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1.
The effect of Si on the austenite stabilization, martensite morphology, and magnetic properties in Fe-26%Ni-x%Si (x=3.5, 5, and 6)alloys have been studied by means of transmission electron microscopy (TEM) and M(o)ssbauer spectroscopy techniques. TEM observations reveal that the martensite morphology is closely dependent on the Si content. The volume fraction changes of martensite and austenite phases,the hyperfine magnetic field, and isomer shift values have been determined by M(o)ssbauer spectroscopy. The M(o)ssbauer study reveals that the hyperfme magnetic field, the isomer shift values and the volume fiaction of martensite decrease with increasing Si content. 相似文献
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A. S. M. A. Haseeb Y. Hayashi M. Masuda M. Arita 《Metallurgical and Materials Transactions B》2002,33(6):921-927
A hard Fe-0.96 mass pct C alloy with a hardness value of 810 HV has been electrochemically synthesized from a ferrous sulfate
bath containing a small amount of citric acid and L-ascorbic acid The nature of the alloy has been investigated by a number
of techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM),
transmission electron microscopy (TEM), M?ssbauer spectroscopy, differential scanning calorimetry (DSC), and magnetic measurements.
The decomposition behavior of the alloy is also studied and compared with that of thermally prepared martensite. It has been
found that the electrochemically deposited Fe-C alloy exists in a state that is ahead of the freshly quenched state of martensite.
It is suggested that the state of the electrochemically deposited Fe-0.96 mass pct C alloy corresponds to the state of thermal
martensite, which had been heated to stage I of tempering. 相似文献
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高能机械球磨表面纳米化过程中发现表面纳米晶层内渗碳体发生溶解现象,采用TEM、三维原子探针和穆斯堡尔谱对渗碳体的溶解进行了表征。TEM观察结果表明,在纳米化的最表层平均晶粒为10 nm,在选区电子衍射花样中没有发现渗碳体的衍射环,表明渗碳体可能发生溶解。三维原子探针分析表明,表面纳米化处理后,铁素体中的碳含量为0.75at%,是基体铁素体碳含量的100倍,表明表面纳米化过程中渗碳体发生了溶解,通过穆斯堡尔谱分析结果表明,渗碳体的溶解量约为47%。表面纳米化过程中渗碳体的溶解可分为三个阶段:①诱导阶段,在表面机械研磨的最初5 min,渗碳体的溶解分数仅为0.4%;②溶解阶段,在表面纳米化处理的5-30 min,渗碳体大量溶解,其体积分数由14.6%降低到8.4%;③饱和阶段,当处理时间达到30 min以上,渗碳体的体积分数基本保持不变。 相似文献
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The microstructural changes of Fe_(83)Si_4B_(13) amorphous mother alloy during the heating process were investigated by Laser Scanning Confocal Microscopy( LSCM),and the phase transformation was determined by the Thermo-Calc calculations. The differences in the melting points measured by Differential Scanning Calorimetry( DSC)and LSCM,and those obtained by Thermo-Calc calculations were also discussed. It is found that the melting points measured by DSC and LSCM are relatively similar,whereas the onset and end of the melting temperatures calculated by Thermo-Calc software are higher than those measured by DSC and observed by LSCM. 相似文献
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The controlled cooling technology following hot rolling process is a vital factor that affects the final microstructure and mechanical properties of the hot-rolled transformation induced plasticity (TRIP) steels. In the present study, low alloy C-Si-Mn TRIP steel was successfully fabricated by hot rolling process with a 450 hot rolling mill. To maximize the volume fraction and stability of retained austenite of the steel, two different cooling methods (air-cooling and ultra-fast cooling “AC-UFC” and ultra-fast cooling, air-cooling and ultra-fast cooling “UFC-AC-UFC”) were conducted. The effects of the cooling method on the microstructure of hot-rolled TRIP steel were investigated via optical microscope, transmission electron microscope and conversion electron Mssbauer spectroscope. The mechanical properties of the steel were also evaluated by conventional tensile test. The results indicated that ferrite and bainite in the microstructure were refined with the cooling method of UFC-AC-UFC. The morphology of retained austenite was also changed from small islands distributing in bainite district (obtained with AC-UFC) to granular shape locating at the triple junction of the ferrite grain boundaries (obtained with UFC-AC-UFC). As a result, the TRIP steel with a content of retained austenite of 1152%, total elongation of 32% and product of tensile strength and total elongation of 27552 MPa·% was obtained. 相似文献
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D. L. Williamson K. Nakazawa G. Krauss 《Metallurgical and Materials Transactions A》1979,10(9):1351-1363
Mössbauer effect spectroscopy has been used to study changes in the microstructure of an Fe-1.22. wt pct C alloy due to tempering between 373 and 523 K. The orthorhombic transition carbide, η-Fe2C, was identified by transmission electron microscopy and the similarity of ∈-carbide electron diffraction patterns to η-carbide diffraction patterns is noted. Systematic changes in the Mosbauer parameters of martensite and austenite are presented for the various stages of tempering. The same amount of C remains randomly dissolved in the retained austenite throughout tempering and some C is retained in the martensite throughout the range of transition carbide formation. Two sets of Mössbauer parameters corresponding to magnetic phases other than martensite and cementite have been found. These parameters may come from η-carbide, but alternative interpretations are presented. 相似文献
