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1.
A particulate Al-30 wt pct TiC composite was employed as a grain refiner for the Al-4.5 wt pct Cu alloy. The composite contains
submicron TiC particles. The addition of the TiC grain refiner to the metal alloy in the amount of 0.1 Ti wt pct effected
a remarkable reduction in the average grain size in Al-4.5 wt pct Cu alloy castings. With the content of over 0.2 Ti wt pct,
the grain refiner maintained its refining effectiveness even after a 3600-second holding time at 973 K. The TiC particles
in the resulting castings were free of interfacial phases. It is concluded that the TiC are the nucleating agents and that
they are resistant to the “fading effect” encountered with most grain refiners. 相似文献
2.
Alumina composites incorporating with 0, 5, 10 15, 20, and 25 vol pct of TiC were consolidated by the spark plasma sintering at 1673 K (1400 °C). The effects of increasing TiC compositions on electrical and mechanical properties of the composites were investigated at room temperature. The dc electrical conductivity behavior demonstrates a transition from insulator to conductor around 12.5 vol pct of TiC in the framework of percolation theory. The conductivity attains a maximum value of ≈230 S/m at 25 vol pct of TiC sufficient to machine the composite by electro discharging machining. The Vickers hardness and fracture toughness of the composites increase with the addition of TiC vol pct, whereas elastic modulus decreases. The results indicate that crack deflection, crack bridging, and crack branching by the TiC particles are responsible for the significantly improved fracture toughness of the composites. 相似文献
3.
Reactive infiltration processing was used to fabricate bulk NiAl and fiber-reinforced NiAl composites. Homogenous, pore-free
materials were obtained by chemical reaction between nickel and aluminum after complete infiltration with liquid aluminum
of preforms of nickel wires (containing tungsten wires for the composites) with low surface-to-volume ratio, high permeability,
and regular infiltration paths. Reactively-processed, monolithic NiAl exhibited compressive creep properties at 715 °C and
1025 °C in good agreement with those of conventionally processed NiAl. The compressive creep behavior of NiAl composites reinforced
with 5 to 20 vol pct W was also characterized at the same temperatures. At 715 °C, the NiAl-W composites exhibited secondary
creep with little primary and tertiary creep, while at 1025 °C, the composites displayed all three stages. Microstructurally,
secondary creep was characterized by pure uniaxial compression of tungsten fibers. The measured composite secondary creep
rates could be predicted reasonably well with the role-of-mixtures isostrain model developed for composites where both phases
undergo creep deformation using tensile creep data measured on the as-received tungsten fibers. 相似文献
4.
Directional solidification (DS) of “powder-cloth” (PC) processed sapphire-NiAl composites was carried out to examine the influence
of fabrication technique on the fiber-matrix interfacial shear strength, measured using a fiber-pushout technique. The DS
process replaced the fine, equiaxed NiAl grain structure of the PC composites with an oriented grain structure comprised of
large columnar NiAl grains aligned parallel to the fiber axis, with fibers either completely engulfed within the NiAl grains
or anchored at one to three grain boundaries. The load-displacement behavior during the pushout test exhibited an initial
“pseudoelastic” response, followed by an “inelastic” response, and finally a “frictional” sliding response. The fiber-matrix
interfacial shear strength and the fracture behavior during fiber pushout were investigated using an interrupted pushout test
and fractography, as functions of specimen thickness (240 to 730 μm) and fabrication technique. The composites fabricated
using the PC and the DS techniques had different matrix and interface structures and appreciably different interfacial shear
strengths. In the DS composites, where the fiber-matrix interfaces were identical for all the fibers, the interfacial debond
shear stresses were larger for the fibers embedded completely within the NiAl grains and smaller for the fibers anchored at
a few grain boundaries. The matrix grain boundaries coincident on sapphire fibers were observed to be the preferred sites
for crack formation and propagation. While the frictional sliding stress appeared to be independent of the fabrication technique,
the interfacial debond shear stresses were larger for the DS composites compared to the PC composites. The study highlights
the potential of the DS technique to grow single-crystal NiAl matrix composites reinforced with sapphire fibers, with fiber-matrix
interfacial shear strength appreciably greater than that attainable by the current solid-state fabrication techniques. 相似文献
5.
