Study on Electrochemical Formation of Neodymium-Iron Alloy

The cyclic voltammetry was used to investigate the electrode processes of Nd(III) reduced on iron electrode and Nd(III),Fe(II) reduced on molybdenum electrode in molten chlorides. The Nd-Fe and Nd-rich RE-Fe alloys contained rare earth up to 90wt% were prepared by consumable cathode and electrolytic codeposition. The mechanism of electrochemical formation of Nd-Fe alloy had been discussed.

A novel biodegradable high nitrogen iron alloy with simultaneous enhancement of corrosion rate and local corrosion resistance

To improve the corrosion rate and suppress the local corrosion,a novel biodegradable high nitrogen(N)FeMnN alloy was developed,and the effects of N content on the corrosion behaviors were systematically investigated.It was found that,as the N content increased,the corrosion rate was significantly enhanced in both Hank’s solution and simulated gastric fluid.Meanwhile,as the N content increased,the size and depth of pits decreased obviously,and the number of pits increased,which presented a more uniform corrosion morphology.X-ray photoelectron spectroscopy(XPS)results indicated that N existed in the form of NH_(4)^(+) in the corrosion products and[FeN]clusters in the matrix.The[FeN]clusters would simultane-ously improve the corrosion rate and suppress the local corrosion,which provides a new perspective for the development of biodegradable Fe alloy.

The Effects of Ce on Hot Corrosion of Iron-based Alloys

Electrochemical polarization resistance technique was employed to study the effects of Ce on hot corrosion resistance of stainless steel 316, and preoxidation of surface-applied CeO2 coating on that of HK40 alloy. It is shown that a little Ce additives may improve hot corrosion resistance of stainless steel 316, especially inhibit the internal sulfidation along grain boundaries. The surface-applied CeO2 coating may greatly improve hot corrosion resistance of HK40 by promoting the formation of Cr2O3 scale.

Properties of a reaction-bonded β-SiAlON ceramic doped with an FeMo alloy for application to molten aluminum environments

An FeMo-alloy-doped β-SiA1ON （FeMo/β-SiA1ON） composite was fabricated via a reaction-bonding method using raw materials of Si, Al2O3, A1N, FeMo, and Sm2O3. The effects of FeMo on the microstructure and mechanical properties of the composite were investi- gated. Some properties of the composite, including its bending strength at 700℃ and after oxidization at 700℃ for 24 h in air, thermal shock resistance and corrosion resistance to molten aluminum, were also evaluated. The results show that the density, toughness, bending strength, and thermal shock resistance of the composite are obviously improved with the addition of an FeMo alloy. In addition, other properties of the composite such as its high-temperature strength and oxidized strength are also improved by the addition of FeMo alloy, and its corrosion re- sistance to molten aluminum is maintained. These findings indicate that the developed FeMo/β-SiA1ON composite exhibits strong potential for application to molten aluminum environments.

Properties of Cross-Rolled Low Alloy White Cast Iron Grinding Ball

The low-energy, multi-impact fracture resistance and the abrasiveness of the cross-rolled low alloy white cast iron grinding balls were studied after heat treatments at residual rolling temperature. Moreover, the means by which they are damaged and characters of the wear surface were analyzed. The results show that high resistance to impact fracture and high abrasiveness can be achieved after appropriate heat treatment at residual rolling temperature. This kind of heat treatment technology has several advantages under low impact and hard abrasive. These results are very useful for determining the optimized heat treatment technology at residual rolling temperatures.

Effect of Rare Earth Elements on Carbide Morphology and Phase Transformation Dynamics of High Ni-Cr Alloy Cast Iron

The effect of rare earth(RE) elements on carbide of high NiCr alloy cast iron was investigated. Meanwhile, the continuous cooling transformation(CCT) curves of cast iron with and without RE addition were determined. The results show that the carbides in high NiCr cast iron can be refined and changed from network and long strip structures into island and block ones. The phase transformation temperature was raised and incubation period of bainite transformation was shortened by adding RE element in high NiCr alloy cast iron.

Effect of arsenic content and quenching temperature on solidification microstructure and arsenic distribution in iron–arsenic alloys

The solidification microstructure, grain boundary segregation of soluble arsenic, and characteristics of arsenic-rich phases were systematically investigated in Fe-As alloys with different arsenic contents and quenching temperatures. The results show that the solidifica- tion microstructures of Fe-0.5wt%As alloys consist of irregular ferrite, while the solidification microstructures of Fe-4wt% As and Fe-10wt%As alloys present the typical dendritic morphology, which becomes finer with increasing arsenic content and quenching temperature. In Fe-0.5wt%As alloys quenched from 1600 and 1200℃, the grain boundary segregation of arsenic is detected by transmission electron microscopy. In Fe-4wt%As and Fe-10wt%As alloys quenched from 1600 and 1420℃, a fully divorced eutectic morphology is observed, and the eutectic Fe2As phase distributes discontinuously in the interdendritic regions. In contrast, the eutecfic morphology of Fe-10wt%As alloy quenched from 1200℃ is fibrous and forms a continuous network structure. Furthermore, the area fraction of the eutectic Fe2As phase in Fe-4wt%As and Fe-10wt%As alloys increases with increasing arsenic content and decreasing quenching temperature.

