Shock-induced phase transition and spalling characteristic in pure iron and FeMnNi alloy

This paper provides an investigation of the phase transition and spalling characteristic induced during shock loading and unloading in the pure iron and the FeMnNi alloy. The impact for the pure iron is symmetric and with the same-thickness for both the flyer and the target plate. It is found that an abnormal multiple spalling happens in the pure iron sample as the pressure exceeds the α- ε transition threshold of 13 GPa. In the symmetric and same-thickness impact and reverse impact experiments of the FeMnNi alloy, two abnormal tension regions occur when the pressure exceeds the α - ε transition threshold of 6.3 GPa, and the reverse phase transition s - ~ begins below 4.2 GP. The experimental process is simulated successfully from the non-equilibrium mixture phase and Boettger＇s model. Such abnormal spalling phenomena are believed to relate to the shocked α - ε phase transition. The possible reasons for the abnormal multiple spalling, which occurs during the symmetric and same-thickness impact experiments of pure iron and FeMnNi alloy, are discussed.

A STUDY ON RECRYSTALLIZATION-INDUCED PLASTICITY INDT4 PURE IRON

The phenomenon of stress-induced recrystallization (SIR) and recrystallization- induced plasticity (RIP) in DT4 pure iron was investigated by means of hightemperature tensile test under a constant elastic stress and microstructural observation. It is shown that the macroscopic plastic flow of cold-rolled specimens, which occured during heating process under pre-loaded elastic stress, resulted from stressinduced recrystallization and recrystallization-induced plasticity. The characteristics and mechanism of this phenomenon were also preliminarily discussed.

Study on Cutting Force,Cutting Temperature and Machining Residual Stress in Precision Turning of Pure Iron with Different Grain Sizes

Pure iron is one of the difficult-to-machine materials due to its large chip deformation,adhesion,work-hardening,and built-up edges formation during machining.This leads to a large workpiece deformation and challenge to meet the required technical indicators.Therefore,under varying the grain size of pure iron,the influence of cutting speed,feed,and depth of cut on the cutting force,heat generation,and machining residual stresses were explored in the turning process to improve the machinability without compromising the mechanical properties of the material.The experimental findings have depicted that the influence of grain size on cutting force in the precision turning process is not apparent.However,the cutting temperature and residual stress of machining fine-grain iron were much smaller than the coarse grain at all levels of cutting parameters.

Microstructure and properties of pure iron/copper composite cladding layers on carbon steel

In the present study, pure iron/copper composite metal cladding was deposited onto carbon steel by tungsten inert gas welding. The study focused on interfacial morphological, microstructural, and mechanical analyses of the composite cladding layers. Iron liquid–solid-phase zones were formed at copper/steel and iron interfaces because of the melting of the steel substrate and iron. Iron concentrated in the copper cladding layer was observed to exhibit belt, globule, and dendrite morphologies. The appearance of iron-rich globules indicated the occurrence of liquid phase separation（LPS） prior to solidification, and iron-rich dendrites crystallized without the occurrence of LPS. The maximum microhardness of the iron/steel interface was lower than that of the copper/steel interface because of the diffusion of elemental carbon. All samples fractured in the cladding layers. Because of a relatively lower strength of the copper layer, a short plateau region appeared when shear movement was from copper to iron.

Influence of Surface Gas-Phase Rare 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 anodic 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.

Cause of stamping cracks in pure iron magnetic shielding covers

This study explores reasons for the random occurrence of stamping cracks during the production of pure iron magnetic shielding covers. Scanning electron microscopy and energy spectrum are used to observe cracks within parts, and results show significant brittle fracture morphology with chunks of manganese silicate and aluminum silicate inclusions present in the fracture surface. The chemical composition, mechanical properties, and microstructure are also analyzed for a corresponding batch of cold rolled pure iron sheet. The oxygen content of the material is found to be high,resulting in the random distribution of a large amount of long chain manganese silicate and aluminum silicate inclusions along the rolling direction, which corresponds to inclusions found on the fractured surface. The stamping cracks are thus assumed to be caused by the randomly distributed chain of inclusions within the cold rolled sheet. It is suggested that the amount of deoxidizer used should be more carefully controlled to decrease the inclusion contents and to thus avoid the recun＇ence of such defects.

