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1.
Results are reported on microstructures of Fe-Cr-Ni alloys, solidified over a range of undercoolings and quenched during or
after recalescence. Alloys studied contained 70 wt pct Fe and with Cr varying from approximately 15 to 20 wt pct. The three
lower Cr alloys were hypoeutectic (with fee as primary phase in equilibrium solidification); the two higher Cr alloys were
hypereutectic (with bcc as primary phase in equilibrium solidification). Results obtained are in agreement with predictions
based on thermal analyses previously presented; they confirm and extend the understanding gained in that work. The primary
phase to solidify in the hypoeutectic alloys is bec when undercooling is greater than an amount which decreases with increasing
Cr content. At the lower Cr contents, the stable fcc phase then forms by solid-state transformation of the metastable phase
and its subsequent engulfment by additional fcc. At the higher Cr content, transformation is by a peritectic-like reaction
in the semisolid state, except near the surface at higher undercoolings where the transformation is massive. In the hypereutectic
alloys, primary solidification at all undercoolings is the stable bcc phase. Partial transformation to fcc occurs in the semisolid
or solid state, depending on composition and undercooling.
Formerly Graduate Student, Department of Materials Science and Engineering, Massachusetts Institute of Technology 相似文献
2.
Toshihiko Koseki Merton C. Flemings 《Metallurgical and Materials Transactions A》1997,28(11):2385-2395
In Parts I and II of this series of articles, it was shown that a range of levitation-melted Fe-Cr-Ni alloys, both hypoeutectic
and hypereutectic, all solidified with the hypereutectic phase (bcc) as their primary phase, except for the hypoeutectic alloys
at low undercoolings. In this article, the effect of heat extraction on phase formation is studied by chill casting the undercooled
alloys before nucleation. Two of the previously studied alloys are examined; one hypoeutectic and the other hypereutectic.
Chill substrates employed were copper, stainless steel, alumina, zirconia, and a liquid gallium-indium bath. Contrary to the
case of levitation melting and solidification, it is found that the dominant primary phase to solidify in both alloys, independent
of chill substrate, is the hypoeutectic phase (fcc). It is concluded that chilling the undercooled melt results in nearly
concurrent nucleation of bcc and fcc. Two different mechanisms are considered as possible explanations of the subsequent fcc
phase selection during growth. These are termed “growth velocity” and “phase stability” mechanisms. Evidence favors a phase
stability mechanism, in which the bcc phase massively transforms to fcc early in solidification so that fcc then grows without
competition. It is suggested that this mechanism may also explain structures observed in welds and other rapid solidification
processes. 相似文献
3.
The solidification behavior of undercooled Fe-Cr-Ni melts is analyzed with respect to the competitive formation of body-centered
cubic (bcc) phase (ferrite) and face-centered cubic (fcc) phase (austenite). The activation energies of homogeneous nucleation
and growth velocities for both phases as functions of undercooling of the melt are calculated on the basis of current theories
of nucleation and dendrite growth using data of thermodynamic properties available in the literature. As model systems for
numerical calculations, the alloys Fe-18.5Cr-11Ni forming primary ferrite and Fe-18.5Cr-12.5Ni forming primary austenite under
near-equilibrium solid-ification conditions are considered. Nucleation of the bcc phase is always promoted in the under-cooled
primary ferrite alloy, whereas the barrier for bcc nucleation falls below that for fcc nucleation for large undercooling in
primary austenite alloys. With rising undercooling, tran-sitions of the fastest growth mode were found from bcc to fcc and
subsequently from fcc to bcc for the primary ferrite forming alloy and from fcc to bcc for the primary austenite forming alloy.
The results of the calculations provide a basis for understanding contradictory experi-mental findings reported in the literature
concerning phase selection in rapidly solidified stainless steel melts for different process conditions.
Formerly Visiting Scientist at the Institut fur Raumsimulation 相似文献
4.
