the basis of material jetting, we studied the fracture behavior of functionally graded soft–hard composites with a pre-existing crack colinear with the gradient direction. We designed, additively manufactured, and mechanically tested the two main types of functionally graded composites, namely, composites with step-wise and continuous gradients. In addition, we changed the length of the transition zone between the hard and soft materials such that it covered 5%, 25%, 50%, or 100% of the width (W) of the specimens. The results showed that except for the fracture strain, the fracture properties of the graded specimens decreased as the length of the transition zone increased. Additionally, it was found that specimens with abrupt hard–soft transitions have significantly better fracture properties than those with continuous gradients. Among the composites with gradients, those with step-wise gradients showed a slightly better fracture resistance compared to those with continuous gradients. In contrast, FGMs with continuous gradients showed higher values of elastic stiffness and fracture energy, which makes each gradient function suitable for different loading scenarios. Moreover, regardless of the gradient function used in the design of the specimens, decreasing the length of the transition zone from 100%W to 5%W increased the fracture resistance of FGMs. We discuss the important underlying fracture mechanisms using data collected from digital image correlation (DIC), digital image microscopy, and scanning electron microscopy (SEM), which were used to analyze the fracture surface.

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.

Fracture Toughness of Aged Stainless Steel Primary Piping and Reactor Vessel Materials

1987 ◽  
Vol 109 (4) ◽  
pp. 440-448 ◽  
Author(s):  
W. J. Mills
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Ductile Fracture ◽  
Thermal Aging ◽  
Fracture Resistance ◽  
Reactor Vessel ◽  
Initiation Toughness ◽  
Second Phase ◽  
Premature Failure ◽  
Fracture Properties

The ductile fracture toughness behavior of FFTF primary piping and reactor vessel construction materials was characterized using the multiple-specimen JR-curve technique before and after 10,000-hr thermal aging treatments. The test materials included Types 304 and 316 stainless steel (SS) and Types 308 and 16–8–2 SS welds. In the unaged condition, these alloys exhibited very high Jc initiation toughness and tearing modulus values at elevated temperatures (427–538°C). The fracture resistance for the 316 SS piping was found to be dependent on orientation; Jc values for the axial (C–L) direction were 60 to 70 percent lower than those for the circumferential (L–C) orientation. The lower fracture properties in the C–L orientation resulted from premature failure of stringers aligned in the axial direction. Thermal aging at 427° C caused no degradation in fracture resistance, while 482 and 566° C agings resulted in a modest 10 to 20 percent reduction in Jc for both base and weld metals. Residual toughness levels after aging are adequate for precluding any possibility of nonductile fracture. Hence, conventional stress and strain limits, such as those provided by the ASME Code, are sufficient to guard against ductile fracture for SS components that have accumulated 10,000-hr exposures at or below 566° C. Metallographic and fractographic examinations revealed that the degradation in fracture properties was associated with aging-induced second-phase precipitation.

Microstructures and Interfaces in Melt-Growth Al2O3-Ln2O3 Based Eutectic Composites

2006 ◽  
Vol 45 ◽  
pp. 1377-1384 ◽  
Author(s):  
Léo Mazerolles ◽  
N. Piquet ◽  
M.F. Trichet ◽  
Michel Parlier
Keyword(s):  
Fracture Toughness ◽  
Single Crystal ◽  
Room Temperature ◽  
Eutectic Composition ◽  
High Strength ◽  
Ternary Systems ◽  
Growth Conditions ◽  
Temperature Influence ◽  
Directionally Solidified ◽  
Orientation Relationships

Directionally solidified oxide eutectic ceramics were prepared from Al2O3, Ln2O3 and ZrO2 based binary or ternary systems. Their microstructures consist of continuous networks of single-crystal Al2O3 and oxide compounds (LnAlO3, Ln3Al5O12) which interpenetrate without grain boundaries. The outstanding stability of these microstructures gives rise to a high strength and creep resistance at high temperature. Influence of growth conditions on the morphology of the as-obtained microstructures was studied. Preferred growth directions, orientation relationships between phases and single-crystal homogeneity of specimen were revealed. Low residual stresses were measured in the binary eutectics and fracture toughness at room temperature was improved by the addition of zirconia at a eutectic composition in ternary systems.

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.