Influence of Cr element on impact fracture process of ductile Ni-resistant alloyed iron at low temperature

In this study, in order to investigate the influence of Cr element on the impact fracture process of ductile Ni-resistant alloyed iron at low temperature, different contents of Cr element were added to ductile Ni-resistant(DNR) austenitic alloyed iron. The experimental results show that Cr addition can increase the hardness of the DNR alloyed iron, but it has an destructive effect on low-temperature impact properties. Through the analysis of the dynamic load and absorbed energy of samples with different Cr contents in the impact fracture process, and the comparison of the impact fracture process at room and low temperatures, it reveals that Cr addition into the DNR alloyed iron can facilitate the formation of the carbide mixture in Mn23C6 and Cr23C6 with homogeneous and discontinuous distribution. Meanwhile, Cr addition also can improve the the maximum dynamic load and crack initiation energy at low temperature, but has no obvious effect on the yield behavior of the DNR alloyed iron in the impact fracture process. Compared with the impact crack propagation process at room temperature, the metastable propagation energy at low temperature declines significantly with an increase in Cr content. This is because the micro-cracks that caused by the carbides weaken the matrix, resulting in the decline of impact crack propagation resistance. The fracture analysis results also show that the impact fracture mechanism gradually transforms from ductile to brittle with an increase in Cr content at low temperature. It explains that too much Cr addition can lead to brittle fracture even though the austenitic matrix has a good toughness at low temperature.

Formation and Growth of Granular Carbides in Multiple Alloying Wear Resistant Cast Iron Containing RE Through Hot Deformation

The granular carbides formed from hot deformation in multiple alloying wear resistant cast iron were studied through the observation by means of optical microscope, SEM and TEM. The experimental results show that carbides with large size are formed from original short rhabdoid carbides existing in cast, those with small size directly nucleate in the matrix. Carbides with the size between the above are formed from precipitation induced by hot deformation. The bigger the deformation is, the larger the number of microsized granular carbides is. The mechanisms of nucleation and growth of granular carbides and the function of RE were discussed.

Role of Ga-doping in iron-gallium alloy clusters

The structural and magnetic properties of Fen-mCam （n = 3 - 6, m = 0 - 2; n = 13, m = 0 - 3） alloy clusters have been studied using density functional theory. The substitutional doping is favourable for small clusters with up to six atoms at low Ga concentration and substitutional Ga atoms in 13-atom clusters prefer surface sites. The Ca-doping generally could reduce the energetic stability but enhance the electronic stability of Fe clusters, along with a decrease of the local magnetic moments of Fe atoms around Ca dopants. These findings provide a microscopic insight into Fe-Ga alloys which are well：known magnetostriction materials.

EFFECT OF TRACE ELEMENTS WITH ZERO SELF－INTERACTIONCOEFFICIENT ON CRYSTALLIZATION TEMPERATUREOF IRON CARBON ALLOYS

The effect of trace elements with zero self-interaction coefficient on crystallization temperature of iron carbon alloys was studied and the mathematic equation was developed based on thermodynamics in the present researeh. With the equation developed in this paper, the effects of nitrogen on crystallization temperature of Fe-3.45C-2.15Si0. 16Mn and Fe-3.45C-2. 15Si-0. 80Mn alloys were discussed.

Influence of Rare Earth on Wear Resistance of Wear Resistant Cast Iron Containing Low Alloy

The Influence of RE on wear resistance of wear resistant cast iron containing low alloy was studied by means of slide wear and impact wear test. Moreover, its microstructure and characteristics of wearing surface was analyzed. The experimental results show that RE can improve the wear resistance of wear resistant cast iron containing low alloy, especially for impact wear resistance. The optimum wear resistance of wear resistant cast iron containing low alloy modified by RE of 0.046% can be obtained by normalization at 950 ℃ for 3 h. Moreover, the coordinated effect of rare earths and heat treatment was also revealed in this paper.