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The effect of plastic deformation of austenite on the nucleation of pearlite was investigated using an Fe–12Mn–0.8C (mass%) alloy. Slight warm deformation of austenite prior to pearlite transformation effectively accelerates the intragranular nucleation of pearlite although intragranular pearlite is hardly formed without deformation. Formation of pearlite at annealing twin boundaries is promoted in the warm‐rolled specimens. Additionally MnS particles are activated as intragranular nucleation sites of pearlite. Cold rolling of austenite introduces many deformation twins in the alloy used. Subsequent isothermal transformation heat treatments result in nucleation of pearlite at intersections of the deformation twins. It is concluded that incoherent portions introduced by deformation onto the annealing or deformation twin boundaries are effective nucleation sites in the pearlite transformation. 相似文献
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Dong-Woo Suh Chang-Seok Oh Sung-Joon Kim 《Metallurgical and Materials Transactions A》2005,36(4):1057-1059
High-angle grain-boundary spacing in deformed austenite is analyzed using Ni-30Fe alloy to explain the change of ferrite grain
size by severe plastic deformation (SPD) of austenite in low carbon steel. It is suggested that constant high-angle grain-boundary
spacing in deformed austenite resulting from dynamic recrystallization (DRX) or geometric DRX is responsible for the limit
of ferrite grain refinement over a certain level of plastic deformation of austenite. 相似文献
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A. I. Uvarov V. A. Sandovskii N. F. Vil’danova E. I. Anufrieva 《Russian Metallurgy (Metally)》2008,(4):347-353
The effect of the generator current frequency f on the magnetic permeability μ of the N30K10T3 invar is studied for its various structural states formed upon the following treatments: phase naklep (i.e., the phase-transformation-induced hardening of austenite), cold plastic deformation, and cooling in liquid nitrogen. The ferromagnetic austenite of the alloy is metastable with respect to the γ → α martensite transformation upon cooling to temperatures below the temperature of the onset of the martensite transformation (M s ≈ ?80°C) and represents a supersaturated solid solution ageable during heating. The types of treatment are shown not to change the linear character of the μ(f) dependence in the frequency range under study (15–50 kHz) and to decrease μ to a certain extent. 相似文献
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The martensite morphology and austenite flow strength have been determined in a variety of ferrous alloys chosen so that the austenites were paramagnetic, ferromagnetic, substitutional strengthened, and interstitial strengthened. It is demonstrated that two of the most important variables in determining the habit plane (and thus morphology) of martensite in a given alloy are the resistances to dislocation motion in austenite and in ferrite (i. e., martensite). In the wide variety of alloys where martensite with a {259}γ habit plane was observed, the austenite flow strength atM s is greater than 30,000 psi. At lower austenite strengths, either {225}γ or {111}γ habit planes are found depending on the resistance to dislocation motion in ferrite. Thus, {225} martensites are not always found as part of the spectrum between {111} and {259} martensites but only in the cases (e. g., interstitial strengthening) where ferrite is preferentially strengthened relative to austenite. All of the observations are consistent with the idea that the habit plane observed in a given alloy is the one involving the minimum plastic work for the lattice invariant shear. 相似文献
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The phase-transformation behavior of a TiNi shape-memory alloy (SMA) under constraint of a constant strain is experimentally
investigated by means of mechanical testing and differential scanning calorimetry (DSC) measurements. It is indicated that
the reverse-transformation-temperature span under constraint is much larger than that of the unconstrained state. After an
incomplete constrained transformation cycle, a two-stage recovery-stress in the constrained state as well as a two-stage recovery-strain
in the unconstrained state emerges upon subsequent heating. This is rationalized on the basis of a mechanism which takes into
account the influence of stress on the formation of the austenite and the plastic deformation of martensite and austenite
during constrained heating. Most importantly, the constrained reverse and forward transformations corresponding to the redeformation
of the oriented martensite and the formation of the stress-induced martensite and thermal martensite, respectively, lead to
the subsequent two-stage recovery-strain and recovery-stress characteristics. Both the prestrain level and the constrained
heating temperature play important roles in the phase transformations and thermomechanical characteristics of the TiNi SMA. 相似文献
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Mohammad Moallemi Abbas Zarei-Hanzaki Mostafa Eskandari Andrew Burrows Hossein Alimadadi 《Metallurgical and Materials Transactions A》2017,48(8):3675-3691