Reaction synthesis of Ni-Al-based particle composite coatings 总被引:1,自引:0,他引:1
D. F. Susan W. Z. Misiolek A. R. Marder 《Metallurgical and Materials Transactions A》2001,32(2):379-390
Electrodeposited metal matrix/metal particle composite (EMMC) coatings were produced with a nickel matrix and aluminum particles.
By optimizing the process parameters, coatings were deposited with 20 vol pct aluminum particles. Coating morphology and composition
were characterized using light optical microscopy (LOM), scanning electron microscopy (SEM), and electron probe microanalysis
(EPMA). Differential thermal analysis (DTA) was employed to study reactive phase formation. The effect of heat treatment on
coating phase formation was studied in the temperature range 415 °C to 1000 °C. Long-time exposure at low temperature results
in the formation of several intermetallic phases at the Ni matrix/Al particle interfaces and concentrically around the original
Al particles. Upon heating to the 500 °C to 600 °C range, the aluminum particles react with the nickel matrix to form NiAl
islands within the Ni matrix. When exposed to higher temperatures (600 °C to 1000 °C), diffusional reaction between NiAl and
nickel produces (γ′)Ni3Al. The final equilibrium microstructure consists of blocks of (γ′)Ni3Al in a γ(Ni) solid solution matrix, with small pores also present. Pore formation is explained based on local density changes during
intermetallic phase formation, and microstructural development is discussed with reference to reaction synthesis of bulk nickel
aluminides. 相似文献
6.
S. N. Tewari R. Asthana R. Tiwari R. R. Bowman J. Smith 《Metallurgical and Materials Transactions A》1995,26(2):477-491
The influence of microstructure of the fiber-matrix interface on the interfacial shear strength, measured using a fiber-pushout
technique, has been examined in a sapphire-fiber-reinforced NiAl(Yb) matrix composite under the following conditions: (1)
as-fabricated powder metallurgy (PM) composites, (2) PM composites after solid-state heat treatment (HT), and (3) PM com-posites
after directional solidification (DS). The fiber-pushout stress-displacement behavior con-sisted of an initial “pseudoelastic”
region, wherein the stress increased linearly with displacement, followed by an “inelastic” region, where the slope of the
stress-displacement plot decreased until a maximum stress was reached, and the subsequent gradual stress decreased to a “fric-tional”
stress. Energy-dispersive spectroscopy (EDS) and X-ray analyses showed that the inter-facial region in the PM NiAl(Yb) composites
was comprised of Yb2O3,O-rich NiAl and some spinel oxide (Yb3Al5O12), whereas the interfacial region in the HT and DS composites was comprised mainly of Yb3Al5O12. A reaction mechanism has been proposed to explain the pres-ence of interfacial species observed in the sapphire-NiAl(Yb)
composite. The extent of inter-facial chemical reactions and severity of fiber surface degradation increased progressively
in this order: PM < HT < DS. Chemical interactions between the fiber and the NiAl(Yb) matrix resulted in chemical bonding
and higher interfacial shear strength compared to sapphire-NiAl composites without Yb. Unlike the sapphire-NiAl system, the
frictional shear stress in the sap-phire-NiAl(Yb) composites was strongly dependent on the processing conditions.
Formerly Research Associate, Department of Chemical Engineering, Cleveland State University 相似文献
7.
D. A. Hardwick C. G. Rhodes L. G. Fritzemeier 《Metallurgical and Materials Transactions A》1993,24(1):27-34
The effect of annealing on the microstructure, texture, and room-temperature mechanical properties ofin situ processed copper-based microcomposites has been investigated. These copper microcomposites, containing 15 vol pct Nb, Cr,
or Ta, were produced by rolling of cast material. Annealing was carried out in vacuum for 10 hours at 250 °C, 400 °C, and
650 °C. Evidence of microstructural coarsening was found even at the lowest annealing temperature. The through-thickness microstructure
of the composites was examined by transmission electron microscopy both before and after the annealing treatments. Texture
of the as-processed micro-composites was assessed using X-ray diffraction methods. The strength of the composites following
annealing was found to scale with the melting point of the second component.
This article is based on a presentation made in the symposium “High Performance Copper-Base Materials” as part of the 1991
TMS Annual Meeting, February 17–21, 1991, New Orleans, LA, under the auspices of the TMS Structural Materials Committee. 相似文献
8.