Effect of RE Modification and Heat Treatment on Formation and Growth of Thermal Fatigue Crack in Wear Resistant Cast Iron Containing Low Alloy

The formation and growth of thermal fatigue crack and the function of RE and heat treatment in wear resistance of cast iron containing low alloy were investigated,and it was analyzed in view of the activation energy for the crack′s propagation. The results show that the thermal fatigue cracks are mainly generated at eutectic carbides,and the cracks are grown by themselves spreading and joining each other. RE can improve the eutectic carbide′s morphology,inhibit the generation and propagation of thermal fatigue cracks,therefore,promote the activation energy for the crack′s propagation,and especially,which is more noticeable in case of the RE modification in combination with heat treatment.

Effect of Rare Earth Elements on Thermal Fatigue of High Ni－Cr Alloy Cast Iron

The effect of RE on crack forming and developing of hot rolled high Ni-Cr alloy cast iron during thermal fatigue test was investigated.It shows that the serviceable life of hot rolled high Ni-Cr alloy cast iron can be improved by RE.The number of cycle before fracture was increased by 42%～163%.The optimum of RE addition is 0.05 wt%～0.15wt%.

Effect of Rare Earth Elements on Dynamics of Thermal Fatigue Crack′s Propagation in Low Alloy White Cast Iron

The effect of rare earth elements on dynamics of thermal fatigue crack′s propagation in low alloy white cast iron was studied. The results show that the generation and growth of the thermal fatigue crack can be restrained and the activation energy for the crack′s propagation can be increased by adding a certain amount of RE, and especially, the restraint for the thermal fatigue crack′s propagation is more evident under the combined action of RE and heat treatment at high working temperatures, which can be attributed to the segregation of RE to interfaces, the participation of granular carbides and the change of eutectic carbide morphology.

Mechanical Property Stability of Cu-Mo-Ni Alloyed Austempered Ductile Iron

The aim of present work is to investigate the influencing factors on mechanical property stability of Cu-Mo-Ni alloyed austempered ductile iron （ADI）. The results show that after austenitized at 900℃ for 2 h followed by austempered at 370℃for another 2 h, the mechanical property of the alloyed ADI can reach the Germanite GGG-100 standard, i.e. σb≮1000 MPa,δ≮5%, at 95% confidence level. And the satisfactory mechanical properties were obtained when the alloyed ADI was austenitized at 850℃ to 1 000 ℃ for 1-4 h, and austempered at 355℃ to 400℃ for another 1 h to 4 h. The microstructures, including nodule number, white bright zone content （martensite-containing interdendritic segregation zone） and retained austenite content, can significantly influence the mechanical properties of the ADI. In order to obtain the good combinations of strength and ductility, the volume fraction of white bright zone should he less than 5%, and the retained austenite contents maintain hetween 30 % and 40%. The application of inoculation techniques to increase graphite nodule number can effectively reduce the white bright zone content in the structure.

A Study of Making Iron Aluminide Alloy Powders with New Rotating Electrode Technology

A new process was used for producing FeAl alloy pow de rs with double consumable rotating electrodes and the powders made in this appar atus were analyzed. In this new technology, tungsten rod serves as a cathode ele ctrode, while the alloy rod as an anode electrode. The conventional rotating ele ctrode process must have an anode with pre-melting alloys; however, in this new process, using pure iron as cathode electrode and pure aluminum as anode electr ode can eliminate the step of pre-melting. The effects of process variables, which include electrode rotational speed, a nd electrode diameter of the mean particle diameter were determined. Results showed that both the rotational speed and diameter of electrodes would a ffect the mean diameter of particles. There are three kinds of powders with diff erent composition produced in this study and the possible mechanisms are discuss ed. The process parameters and volume mean diameter of the powders have been cor related to find an experimental equation. The results show that when the rotational speed and the diameter of the anode el ectrode are increased, the powders size will decrease. However, the powders size will increase with cathode electrode.

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.

Fracture Behaviour of Laser Clad Fe-and Ni-base Alloy Coatings on a Cast Iron under SEMI Loading

Laser cladding technique has been applied to renovate some partially-damaged (or worn) components with Fe, Ni, Co-base alloys, hence to improve their hardness values and wear resistance successfully in previous reports. But for some punching or shearing cast iron dies damaged or worn in automobile manufacture, the renovated surfaces also bear some impact loading. Therefore, a small-energy and multi-impact (SEMI) test was designed to investigate the fracture behaviour of renovated cast iron dies achieved by laser cladding of Fe and Ni-base alloys under SEMI loading to meet above requirement. observations show that the fracture took place in the substrate near to the substrate/coating interface rather than at the interface. The tempering temperature has a great influence on the cycles to fracture of laser-clad samples under SEMl loading, i.e. the low tempering temperature of 300℃ gives a maximum cycle to fracture, while a higher tempering temperature of 400℃ has a minimum. Furthermore, the fracture mechanism has also been discussed in present study