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ISSN: 1006-7191
CN: 21-1361/TG
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DETERMINATION AND APPLICATION OF LARSON-MILLER PARAMETER FOR HEAT RESISTANT STEEL 12CrlMoV AND 15CrMo
R.C.Yang, K.Chen, H.X.Feng, H.Wang
Acta Metall Sin(English)    2004, 17 (4): 471-476 .  
Abstract   PDF (127KB)  
Based on the analysis and processing on relative empirical formula and data, C-values in Larson-Miller (P) expression, P = T(C + lgt), have determined for pearlitic heat resistant steel 12Cr1Mo V and 15 CrMo (20. 62 and 20. 30). The simulation experiments of high temperature aging, heated from 1.5 to 873 hours, have been designed and performed for its verification. And in combination with published information and the present nearly quantitative works, it has further been verified that both the degradations of microstructures and mechanical properties show a good accuracy and practicability using the Larson-Miller parameter with the present determined C-values. Finally, the effects of carbon content on C-value are analyzed by the empirical electron theory of solids and molecules (EET).
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Microstructure in the Semi-solid State and Mechanical Properties of AZ80 Magnesium Alloy Reheated from the As-cast and Extruded States
Wenyong JIANG, Tian CHEN, Liping WANG, Yicheng FENG, Yan ZHU, Kaifeng WANG, Jiapeng LUO, Shouwei ZHANG
Acta Metallurgica Sinica(English letters)    2013, 26 (4): 473-482.   DOI: 10.1007/s40195-012-0176-3
Abstract   PDF (40114KB)  

The multi-axial forging (MAF) process was introduced into the strain induced metal activation (SIMA) process to replace conventional forging. Microstructure evolution of MAF formed AZ80 magnesium alloy during partial remelting was investigated. Furthermore, the tensile mechanical properties for AZ80 magnesium alloy thixoextruded from the starting materials treated by MAF were determined. For comparison, as-cast AZ80 magnesium alloy was also thixoextruded. The results show that the SIMA route produced ideal, fine semi-solid microstructure, in which almost completely spheroidal primary solid grains had a little amount of entrapped liquid. The microstructure of the as-cast alloy in the semi-solid state is less spheroidized compared with the MAF alloy under the similar isothermal holding conditions. With prolonged holding time, the size of the solid grain increases and the degree of spheroidization is improved in the MAF formed alloys. However, the solid grain size of the as-cast alloys decreases initially, and then increases with further increasing temperature. The tensile mechanical properties for AZ80 magnesium alloy thixoextruded from the starting material produced by MAF are better than those of AZ80 magnesium alloy thixoextruded from the starting material produced by casting. The ultimate tensile strength, yield strength and elongation of the alloy thixoextruded from the starting material produced by MAF are 314 MPa, 238 MPa and 14%, respectively.

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An Overview of High-Performance Aircraft Structural Al Alloy-AA7085
T. Ram Prabhu
Acta Metallurgica Sinica(English letters)    2015, 28 (7): 909-921.   DOI: 10.1007/s40195-015-0275-z
Abstract   HTML PDF (793KB)  
AA7085 Al alloy is a new-generation, high-strength, quench-insensitive alloy that features in airframe applications such as massive bulkhead and wing spars structures in Airbus A380 and Joint Strike Fighter aircrafts. This alloy has a great potential in replacing currently used high-strength AA7xxx alloys in many international and national military aircraft programs [Hawk, Su-30, MiG series, light combat aircraft (Tejas), Hindustan turbo/jet trainer, light combat helicopter, advanced light helicopter, and fifth-generation fighter aircrafts]. An effort has been made to highlight the processing, heat treatment, properties and applications of the AA7085 Al alloy from the existing literature on the AA7085 alloy. The potential applications of this alloy are presented and compared with the currently used AA7075 Al alloy. A typical process cycle involved in the manufacturing of wrought AA7085 alloy products is described in detail. Particularly, the precipitation mechanisms involved in the different temper conditions are critically reviewed with the supporting microstructures. The mechanical properties with a particular emphasis on tensile, fatigue, and fracture toughness properties are discussed in detail based on the analysis of experimental data. The effects of temper conditions on the stress corrosion cracking and exfoliation corrosion have also been reviewed critically.