Mingjun Li Ph.D. Candidate Gencang Yang Yaohe Zhou 《Metallurgical and Materials Transactions A》1999,30(11):2941-2949
Fe-Co alloy melts with Co contents of 10, 30, and 60 at. pct were undercooled to investigate the dependence of the primary
phase on grain coarsening. A pronounced characteristic is that the metastable fcc phase in the Fe-10 at. pct Co alloy and
the metastable bcc phase in the Fe-30 at. pct Co alloy will primarily nucleate when undercoolings of the melts are larger
than the critical undercoolings for the formation of metastable phases in both alloys. No metastable bcc phase can be observed
in the Fe-60 at. pct Co alloy, even when solidified at the maximum undercooling of ΔT = 312 K. Microstructural investigation shows that the grain size in Fe-10 and Fe-30 at. pct Co alloys increases with undercoolings
when the undercoolings of the melts exceed the critical undercoolings. The grain size of the Fe-60 at. pct Co alloy solidified
in the undercooling range of 30 to 312 K, in which no metastable phase can be produced, is much finer than those of the Fe-10
and Fe-30 at. pct Co alloys after the formation of metastable phases. The model for breakage of the primary metastable dendrite
at the solid-liquid interface during recalescence and remelting of dendrite cores is suggested on the basis of microstructures
observed in the Fe-10 and Fe-30 at. pct Co alloys. The grain coarsening after the formation of metastable phases is analyzed,
indicating that the different crystal structures present after the crystallization of the primary phase may play a significant
role in determining the final grain size in the undercooled Fe-Co melts. 相似文献
5.
J. Zhang D. B. Williams J. I. Goldstein 《Metallurgical and Materials Transactions A》1994,25(8):1627-1637
The low-temperature (<500 °C) decomposition of Fe-Ni martensite was studied by aging martensitic Fe-Ni alloys at temperatures
between 300 °C and 450 °C and by measuring the composition of the matrix and precipitate phases using the analytical electron
microscope (AEM). For aging treatments between 300 °C and 450 °C, lath martensite in 15 and 25 wt pct Ni alloys decomposed
with γ [face-centered cubic (fcc)] precipitates forming intergranularly, and plate martensite in 30 wt pct Ni alloys decomposed
with γ (fcc) precipitates forming intragranularly. The habit plane for the intragranular precipitates is {111}fcc parallel to one of the {110}bcc planes in the martensite. The compositions of the γ intergranular and intragranular precipitates lie between 48 and 58 wt
pct Ni and generally increase in Ni content with decreasing aging temperature. Diffusion gradients are observed in the matrix
α [body-centered cubic (bcc)] with decreasing Ni contents close to the martensite grain boundaries and matrix/precipitate
boundaries. The Ni composition of the matrix α phase in decomposed martensite is significantly higher than the equilibrium
value of 4 to 5 wt pct Ni, suggesting that precipitate growth in Fe-Ni martensite is partially interface reaction controlled
at low temperatures (<500 °C). The results of the experimental studies modify the γ/α + γ phase boundary in the present low-temperature
Fe-Ni phase diagram and establish the eutectoid reaction in the temperature range between 400 °C and 450 °C.
Formerly Research Assistant, Department of Materials Science and Engineering, Lehigh University 相似文献
6.
Y. Wu T. J. Piccone Y. Shiohara M. C. Flemings 《Metallurgical and Materials Transactions A》1988,19(4):1109-1119
Studies were made of structure and solute distribution in undercooled droplets of nickel-25 wt pct tin alloy and the eutectic
nickel-32.5 wt pct tin alloy. Structures of levitation melted droplets of the Ni-25 wt pct Sn alloy showed a gradual and continuous
transition from dendritic to fine-grained spherical with increasing initial undercooling up to about 180 K. Results suggest
that all samples solidified dendritically and that the final structures obtained were largely the result of ripening. Experimental
data on minimum solute composition in the samples produced are bounded by two calculated curves, both of which assume equilibrium
at all liquid-solid interfaces during recalescence and subsequent cooling. One assumes complete diffusion in the solid during
recalescence; the other assumes limited diffusion, but partial remelting to avoid superheating of the solid. Several observations
support the view that the eutectic alloy solidifies dendritically, much as the hypoeutectic alloy does. Surface dendrites
were seen in regions of surface shrinkage cavities and a coarse “dendritic” structure can be discerned on polished sections,
which seems to correspond to the large surface “dendrites” seen by high-speed photographs of the hypoeutectic alloy. The structure
of highly undercooled eutectic samples is composed fully of an anomalous eutectic. Samples solidified with intermediate amounts
of undercooling possess some lamellar eutectic which, it is believed, solidified after recalescence was complete. 相似文献
7.