Liquid structure of pure iron by X-ray diffraction

The liquid structure of pure iron at 1540, 1560 and 1580 deg C was studied byX-ray diffraction. The results show that near the melting point there is a medium-range orderstructure that fades away with the increasing temperature. The average nearest distance of atoms isalmost independent of the melts temperature, but the average coordination number, the atom clustersize and the atom number in an atom cluster all decrease with the increasing temperature of themelt. Near the melting point there are a lot of atom clusters in the pure iron melt. The atomcluster of pure iron has the body-centered cubic lattices, which are kept from the solid state. Andthe body-centered cubic lattices connect into network by occupying a same edge. The atoms in thesurrounding of the atom clusters are arranged disorderly.

Effect of decarburization annealing temperature and time on the carbon content, microstructure, and texture of grain-oriented pure iron

In this study,the effect of decarburization annealing temperature and time on the carbon content,microstructure,and texture of grain-oriented pure iron was investigated by optical microscopy and scanning electron microscopy with electron-backscatter diffraction. The results showed that the efficiency of decarburization dramatically increased with increasing decarburization temperature. However,when the annealing temperature was increased to 825°C and 850°C,the steel's carbon content remained essentially unchanged at 0.002%. With increasing decarburization time,the steel's carbon content generally decreased. When both the decarburization temperature and time were increased further,the average grain size dramatically increased and the number of fine grains decreased; meanwhile,some relatively larger grains developed. The main texture types of the decarburized sheets were approximately the same: {001}<110> and {112~115}<110>,with a γ-fiber texture. Furthermore,little change was observed in the texture. Compared with the experimental sheets,the texture of the cold-rolled sheet was very scattered. The best average magnetic induction(B_(800)) among the final products was 1.946 T.

Denaturation behavior of inclusions in industrial pure iron by calcium treatment

Only a few Chinese enterprises can produce high-quality industrial pure iron,and studies on the smelting process of industrial pure iron were limited.The inclusions in a melting process were characterized by means of electron microscopy and an automatic inclusion analysis system,and the evolution mechanism of inclusion was studied using thermodynamic calculation to optimize the calcium alloy addition in liquid window.The results show that during the smelting process,inclusions mainly composed of Al_(2)O_(3)and spinel are formed before calcium treatment.After calcium treatment,they continuously react with[Ca],[S]and[Ti],grow up,and are removed during refining and tundish pouring.In the end,there are more small-sized inclusions containing CaS,and the contents of Al_(2)O_(3)and spinel are less.According to thermodynamic calculations,the appropriate calcium treatment liquid window for the molten steel composition is(10-38)×10^(-6).Calcium treatment has changed the main types of inclusions in industrial pure iron from Al_(2)O_(3)to small-sized inclusions containing CaS and effectively reduces the influence of Al_(2)O_(3)inclusions on the quality of industrial pure iron.

Elliptical vibration cutting of large-size thin-walled curved surface parts of pure iron by using diamond tool with active cutting edge shift

