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1.
Steels containing about 12 pct Cr, 10 pct Mn, and 0.2 pct N have been shown to have an unstable austenitic microstructure
and have good ductility, extreme work hardening, high fracture strength, excellent toughness, good wear resistance, and moderate
corrosion resistance. A series of alloys containing 9.5 to 12.8 pct Cr, 5.0 to 10.4 pct Mn, 0.16 to 0.32 pct N, 0.05 pct C,
and residual elements typical of stainless steels was investigated by microstructural examination and mechanical, abrasion,
and corrosion testing. Microstructures ranged from martensite to unstable austenite. The unstable austenitic steels transformed
to α martensite on deformation and displayed very high work hardening, exceeding that of Hadfield’s manganese steels. Fracture
strengths similar to high carbon martensitic stainless steels were obtained while ductility and toughness values were high,
similar to austenitic stainless steels. Resistance to abrasive wear exceeded that of commercial abrasion resistant steels
and other stainless steels. Corrosion resistance was similar to that of other 12 pct Cr steels. Properties were not much affected
by minor compositional variations or rolled-in nitrogen porosity. In 12 pct Cr-10 pct Mn alloys, ingot porosity was avoided
when nitrogen levels were below 0.19 pet, and austenitic microstructures were obtained when nitrogen levels exceeded 0.14
pct. 相似文献
2.
S. V. Raj J. A. Salem I. E. Locci R. J. Pawlik 《Metallurgical and Materials Transactions A》2002,33(3):597-612
Directionally solidified (DS) Ni-33(at. pct)Al-33Cr-1Mo and Ni-33(at. pct)Al-31Cr-3Mo eutectic alloys were grown at different
rates varying from 7.6 to 508 mm h−1. The microstructures consisted of eutectic colonies with parallel lamellar NiAl/(Cr,Mo) plates for solidification rates at
and below 12.7 mm h−1. Cellular eutectic microstructures were observed at higher solidification rates, where the plates exhibited a radial pattern.
Room-temperature fracture-toughness tests were conducted using a modified ASTM E-399 technique. The average fracture-toughness
values for specimens with planar eutectic and cellular microstructures were about 12 to 15 and 17 MPa
, respectively, for both alloys. However, the Ni-33(at. pct)Al-33Cr-1Mo specimens grown at and above 254 mm h−1 exhibited fracture toughness values of about 8 MPa
due to the presence of short (Cr,Mo) plates. The fracture toughness values for the Ni-33(at. pct)Al-31Cr-3Mo alloy were also
correlated with quantitative microstructural data in an attempt to identify the relevant elements of the microstructure determining
resistance to fracture. A phenomenological fracture model is presented in an attempt to rationalize the present observations. 相似文献
3.
D. Eylon J. A. Hall C. M. Pierce D. L. Ruckle 《Metallurgical and Materials Transactions A》1976,7(11):1817-1826
To establish correlations between microstructure and mechanical properties for the Ti-ll alloy, twelve different combinations
of hot die forging and heat treatment, in the a + 8 and Β phase regions, were investigated. The resulting heat treated forgings
were classified into four distinct categories based on their microstructural appearance. The room temperature tensile, post-creep
tensile, fracture toughness and fatigue crack propagation properties were measured along with creep and low cycle fatigue
at 566‡C. The creep, tensile, fatigue crack propagation and fracture toughness properties, grouped in a manner similar to
the microstructural categories. The fracture appearance and behavior of the cracks during propagation in fatigue and in fracture
toughness tests were examined, and correlations with the microstructure discussed. In the case of the fully transformed acicular
microstructure, it was found that the size and the orientation of colonies of similarly aligned α needles are dominant factors
in the crack behavior.
Formerly a National Research Council Associate, Air Force Materials Laboratory
Formerly with AFML 相似文献
4.
