Effect of Plastic Deformation on Magnetic Properties of Fe-40%Ni-2%Mn Austenitic Alloy

The effects of plastic deformation on the magnetic properties of austenite structure in an Fe-40% Ni-2 % Mn alloy is investigated by using Mossbauer spectroscopy and Differential Scanning Calorimetry （DSC） techniques The morphology of the alloy has been obtained by using Scanning Electron Microscopy （SEM）. The magnetic behaviour of austenite state is ferromagnetic. After plastic deformation, a mixed magnetic structure including both paramagnet- ic and ferromagnetic states has been obtained at the room temperature. The volume fraction changes, the effective hyperfine fields of the ferromagnetic austenite phase and isomery shift values have also been determined by Mossbauer spectroscopy. The Curie point （Tc） and the Neel temperature （TN） have been investigated by means of DSC system for non-deformed and deformed Fe-Ni-Mn alloy. The plastic deformation of the alloy reduces the TN and enhances the paramagnetic character of austenitic Fe-Ni-Mn alloy.     

Influence of Mn Content and Hot Deformation on Transformation Behavior of CMn Steels

The hot deformation behaviors and the microstructural evolution of plain CMn steels with similar contents of C and Si but different contents of Mn have been investigated by compressive processing using Gleeble1500 mechanical simulator. Influence of Mn and hot deformation on continuous cooling transformation of steels has been studied. The experimental results showed that deformation in austenite region accelerated transformation process, and the extent is dependent on the hot deformation and cooling conditions. The hot deformation would promote transformation process, but the increase of transformation temperature is dependent on Mn contents. The results have also shown that the effect of deformation on ferrite transformation becomes more obvious with the increase of Mn content at relatively low cooling rate.     

Improvement of Mechanical Properties of CrNiMoCuTi Stainless Steel With Addition of Vanadium

 The effect of vanadium (V) addition on the mechanical properties of a Cr Ni Mo Cu Ti stainless steel was studied and its influence on microstructural changes was also investigated. Results indicate that the structure of the solution treated specimens mainly comprises of austenite martensite, and adding V leads to the formation of a considerable amount of ferrite. Under this condition, austenite phase is not mechanically stable, and transforms to martensite by plastic deformation. The addition of 05% - 10% (in mass percent) of V increases the hardness and the strength of the 80% cold rolled and aged steel, without any effect on ductility. Improvement in mechanical properties is presumably attributed to the formation of a small amount of ferrite in the primary structure, and the formation of certain precipitates is accelerated by the addition of V during aging. By contrast, excessive V decreases the strength and ductility simultaneously. This is due to the strong effect of ferrite formation compared to the beneficial effect of precipitation. The loss of ductility caused by adding higher amount of V is due to the formation of ferrite phases which in turn are suitable nucleation sites for crack propagation.     

Effect of Dissolved and Precipitated Niobium in Microalloyed Steel on Deformation Induced Ferrite Transformation （DIFT）

 Hot deformation processing was designed to study the effects of niobium (Nb) on DIFT. A prestrain of 051 at 880 ℃ for different isothermal time was used for adjusting the deformed austenite constitution and Nb existing state, followed by a secondary heavy deformation at 780 ℃ for inducing the ferrite transformation. The volume fraction and grain size of deformation induced ferrite (DIF) obtained at different isothermal time between double hits were investigated. It was found that Nb dissolved in austenite is adverse to DIFT; however, the precipitation of Nb is beneficial to DIFT. As Nb plays the role in the conventional TMCP, Nb retards the recrystallization of deformed austenite and enhances the deformation stored energy in the multipass deformation, and in result, Nb promotes DIFT.     

Mechanism of Austenite Evolution During Deformation of UltraHigh Carbon Steel

The mechanism of transformation of austenite to cementite and pearlite during the deformation of ultrahigh carbon steel was discussed. The results indicate that the pearlite and cementite can be induced by deformation between Acm to Arcm. The transformation during deformation is still considered as a diffusioncontrolled process. With the increase of time and reduction, the pearlite fraction increased. At the beginning of the transformation, the pearlite was lamelliform. When the rate of reduction was increased to 70%, some of the induced lamellar pearlite was broken up under deformation.     