“Clean” 3.5NiCrMoV steels with limited contents in trace elements (P, Sn, As, Sb) are commonly provided for manufacturing
big rotor shafts. The possible increase in temperature in future steam turbines has promoted the development of “superclean”
steels characterized by an extra drastic decrease of manganese and silicon contents. Their higher cost in comparison to “clean”
steels leads to concern above which temperature they must be considered as mandatory for resisting aging embrittlement in
operation. 3.5NiCrMoV “clean” steel samples (Mn = 0.30 pct; Si = 0.10 pct) were aged at 300 °C, 350 °C, and 400 °C for 10,000
hours up to 30,000 hours. No embrittlement results from aging at 300 °C and 350 °C, but holding at 400 °C is highly detrimental.
Auger spectroscopy confirms that, when aging at 400 °C, phosphorus is the main embrittling trace element. It is suggested
that grain boundary embrittlement is associated with the building of a layer that contains, on the one hand, Ni and P and,
on the other hand, Mo and Cr.
Head of the Testing and
Head of the Testing and
Head of the Testing and 相似文献
9.
The present study was undertaken to investigate the effect of solution treatment (in the temperature range 520 °C to 550 °C)
and artificial aging (in the temperature range 140 °C to 180 °C) on the variation in the microstructure, tensile properties,
and fracture mechanisms of Al-10 wt pct Si-0.6 wt pct Mg/SiC/10p composite castings. In the as-cast condition, the SiC particles are observed to act as nucleation sites for the eutectic
Si particles. Increasing the solution temperature results in faster homogenization of the microstructure. Effect of solution
temperature on tensile properties is evident only during the first 4 hours, after which hardly any difference is observed
on increasing the solution temperature from 520 °C to 550 °C. The tensile properties vary significantly with aging time and
temperature, with typical yield strength (YS), ultimate tensile strength (UTS), and percent elongation (EL) values of ∼300
MPa, ∼330 MPa, and ∼1.4 pct in the underaged condition, ∼330 MPa, ∼360 MPa, and ∼0.65 pct in the peakaged condition, and ∼323
MPa, ∼330 MPa, and ∼0.8 pct in the overaged condition. Prolonged solution treatment at 550 °C for 24 hours results in a slight
improvement in the ductility of the aged test bars. The fracture surfaces exhibit a dimple morphology and cleavage of the
SiC particles, the extent of SiC cracking increasing with increasing tensile strength and reaching a maximum in the overaged
condition. Microvoids act as nucleation sites for the formation of secondary cracks that promote severe cracking of the SiC
particles. A detailed discussion of the fracture mechanism is given. 相似文献
10.
Nb-1 wt pct Zr/218W long-fiber composite monotapes, nominally containing 0 to 70 vol pct of 218 tungsten fibers, were fabricated
by arc spraying the Nb-1 pct Zr matrix onto the tungsten fibers. The monotapes were consolidated by hot pressing and hot isostatic
pressing techniques. Tensile tests conducted between 1400 and 1600 K, under engineering strain rates varying between 1.5×10−5 and 1.5×10−3 s−1, demonstrated that composites containing 70 vol pct of fibers had the highest strength-to-density ratio. Microstructural
observations of specimens tested at 1400 K revealed that composites containing less than 50 vol pct of fibers showed extensive
matrix cavitation, fiber-matrix debonding, and necking of the fibers. Above 50 vol pct, the composite matrix was less prone
to cavitation, with an increasing tendency toward shear deformation of the fibers as the fiber volume fraction increased.
No fiber damage was observed at 1400 K away from the fractured end, but significant fiber damage was observed at higher temperatures.
A phenomenological model is presented to rationalize these observations.
This article is based on a presentation made in the Symposium “Mechanisms and Mechanics of Composites Fracture” held October
11–15, 1998, at the TMS Fall Meeting in Rosemont, Illinois, under the auspices of the TMS-SMD/ASM-MSCTS Composite Materials
Committee. 相似文献
11.
The transverse fatigue crack growth resistance of unidirectional 8 and 35 pct 1140+/Ti-6-4 fiber-reinforced composites has
been investigated. It has been found that, at a low fiber volume fraction, the transverse fatigue crack growth resistance
of metal-matrix composites (MMCs) is improved with respect to the monolithic matrix alloy. This occurs because “holes” from
debonded interfaces can trap the crack and reduce the average fatigue crack growth rates by periodically increasing the effective
crack-tip radius. However, an increase of fiber volume fraction from 8 to 35 pct decreases the fatigue crack growth resistance
dramatically, due to the significant increase of the frequency of interaction and coalescence between the main crack, the
debonded interfaces, and microcracks. 相似文献
12.