The effect of deformation-induced transformation on the fracture toughness of commercial titanium alloys 总被引:2,自引:0,他引:2
M. Niinomi T. Kobayashi I. Inagaki A. W. Thompson 《Metallurgical and Materials Transactions A》1990,21(6):1733-1744
The effect of deformation-induced transformation of metastableβ phase on the ductility and toughness of four commercial titanium alloys was investigated. Tensile tests, Charpy impact tests,
and both static and dynamic fracture toughness tests were carried out at temperatures between 77 and 473 K on four titanium
alloys containing metastableβ phase. Deformation-inducedα″ (orthorhombic martensite) was observed in an (α + β)-type Ti-6Al-2Sn-4Zr-6Mo alloy. The dynamic fracture toughness of this
alloy increased considerably at 223 K compared to those at other temperatures. In another (α + β)-type Ti-6A1-4V alloy, the
static fracture toughness at 123 K and the dynamic fracture toughness at 223 K were increased considerably by the presence
of deformation-induced martensite compared to those at other temperatures. The strength increased as the temperature decreased
in this alloy. An abnormal elongation of aβ-type alloy, Ti-15V-3Al-3Sn-3Cr, at 123 K was attributed to the mechanical twinning of theβ phase. However, the effect of deformation-induced transformation on the fracture toughness of Ti-3Al-8V-6Cr-4Mo-4Zr alloy
was not observed.
Formerly Visiting Associate Professor, Department of Metallurgical Engineering and Materials Science, Carnegie Mellon University,
Pittsburgh, PA.
Formerly with the Department of Production Systems Engineering, Toyohashi University of Technology. 相似文献
5.
The microstructural changes and grain boundary chemistry of high strength, age hardenable Ni-Cr-Fe alloy, INCONEL * X-750,
have been studied using electron and Auger microscopy following a sequence of thermal treatments in the carbide precipitation
temperature zone of 704 ‡C to 871 ‡C. The thermal treatment consisted of a solution anneal and quench from 1075 ‡C followed
by aging up to 200 hours in this temperature region. An attempt has been made to correlate the microstructural data with Charpy
impact test results, hardness values, and modified Huey Corrosion Test results (ASTM G28-72). Aging was conducted in a vacuum
and in air from which the specimens were cooled at different rates. Aging at 871 ‡C for 50 to 100 hours under both air and
vacuum furnace cooling conditions resulted in increased mechanical strength and corrosion resistance compared with aging at
704 ‡C or 760 ‡C, in which temperature range both apparent fracture toughness and corrosion rate deteriorate. The reprecipitation
of secondary carbides along with a possible 17 phase precipitation upon aging at 871 ‡C for 200 hours under vacuum furnace
cooling resulted in poor corrosion resistance and inferior impact properties. 相似文献
6.
Supertransus processing of TiAl-Based alloys 总被引:2,自引:0,他引:2
G. E. Fuchs 《Metallurgical and Materials Transactions A》1998,29(1):27-36
Fine-grained lamellar microstructures would be expected to exhibit high strength, creep resistance, fracture toughness, and
moderate ductility. High-temperature extrusion was used to produce fine-grained lamellar microstructures in both ingot metallurgy
(I/M) and powder metallurgy (P/M) Ti-48Al-2Nb-2Cr alloys. The effect of processing parameters, such as extrusion temperature
and cooling rate, on the microstructure and properties was determined. In addition, the thermal stability of the microstructure
was evaluated by subsequent heat treatments. Although fine-grained lamellar microstructures were generated in both ingot and
powder metallurgy materials, processing had a significant effect on the microstructure and properties of the resultant materials.
This article is based on a presentation made in the symposium “Fundamentals of Gamma Titanium Aluminides,” presented at the
TMS Annual Meeting, February 10–12, 1997, Orlando, Florida, under the auspices of the ASM/MSD Flow & Fracture and Phase Transformations
Committees. 相似文献
7.
The fatigue and fracture resistance of a TiAl alloy, Ti-47Al-2Nb-2Cr, with 0.2 at. pct boron addition was studied by performing
tensile, fracture toughness, and fatigue crack growth tests. The material was heat treated to exhibit a fine-grained, fully
lamellar microstructure with approximately 150-μm grain size and 1-μm lamellae spacing. Conventional tensile tests were conducted as a function of temperature to define the brittle-to-ductile
transition temperature (BDTT), while fracture and fatigue tests were performed at 25 °C and 815 °C. Fracture toughness tests
were performed inside a scanning electron microscope (SEM) equipped with a high-temperature loading stage, as well as using
ASTM standard techniques. Fatigue crack growth of large and small cracks was studied in air using conventional methods and
by testing inside the SEM. Fatigue and fracture mechanisms in the fine-grained, fully lamellar microstructure were identified
and correlated with the corresponding properties. The results showed that the lamellar TiAl alloy exhibited moderate fracture
toughness and fatigue crack growth resistance, despite low tensile ductility. The sources of ductility, fracture toughness,
and fatigue resistance were identified and related to pertinent microstructural variables. 相似文献
8.
