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1.
The martensite start temperature (Ms), the martensite austenite re‐transformation start temperature (As) and the re‐transformation finish temperature (Af) of six high alloyed Cr‐Mn‐Ni steels with varying Ni and Mn contents in the wrought and as‐cast state were studied. The aim of this investigation is the development of the relationships between the Ms, As, Af, T0 temperatures and the chemical composition of a new type of Cr‐Mn‐Ni steels. The investigations show that the Ms, As and Af temperatures decrease with increasing nickel and manganese contents. The Af temperature depends on the amount of martensite. Regression equations for the transformation temperatures are given. The experimental results are based on dilatometer tests and microstructure investigations. 相似文献
2.
The reverse martensitic transformation in cold‐rolled metastable austenitic stainless steel has been investigated via heat treatments performed for various temperatures and times. The microstructural evolution was evaluated by differential scanning calorimetry, X‐ray diffraction and microscopy. Upon heat treatment, both diffusionless and diffusion‐controlled mechanisms determine the final microstructure. The diffusion reversion from α′‐martensite to austenite was found to be activated at about 450°C and the shear reversion is activated at higher temperatures with Af′ ~600°C. The resulting microstructure for isothermal heat treatment at 650°C was austenitic, which inherits the α′‐martensite lath morphology and is highly faulted. For isothermal heat treatments at temperatures above 700°C the faulted austenite was able to recrystallize and new austenite grains with a low defect density were formed. In addition, carbo‐nitride precipitation was observed for samples heat treated at these temperatures, which leads to an increasing Ms‐temperature and new α′‐martensite formation upon cooling. 相似文献
3.
Microstructure-composition relationships and Ms temperatures have been determined in high purity nitrided Fe-Cr-Mn alloys, as part of a program to develop improved corrosion-abrasion
resistant steels with unstable austenitic microstructures. Compositions in the range 8 to 12 pct Cr, 0 to 10 pct Mn, and 0
to 0.6 pct N were investigated by a resistivity technique to determine Ms temperatures and by X-ray diffraction and metallography to determine constitution. Hardness measurements were also made.
At the low alloy end of the range, microstructures after annealing and air cooling are fully martensitic while at the high
alloy end they are fully austenitic. At intermediate compositions, mixed martensite-austenite microstructures (with epsilon
present as a minor phase in some cases) and unstable austenitic microstructures are obtained. The austenitic alloys contain
a high density of stacking faults and the unstable austenitic alloys transform to martensite on deformation. At low N contents
(up to at least 0.25 pct N) the Ms-composition relationship is linear and described by: Ms = 555 - 9(Cr - 8) - 40Mn - 450N [1] where Ms is in °C and Cr, Mn, and N are the weight percentages of these elements. At higher N contents, the Ms generally falls more rapidly with increasing nitrogen content. Nitrogen solubility at 1050 °C exceeds about 0.3 pct in all
alloys and increases with increasing Cr and Mn content. In commercial purity steels, unstable austenitic microstructures are
expected to be obtained in compositions around 10 to 14 pct Cr, 8 to 12 pct Mn, and 0.1 to 0.3 pct N when the total level
of these elements is selected to ensure the Ms is below room temperature. 相似文献
4.
M. Arbab Rehan Anna Medvedeva Lars-Erik Svensson Leif Karlsson 《Metallurgical and Materials Transactions A》2017,48(11):5233-5243
Retained austenite transformation was studied for a 5 wt pct Cr cold work tool steel tempered at 798 K and 873 K (525 °C and 600 °C) followed by cooling to room temperature. Tempering cycles with variations in holding times were conducted to observe the mechanisms involved. Phase transformations were studied with dilatometry, and the resulting microstructures were characterized with X-ray diffraction and scanning electron microscopy. Tempering treatments at 798 K (525 °C) resulted in retained austenite transformation to martensite on cooling. The martensite start (M s ) and martensite finish (M f ) temperatures increased with longer holding times at tempering temperature. At the same time, the lattice parameter of retained austenite decreased. Calculations from the M s temperatures and lattice parameters suggested that there was a decrease in carbon content of retained austenite as a result of precipitation of carbides prior to transformation. This was in agreement with the resulting microstructure and the contraction of the specimen during tempering, as observed by dilatometry. Tempering at 873 K (600 °C) resulted in precipitation of carbides in retained austenite followed by transformation to ferrite and carbides. This was further supported by the initial contraction and later expansion of the dilatometry specimen, the resulting microstructure, and the absence of any phase transformation on cooling from the tempering treatment. It was concluded that there are two mechanisms of retained austenite transformation occurring depending on tempering temperature and time. This was found useful in understanding the standard tempering treatment, and suggestions regarding alternative tempering treatments are discussed. 相似文献
5.