P. R. Subramanian M. G. Mendiratta D. B. Miracle 《Metallurgical and Materials Transactions A》1994,25(12):2769-2781
The phase relationship in the NiAI-Mo system is characterized by a eutectic equilibrium between binary NiAl and the terminal
(Mo) solid solution, thereby offering the potential for development of ductile-phase-toughened composites. A study was conducted
to evaluate the effect of varying volume fraction of the (Mo) phase on the microstructure, bend strength, and ambient temperature
fracture behavior of selected NiAI-Mo two-phase alloys. Above room temperature, the NiAI-Mo alloys showed an increase in bend
strength compared to monolithic NiAl, with reasonable strength retention up to ≈800 °C. The results demonstrated moderate
improvements in toughness in the NiAI-Mo alloys in comparison to monolithic NiAl. A further enhancement in toughness was realized
through hot working. Fractography studies showed evidence for substantial decohesion between the (Mo) phase and the NiAl matrix,
thereby suggesting the presence of a weak interface. This weak interface between the (Mo) phase and the NiAl matrix, in conjunction
with modulus mismatch stresses, causes the crack to deflect from the (Mo) rein-forcement and propagate preferentially along
the (Mo)/NiAl interface. These attributes limit the potential for significant ductile-phase toughening in the NiAI-Mo system.
An addition of 0.2 at. pct Ti resulted in a marked improvement in the room-temperature fracture toughness of NiAI-Mo. Fractography
observations show some evidence for (Mo)/NiAl interface strengthening with the Ti addition. 相似文献
13.
Nb-1 wt pct Zr/218W long-fiber composite monotapes, nominally containing 0 to 70 vol pct of 218 tungsten fibers, were fabricated
by arc spraying the Nb-1 pct Zr matrix onto the tungsten fibers. The monotapes were consolidated by hot pressing and hot isostatic
pressing techniques. Tensile tests conducted between 1400 and 1600 K, under engineering strain rates varying between 1.5×10−5 and 1.5×10−3 s−1, demonstrated that composites containing 70 vol pct of fibers had the highest strength-to-density ratio. Microstructural
observations of specimens tested at 1400 K revealed that composites containing less than 50 vol pct of fibers showed extensive
matrix cavitation, fiber-matrix debonding, and necking of the fibers. Above 50 vol pct, the composite matrix was less prone
to cavitation, with an increasing tendency toward shear deformation of the fibers as the fiber volume fraction increased.
No fiber damage was observed at 1400 K away from the fractured end, but significant fiber damage was observed at higher temperatures.
A phenomenological model is presented to rationalize these observations.
L.J. GHOSN, formerly Researcher with Case Western Reserve University, Cleveland, OH 44115
This article is based on a presentation made in the Symposium “Mechanisms and Mechanics of Composites Fracture” held October
11–15, 1998, at the TMS Fall Meeting in Rosemont, Illinois, under the auspices of the TMS-SMD/ASM-MSCTS Composite Materials
Committee. 相似文献
14.
Seong-Hun Choo Sunghak Lee Soon-Ju Kwon 《Metallurgical and Materials Transactions A》1999,30(12):3131-3141
Surface composites reinforced with TiC particulates were fabricated by high-energy electron-beam irradiation. In order to
investigate the effects of flux addition on the TiC dispersion in surface composite layers, four kinds of powder mixtures
were made by mixing TiC with 5, 10, 20, and 40 wt pct of the flux components (MgO-CaO). To fabricate TiC-reinforced surface
composites, the TiC-flux mixtures were deposited evenly on a plain carbon steel substrate, which was subjected to electron-beam
irradiation. Microstructural analysis was conducted using X-ray diffraction and Mossbauer spectroscopy as well as optical
and scanning electron microscopy. The microstructure of the surface composites was composed of a melted region, an interfacial
region, a coarse-grained heat-affected zone (HAZ), a fine-grained HAZ, and an unaltered original substrate region. TiC agglomerates
and residual pores were found in the melted region of materials processed without flux, but the number of agglomerates and
pores was significantly decreased in materials processed with a considerable amount of flux. As a result of irradiation, TiC
particles were homogeneously distributed throughout the melted region of 2.5 mm in thickness, whose hardness was greatly increased.