9.
The influence of strain rate and environment on the fracture behavior of a two-phase TiAl-alloy, Ti-47Al-2.6Nb-2(Cr + V),
heat-treated to a nearly fully lamellar microstructure has been studied by performing conventional tensile, compression, and
fracture toughness tests in air, argon, and vacuum at 25 °C and 800 °C. Both tensile and compression tests were conducted
at strain rates of 1 × 10−3 and 1 × 10−5 s−1, and fracture toughness tests were performed under displacement rates of 0.25 to 2.5 mm/min. In addition,in situ fracture toughness tests were conducted at slow rates both in vacuum and in air. The results indicated that both strain rate
and environment affected the tensile stress-strain behavior and ductility and the fracture resistance of the TiAl-alloy at
800 °C. In contrast, neither the tensile ductility nor the fracture toughness was significantly affected by the environment
at ambient temperature. For compression in air, the stress-strain behavior was insensitive to both strain rate and test temperature
within the conditions tested. Studies of fracture surfaces revealed that low tensile ductility in this alloy at ambient temperature
is associated with the tendency to delaminate alongγ/γ andγ/α
2 interfaces.
formerly with Metcut-Materials Research Group, Wright-Patterson AFB, Dayton, OH 45433-0511 相似文献
10.
D. Eylon J. A. Hall C. M. Pierce D. L. Ruckle 《Metallurgical and Materials Transactions A》1976,7(12):1817-1826
To establish correlations between microstructure and mechanical properties for the Till alloy, twelve different combinations
of hot die forging and heat treatment, in the α+β and β phase regions, were investigated. The resulting heat treated forgings
were classified into four distinct categories based on their microstructural appearance. The room temperature tensile, post-creep
tensile, fracture toughness and fatigue crack propagation properties were measured along with creep and low cycle fatigue
at 566°C. The creep, tensile, fatigue crack propagation and fracture toughness properties, grouped in a manner similar to
the microstructural categories. The fracture appearance and behavior of the cracks during propagation in fatigue and in fracture
toughness tests were examined, and correlations with the microstructure discussed. In the case of the fully transformed acicular
microstructure, it was found that the size and the orientation of colonies of similarly aligned α needles are dominant factors
in the crack behavior. 相似文献
11.
Y. F. Gu Y. Ro T. Kobayashi H. Harada 《Metallurgical and Materials Transactions A》2005,36(3):577-582
In an effort to enhance ductility and strength of Cr-base alloys, a series of Cr-Ru alloys with Ru contents ranging from 3
to 30 at. pct were made to study their microstructure evolution and mechanical properties. The microstructure of the alloys
with 6 to 20 at. pct Ru showed signs of a eutectic structure. However, no corresponding eutectic reaction is indicated in
the published Cr-Ru phase diagram. The yield strength of the Cr-Ru alloys increased with increasing Ru content at both room
temperature and 1200 °C. The tensile ductility of Cr-3 at. pct Ru is about 1.5 pct at room temperature, while the alloys containing
6 at. pct or more Ru showed zero tensile elongation. The deformation mechanisms of the Cr-Ru alloys are discussed in terms
of the microstructure and fracture behavior.
This article is based on a presentation made in the symposium entitled “Beyond Nickel-Base Superalloys,” which took place
March 14–18, 2004, at the TMS Spring meeting in Charlotte, NC, under the auspices of the SMD-Corrosion and Environmental Effects
Committee, the SMD-High Temperature Alloys Committee, the SMD-Mechanical Behavior of Materials Committee, and the SMD-Refractory
Metals Committee. 相似文献
12.