Effect of Cooling Rate after hot Deformation on Structure and Mechanical Properties of Low Alloy Wear Resistance Cast iron

The effect of cooling rate after 40% hot deformation on structure and mechanical properties of low alloy wear resistance cast iron was investigated by metallographic, scanning electron microscopes and detection of properties. The results show that for the cast steel after deformed, the amount of granular carbides of precipitation during the cooling decreased with the increase of the cooling rate, but the hardness was obviously enhanced, as a result, better mechanical properties will be obtained by force air cooling (cooling rate is about 7℃·s-1). And the reason of the change for structure and mechanical properties of the cast steel were analyzed.     

Effect of Deformation Temperature on Deformation Mechanism of Fe-6.5Si Alloys with Different Initial Microstructures

Deformation behaviors and mechanisms under different temperatures for columnar-grained Fe-6.5Si(mass%)alloys fabricated by directional solidification and equiaxed-grained Fe-6.5Si alloy fabricated by forging were comparatively investigated.The results showed that,with increasing the deformation temperature from 300 ℃ to500 ℃,the elongation increased from 2.9%to 30.1%for the equiaxed-grained Fe-6.5Si alloy,while from 6.6%to about 51%for the columnar-grained Fe-6.5Si alloy.The deformation mode of equiaxed-grained Fe-6.5Si alloy transferred from nearly negligible plastic deformation to large plastic deformation dominated by dislocation slipping.Comparatively,the deformation mode of the columnar-grained alloy transferred from nearly negligible plastic deformation to plastic deformation dominated by the twining,and finally to plastic deformation dominated by dislocation slipping.Meanwhile,compared with the alloy with equiaxed grains,it was found that ultimate tensile strength and elongation could be increased simultaneously,which was ascribed for the twinning deformation in columnar-grained Fe-6.5Si alloy.This work would assist us to further understand the plastic deformation mechanism of Fe-6.5Si alloy and provide more clues for high-efficiency production of the alloy.     

Changes of Structure and Magnetic Properties during Crystallization in Cast Nd60Fe20Al8Co10B2 Alloy

The Nd60Fe20Al8Co10B2 alloy was prepared by suction casting of the molten alloy into a copper mold under argon atmosphere. The micro-structural and magnetic property changes in the Nd60Fe20Al8Co10B2 alloy during crystallization were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscope (SEM) and the vibrating sample magnetometer (VSM). The precipitation and Nd-rich and Fe-rich phases have no significant effect on the intrinsic coercitity for Nd60Fe20Al8Co10B2 alloy annealed below 723 K. However, the growth of Fe-rich phase decreases the saturate magnetization and remanence of the alloy. The hard magnetic behavior is disappeared when the alloy is fullycrystallized.     

Effect of Cooling Method on Microstructure and Mechanical Properties of Hot-Rolled C-Si-Mn TRIP Steel

 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 Mssbauer 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 1152%, total elongation of 32% and product of tensile strength and total elongation of 27552 MPa·% was obtained.     

Hot Compression Behavior of AsCast Precipitation Hardening Stainless Steel

 High temperature deformation characteristics of a semiaustenitic grade of precipitation hardening stainless steels were investigated by conducting hot compression tests at temperatures of 900-1 100 ℃ and strain rates of 0001-1 s-1. Flow behavior of this alloy was investigated and it was realized that dynamic recrystallization (DRX) was responsible for flow softening. The correlation between critical strain for initiation of DRX and deformation parameters including temperature and strain rate, and therefore, Zener Hollomon parameter (Z) was studied. Metallographic observation was performed to determine the as deformed microstructure. Microstructural observation shows that recrystallized grain size increases with increasing the temperature and decreasing the strain rate. The activation energy required for DRX of the investigated steel was determined using correlations of flow stress versus temperature and strain rate. The calculated value of activation energy, 460 kJ/mol, is in accordance with other studies on stainless steels. The relationship between peak strain and Z parameter is proposed.     