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SIMULATION OF VIBRATION STRESS RELIEF AFTER WELDING BASED ON FEM
X.C. Zhao, Y.D. Zhang, H.W.Zhang, Q. Wu
Acta Metall Sin(English)    2008, 21 (4): 289-294 .  
Abstract   PDF (1168KB)  
A finite element model is developed for the simulation of vibration stress relief (VSR) after welding. For the nonresonant vibration, the reduction in stress strongly depends on the amplitude of vibration. For the resonant vibration, the vibration frequency is the key for stress relief. The vibration frequency should be close to the structure natural frequency for the desired vibration mode. Only small vibration amplitude is required, which will be amplified during vibration. Vibration time does not have a major impact on vibration stress relief. When the amplitude of vibration stress relief is large, the treatment will be more effective.
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Review On Research And Development Of Magnesium Alloys
Z. Yang, J.P. Li, J.X. Zhang, G.W.Lorimer, J. Robson
Acta Metall Sin(English)    2008, 21 (5): 313-328 .  
Abstract   PDF (394KB)  
The current research and development of magnesium alloys is summarized. Several aspects of magnesium alloys are described: cast Mg alloy, wrought Mg alloy, and novel processing. The subjects are discussed individually and recommendations for further study are listed in the final section.
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CORROSION RESISTANCE OF HOT DIP GALVANIZED STEEL PRETREATED WITH BIS-FUNCTIONAL SILANES MODIFIED WITH NANOALUMINA
F.J. Shan, C.S. Liu, S.H. Wang, G.C. Qi
Acta Metall Sin(English)    2008, 21 (4): 245-252 .  
Abstract   PDF (731KB)  
The corrosion behavior of hot dip galvanized steel pretreated with bis-[triethoxy-\linebreak\noindent silylpropyl] tetrasulfide (BTESPT) modified with alumina particles was studied. The corrosion resistance of the passiving films was evaluated by Tafel polarization curve and electrochemical impedance spectroscopy. The films formed on the galvanized steel substrate were characterized by Fourier transform infrared spectroscopy and energy dispersive X-ray spectrometry. The surface morphology of the treated hot dip galvanized steel samples was observed by Field Emission Scanning Electron Microscope. The results show that the pretreatments on the basis of silane films modified with nanoalumina particles have reduced both anodic and cathodic current densities, and increased total impedance in the measured frequency, consequently, improving corrosion protection for hot dip galvanized steel during immersion in NaCl solutions compared to chromate films and silane films.
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Effects of Thermal Cycle on Mechanical Properties and Fractography in HAZ of HQ130 Steel
B. Liu, J.X. Qu , W.J. Sun
Acta Metall Sin(English)    2004, 17 (3): 274-278 .  
Abstract   PDF (2729KB)  
The effect of di®erent peak temperature (Tp) and cooling time (t8=5) on hardness, impact toughness and fracture morphology in the heat-affected zone (HAZ) of HQ130 steel was studied by using welding thermo-simulation test. Experimental results show that the impact toughness and hardness decrease with the decrease of Tp or increase of t8=5 under the condition of a single thermal cycle. There is a brittle zone in the vicinity of Tp=800±C,where the impact toughness is considerably low. There is softened zone in vicinity of Tp=700±C,Where the hardness decreases but the toughness increases. In the practical application of multi-layer and multi-pass welding, the welding heat input should be strictly limited (t8=5<=20s) so as to reduce the softness and brittleness in the HAZ of HQ130 steel.
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Effect of chloride ions on 316L stainless steel in cyclic cooling water
Zuojia LIU, Xuequn CHENG,Shengjie LU, Xiaogang LI
Acta Metall Sin(English)    2010, 23 (6): 431-438.   DOI: 10.11890/1006-7191-106-431
Abstract   PDF (1325KB)  
The effect of Cl- on the 316L stainless steel in simulated cooling water has been studied using polarization curves, electrochemical impedance spectroscopy (EIS), Mott-Schottky plot and scanning electron microscopy (SEM) techniques. Cl- concentrations vary from 200 to 900 mg/L. Results reveal that the corrosion resistance increases with the decrease of Cl- concentration in simulated cooling water. The increase of Cl-concentration leads to the shift of the corrosion potential towards the positive direction. Mott-Schottky curves show that in the passive film, Cr2O3 and FeO at the inner layer exhibit P-type but Fe2O3 and CrO3 (CrO42-) N-type semiconductive properties. The SEM/EDX data demonstrate that elements such as Fe, O, C, Si and Cl as well as the presence of calcium and aluminum are presented on the surface of the metal.