G. Terlinde H. -J. Rathjen K. -H. Schwalbe 《Metallurgical and Materials Transactions A》1988,19(4):1037-1049
Fracture mechanics and tensile tests have been performed on the metastable β-Ti alloy Ti-IOV-2Fe-3AI. A variety of microstructures
was established by several combinations of forging and heat treatment resulting in different types, morphologies, and volume
fractions of the a-phase which precipitates from the matrix-β phase. Both fracture toughness and ductility are strongly reduced
by increasing hardening by the secondary a-phase. An elongated primary a-phase (α
p
) shows higher toughness compared to a globular α
p
-phase. A thick, continuous subgrain boundary a-film lowers the toughness significantly. For microstructures without primary
a a grain boundary α-film does not affect the toughness, while the ductility is drastically reduced. Very attractive combinations
of fracture toughness and ductility were found for a microstructure without primary a and without grain boundary α. The results
are discussed based on the fractographic observations, and a model is proposed which includes the effect of microstructure
and slip distribution on the crack nucleation, the crack growth path, and the crack deviation. 相似文献
13.
In the 2Si-3Ni steel intercritically treated in the range of 720 ‡C to 790 ‡C, the fracture behavior under the impact testing
has been analyzed and the post-tempering effect has also been investigated. The transgranular fracture occurred in the specimens
treated below and at 730 ‡C (SN73 specimen) in relatively low intercritical temperature range, but the intergranular fracture
occurred in the specimens treated at 750 ‡C and 770 ‡C (SN75 and SN77 specimens) in relatively high intercritical temperature
range. In the SN73 specimen, there was little coarse martensite at the prior austenite grain boundaries, whereas there was
continuous, coarse martensite at those boundaries in the SN75 and SN77 specimens. The fracture behavior was mainly discussed
in terms of the microstructural differences. In addition, no or a little increase in impact toughness, in spite of great decreases
in hardness, in the SN75 and SN77 specimens tempered at 600 ‡C is correlated with the easy occurrence of intergranular fracture,
which is caused by the carbide aggregates formed in the continuous, coarse martensite at the grain boundaries. 相似文献
14.
TheresearchshowedthatmostofNiAl basedalloysexhibitedratherlowroomtemper atureductilityexceptNi 2 0Al 3 0Fe(% ,un lessotherwisenoted ,allcompositionsareinatomicpercent)andsinglecrystallineNiAlal loyedwithminorFe ,Mo ,Ga[1,2 ] .Inrecentyears ,itobtainedacombinationofg… 相似文献
15.
The variation of the tensile mechanical properties and hardness (at 25‡C) of three Ni-Cr alloys has been determined as a function
of aging time (up to 4 months) in the range 290 to 530‡C. Aging has a negligible effect on the 10 pct Cr alloy, and only a
slight effect on the 20 pct Cr alloy. However, the 30 pct Cr alloy showed a marked sensitivity to aging; for example, at 479‡C
the yield strength doubled after about 1 month, then decreased slightly at 4 months. The effect in the 30 pct Cr alloy is
due to the formation of the Ni2Cr superlattice. 相似文献
16.
The influence of microstructure on the fracture toughness of Ti-23A1-9Nb-2Mo-1Zr-1.2Si (at. pct) and Ti-23A1-11Nb-0.9Si (at.
pct) Ti3Al-based alloys has been investigated. Basket-weave microstructures comprising different volume fractions of α
2 and retained β phases were produced by systematic heat treatments. Besides the volume fraction of the retained β phase, the average size of the β laths has also been used to characterize these microstructures. The toughness of both alloys was examined at room temperature,
and the brittle transgranular fracture modes were found to be controlled by microstructure. However, the toughness is not
determined solely by the volume fraction of the retained β phase, and a linear relationship has been obtained between the fracture toughness and the average size of the retained β laths. It appears therefore that the toughness of Ti3Al-based alloys at room temperature is controlled primarily by the width of retained β laths rather than by the retained β volume fraction. 相似文献
17.
D. J. Gaydosh S. L. Draper M. V. Nathal 《Metallurgical and Materials Transactions A》1989,20(9):1701-1714
The influence of small additions of C, Zr, and Hf, alone or in combination with B, on the microstructure and tensile behavior
of substoichiometric FeAl was investigated. Tensile prop-erties were determined from 300 to 1100 K on powder which was consolidated
by hot extrusion. All materials possessed some ductility at room temperature, although ternary additions generally reduced
ductility compared to the binary alloy. Adding B to the C- and Zr-containing alloys changed the fracture mode from intergranular
to transgranular and restored the ductility to ap-proximately 5 pct elongation. Additions of Zr and Hf increased strength
up to about 900 K, which was related to a combination of grain refinement and precipitation hardening. Fe6Al6Zr and Fe6Al6Hf precipitates, both with identical body-centered tetragonal structures, were iden-tified as the principal second phases
in these alloys. Strength decreased steadily as temperature increased above 700 K, as diffusion-assisted mechanisms, including
grain boundary sliding and cavitation, became operative. Although all alloys had similar strengths at 1100 K, Hf additions
significantly improved high-temperature ductility by suppressing cavitation. 相似文献
18.
