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1.
A systematic study of stress-induced and thermal-induced transformation of retained austenite in carburized 4320 steel with
an initial retained austenite of 35 pct has been conducted. The transformation was monitored by recording the change in volume
of smooth fatigue specimens. Stress-induced transformation was studied by conducting monotonic and cyclic tests at temperatures
in the range from 22 °C to 150 °C. The volumetric transformation strain was as large as 0.006 at 22 °C. The anisotropy of
the transformation was such that the axial transformation strain component exceeded the diametral transformation strain component
by a factor of 1.4. Thermal-induced transformation was investigated with temperature stepup tests in the range from 150 °C
to 255 °C at constant stress (-500 MPa, 0 MPa, and 500 MPa) and with static tests where temperature was held constant at zero
load. The maximum thermal-induced volumetric transformation strain of 0.006 was independent of stress. However, the anisotropy
of the transformation strain components was dependent on stress direction and magnitude. An axial tensile stress increased
the axial transformation strain relative to the diametral transformation strain. The influence of low-temperature creep(T = 150 °C) on the anisotropy of strains is noted. The differences between stress-induced and thermal-induced transformation
mechanisms are discussed. Thermal-induced transformation primarily occurred at temperatures between 100 °C and 200 °C, with
the rate of transformation increasing with temperature, while the stress-induced transformation primarily occurred at 22 °C,
with the rate of transformation decreasing with increasing temperature. There was no stress-induced transformation above 60
°C. 相似文献
2.
Austenite formation from different microstructural conditions has been studied in an Fe-lV-0.2C steel. The starting microstructures
of ferrite, bainite, and martensite, and the morphology of austenite formation have been examined in detail by light microscopy
and transmission electron microscopy. Retained austenite in quenched martensitic areas has been used to establish the crystallographic
relationships during austenite nucleation, and to indicate the behavior of the initial vanadium carbide dispersion present
in the ferrite starting microstructure. Limited measurements were also made of the kinetics of austenitization.
Formerly Research Student, Department of Metallurgy and Materials Science, University of Cambridge.
Formerly of Royal Society, Warren Research Fellow, Department of Metallurgy and Materials Science, University of Cambridge. 相似文献
3.
The kinetics of the thermal stabilization of austenite have been studied in a 0.5 pct C 19 pct Ni steel within the range +300°C
to -78°C. The Kinsman-Shyne model for stabilization is seen to be inadequate outside the temperature range +150°C to -20°C
for this alloy. Stabilization at subzero temperatures can exhibit thermal reversibility without, however, requiring the fundamental
mechanism itself to be similarly reversible.
Formerly Research Student, Department of Metallurgy, University of Sheffield. 相似文献
4.
This paper is concerned with the direct transformation of austenite at high temperatures to form ferrite and alloy carbide
dispersions. The ferrite/austenite interfaces vary from high energy random boundaries to low energy planar boundaries which
grow by step propagation, while the alloy carbide morphologies include a pearlitic form, fine fibers and fine banded arrays
of particles. It is shown that these morphologies are closely related to the mode of growth of the ferritic matrix. The role
of various alloying elements on the carbide dispersion is examined, and the effects of other metallurgical variables on the
banded dispersions are discussed, including factors which influence the dispersion stability. The mechanical properties of
directly transformed alloy steels are shown to depend largely on the ferrite grain size and the state of the carbide dispersion.
Micro-alloyed steels subjected to controlled rolling provide an excellent example of the achievement of high strength and
toughness levels by control of these variables. The paper finally attempts to show how such benefits can be achieved in low
and medium alloy steels, and in particular where resistance to creep failure at elevated temperatures is an important property. 相似文献
5.
This paper is concerned with the direct transformation of austenite at high temperatures to form ferrite and alloy carbide
dispersions. The ferrite/austenite interfaces vary from high energy random boundaries to low energy planar boundaries which
grow by step propagation, while the alloy carbide morphologies include a pearlitic form, fine fibers and fine banded arrays
of particles. It is shown that these morphologies are closely related to the mode of growth of the ferritic matrix. The role
of various alloying elements on the carbide dispersion is examined, and the effects of other metallurgical variables on the
banded dispersions are discussed, including factors which influence the dispersion stability. The mechanical properties of
directly transformed alloy steels are shown to depend largely on the ferrite grain size and the state of the carbide dispersion.
Micro-alloyed steels subjected to controlled rolling provide an excellent example of the achievement of high strength and
toughness levels by control of these variables. The paper finally attempts to show how such benefits can be achieved in low
and medium alloy steels, and in particular where resistance to creep failure at elevated temperatures is an important property. 相似文献
6.
7.