Fracture Behavior of Polypropylene /Elastomer Blends

2008 ◽  
Vol 47-50 ◽  
pp. 278-281 ◽  
Author(s):  
M. Hernández ◽  
M.N. Ichazo ◽  
J. González ◽  
C. Albano ◽  
Orlando Santana
Keyword(s):  
Fracture Toughness ◽  
Plastic Deformation ◽  
Energy Dissipation ◽  
Fracture Resistance ◽  
Fracture Behavior ◽  
Thermoplastic Elastomer ◽  
Test Results ◽  
Essential Work ◽  
Dynamic Vulcanization ◽  
Injection Molded

In this paper, effort has been undertaken to study the fracture behavior of thermoplastic/elastomer (PP/SBS) dynamically vulcanized blends by analyzing the EWF test results. PP/SBS blends were prepared with concentrations of SBS of 15, 30 and 40 wt%. Deeply double edged notched tension (DDENT) specimens were cut from injection molded plaques for fracture testing. It should be noted that the incorporation of SBS to PP seems to enhance fracture toughness, thus the specific essential work (we) increases with elastomer content. The elastomer particles contribute to the energy dissipation at the fracture surface and in the outer plastic zone in which various types of deformation might have been at work. Also, it seems that the fracture toughness value levels-off from 30 wt% rubber on. In addition, the incorporation of SBS triggers a considerable plastic deformation, since the non-essential work ( βwp) increases compared to the value of pure PP. Nonetheless, a decrease in βwp is present with increasing amount of rubber. So the EWF method revealed that the dynamic vulcanization method can impair fracture resistance to PP/SBS blends.

J-R Fracture Toughness of Nuclear Piping Materials Under Excessive Seismic Loading Condition

2016 ◽  
Author(s):  
Jin Weon Kim ◽  
Myung Rak Choi ◽  
Sang Bong Lee ◽  
Yun Jae Kim
Keyword(s):  
Fracture Toughness ◽  
Cyclic Loading ◽  
Fracture Resistance ◽  
Cyclic Load ◽  
Fracture Behavior ◽  
Loading Rate ◽  
Seismic Loading ◽  
Monotonic Loading ◽  
Rate Effect ◽  
Loading Conditions

This study investigated the loading rate effect on the fracture resistance under cyclic loading conditions to clearly understand the fracture behavior of piping materials under excessive seismic conditions. J-R fracture toughness tests were conducted under monotonic and cyclic loading conditions at various displacement rates at room temperature (RT) and the operating temperature of nuclear power plants (NPPs), i.e., 316°C. SA508 Gr. 1a lo w-alloy steel (LAS) and SA312 TP316 stainless steel (SS) piping materials were used for the tests. The fracture resistance under a reversible cyclic load was considerably lower than that under monotonic load regardless of test temperature, material, and loading rate. Under both cyclic and monotonic loading conditions, the fracture behavior of SA312 TP316 SS was independent of the loading rate at both RT and 316°C. For SA508 Gr. 1a LAS, the loading rate effect on the fracture behavior was appreciable at 316°C under both cyclic and monotonic loading conditions. However, the loading rate effect diminished when the cyclic load ratio (R) was −1. Thus, it was recognized that the fracture behavior of piping materials, including seismic loading characteristics, can be evaluated when tested under a cyclic load of R = −1 at a quasi-static loading rate.

Study on Fracture Behavior of γ-TiAl Based Alloys

2007 ◽  
Vol 546-549 ◽  
pp. 1437-1442 ◽  
Author(s):  
Rui Cao ◽  
Jian Hong Chen ◽  
J. Zhang
Keyword(s):  
Fracture Toughness ◽  
Main Crack ◽  
Fracture Behavior ◽  
Fracture Mechanisms ◽  
Narrow Strip ◽  
Tial Alloys ◽  
Notched Specimen ◽  
Crack Tips ◽  
Fully Lamellar ◽  
Crack Bifurcation

Fracture behavior of fully lamellar (FL) and duplex phase (DP) TiAl alloys is reported in this paper. It was found that the inverse behavior of coarse FL TiAl alloy showing inferior tensile properties but superior fracture toughness resulted from the different fracture mechanisms of these two types’ tests. In tensile specimens, the final fracture happened at a section that was most heavily damaged by the accumulation of large interlamellar microcracks and arbitrarily located within the gauge-limited volume. In 3PB notch specimens, the propagation of the main crack was constrained within a narrow strip nearby the centerline where the normal stress was the highest. Large lamellar grains caused serious damage in tensile tested specimens. However multi-oriented large lamellar grains formed seriously bifurcated crack tips, which made the crack propagation more difficult in 3PB notched specimen. The main mechanisms of toughening in FL specimens were the deflection of main crack, bifurcation and blunting of crack tip and formation of a diffuse zone of microcracks. These phenomena reduced the driving force for crack extending and then increased the fracture toughness.

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.

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