Large-size thin-walled curved surface parts of pure iron are crucial in aerospace,national defense,energy and precision physical experiments.However,the high machining accuracy and surface quality are difficult to achieve due to the serious tool wear and deformation when machining the parts with conventional cutting tools.In this paper,an elliptical vibration cutting(EVC)with active cutting edge shift(ACES)based on a long arbor vibration device is proposed for ultraprecision machining the pure iron parts by using diamond tool.Compared with cutting at a fixed cutting edge,the influence of ACES on the EVC was analyzed.Experiments in EVC of pure iron with ACES were conducted.The evolutions of the surface roughness,surface topography,and chip morphology with tool wear in EVC with ACES are revealed.The reasonable parameters of ultraprecision machining the pure iron parts by EVC with ACES were determined.It shows that the ACES has a slight influence on the machined surface roughness and surface topography.The diamond tool life can be significantly prolonged in EVC of pure iron with ACES than that with a fixed cutting edge,so that high profile accuracy and surface quality could be obtained even at higher nominal cutting speed.A typical thin-walled curved surface pure iron part with diameter φ240 mm,height 122 mm,and wall thickness 2 mm was fabricated by the presented method,and its profile error and surface roughness achieved PV 2.2μm and Ra less than 50 nm,respectively.

Al 1060/Pure Iron Clad Materials by Vacuum Roll Bonding and Their Solderability

Al 1060/pure iron clad materials were produced by vacuum roll bonding. The effects of preheating temperature, vacuum roll reduction and initial thickness of the A11060 sheet on the metal interface and bonding strength were investigated. The interfacial microstructure was investigated and the mechanical properties of the joint were evaluated by shear testing. The bonding strength of the clad materials was generally enhanced by increasing the total reduction or preheating temperature, which caused the metal interface to flatten. No obvious reaction or diffusion layer was observed at the interface between Al 1060 and pure iron. The bonding strength increased with decreasing the initial thickness of the Al 1060 sheets. The Al 1060/pure iron clad materials were soldered with Zn-Al alloy by using an ultrasonic-assisted method. Strong bonding of the Al 1060 layer and Al 7N01 was realized without obvious Al 1060 dissolution or effect on the initial interface of Al 1060/pure iron clad materials by soldering at relatively low temperature.

Texture and inhibitor features of grain-oriented pure iron produced by different cold-rolling processes

To promote the manufacture of grain-oriented pure iron, the texture and inhibitor features of two samples A and B produced by different cold-rolling processes were studied by optical microscopy, X-ray diffraction, and transmission electron microscopy. The results showed that a higher content of inhibitor elements directly resulted in a greater number of fine inhibitors, which exhibited strong inhibitory ability, leading to more fine precipitates of appropriate size effectively inhibiting the growth of primary grains in decarburized bands （sheets） during the single-stage cold-rolling process. The formation of the component with { 110}〈001〉 Goss orientation was greatly suppressed in the stage of primary recrystallization, and this component could hardly be observed in the decarburized band; by contrast, the {411 }〈148〉-oriented grains grew. During the process of high-temperature annealing, abnormal growth occurred and secondary recrystallized grains （Goss orientation） merged with other matrix grains such as { 111 }〈112〉 and {411 }〈148〉. The magnetic induction of samples A and B at 800 Aim was 1.939 T and 1.996 T, respectively.

Influence of Surface Nanocrystallization on Ti Ion Implantation of Pure Iron

In order to increase the depth or concentration of Ti ion implantation of pure iron, the surface mechanical attrition treatment(SMAT), which can fabricate a nanometer-grained surface layer without porosity and contamination in a pure iron plate, was used before ion implantation. Ti ion was implanted into the SMA treated sample and coarse-grained counterpart by using a metal vapor vacuum arc source implanter. The changing of depth and concentration of Ti was studied in a function of implantation time.By optical microscopy, transmission electron microscopy and X-ray diffraction, the grain size of the nano structured surface was studied. Micro-hardness, friction and wear behavior of nano surface layers were studied. By energy dispersive X-ray spectroscopy and Auger electron spectroscopy, the chemical composition and concentration of Ti ion in the surface implantation layer were studied. Experimental results showed that the concentration of Ti increased dramatically compared with untreated coarsegrained samples, which is attributed to the existence of higher density of defects(supersaturated vacancies, dislocations, non-equilibrium grain boundaries etc.) and compression stress field in the SMA treated nanocrystallined surface layer. The interaction between the defects and the implanted solute atoms leads to the increment of solid solubility. But the implantation depth showed inconspicuous change. It is shown that the ion range is just relevant to the energy and mass of the ion, dose of injection,the mass and density of target material.