Effect of Niobium on Isothermal Transformation of Austenite to Ferrite in HSLA LowCarbon Steel

Using thermomechanical simulation experiment, the kinetics of the isothermal transformation of austenite to ferrite in two HSLA lowcarbon steels containing different amounts of niobium was investigated under the conditions of both deformation and undeformation. The results of optical microstructure observation and quantitative metallography analysis showed that the kinetics of the isothermal transformation of austenite to ferrite in lower niobium steel with and without deformation suggests a stage mechanism, wherein there exists a linear relationship between the logarithms of holding time and ferrite volume fraction according to Avrami equation, whereas the isothermal transformation of austenite to ferrite in high niobium steel proceeds via a two stage mechanism according to micrographs, wherein, the nucleation rate of ferrite in the initial stage of transformation is low, and in the second stage, the rate of transformation is high and the transformation of residual austenite to ferrite is rapidly complete. Using carbon extraction replica TEM, niobium carbide precipitation for different holding time was investigated and the results suggested that NbC precipitation and the presence of solute niobium would influence the transformation of austenite to ferrite. The mechanism of the effect of niobium on the isothermal transformation was discussed.     

Modeling of Austenite Decomposition in Low SiMn TRIP Steel During Cooling

Transformation behavior in low carbon SiMn TRIP steel was investigated by means of microstructural observation and computer modelling. A transformation model in which transformation is controlled by carbon diffusion was suggested, which well described the volume fractional change of ferrite, pearlite, and bainite during continuous cooling. The influence of Si content and austenite grain size was thoroughly investigated. The calculated results indicated that Si retards pearlite transformation, accelerates polygonal ferrite transformation, refines the austenite grain, and increases the ferrite transformation rate.     

Magnetic State of Deformed Austenite Before and After Martensite Nucleation in Austenitic Stainless Steels

 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.     

Synthesis of Mono-esters of Phenyl-and Substituted Phenylphosphonic Acids and Their Performance in Rare Earth Extraction

Methodsfor the synthesis of acidic phenyl-and substituted phenylphosphonates bearing a branched longchain ester alkyl group are described.These synthetic routes are incomparably superior to other methods in vari-ous aspects including better reaction yield and higher purity of the product.The behaviour of themono(2-butyloctyl)esters and mono(2-methyldodecyl)esters of both phenyl-and o-methylphenylphosphonicacids thus obtained in extraction of lanthanum,praseodymium,neodymium and lutecium as representatives oflight and heavy rare earths,is investigated and discussed on the basis of their chemical structure.The dependenceof the extraction constants and separation factors accords with the Reactivity-Selectivity Principle in solvent ex-traction proposed by us.The composition and structure of the extracted species have been characterized byinfra-red and proton nuclear magnetic resonance spectroscopy in addition to elemental analyses.     

Development of TiMicroalloyed 600 MPa Hot Rolled High Strength Steel

 A high strength steel with tensile strength on the order of 710MPa had been development successfully with only addition of titanium alloy element based on a low carbon steel. The results show the hot deformation accelerates ferrite and pearlite transformation and retards bainite transformation under continuous cooling condition. The microstructure of this steel is mainly composed of fine-grained ferrite and carbides distributed along the ferrite grain boundaries. The yield and tensile strengths of steels are about 620～650MPa and 720～740MPa, respectively, and the values of strain hardening exponent (n) and plastic strain ratio (r) are 0.12 and 0.80, respectively, thus providing well-matched strength with toughness. In short, the fine-grained ferrite and TiC nano-precipitates play an effective role in strengthening the steel.     

Effects of manganese doping on magnetocaloric effect in Ge-rich Gd_5Ge_（2.05）Si_（1.95） alloy

The structure, magnetic and magnetocaloric properties of the Ge-rich Gd5Ge2.05-xSi1.95-xMn2x (x=0.01 and 0.03) alloys were investigated by scanning electron microscopy, X-ray powder diffraction, differential scanning calorimeter (DSC) and magnetization measurements. The results of energy dispersive X-ray analysis (EDX) and X-ray diffraction analyses showed that the composition and crystal structure of the alloys were desired. DSC measurements were performed to determine the transformation temperatures for each alloy. Both alloys exhibited the first order phase transition around room temperature. The alloys showed an anti-ferromagnetic transition around 60 K. The isothermal magnetic entropy changes of the alloys were determined from the isothermal magnetization measurements by using the Maxwell relation. The maximum values of isothermal magnetic entropy change of the Gd5Ge2.05-xSi1.95-xMn2x alloy with x=0.01 was found to be -12.1 and -19.8 J/(kg·K) using Maxwell equation around 268 K in applied fields of 2 and 5 T, respectively.     