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THE BAND STRUCTURE AND WORK FUNCTION OF TRANSPARENT CONDUCTING ALUMINUM AND MANGANESE CO-DOPED ZINC OXIDE FILMS
H.T.Cao
Acta Metall Sin(English)    2005, 18 (3): 356-362 .  
Abstract   PDF (232KB)  
Al and Mn co-doped-ZnO films have been prepared at room temperature by DC reactive magnetron sputtering technique. The optical absorption coefficient, apparent and fundamental band gap, and work function of the films have been investigated using optical spectroscopy, band structure analyses and ultraviolet photoelectron spectroscopy (UPS). ZnO films have direct allowed transition band structure, which has been confirmed by the character of the optical absorption coefficient. The apparent band gap has been found directly proportional to N^2/3, showing that the effect of Burstein-Moss shift on the band gap variations dominates over the many-body effect. With only standard cleaning protocols, the work function of ZnO: (Al, Mn) and ZnO: Al films have been measured to be 4.26 and 4.21eV, respectively. The incorporation of Mn element into the matrix of ZnO, as a relatively deepd onor, can remove some electrons from the conduction band and deplete the density of occupied states at the Fermi energy, which causes a loss in measured photoemission intensity and an increase in the su,rface work function. Based on the band gap and work function results, the energy band diagram of the ZnO: (Al, Mn) film near its surface is also given.
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IMPROVED COHESIVE ZONE MODEL AND ITS APPLICATION IN INTERFACE CONTACT ANALYSIS
Y. Wang, J. Chen, H.B. Li
Acta Metall Sin(English)    2008, 21 (4): 295-302 .  
Abstract   PDF (1036KB)  
An improved interface cohesive zone model is developed for the simulation of interface contact, under mixed-mode loading. A new debonding initiation criterion and propagation of debonding law, taking into account the pressure stress influence on contact shear strength, is proposed. The model is implemented in a finite-element program using subroutine VUINTER of ABAQUS Explicit. An edge-notch four-point bending process and laminated vibration damping steel sheet punch forming test are simulated with the improved model in ABAQUS Explicit. The numerical predictions agree satisfactorily with the corresponding experimental results.
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Mechanical Properties Of Longitudinal Submerged Arc Welded Steel Pipes Used For Gas Pipeline Of Offshore Oil
Z.Z. Yang, W. Tian, Q.R. Ma
Acta Metall Sin(English)    2008, 21 (2): 85-93 .  
Abstract   PDF (925KB)  
Since the development of offshore oil and gas, the increased submarine oil and gas pipelines were installed. All the early steel pipes of submarine pipeline were depended on importing because of the strict requirements of comprehensive properties such as anti-corrosion, resistance to pressure and so on. In order to research and develop domestic steel pipe used for submarine pipeline, the Longitudinal-seam Submerged Arc Welded (LSAW) pipes were made of steel plates cut from the levelled steel rolls by both JCOE and UOE forming process. And the mechanical properties of the pipe base metal and weld metal were tested, the results were in accord with the corresponding pipe specification API SPEC 5L or DNV-OS-F101, which showed the domestic LSAW pipes could be used to the submarine oil and gas pipeline.
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Yield criterions of metal plasticity in different stress states
Fengping YANG,Qin SUN,Wei HU
Acta Metall Sin(English)    2009, 22 (2): 123-130.   DOI: 10.1016/S1006-7191(08)60079-4
Abstract   PDF (11824KB)  

Five types of tensile tests were conducted to study the yield behavior of 2A12-T4 aluminum alloy. Parallel finite element models were built for each test and solved with ABAQUS with different yield criterions. The result shows that any of the four criterions: von Mises yield criterion, Tresca criterion, Twin-Shear criterion and von Mises criterion with hydrostatic pressure correction, overestimates the yield strengths of the specimens. Rather than hydrostatic pressure, Lode stress parameter is the key factor that affects the differences between experimental and simulation results. Based on this concept, a new yield model with Lode dependence modified from von Mises criterion is postulated. Although one more parameter needs to be confirmed, the simulation results of this yield model are better than those of other criterions.