Wei-Chun Cheng 《Metallurgical and Materials Transactions A》2005,36(7):1737-1743
The observation of a new phase precipitated in the bcc matrix of a Fe-Mn-Al alloy heated at 1573 K and air cooled to room temperature is reported. The composition of the alloy was Fe-24.1 wt pct Mn-7.6 wt pct Al-0.03 wt pct C. These precipitates had a morphology of Widmanstätten side plates distributed uniformly in bcc grains, and some precipitates resided along the bcc grain boundaries. From transmission electron microscopy (TEM) and X-ray analyses, the crystal structure of the new phase was identified as a simple cubic (SC) Bravais lattice and was related to an ordered fcc phase. The new phase is similar to the L12 crystal structure. The orientation relationships between the SC Widmanstätten side plate and the ferrite matrix are [011]SC//[111]bcc and \((1\bar 11)\) SC//\((10\bar 1)\) bcc, which correspond to the well-know Kurdjumov-Sachs (K-S) orientation relationship. The formation of SC annealing twins from the ferrite phase at the initial stage of the nucleation during air cooling was observed for the first time in the Fe-Mn-Al alloys. It is noted that both twin grains grow within the ferrite matrix and maintain both the K-S orientation relationship with the parent ferrite phase and the twinning orientation relationship between them. 相似文献
8.
The selection of the primary solidifying phase in undercooled stainless steel melts is theoretically analyzed in terms of
nucleation theory. Nucleation phenomena are considered using different models for the solid-liquid interface energy. The classical
nucleation theory for sharp interfaces and an improved modification, the diffuse interface theory, are applied. The influence
of deviations of the nucleus composition from the overall alloy composition is also revealed. A preferred nucleation of the
metastable bcc phase in fcc equilibrium solidification-type alloys is predicted. The critical undercooling of metastable crystallization
as a function of alloy composition is calculated for an isoplethal section at 69 at. pct Fe of Fe69Cr31-x
Ni
x
alloys. The results are summarized in a phase selection diagram predicting the primary solidification mode as a function
of undercooling and melt composition. 相似文献
9.
Thomas Hartmut Ludwig Paul Louis Schaffer Lars Arnberg 《Metallurgical and Materials Transactions A》2013,44(13):5796-5805
The role of phosphorus (P) in the heterogeneous nucleation of eutectic silicon (Si) and the evolution of eutectic grains in hypoeutectic aluminum-silicon alloys were investigated. Systematic additions of P in the range of 0.5 to 20 ppm to Al-7 wt pct Si alloys of different purities have shown that the morphology of the eutectic Si changes from a fine plate- to a coarse flake-like structure. The growth of eutectic grains was investigated by interrupting the eutectic reaction by quenching experiments. Moreover, the macroscopic growth mode of the eutectic grains was characterized by electron backscatter diffraction. An increase in P concentration from 2 to 3 ppm resulted in a transition of the macroscopic growth mode of the Al-Si eutectic in high purity alloys from growth with a planar front with a strong dependence of the thermal gradient, to nucleation in the vicinity of the primary Al dendrites and subsequent growth of distinct eutectic grains. It is suggested that AlP particles are the key impurities acting as potential nucleation sites for eutectic Si. This is further substantiated as with increasing P concentration nucleation and growth of the Al-Si occurred at higher temperatures close the equilibrium Al-Si eutectic solidification temperature at 850 K (577 °C). In addition, the recalescence undercooling ΔT R,eu was reduced from 4.5 K (0.5 ppm P) to 1.5 K (20 ppm P) in high purity alloys. This was accompanied by a drastic increase of the nucleation rate of the eutectic grains. 相似文献
10.
Y. Wu T. J. Piccone Y. Shiohara M. C. Flemings 《Metallurgical and Materials Transactions A》1987,18(6):925-932
High-speed optical temperature measurements were made of the solidification behavior of levitated metal samples within a transparent
glass medium. Two undercooled Ni-Sn alloys were examined, one a hypoeutectic alloy and the other of eutectic composition.