Stress‐Temperature‐Transformation (STT) and Deformation‐Temperature‐Transformation (DTT) diagrams are well‐suited to characterize the TRIP (transformation‐induced plasticity) and TWIP (twinning‐induced plasticity) effect in steels. The triggering stresses for the deformation‐induced microstructure transformation processes, the characteristic temperatures, the yield stress and the strength of the steel are plotted in the STT diagram as functions of temperature. The elongation values of the austenite, the strain‐induced twins and martensite formations are shown in the DTT diagram. The microstructure evolution of a novel austenitic Cr‐Mn‐Ni (16%Cr, 6% Mn, 6% Ni) as‐cast steel during deformation was investigated at various temperatures using static tensile tests, optical microscopy and the magnetic scale for the detection of ferromagnetic phase fraction. At the temperatures above 250 °C the steel only deforms by glide deformation of the austenite. Strain‐induced twinning replaces the glide deformation at temperatures below 250 °C with increasing strain. Below 100 °C, the strain‐induced martensite formation becomes more pronounced. The kinetics of the α'‐martensite formation is described according to stress and deformation temperatures. The STT and DTT diagrams, enhanced with the kinetics of the martensite formation, are presented in this paper. 相似文献
6.
The TRIP effect in austenitic stainless steels leads to temperature dependent mechanical properties. As this is caused by stress or strain induced austenite/martensite transformation a predeformation at low temperatures (cryoforming) will change the microstructure and the transformation behaviour of the remaining austenite constituent. The mechanical properties in tensile tests and the J‐integral of the chromium and nickel alloyed steels 1.4301 and 1.4571 have been tested in the temperature range from 123 to 323 K in the as‐industrially supplied condition and after 10 % cryoforming at 77 K. The temperature dependence of the elongation values and the strain hardening behaviour of the undeformed steels is much more pronounced than of the yield and tensile strength. The mechanical behaviour can be explained by differences in response to the ?‐, the αe'‐ and the αg'‐martensite transformation. A cryoforming changes the mechanical properties of the examined austenitic stainless steels. 相似文献
7.
Xiang-Mingh He Li-Jian Rong Yi-Yi Li De-Sheng Yan Zhi-Min Jiang 《Metallurgical and Materials Transactions A》2004,35(9):2783-2788
The shape-memory characteristics in the Ni41.3Ti38.7Nb20 alloy have been investigated by means of cryogenic tensile tests and differential scanning calorimetry measurement. The martensite
start temperature M
s
could be adjusted to around the liquid nitrogen temperature by controlling the cooling condition. The reverse transformation
start temperature A′
s
rose to about 70 °C after the specimens were deformed to 16 pct at different temperatures, where the initial states of the
specimens were pure austenite phase, martensite phase, or duplex phase. The shape-memory effect and the reverse transformation
temperatures were studied on the specimens deformed at (M
s
+30 °C). It was found that once the specimens deformed to 16 pct, a transformation hysteresis width around 200 °C could be
attained and the shape recovery ratio could remain at about 50 pct. The Ni41.3Ti38.7Nb20 alloy is a promising candidate for the cryogenic engineering applications around the liquid nitrogen temperature. The experimental
results also indicated that the transformation temperature interval of the stress-induced martensite is smaller by about one
order of magnitude than that of the thermal-induced martensite. 相似文献
8.
Thecavitationerosionisasolidsurfacedamageattributedtomechanicaleffectsofmicro jet′sshock ingloadingresultedfrom gaseousand orvaporouscavityimplosion .Cavitationdamageisaseriousprobleminhydraulicmachines ,resultinginlossesofefficiencyandreductionofpower .Soapplicationofmorecavitationerosionresistantmaterialsisveryim portantto preventorreducecavitationdamage .Manymetalsandalloyshavebeenresearchedundercavitationerosionconditions[1-12 ] .Thecrystalstruc ture ,martensitictransformation ,workharden… 相似文献
9.