The optimum flux amount, which resulted in surface composites containing homogeneously dispersed TiC particles, was found
to be in the range of 10 to 20 pct to obtain excellent surface composites. 相似文献
15.
The local chemistry and structure of α-iron/molybdenum nitride heterophase interfaces is studied on a subnanometer scale by atom-probe field-ion microscopy (APFIM),
three-dimensional atom-probe microscopy (3DAPM) and both conventional transmission electron microscopy (CTEM) and highresolution
electron microscopy (HREM). Molybdenum nitride precipitates are generated by annealing Fe-2 at. pct Mo-X, where X=0.4 at.
pct Sb or 0.5 at. pct Sn, at 550 °C or 600 °C, in an ammonia/hydrogen mixture. Internal nitridation at 550 °C produces thin,
coherent platelet-shaped molybdenum nitride precipitates. Nitridation at 600 °C generates a much coarser structure with semicoherent
thick plate-shaped and spheroidal precipitates in addition to the thin-platelet structure. The APFIM and 3DAPM analyses of
the heterophase interfaces show substantial segregation of the solute species Sn and Sb only at the coarse precipitates, with
Gibbsian interfacial excesses of up to 7±3 nm−2, whereas the broad faces of the thin platelets have no detectable segregation. The TEM and HREM analyses show that the coarse
precipitates are semicoherent, whereas the thin platelets are either coherent or have much fewer misfit dislocations than
geometrically necessary. This demonstrates that Sn and Sb segregation is related to the presence of misfit dislocations at
the interfaces of the coarse precipitates.
This article is based on a presentation made at the symposium entitled “The Mechanisms of the Massive Transformation,” a part
of the Fall 2000 TMS Meeting held October 16–19, 2000, in St. Louis, Missouri, under the auspices of the ASM Phase Transformations
Committee. 相似文献
16.
T. Fujii D. R. Poirier M. C. Flemings 《Metallurgical and Materials Transactions A》1982,13(12):2143-2153
A model to simulate the diffusion-controlled coarsening and dissolution kinetics of particles within a metallic matrix is
formulated. With an arbitrary size distribution of particles, the model can be used to calculate the change in the size distribution
of particles during coarsening or dissolution. Other system parameters, such as average radius of particles, volume fraction,
average distance between particles, surface area, and matrix composition are also calculated. An important result is that
kinetics do not generally obey the often-applied Lifshiftz-Slyozov-Wagner theory for diffusion controlled coarsening based
upon concentration profiles around isolated spheres. In such a formulation, the direct effect of the surrounding particles
is neglected. In our model, which is a modification of the coarsening kinetics described by Weins and Cahn, the effect of
surrounding particles is incorporated because the system is taken to be a system of point potentials, each with a potential
according to its radius of curvature. Calculations are on silica particles in a copper matrix and on manganese sulfide inclusions
in iron, with emphasis on the latter, in order to predict their behavior during homogenization or soaking treatments. The
effect of the composition of manganese, from 0.1 to 1.2 wt pct, on the coarsening of sulfides in a “high” sulfur (0.017 wt
pct) steel and a “low” sulfur (0.003 wt pct) steel was investigated. As expected, the model predicts that manganese strongly
reduces the rate of coarsening, particularly for times of ten hours or less in the temperature range of 1100 to 1400 °C. Calculated
results also indicate that the rate of dissolution is very low at temperatures greater than the solvus for manganese sulfide
inclusions in austenite. 相似文献
17.
TiAl-based titanium aluminide alloys and their composites reinforced with ceramic particles are considered to be important
candidate materials for high-temperature structural applications. Laser-engineered net shaping (LENS) is a layered manufacturing
process, which involves laser processing fine powders into three-dimensional components directly from a computer-aided design
(CAD) model. In this work, the LENS process was employed to fabricate carbide-particle-reinforced titanium aluminide-matrix
composites using TiC and gas-atomized Ti-48Al-2Cr-2Nb powders as the feedstock materials. The composites deposited by the
LENS process were susceptible to solid-state cracking due to high thermal stresses. The microstructures of the laser-deposited
monolithic and composite titanium aluminide materials were characterized using light optical microscopy (LOM), scanning electron
microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS) analysis, electron-probe microanalysis (EPMA), and X-ray diffraction
(XRD) techniques. Effects of the LENS processing parameters on the cracking susceptibility and microstructure were studied.