The results of a recent study of the effects of ternary alloying with Ti on the fatigue and fracture behavior of a new class
of forged damage-tolerant niobium aluminide (Nb3Al-xTi) intermetallics are presented in this article. The alloys studied have the following nominal compositions: Nb-15Al-10Ti
(10Ti alloy), Nb-15Al-25Ti (25Ti alloy), and Nb-15Al-40Ti (40Ti alloy). All compositions are quoted in atomic percentages
unless stated otherwise. The 10Ti and 25Ti alloys exhibit fracture toughness levels between 10 and 20 MPa√m at room temperature.
Fracture in these alloys occurs by brittle cleavage fracture modes. In contrast, a ductile dimpled fracture mode is observed
at room-temperature for the alloy containing 40 at. pct Ti. The 40Ti alloy also exhibits exceptional combinations of room-temperature
strength (695 to 904 MPa), ductility (4 to 30 pct), fracture toughness (40 to 100 MPa√m), and fatigue crack growth resistance
(comparable to Ti-6Al-4V, monolithic Nb, and inconnel 718). The implications of the results are discussed for potential structural
applications of the 40Ti alloy in the intermediate-temperature (∼700 °C to 750 °C) regime. 相似文献
19.
T. Tsuyumu Y. Kaneno H. Inoue T. Takasugi 《Metallurgical and Materials Transactions A》2003,34(3):645-655
By using isothermally forged TiAl-based intermetallic alloys, various microstructures (of γ-grain, duplex, dual-phase, and fully lamellar microstructures) were prepared. These TiAl-based intermetallic alloys were
tensile tested in vacuum and air as functions of strain rate and temperature to investigate microstructural effects on the
moisture-induced embrittlement. All the intermetallic alloys with different microstructures showed different levels of reduced
tensile stress (or elongation) in air at room temperature. The reduction in tensile stress (or elongation) due to testing
in air diminishes as the testing temperature (or strain-rate) increases. From the fracture stress-temperature curves, it was
found that the γ-grain microstructure was the most resistant to the moisture-induced embrittlement, and the dual-phase microstructure was
the most susceptible to the moisture-induced embrittlement. Also, the moisture-induced embrittlement of the TiAl-based intermetallic
alloys with a fully lamellar microstructure depends on the lamellar spacing and is reduced with decreasing lamellar spacing.
The possible reasons for the observed microstructural effect on the moisture-induced embrittlement were discussed, in association
with hydrogen behavior and properties in the constituent phases and at some interfaces. 相似文献
20.
P. J. Grobner 《Metallurgical and Materials Transactions B》1973,4(1):251-260
The 885odgF (475°C) embrittlement of seven heats of chromium steels was investigated: four vacuum-melted heats with C + N
< 0.008 pct and 14 pct Cr, 14 pet Cr-2 pet Mo, 18 pct Cr, or 18 pet Cr-2 pet Mo, and three air-melted heats with C + N > 0.09
pet and 18 pet Cr, 18 pct Cr-2 pet Mo, or 18 pet Cr-2 pet Mo-0.5 pct Ti. The steels were heated at 600° (316°), 700° (371°),
800° (427°), 900° (482°), and 1000°F (538°C) for various times up to 4800 h and the influence of this aging was investigated
by hardness measurements, impact tests, and electron metallography. It was demonstrated that the embrittlement due to 885°F
(475°C) exposure was caused by precipitation of a chromium-rich α’ phase on dislocations. The nucleation rate of α’ was calculated with the aid of Becker’s theory and the results were used to extrapolate experimental data obtained in this
study. After an exposure of about 1000 h at 1000°F (538°C), a decrease in room temperature toughness was observed for all
steels investigated. The decrease in toughness was not caused by immobilization of dislocations by α’, but by precipitation of carbonitrides. 相似文献