Temperature Dependent Deformation Mechanisms of a High Nitrogen‐Manganese Austenitic Stainless Steel
The influence of temperature on the deformation behaviour of a Fe‐16.5Cr‐8Mn‐3Ni‐2Si‐1Cu‐0.25N (wt%) austenitic stainless steel alloy was investigated using transmission electron microscopy and X‐ray diffraction measurements. Recrystallized samples were deformed under tension at ?75°C, 20°C, and 200°C and the microstructures were characterized after 5% strain and after testing to failure. Deformation to failure at ?75°C resulted in extensive transformation induced plasticity (TRIP) with over 90% α′‐martensite. The sample deformed to 5% strain at ?75°C shows that the austenite transformed first to ?‐martensite which served to nucleate the α′‐martensite. Transformation induced martensite prohibits localized necking providing total elongation to failure of over 70%. At room temperature, in addition to some TRIP behaviour, the majority of the deformation is accommodated by dislocation slip in the austenite. Some deformation induced twinning (TWIP) was also observed, although mechanical twinning provides only a small contribution to the total deformation at room temperature. Finally, dislocation slip is the dominant deformation mechanism at 200°C with a corresponding decrease in total elongation to failure. These changes in deformation behaviour are related to the temperature dependence on the relative stability of austenite and martensite as well as the changes in stacking fault energy (SFE) as a function of temperature. 相似文献
10.
Metallographic studies have been conducted on a 0.024 pct C-16 pct Cr-1.5 pct Mo-5 pct Ni stainless steel to study the phase reactions associated with heat treatments and investigate the strengthening mechanisms of the steel. In the normalized condition, air cooled from 1010 °C, the microstructure consists of 20 pct ferrite and 80 pct martensite. Tempering in a temperature range between 500 and 600 °C results in a gradual transformation of martensite to a fine mixture of ferrite and austenite. At higher tempering temperatures, between 600 and 800 °C, progressively larger quantities of austenite form and are converted during cooling to proportionally increasing amounts of fresh martensite. The amount of retained austenite in the microstructure is reduced to zero at 800 °C, and the microstructure contains 65 pct re-formed martensite and 35 pct total ferrite. Chromium rich M23C6 carbides precipitate in the single tempered microstructures. The principal strengthening is produced by the presence of martensite in the microstructure. Additional strengthening is provided by a second tempering treatment at 400 °C due to the precipitation of ultrafine (Cr, Mo) (C,N) particles in the ferrite. 相似文献
11.
Alexander Kovalev Andreas Jahn Andreas Weiß Steffen Wolf Piotr R. Scheller 《国际钢铁研究》2012,83(6):576-583
The mechanical behavior and microstructure evolution during deformation of novel austenitic Cr–Mn–Ni as‐cast steels with varied Ni content were investigated at various temperatures using static tensile tests, optical microscopy, and the magnetic scale for the detection of ferromagnetic phase fraction. To summarize all knowledge about the deformation‐induced processes, the STT and DTT diagrams were developed for Cr–Mn–Ni steels. The diagrams illustrate the different deformation mechanisms depending on temperature and tension load, and quantify the elongation of the deformation mechanisms. The deformation‐induced ε‐ and α' martensite formation and twinning – the TRIP and TWIP effects – occur in the Cr–Mn–Ni steels depending on the chemical composition and temperature. The differences of deformation‐induced processes depend on thermodynamics and are confirmed by thermodynamic calculations. The nucleation threshold of γ → α′ transformation was determined for the investigated Cr–Mn–Ni steels. 相似文献
12.
The knowledge of the stress‐ and deformation‐induced martensite formation in metastable austenitic steels including the formation temperatures and amounts formed is of considerable importance for the understanding of the transformation induced plasticity. For this purpose a stress‐temperature‐transformation (STT) and a deformation‐temperature‐transformation (DTT) diagram have been developed for the steel X5CrNi 18 10 (1.4301, AISI 304). It is shown that the Md‐temperature for γ→?, ?→α', γ→?→α’ and γ→α’ martensite formation is defined by two stress‐temperature curves which show a different temperature dependence. They specify the beginning and the end of the deformation‐induced martensite formation in the range of uniform elongation. The intersection point defines the corresponding Md‐temperature. The stress difference which results from the stresses for the end and the beginning of the martensite formation shows positive values below the Md‐temperature. It defines the amount of martensite being formed. When the Mdγ→? temperature is reached and the formation of the first deformation‐induced amount of ?‐martensite appears, an anomalous temperature dependence of the maximum uniform elongation starts. The highest values of the maximum uniform elongation are registered for the tested steel in the immediate vicinity of the Mdγ→α' or the Mdγ→?→α' temperature ‐ similar as in other metastable austenitic CrNi steels. At this temperature the highest amount of deformation‐induced ?‐phase exists. The transformation plasticity in the test steel is considerably caused by the deformation‐induced ? and α’ martensite formation. Using the new evaluation method, the increase of plasticity ΔA (TRIP‐effect) and strength ΔR can be quantified. 相似文献
13.