Recalescence times for the 9 mm diameter samples studied decreased with increasing undercooling from the order of 1.0 second
at 50 K under-cooling to less than 10−3 second for undercoolings greater than 200 K. Both alloys recalesced smoothly to a maximum recalescence temperature at which
the solid was at or near its equilibrium composition and equilibrium weight fraction. For the samples of hypoeutectic alloy
that recalesced above the eutectic temperature, a second nucleation event occurred on cooling to the eutectic temperature.
For samples which recalesced only to the eutectic temperature, no subsequent nucleation event was observed on cooling. It
is inferred in this latter case that both the α and β phases were present at the end of recalescence. The thermal data obtained
suggest a solidification model involving (1) dendrites of very fine structure growing into the melt at temperatures near the
bulk undercooling temperature, (2) thickening of dendrite arms with rapid recalescence, and (3) continued, much slower recalescence
accompanying dendrite ripening. 相似文献
11.
The phase relationships between the liquid phase and the primary solid phases were investigated in the iron-rich corner of
the Fe-Cr-Ni system as part of a larger study of the Fe-Cr-Ni-C system. The investigation consisted of measurements and modeling
of tie-lines and the liquidus surfaces of the liquid-delta (bcc) and liquid-gamma (fcc) equilibria and the peritectic surface
involving all three phases in the iron-rich corner of the Gibbs triangle bounded by 0 to 25 wt pct Cr and 0 to 25 wt pct Ni
(bal Fe). The temperature ranged from the melting point of iron (1811 K) to about 1750 K. Compositions for tie-lines were
obtained from liquid-solid equilibrium couples and temperatures for the surfaces were obtained by differential thermal analysis.
Parameters for modeling the system were then selected in the subregular solution model to minimize the square of the difference
between experimental and calculated tie-lines. With one ternary parameter employed for each phase, calculations by the model
are in excellent agreement with the tie-line and liquidus measurements and in fair agreement with the temperatures for the
peritectic surfaceL + δ/L + δ + γ. The usefulness of the model is demonstrated by calculation of the solidification paths of selected alloys in the
composition field investigated for the limiting cases of (a) complete equilibrium followed by the alloy system, and (b) no
solid diffusion (i.e., segregation) with equilibrium maintained at the solidifying front and complete mixing in the liquid
phase. 相似文献
12.
D. M. Kundrat M. Chochol J. F. Elliott 《Metallurgical and Materials Transactions B》1984,15(4):663-676
The phase relationships between the liquid phase and the primary solid phases were investigated in the iron-rich corner of
the Fe-Cr-C system. The investigation consisted of measurements of tie-lines and the liquidus surface of the liquid-delta
(bcc) and liquid-gamma (fcc) equilibria in the Gibbs triangle, bounded by 0 to 1.4 wt pct C and 0 to 25 wt pct Cr (bal. Fe).
The peritectic surface of the three-phase equilibrium was also measured. The temperature ranged from 1811 to about 1750 K.
The tie-lines were obtained from liquid-solid equilibrium couples, and the liquidus and peritectic surfaces, by differential
thermal analysis (DTA). A statistical procedure was applied to determine from the experimental results the parameters required
for a thermodynamic model of the system. Calculations by the model are in good agreement with the experimental results. As
a consequence the model can be used to interpolate and extrapolate properties and compositions of phases in equilibrium in
the system within the composition and temperature field investigated.
D.M. KUNDRAT, formerly Research Fellow at Massachusetts Institute of Technology
M. CHOCHOL, formerly Research Assistant, Massachusetts Institute of Technology 相似文献
13.
D. M. Kundrat 《Metallurgical and Materials Transactions A》1986,17(10):1825-1835
The phase relationships between the liquid phase and the primary solid phases were investigated in the iron-rich corner of
the quinary system Fe-Cr-Mn-Ni-C. Of the five quaternary systems that comprise the quinary system, this study was limited
to the three quaternary systems which contain both carbon and iron as two of the components;viz.: Fe-Cr-Mn-C, Fe-Cr-Ni-C, and Fe-Mn-Ni-C, as well as all of the binary and ternary subsystems that have iron as a component.