Crack-free deposits were fabricated by preheating the substrate to 450 °C to 500 °C during LENS processing. The fabricated
composite deposits exhibit a hardness of more than twice the value of the Ti-6Al-4V alloy. 相似文献
18.
Amit S. Sharma Krishanu Biswas Bikramjit Basu Dibyendu Chakravarty 《Metallurgical and Materials Transactions A》2011,42(7):2072-2084
For the first time, we report here that high purity nanocrystalline Cu and Cu-10 wt pct Pb alloys can be densified with more
than 90 pct theoretical density at a low temperature of 623 K (350 °C) using spark plasma sintering (SPS) in argon atmosphere
at a pressure of 100 MPa. Scanning electron microscopy (SEM) analysis indicates that molten Pb particles travel through Cu
grain boundaries, delineating a “flowlike” pattern in the microstructure. An extensive transmission electron microscopy (TEM)
analysis of the ultrafine scale microstructure reveals partial wetting of Cu by liquid Pb as well as entrapment of Pb particles
within the Cu matrix. The sintering kinetics and microstructural evolution are discussed in reference to the intrinsic characteristics
of SPS as well as phase equilibria in the Cu-Pb system. An important result is that high hardness of around 2 GPa is measured
in the Cu-10 wt pct Pb nanostructured alloy, SPS at 573 K to 623 K (300 °C to 350 °C). 相似文献
19.
Steel-matrix particulate composites were processed by direct addition of an Fe-TiB2 master alloy powder to a BS970:080M30 medium-carbon steel. This powder was produced using a self-propagating, high-temperature
synthesis (SHS) reaction and consisted of a dispersion of fine TiB2 particles (2 to 5 μm), respectively, in an iron binder. The addition of the Fe-TiB2 powder resulted in the formation a parasitic Fe2B phase and TiC within the steel microstructure. In response to this, an SHS master alloy composed of Fe-(50 pct TiB2+50 pct Ti) was manufactured, which, when added to the steel, prevented the formation of Fe2B and resulted in a composite containing a mixture of TiB2 and TiC particles. The effect of master alloy composition and addition level on the microstructural phases generated is discussed
in detail. The response to heat treatment of composite materials manufactured in this way was also investigated. It was found
that an isothermal hold at 840 °C leads to a substantial softening of the material processed using the Fe-TiB2 additive, while at 1000 °C, a hardness level equivalent to that of the as-cast material was maintained. The same heat treatment
of samples in which the formation of Fe2B was suppressed resulted in no appreciable difference in hardness level or microstructure. 相似文献
20.
Separate 200, 020, and 002 X-ray peaks were recorded for 0.0, 0.4, and 0.8 wt pct carbon (18 pct Ni) martensites after tempering
between 25 and 500°C. The carbon bearing martensites studied here have been tempered initially enough to eliminate the “high
tetragonality” 002 peak usually recorded for as-quenched martensite and the present results apply to tempered martensite only.
The peak maximum is taken to determine the lattice parameter and the peak shape is recorded. At all carbon levels and after
all tempering treatments, the “crd parameter is larger than or equal to the “a” or “b”. The relative enlargement is very small
(0.08 pct) for the lowest carbon level and for any carbon level after severe tempering (500°C for 15 min). For the two higher
carbon alloys tempered at temperatures below 400°C (for 15 min) the “c” parameter is significantly larger than the “a” and
“b” and for the 0.4 wt pct C alloy the “b” is significantly smaller than the“a” whereas in the 0.8 pct C alloy the “b” is slightly larger than the “a”. Within experimental error the mean volume of the
unit cell does not change during the tempering studied here and is nearly unaffected by the initial carbon content. This indicates
that little (at most 0.1 wt pct) carbon is dissolved in tempered martensite. In the low carbon alloy the peaks are symmetric
and sharpen symmetrically during tempering. In the higher carbon alloys the peaks are nearly symmetric and sharp after severe
tempering. After less severe tempering the 002 peak is asymmetrically broadened toward lower9 values (higher lattice parameters) whereas the 200 and 020 peaks are asymmetrically broadened toward higher 0 values corresponding
to lower lattice parameters. This collection of results is tentatively interpreted as being due to strains in martensite due
to transformation induced substructure and precipitated carbides. 相似文献