S. F. Dirnfeld B. M. Korevaar F. Van't Spijker 《Metallurgical and Materials Transactions B》1974,5(6):1437-1444
The transformation to austenite in a fine grained tool steel has been investigated quantitatively until the disappearance
of the ferrite. The initial structure of the steel consisted of ferrite and globular carbides. The nucleation starts at carbides
which lie at the ferrite grain boundaries. The kinetics are in good agreement with Cahn's theory of grain boundary nucleated
transformation. A constant growth rate was found up to 30 pct transformation. Site saturation occurs early in the reaction;
this was confirmed by metallographic examination. The rate law is controlled by growth and is independent of the nucleation
rate. The mechanism which is controlling this growth is the advancing ferrite-austenite interface reaction. The alloying elements
influence the atomic mobilities, increasing the necessary activation energy to about 110 kcal/mol.
Formerly Research Engineer, Metallurgical Department, Delft University of Technology 相似文献
8.
A. I. Popelyukh A. A. Bataev A. M. Teplykh A. Yu. Ognev E. D. Golovin 《Steel in Translation》2011,41(4):361-364
Heat treatment with mixed martensite-bainite transformation of austenite is optimized in terms of strength and fatigue-crack
resistance. For the manufacture of components in impact mechanisms, the best combination of strength, hardness, and crack
resistance is obtained for steel in which 40% martensite is formed on intermediate cooling, while isothermal heating converts
the residual supercooled austenite to lower bainite. This increases the strength by 200–250 N/mm2 in relation to quenching + tempering + isothermal quenching (with comparable crack resistance) and increases the resistance
to fatigue-crack propagation by a factor of 1.3–2 (with analogous strength). 相似文献
9.
以Mn13钢为基础,在其他基本成份不变的情况下,对不同锰含量的奥氏体锰钢性能进行了研究,表明锰含量在7%-20%均可得到单一奥氏体组织的锰钢。 相似文献
10.
Studies on the morphology and crystallography of austenite precipitated from ferrite were performed in an Fe-22.5 pct Cr-4.7
pct Ni-3 pct Mo-duplex stainless steel. Samples were solution treated at 1325°C (yielding a grain size of approximately 2
mm), water quenched, and then aged at temperatures ranging from 700 °C to 1100 °C for times ranging from 5000 to 30,000 seconds.
The morphology of grain boundary precipitates depends on the grain boundary segment at which the precipitates are formed,
and may be adequately described by the Dubé classification system. Orientation relationships (ORs) between austenite and the
ferritic matrix were determined with electron backscattered diffraction (EBSD) analysis, employing graphic and algebraic methods.
Grain boundary precipitates exhibited Kurdjumov-Sachs (K-S) or Nishyiama-Wassermann (N-W) ORs with at least one of the adjacent
grains, and in some cases relationships intermediate between K-S and N-W appeared. In approximately 60 pct of the cases examined,
grain boundary precipitates show K-S or N-W ORs with both grains forming a boundary, though with small deviations (up to 5
deg) from the exact relationships.
This article is based on a presentation made in the “Hume-Rothery Symposium on Structure and Diffusional Growth Mechanisms
of Irrational Interphase Boundaries,” which occurred during the TMS Winter meeting, March 15–17, 2004, in Charlotte, NC, under
the auspices of the TMS Alloy Phases Committee and the co-sponsorship of the TMS-ASM Phase Transformations Committee. 相似文献
11.
Studies on the morphology and crystallography of austenite precipitated from ferrite were performed in an Fe-22.5 pct Cr-4.7
pct Ni-3 pct Mo-duplex stainless steel. Samples were solution treated at 1325°C (yielding a grain size of approximately 2
mm), water quenched, and then aged at temperatures ranging from 700 °C to 1100 °C for times ranging from 5000 to 30,000 seconds.
The morphology of grain boundary precipitates depends on the grain boundary segment at which the precipitates are formed,
and may be adequately described by the Dubé classification system. Orientation relationships (ORs) between austenite and the
ferritic matrix were determined with electron backscattered diffraction (EBSD) analysis, employing graphic and algebraic methods.
Grain boundary precipitates exhibited Kurdjumov-Sachs (K-S) or Nishyiama-Wassermann (N-W) ORs with at least one of the adjacent
grains, and in some cases relationships intermediate between K-S and N-W appeared. In approximately 60 pct of the cases examined,
grain boundary precipitates show K-S or N-W ORs with both grains forming a boundary, though with small deviations (up to 5
deg) from the exact relationships.
This article is based on a presentation made in the “Hume-Rothery Symposium on Structure and Diffusional Growth Mechanisms
of Irrational Interphase Boundaries,” which occurred during the TMS Winter meeting, March 15–17, 2004, in Charlotte, NC, under
the auspices of the TMS Alloy Phases Committee and the co-sponsorship of the TMS-ASM Phase Transformations Committee. 相似文献
12.
Studies on the morphology and crystallography of austenite precipitated from ferrite were performed in an Fe-22.5 pct Cr-4.7
pct Ni-3 pct Mo-duplex stainless steel. Samples were solution treated at 1325°C (yielding a grain size of approximately 2
mm), water quenched, and then aged at temperatures ranging from 700 °C to 1100 °C for times ranging from 5000 to 30,000 seconds.