Effects of Different Substrates on Microstructures and Mechanical Properties of a Bulk Nanocrystalline Structure Pure Iron Prepared by Aluminothermic Reaction Casting

A simple method was developed to produce the nanocrystalline pure iron by aluminothermic reaction cast- ing. The mierostructure of the iron was investigated by optical microseope （OM）, transmission electron microscope （TEM）, electron probe micro-analyzer （EPMA）, scanning electron microscope （SEM） and X-ray diffraction （XRD）. The mechanical performances of nanoerystalline pure iron were tested. It is found that the pure iron consists of nanoerystalline ferrite. For different substrates of eopper and glass, the average grain size of the ferrite was 38 and 35 nm, respectively, which is larger on copper substrate than that on glass. The hardness, compressive strength, tensile strength, and total elongation are 167 and 137 HB, 400 and 500 MPa, 243 and 185 MPa, 16% and 10% on copper substrate and glass suhstrate, respectively. The hardness, tensile strength and total elongation are all larger on copper substrate than those on glass substrate, while the eompressive strength is lower. The large supercooling in the product solidification provides the condition for high nucleation rate and thus leads to nano-grained austenite and final nano-grained ferrite transformed from those small austenite grains.

Abnormal austenite-ferrite transformation behavior in pure iron

The austenite ferrite transformation is the most important reaction route in the manufacture of Fe-based materials. Here the austenite (g) ferrite (a) transformation of pure iron was systematically explored by high-resolution dilatometry. Abnormal transformation ki-netics, multi-peak discontinuous reaction, was recognized in pure iron according to the variation of the ferrite-formation rate. The occurrence the one or the other type of ga trans-formation strongly depends on the grain size: the transfor-mation type changes from abnormal to normal (single-peak continuous reaction) with decreasing grain size. The inherent reason for the occurrence of abnormal transformation could be attributed to the repeated nucleation in front of the mov-ing g/a interface induced by the accumulation of elastic and plastic accommodation energy.

Effect of oxide film on nanoscale mechanical removal of pure iron

In this paper, the properties of an oxide film formed on a pure iron surface after being polished with an H_2O_2-based acidic slurry were investigated using an atomic force microscope(AFM), Auger electron spectroscopy(AES), and angle-resolved X-ray photoelectron spectroscopy(AR-XPS) to partly reveal the material removal mechanism of pure iron during chemical mechanical polishing(CMP). The AFM results show that, when rubbed against a cone-shaped diamond tip in vacuum, the material removal depth of the polished pure iron first slowly increases to 0.45 nm with a relatively small slope of 0.11 nm/μN as the applied load increases from 0 to 4 μN, and then rapidly increases with a large slope of 1.98 nm/μN when the applied load further increases to 10 μN. In combination with the AES and AR-XPS results, a layered oxide film with approximately 2 nm thickness(roughly estimated from the sputtering rate) is formed on the pure iron surface. Moreover, the film can be simply divided into two layers, namely, an outer layer and an inner layer. The outer layer primarily consists of FeO OH(most likely α-FeOOH) and possibly Fe_2O_3 with a film thickness ranging from 0.36 to 0.48 nm(close to the 0.45 nm material removal depth at the 4 μN turning point), while the inner layer primarily consists of Fe_3O_4. The mechanical strength of the outer layer is much higher than that of the inner layer. Moreover, the mechanical strength of the inner layer is quite close to that of the pure iron substrate. However, when a real CMP process is applied to pure iron, pure mechanical wear by silica particles generates almost no material removal due to the extremely high mechanical strength of the oxide film. This indicates that other mechanisms, such as in-situ chemical corrosion-enhanced mechanical wear, dominate the CMP process.