This paper discusses the modeling efforts for these systems, with particular emphasis on the ternary systems Fe-Cr-Mn and
Fe-Mn-Ni and the quaternary systems Fe-Cr-Mn-C and Fe-Mn-Ni-C. The experimental investigation consisted of measurements of
tie-lines for the liquid-delta (bcc) and the liquid-gamma (fcc) equilibria in the iron-rich corner of the Gibbs simplex bounded
by 0 to 25 wt pct Cr, 0 to 12 wt pct Mn, 0 to 25 wt pct Ni, and 0 to 1.2 wt pct C (bal. Fe). The temperature ranged from 1811
to about 1750 K. Compositions for the tie-lines were obtained from liquid-solid equilibrium couples, and the temperatures
for the equilibrium by differential thermal analysis (DTA). Parameters were selected in a thermodynamic model of the alloy
system to minimize the square of the difference between experimentally and calculated tie-lines, the latter being implicitly
a function of the derived parameters in the model. Binary and higher-order parameters were generally required. Ternary parameters
were obtained on ironcarbon base alloys Fe-Cr-C, Fe-Mn-C, and Fe-Ni-C, and for the Fe-Cr-Ni system, but not for the Fe-Cr-Mn
and Fe-Mn-Ni systems. Of the quaternary systems investigated, quaternary parameters were required only for theL/δ equilibrium in the Fe-Cr-Ni-C system; the Fe-Cr-Mn-C and Fe-Mn-Ni-C systems were found to be represented adequately by employing
only binary and ternary parameters. 相似文献
14.
Formation and Stability of Equiatomic and Nonequiatomic Nanocrystalline CuNiCoZnAlTi High-Entropy Alloys by Mechanical Alloying 总被引:1,自引:0,他引:1
Varalakshmi S. Kamaraj M. Murty B.S. 《Metallurgical and Materials Transactions A》2010,41(10):2703-2709
Nanocrystalline equiatomic high-entropy alloys (HEAs) have been synthesized by mechanical alloying in the Cu-Ni-Co-Zn-Al-Ti
system from the binary CuNi alloy to the hexanary CuNiCoZnAlTi alloy. An attempt also has been made to find the influence
of nonequiatomic compositions on the HEA formation by varying the Cu content up to 50 at. pct (Cu
x
NiCoZnAlTi; x = 0, 8.33, 33.33, 49.98 at. pct). The phase formation and stability of mechanically alloyed powder at an elevated temperature
(1073 K [800 °C] for 1 hour) were studied. The nanocrystalline equiatomic Cu-Ni-Co-Zn-Al-Ti alloys have a face-centered cubic
(fcc) structure up to quinary compositions and have a body-centered cubic (bcc) structure in a hexanary alloy. In nonequiatomic
alloys, bcc is the dominating phase in the alloys containing 0 and 8.33 at. pct of Cu, and the fcc phase was observed in alloys
with 33.33 and 49.98 at. pct of Cu. The Vicker’s bulk hardness and compressive strength of the equiatomic nanocrystalline
hexanary CuNiCoZnAlTi HEA after hot isostatic pressing is 8.79 GPa, and the compressive strength is 2.76 GPa. The hardness
of these HEAs is higher than most commercial hard facing alloys (e.g., Stellite, which is 4.94 GPa). 相似文献
15.
M. Wenderoth U. Glatzel R. Völkl L. A. Cornish R. Süss S. Vorberg B. Fischer 《Metallurgical and Materials Transactions A》2005,36(3):567-575
The objective of this work is to mimic the microstructure and strengthening mechanisms of Ni-based superalloys in a new group
of high-temperature alloys based on the system Pt-Al. The elements Cr and Ni were chosen as further alloying components. Having
a face-centered cubic (fcc) crystal structure with an Ll2-ordered and coherently embedded phase, these new alloys should increase creep and corrosion resistance beyond Ni-based superalloys.
After arc melting and heat treatment, the alloys were investigated by means of scanning electron microscopy (SEM) and X-ray
diffraction (XRD). In the aged condition, the alloy composition 13 at. pct Al, 3 at. pct Cr, 7 at. pct Ni, and balance Pt
showed the most promising microstructure with cubical precipitates, 30 pct precipitate volume fraction, and a lattice misfit
of about −0.1 pct at room temperature.
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
16.