The morphology of grain boundary precipitates depends on the grain boundary segment at which the precipitates are formed,
and may be adequately described by the Dubé classification system. Orientation relationships (ORs) between austenite and the
ferritic matrix were determined with electron backscattered diffraction (EBSD) analysis, employing graphic and algebraic methods.
Grain boundary precipitates exhibited Kurdjumov-Sachs (K-S) or Nishyiama-Wassermann (N-W) ORs with at least one of the adjacent
grains, and in some cases relationships intermediate between K-S and N-W appeared. In approximately 60 pct of the cases examined,
grain boundary precipitates show K-S or N-W ORs with both grains forming a boundary, though with small deviations (up to 5
deg) from the exact relationships.
This article is based on a presentation made in the “Hume-Rothery Symposium on Structure and Diffusional Growth Mechanisms
of Irrational Interphase Boundaries,” which occurred during the TMS Winter meeting, March 15–17, 2004, in Charlotte, NC, under
the auspices of the TMS Alloy Phases Committee and the co-sponsorship of the TMS-ASM Phase Transformations Committee. 相似文献
13.
Hermann Vetters 《国际钢铁研究》1996,67(10):408-411
The stress induced martensitic transformation in the upper metastable intermediate state of γ-α transformation in ferrous materials, structured as ferritic bainite, is discussed. The fibrous structured ferritic bainite consists of retained austenite and ferrite platelets growing in the [111]α//[101]γ direction. The ferrite growth Induces carbon enrichment of the adjacent austenite at the phase boundaries. Strengthening at high stress levels up to the yield point causes dislocation tangles in the ferrite fibre and the formation of shear bands crossing each other in the retained austenite. At lower carbon contents of the austenite, lath martensite precipitates at the shear band intersections and at high shear band densities martensite blocks are observed. In carbon enriched austenite martensite lenses formed by shear processes have been observed. At alternating loading conditions, exceeding the stress level for athermic martensite formation, various shear planes are activated forming characteristic patterns of plate martensite. 相似文献
14.
15.
伍千思 《冶金标准化与质量》2004,42(6):34-37
奥氏体不锈钢可分为Cr-Ni系和Cr-Mn系两个系列。随着我国不锈钢消费量迅速增长 ,Cr-Mn系奥氏体不锈钢发展很快 ,进口量大。为做到对奥氏体不锈钢合理选材用材 ,概括介绍了我国GB、美国ASTM、日本JIS、欧洲EN、国际ISO等不锈钢标准中的Cr-Mn系 (美国 2 0 0系 )奥氏体不锈钢的牌号和化学成分 ,并列表简介我国GB中七个Cr-Mn奥氏体不锈钢牌号的主要特性和用途。 相似文献
16.
V. M. Chertov 《Metallurgist》2010,54(3-4):171-172
17.
A determination of stacking fault energy (SFE) of the austenite phase of a duplex stainless steel, material no. 1.4462, has been carried out using transmission electron microscopy (TEM). Furthermore, cold rolling tests and microstructural analysis have been realized in order to allow a detailed discussion of the obtained SFE-values. The results of this Investigation indicate that the stacking fault energy of the austenite phase within the duplex stainless steel Is lower than those of single-phase austenitic stainless steels. This is justified by the chemical composition; mainly by the Cr and Ni alloying contents. Nevertheless, work hardening of the austenite during cold deformation is not as accentuated as expected by the low SFE-values, because at higher deformation levels the deformation mainly occurs within the ferrite phase. 相似文献
18.
It was reported in previous studies that the growth of austenite was inhibited by the pinning effect of Nb containing precipitates and the solute dragging effect of solute Nb. The effect of Nb on austenite grain growth of high carbon steel was investigated by laser scanning confocal microscope (LSCM). Microstructure evolution during heating process of the tested steel was observed by in situ observation. The results show that even without the pinning effect of Nb containing precipitates (at high temperatures), Nb can hinder the growth of austenite grains due to the solute dragging effect of Nb. Two models were used to fit the austenite grain growth process, and the Beck growth models of Nb microalloyed high carbon steels at different heating temperatures were established. The austenite grain growth kinetics model considering the influence of heating temperature and holding time can accurately predict the austenite grain growth process of Nb microalloyed high carbon steels. 相似文献
19.
20.
摘要:以往研究表明Nb析出相钉扎和固溶Nb溶质拖曳作用共同阻碍奥氏体晶粒长大。采用高温共聚焦显微镜研究了Nb对一种高碳含Nb钢奥氏体晶粒长大的影响,对含Nb钢加热过程组织演变进行原位观察。结果表明,Nb在没有钉扎作用下(即高温条件下)仍能起到阻碍奥氏体晶粒长大的作用,该阻碍效果主要是固溶Nb的溶质拖曳作用引起的。采用2种模型对奥氏体晶粒长大行为进行拟合,给出了不同加热温度下Nb微合金化高碳钢的Beck长大方程,同时考虑到加热温度和保温时间的共同影响,根据原位观察结果得到实验钢的奥氏体晶粒长大动力学模型,该模型能够较准确地预测Nb微合金化高碳钢奥氏体晶粒长大行为。 相似文献