A new metastable Ni-free duplex stainless steel has been designed with superior plasticity by optimizing austenite stability using thermodynamic calculations of stacking fault energy and with reference to literature findings. Several characterization methods comprising optical microscopy, magnetic phase measurements, X-ray diffraction (XRD) and electron backscattered diffraction were employed to study the plastic deformation behavior and to identify the operating plasticity mechanisms. The results obtained show that the newly designed duplex alloy exhibits some extraordinary mechanical properties, including an ultimate tensile strength of ~900 MPa and elongation to fracture of ~94 pct due to the synergistic effects of transformation-induced plasticity and twinning-induced plasticity. The deformation mechanism of austenite is complex and includes deformation banding, strain-induced martensite formation, and deformation-induced twinning, while the ferrite phase mainly deforms by dislocation slip. Texture analysis indicates that the Copper and Rotated Brass textures in austenite (FCC phase) and {001}〈110〉 texture in ferrite and martensite (BCC phases) are the main active components during tensile deformation. The predominance of these components is logically related to the strain-induced martensite and/or twin formation. 相似文献
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G. F. Korznikova I. M. Milyaev A. I. Milyaev N. M. Mamaev V. S. Yusupov A. V. Korznikov 《Russian Metallurgy (Metally)》2010,(5):434-436
The structure and magnetic hysteresis characteristics of anisotropic samples of a hard magnetic alloy Fe-22% Cr-15% Co subjected
to uniaxial plastic deformation at a temperature up to 400°C are investigated. It is established that the maximum energy product
of the anisotropic samples decreases substantially after deformation at a retained coercive force and remanence, while the
maximum energy product of isotropic samples increases somewhat after deformation. The variation of the magnetic properties
is related to the structure evolution during deformation. 相似文献
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The effect of the increase in the paramagnetic susceptibility of austenite up to the true value of the deformation-induced martensite transition point εs has been experimentally established in steels X6CrNiTi18-10 (corresponding to AISI 321 steels). At this point nucleation and accumulation of martensite with the increase in the extent of deformation but at a constant magnetic state of austenite takes place. 相似文献
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Magnetocaloric Effect of Ni56Mn18.8Ga24.5 Gd0.7 Alloy 总被引:1,自引:0,他引:1
Zhang Zeyu ~ Long Yi ~ Duan Jingfang ~ Huang Peng ~ Wu Guangheng ~ Chang Yongqin ~ 《中国稀土学报(英文版)》2006,24(5):579-581
Inrecent years materials with high magnetocaloriceffect (MCE) have attracted considerable attention ow-ingto its potential application as a magnetic refriger-ant .Many material systemsthat underwentthefirst-or-der magnetic transition have been found to exhibit agiant MCE. Their typical representatives areGd5(SixGe1 -x)4[1 ,2]and La (FexSi1 -x)13[3 ,4]alloys .Ni MnGa is aferromagnetic shaped memory alloy whichundergoes a reversible first-order structural phase tran-sition (SPT) with the … 相似文献
18.
L. E. Pope 《Metallurgical and Materials Transactions B》1972,3(8):2151-2156
The effect of plastic deformation introduced by rolling at room temperature on the austenite start temperature of an Fe-30.3
wt pct Ni-0.005 wt pct C alloy has been determined. The austenite start temperature increases monotonically with deformation.
Microhardness measurements show that the austenite start temperature increases with the yield strength of the martensite.
The temperature at which martensite reversal initiates is not affected by the amount of martensite present, and, therefore,
is not dependent on the martensite plate size. It is suggested that the reverse martensite transformation initiates at the
martensite-austenite interface and is controlled by interface propagation. 相似文献
19.
A previous study suggested that precipitated austenite in “QLT? 6Ni steel is sufficiently stable to avoid transforming to martensite in the path of a propagating crack. Impact specimens of “QLT? 6Ni steel with differing geometries were broken at 77 K and 290 K. The depth of transformation of the austenite below the fracture surfaces was measured by backscatter electron Mössbauer spectrometry. The depth of transformation correlated with the impact energy and with the depth of the plastic zone, but was mostly independent of temperature. It is concluded that the martensitic transformation of precipitated austenite occurs in the plastic deformation ahead of the crack, and in ductile fracture the precipitated austenite will not remain to interfere directly with crack propagation. 相似文献
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A previous study suggested that precipitated austenite in “QLT” 6Ni steel is sufficiently stable to avoid transforming to martensite in the path of a propagating crack. Impact specimens of “QLT” 6Ni steel with differing geometries were broken at 77 K and 290 K. The depth of transformation of the austenite below the fracture surfaces was measured by backscatter electron Mössbauer spectrometry. The depth of transformation correlated with the impact energy and with the depth of the plastic zone, but was mostly independent of temperature. It is concluded that the martensitic transformation of precipitated austenite occurs in the plastic deformation ahead of the crack, and in ductile fracture the precipitated austenite will not remain to interfere directly with crack propagation. 相似文献