蒲公英叶提取物在盐酸中对铁片的缓蚀行为研究

通过浸提法从蒲公英叶中提取植物缓蚀剂,采用失重法、傅里叶红外光谱测试、腐蚀形貌表征法及吸附等温曲线拟合,研究了蒲公英叶提取物在1 mol/L HCl中对纯铁的缓蚀性能和机制。结果表明:蒲公英叶提取物对铁片均有显著的缓蚀效果,在35℃下,0.8 g/L的蒲公英叶提取物对铁片的缓蚀效率高达97.45%,效果最佳;蒲公英叶提取物中的活性分子官能团,以物理吸附的形式占据铁片表面反应位点来抑制铁片腐蚀。吸附等温线拟合结果显示,蒲公英叶提取物在铁片表面的吸附为单分子层吸附,吸附过程符合Langmuir吸附等温模型。

磁控溅射AlCr涂层对电工纯铁防腐性能的影响

为了提高电工纯铁的耐腐蚀性能,基于磁控溅射技术,在电工纯铁表面制备了Al Cr涂层。采用X射线衍射仪、扫描电子显微镜对涂层表面形貌、结构和元素组成进行分析,并通过中性盐雾及电化学测试,分析了电工纯铁基体及Al Cr涂层的耐腐蚀性能。结果表明,适量Cr元素掺杂可以使涂层致密化,在Cr靶功率为75 W时效果最好。随着Cr的加入,Al Cr涂层呈现不同的化合物态,包括Al_(8)Cr_(5)、Al1_(3)Cr_(2)等相。中性盐雾及电化学测试结果均表明Cr-75涂层的耐腐蚀性能最好,在经过158 h的盐雾测试之后涂层依然没有被腐蚀;Cr-75涂层阻抗比纯铁高约2个数量级,腐蚀电流密度为7.4×10^(-9)A/cm^(2),相对于电工纯铁(1.6×10^(-6)A/cm^(2))降低了约3个数量级,点蚀电位与腐蚀电位之间的电位差最大(0.272 V),抗点蚀性能最好,保护效率高达98.8%。

河北某普通磁铁矿制备超纯铁精矿试验研究

河北某普通磁铁矿TFe品位为65.25%,矿石性质结构简单,具有制备超纯铁精矿的潜力。研究采用多元素及X射线衍射图、物相分析等方法对原矿进行了工艺矿物学研究,并在此基础上对其进行了提纯试验。结果表明,原矿经过弱磁选粗选后,在磨矿细度-0.038 mm占85%的条件下经弱磁选再选、磁选柱精选得到TFe品位为71.31%的磁选柱精矿以及TFe品位68.12%、产率为3.32%的磁选柱铁尾矿。通过进一步考察药剂制度和工艺流程对铁矿精矿品位、回收率等选别指标的影响,确定了合适的药剂制度。而后磁选柱精矿经1粗3精反浮选降硅工艺试验流程,最终可获得含TFe品位71.95%、综合回收率为80.50%的超纯铁精矿,浮选尾矿TFe品位68.17%符合普通铁精矿标准。通过对选别产品进行试样化学成分分析及残余药剂测定,进一步证明该工艺流程可以实现超纯铁精矿的制备。该工艺在抛尾率为10.79%条件下,将原矿样的73.04%转化为超纯铁精矿,对这一地区超纯铁精矿的制备具有重要的指导意义,也为国内其他地区磁铁矿制备超纯铁精矿的研究提供了一定的参考价值。

Production of Reduced Iron Powder Using Ultra-Fine Iron Concentrate

The using of the iron to extract reduced iron with T Fe ≥ 69.5% Al 2O 3+SiO 2<0.3% was studied. Preparation of reduced iron powder in this experimental research can produce ultra pure magnetite concentrate. The quality of the final product reaches the product standard of SC 100.26 and NC 100.24.