The equilibrium conditions of four duplex stainless steels; Fe‐23Cr‐4.5Ni‐0.1N, Fe‐22Cr‐5.5Ni‐3Mo‐0.17N, Fe‐25Cr‐7Ni‐4Mo‐0.27N and Fe‐25Cr‐7Ni‐4Mo‐1W‐1.5Cu‐0.27N were studied in the temperature region from 700 to 1000 °C. Phase compositions were determined with SEM EDS and the phase fractions using image analysis on backscattered SEM images. The results showed that below 1000 °C the steels develop an inverse duplex structure with austenite and sigma phase, of which the former is the matrix phase. With decreasing temperature, the microstructure will be more and more complex and finely dispersed. The ferrite is, for the higher alloyed steels, only stable above 1000 °C and at lower temperatures disappears in favour of intermetallic phases. The major intermetallic phase is sigma phase with small amounts of chi phase, the latter primarily in high Mo and W grades. Nitrides, not a focus in this investigation, were present as rounded particles and acicular precipitates at lower temperatures. The results were compared to theoretical predictions using the TCFE5 and TCFE6 databases. 相似文献
14.
The characteristics of the B2(β) to L10(β′) martensitic transformation in NiAl base alloys containing a small amount of third elements have been investigated by
differential scanning calorimetry (DSC), X-ray diffraction (XRD), and transmission electron microscopy (TEM). It is found
that in addition to the normal Ll0 (3R) martensite, the 7R martensite is also present in the ternary alloys containing Ti, Mo, Ag, Ta, or Zr. While the addition
of third elements X (X: Ti, V, Cr, Mn, Fe, Zr, Nb, Mo, Ta, W, and Si) to the binary Ni64Al36 alloy stabilizes the parentβ phase, thereby lowering the Ms temperature, addition of third elements such as Co, Cu, or Ag destabilizes theβ phase, increasing the Ms temperature. The occurrence of the 7R martensite structure is attributed to solid solution hardening arising from the difference
in atomic size between Ni and Al and the third elements added. The variation in Ms temperature with third element additions is primarily ascribed to the difference in lattice stabilities of the bcc and fcc
phases of the alloying elements. 相似文献
15.
Influence of annealing treatment on the formation of nano/submicron grain size AISI 301 Austenitic stainless steels 总被引:1,自引:0,他引:1
D. L. Johannsen A. Kyrolainen P. J. Ferreira 《Metallurgical and Materials Transactions A》2006,37(8):2325-2338
Nano/submicron austenitic stainless steels have attracted increasing attention over the past few years due to fine structural
control for tailoring engineering properties. At the nano/submicron grain scales, grain boundary strengthening can be significant,
while ductility remains attractive. To achieve a nano/submicron grain size, metastable austenitic stainless steels are heavily
cold-worked, and annealed to convert the deformation-induced martensite formed during cold rolling into austenite. The amount
of reverted austenite is a function of annealing temperature. In this work, an AISI 301 metastable austenitic stainless steel
is 90 pct cold-rolled and subsequently annealed at temperatures varying from 600 °C to 900 °C for a dwelling time of 30 minutes.
The effects of annealing on the microstructure, average austenite grain size, martensite-to-austenite ratio, and carbide formation
are determined. Analysis of the as-cold-rolled microstructure reveals that a 90 pct cold reduction produces a combination
of lath type and dislocation cell-type martensitic structure. For the annealed samples, the average austenite grain size increases
from 0.28 μm at 600 °C to 5.85 μm at 900 °C. On the other hand, the amount of reverted austenite exhibits a maximum at 750
°C, where austenite grains with an average grain size of 1.7 μm compose approximately 95 pct of the microstructure. Annealing
temperatures above 750 °C show an increase in the amount of martensite. Upon annealing, (Fe, Cr, Mo)23C6 carbides form within the grains and at the grain boundaries. 相似文献
16.
The effects of transformation cycling between the parent (P) and martensite (M) phases of selected Cu-Zn-Al: alloys were studied.