Model of Calculating Activity of Nitrogen and Vanadium in FeCVN Molten Metal

The solubility of nitrogen in the FeCVN system was measured at 1 708 K and the model of calculating activity (action concentration) of nitrogen (N) and vanadium (V) was derived according to the phase diagram and the coexistence theory of the metal melt structure. The solubility expression of nitrogen in the FeCVN system at 1 708 K was wN=0058 194-0010 367wC+0005 543 4wV. Comparing the computing results with the experimental results, a satisfactory conclusion could be obtained. The analysis of the FeCVN system using this model showed that VN was present in a high temperature metal melt, which would reduce the action concentration of nitrogen obviously. It was consequently disadvantageous to the removal of nitrogen from hot metal.     

Effect of Alloying Method on Microstructure and Wear Resistance of Fe-Cr-V-B Based Alloy

The microstructure and wear behavior of Fe-Cr-V-B based alloy was investigated.Each of the specimens was characterized by metallographic techniques and hardness test.Phase analysis of alloy was performed by X-ray diffraction(XRD),scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS).The results showed that the microstructure of Fe-Cr-V-B based as-cast alloy containing 8.6mass% V was composed ofα-(Fe,Cr)solid solution,VC carbides,and V_3B_4 borides,whereas the as-cast alloy containing 24.8mass% Cr was composed ofα-(Fe,Cr)solid solution and V_3B_4borides;the eutectic V_3B_4 borides mainly comprise M2B-type borides(M presents Fe and Cr).The existence of a large amount of V atoms affects the growth pattern of eutectic borides,which mainly display rod-like and grainy structure.The wear behavior of the experimental alloy has been investigated using pin-on-disk type friction and wear apparatus.The comparison of experimental results indicated that the relative wear resistance of the alloy containing 8.6mass% V after destabilization heat treatment in a conventional furnace at 1 373 K for 2hwas about six times higher than that of the high chromium(19mass%)cast iron.     

Effect of initial grain size of austenite on hot-deformed structure of Ni-30Fe alloy

The microstructural evolutions of Ni-30Fe alloys during hot deformation are investigated. Hot-deformed structures of Ni-30Fe alloys with initial austenite grain sizes of 20 and 140 μm are examined under various compressive strains and deformation temperatures. As the initial austenite grain size decreases, dynamic recrystallization (DRX) occurs at lower compressive strain and lower deformation temperature. At deformation temperatures where dynamic recovery occurs instead of the DRX, hot-deformed structures consist of recovered elongated grains until fine-equiaxed grains are evolved by geometric DRX. Critical compressive strain for the geometric DRX decreases with the decrease of initial austenite grain size. Geometric DRX is evolved by the impingement of serrated grain boundaries. The decrease of initial grain size is considered to reduce the critical compressive strain needed for the impingement of serrated grain boundaries. The changes in the effective thickness of austenite grain according to the compressive deformation are examined and the effects of the restoration processes on the effective thickness of austenite grain are discussed.     

Influence of Surface Gas-Phase Earth Permeation Plus Laser Melting Solidification on Microstructure and Corrosion Resistance of Pure Iron

The samples of pure Fe were treated by surface gas-phase RE permeation plus laser melting solidification (LMS). The microstructures were observed by Scanning Electron Microscope (SEM) and X-ray Photoelectron Spectroscopy (XPS), meanwhile the corrosion resistance was investigated by electrochemical impedance spectroscopy (EIS) and anedic polarization. The results show that this treatment can remarkably improve the density and uniformity of microstructure, and enhance corrosion resistance of the pure Fe surface.