Modification in the aluminum silicon system 总被引:2,自引:0,他引:2
Alloys in the range 0 to 24 wt pct Si have been examined by careful thermal analysis, macroand microscopical study with modification
by a mixed alkali fluoride flux, and by separate additions of sodium, potassium, lithium, and strontium. Sodium and strontium
exert similar effects and potassium and lithium differing and minor effects; with a mixed alkali flux the influence of sodium
is dominant. The normal and modified eutectic arrests in the presence of primary aluminum both show comparable supercoolings
and recalescence behavior relative to the horizontal growth temperatures, but this is not observed in hypereutectic alloys
containing primary silicon. Both normal and modified eutectics grow radially inward from crucible walls, but the details of
the growth fronts are very different: there is no nucleation from the bulk liquid in modified alloys and it is uncertain if
this occurs in normal alloys. It is concluded that the structural modification in furnace cooled ingots, as in directionally
grown samples, is primarily caused by modified growth of silicon. The mechanism(s) for such modification are briefly discussed.
Formerly Postdoctoral Research Associate, Michigan Technological University. 相似文献
17.
18.
Daniel P. Abraham Sean M. McDeavitt Jangyul Park 《Metallurgical and Materials Transactions A》1996,27(8):2151-2159
Stainless steel-zirconium alloys have been developed at Argonne National Laboratory to contain radioactive metal isotopes
isolated from spent nuclear fuel. This article discusses the various phases that are formed in as-cast alloys of type 304
stainless steel and zirconium that contain up to 92 wt pct Zr. Microstructural characterization was performed by scanning
electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS), and crystal structure information was obtained by
X-ray diffraction. Type 304SS-Zr alloys with 5 and 10 wt pct Zr have a three-phase microstructure—austenite, ferrite, and
the Laves intermetallic, Zr(Fe,Cr,Ni)2+x. whereas alloys with 15, 20, and 30 wt pct Zr contain only two phases—ferrite and Zr(Fe,Cr,Ni)2+x. Alloys with 45 to 67 wt pct Zr contain a mixture of Zr(Fe,Cr,Ni)2+x and Zr2(Ni,Fe), whereas alloys with 83 and 92 wt pct Zr contain three phases—α-Zr, Zr2(Ni,Fe), and Zr(Fe,Cr,Ni)2+x. Fe3Zr-type and Zr3Fe-type phases were not observed in the type 304SS-Zr alloys. The changes in alloy microstructure with zirconium content have
been correlated to the Fe-Zr binary phase diagram. 相似文献
19.
Deformation-processed metal-metal composites (DMMC) of Mg-Li alloys containing steel reinforcing fibers were prepared by infiltrating
a preform of steel wool with the molten matrix. The Li content was varied to control the crystal structure of the matrix;
Mg-4 wt pct Li is hexagonal close packed (hcp), while Mg-12 wt pct Li is body-centered cubic (bcc). The low carbon steel used
as the reinforcing fiber is essentially bcc. The hcp/bcc and bcc/bcc composites were subsequently deformed by rolling and
by extrusion/swaging and mechanically tested to relate the tensile strength of the composites to true deformation strain.
The hcp/bcc composites had limited formability at temperatures up to 400 °C, while the bcc/bcc composites had excellent formability
during sheet rolling at room temperature but limited formability during swaging at room temperature. The tensile strengths
of the hcp/bcc composite rod and the bcc/bcc composite sheet and rod increased moderately with deformation, though less than
predicted from rule-of-mixtures (ROM) calculations. This article presents the experimental data for these DMMC materials and
comments on the possible effect of texture development in the matrix and fiber phases on the deformation characteristics of
the composite material. 相似文献
20.
The phase transformations of five binary iron‐manganese (Fe‐Mn) alloys with manganese contents ranging from 1 to 21 weight percent have been characterized in the temperature range between room temperature and 1250 °C. Differential scanning calorimetry and dilatometry were used to experimentally characterize both the phases and magnetic transformation temperatures. X‐ray diffraction and light optical microscopy were employed for the room temperature microstructure characterization. Depending on the manganese content of the alloy, three different crystal structures can be found: body centered cubic (bcc) (α/α'), face centered cubic (fcc) (γ), and hexagonal compact (hcp) (?). At manganese contents lower than 10% the phases present are the α/α’ (bcc) and γ (fcc). Above ~10 weight percent manganese increasing amounts of ? (hcp) is formed at the expense of the body centered cubic structures, and no α/α’ (bcc) is observed for the 21 weight‐percent manganese alloy. 相似文献