Using differential scanning calorimetry it was observed that the martensite start temperature, Ms, progressively shifts upward with cycling. Also, the proportion of the microstructure actually undergoing P↔M transformation
decreases. Transmission electron microscope observations reveal dislocation substructures generated by martensite transformation
and reversion. 相似文献
17.
The concept of combined addition of C and N, as persued in previous work on martensitic steels, is transferred to austenitic stainless steels in order to gain highest phase stability. Thermodynamic calculations with special respect to the influence of temperature and interstitial content (C, N or C + N) were studied in the FeCrMnNC‐system. Promising compositions like Fe‐13Cr‐17Mn and Fe‐13Cr‐21Mn revealed an extended austenitic phase field. Some appropriate alloys were investigated with regard to their microscopic and electron structure. The concentration of free electrons in the austenite as the origin of phase stabilitiy increased in the order of C, N, C + N being added. Thus, the metallic character of interatomic bonding is enhanced, which entails short range atomic order. Hence, the substitutional alloy content can be minimized. 相似文献
18.
M. J. Cieslak J. A. Vandenavyle M. J. Carr C. R. Hills R. E. Semarge 《Metallurgical and Materials Transactions A》1988,19(12):3063-3069
The partitioning of alloying elements in as-solidified PH 13-8 Mo stainless steel containing up to 1.02 wt pct Pd has been
investigated. The as-solidified structure is composed of two major phases, martensite and ferrite. Electron probe microanalysis
reveals that Mo, Cr, and Al partition to the ferrite phase while Fe, Ni, Mn, and Pd partition to the martensite (prior austenite)
during solidification and cooling from the solidus. In addition to bulk segregation between phases, precipitation of the intermetallic,
PdAI, in the retained ferrite is observed. Precipitation of the normal hardening phase, β-NiAl, is also observed in the retained
ferrite. Partition ratios of the various alloying elements are determined and are compared with those observed previously
in duplex Fe-Cr-Ni stainless steel solidification structures. The martensite start temperature (Ms) was observed to decrease with increasing Pd concentration. 相似文献
19.
Tensile properties of high Mn austenitic Fe‐26.5Mn‐3.6Al‐2.2Si‐0.38C‐0.005B (HM1) and Fe‐18.9Mn‐0.62C‐0.02Ti‐0.005B (HM2, in mass%) steels after different solution treatments have been investigated. The results show that the solution treatment has a significant influence on microstructure and mechanical properties of the investigated steels. By appropriate solution treatment the product of tensile strength (Rm) and total elongation (A50) of the hot rolled steel can be improved from ? 40000‐50000 MPa% to ? 55000‐65000 MPa% depending on the steel chemical composition. A solution treatment with a very high temperature, e.g. at 1100 °C for the Fe‐18.9Mn‐0.62C‐0.02Ti‐0.005B steel, results in a significant increase in the ?‐martensite fraction during quenching. This deteriorates the ductility of the steel. A solution treatment at low temperature in the austenitic range, e.g. at 700 °C for the Fe‐18.9Mn‐0.62C‐0.02Ti‐0.005B steel, results in a decrease in the grain size of the steel. This suppresses the ?‐martensite transformation during cooling. EBSD measurements revealed the mechanisms contributing to the overall plasticity of the investigated steels on the microscale. The plasticity of the 26.5Mn‐3.6Al‐2.2Si‐0.38C‐0.005B steel is produced mainly by TWIP mechanism under the examined experimental conditions, whereas for the Fe‐18.9Mn‐0.62C‐0.02Ti‐0.005B steel TWIP and TRIP mechanisms occur with different degrees depending on the test temperature of the tensile test. 相似文献
20.
《粉末冶金学》2013,56(3):331-337
AbstractThe effect of austenitisation temperature on austenite transformations on 0·7%C Astaloy CrL steel was studied by dilatometry. The steel has a good hardenability, forming martensite at most of the austenitisation temperatures and cooling rates investigated. Only on cooling from 1073 K, austenite transforms into bainite completely at 3 K s?1 and partially at 12·5 K s?1. The effect of austenitisation temperature on the prior austenitic grain size is quite poor because of the pinning effect of pores. The martensite start temperature Ms increases slightly with the austenitisation temperature up to 1173 K and decreases at 1523 K. This trend is due to the presence of nanometric carbides (Cr23C6), which were detected at TEM. They dissolve almost completely in austenite at 1523 K only, increasing the stability of austenite against the martensitic transformation. The effect of temperature in the range from 1073 K up to 1523 K is poor. As a consequence, the microstructural characteristics of hardened steels are very similar. 相似文献