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Improving the Mechanical Properties of Copper
M.C. Somani , L.P. Karjalainen
Acta Metall Sin(English)    2004, 17 (2): 111-117 .  
Abstract   PDF (8408KB)  
Systematic physical simulation of thermo-mechanical processing routes has been applied on a Gleeble 1500 simulator to four copper alloys (mass %) Cu-0.57Co-0.32Si, Cu-0.55Cr-0.065P, Cu-0.22Zr-0.035Si and Cu-1.01Ni-0.43Si aimed at clarifying the influences of processing conditions on their final properties, strength and electrical conductivity. Flow curves were determined over wide temperature and strain rate ranges. Hardness was used as a measure of the strength level achieved. High hardness was obtained as using equal amounts (strains 0.5) of cold deformation before and after the precipitation annealing stage. The maximum values achieved for the Cu-Co-Si, Cu-Cr-P, Cu-Zr-Si and Cu-Ni-Si alloys were 190, 165, 178 and 193 HV5, respectively. A thermo-mechanical schedule involving the hot deformation-ageing-cold deformation stages showed even better results for the Cu-Zr-Si alloy. Consequently, the processing routes were designed based on simulation test results and wires of 5 and 2mm in diameters have been successfully processed in the industrial scale.
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Microbridge Testing of Young's Modulus and Residual Stress of Nickel Film Electroplated on Silicon Wafer
Y. Zhou, C.S. Yang, J.A. Chen, G.F. Ding, L. Wang, M.J. Wang, Y.M. Zhang , T.H. Zhang
Acta Metall Sin(English)    2004, 17 (3): 247-254 .  
Abstract   PDF (2406KB)  
Microbridge testing is used to measure the Young's modulus and residual stresses of metallic films. Nickel film microbridges with widths of several hundred microns are fabricated by Microelectromechanical Systems. In order to measure the mechanical properties of nickel film microbridges, special shaft structure is designed to solve the problem of getting the load-deflection curves of metal film microbridge by Nanoindenter XP system with normal Berkovich probe. Theoretical analysis of the microbridge load-deflection curve is proposed to evaluate the Young's modulus and residual stress of the films simultaneously. The calculated results based on the experimental measurements show that the average Young's modulus and residual stress are around 190GPa and 175MPa respectively, while the Young's modulus measured by Nano- hardness method on nickel film with silicon substrate is 186.8±7.34GPa.
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Numerical Simulation of Macro-Segregation in Steel Ingot During Solidification
C.W. Ma, H.F. Shen, T.Y. Huang , B.C. Liu
Acta Metall Sin(English)    2004, 17 (3): 288-294 .  
Abstract   PDF (3263KB)  
A mathematical model coupling the momentum, energy and species conservation equa- tions was proposed to calculate the macro-segregation of Fe-C alloy ingot during solidification. The corresponding simulation software which concurrently solves the macro- scopic mass, momentum, energy and species conservation equations has been developed by applying the SIMPLE algorithm. The thermo-solutal convection in a NH4Cl-H2O ingot is verified and the result shows good agreement with that reported. Then macro-segregation in a steel ingot is simu- lated by using the developed program. The steel ingot is in a rectangular mold with a riser. The fluid flow is mainly induced by the temperature field and the solid fraction. The macro-segregation pattern is mainly affected by the thermo-induced convection in the mushy zone. The negative segregation forms along the walls of the casting. The positive segregation forms at the top center of the casting into the riser. The species concentration reaches the peak in the center of the ingot where solidi¯cation ends lastly.
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Effect of the current density on electrodepositing alpha-lead dioxide coating on aluminum substrate
Buming CHEN,Zhongcheng GUO,Hui HUANG,Xianwan YANG,Yuandong CAO
Acta Metall Sin(English)    2009, 22 (5): 373-382.   DOI: 10.1016/S1006-7191(08)60111-8
Abstract   PDF (1868KB)  

The α-PbO2  electrodes are prepared by anodic electrodeposition on A1/conductive coating electrode from alkaline plumbite solutions in order to investigate the effect of the different current densities on the properties of  α-PbO2  electrodes. The physicochemical properties of the  α-PbO2  electrodes are analyzed by using SEM, EDS, XRD, Tafel plot, linear sweep voltammetry (LSV) and A.C. impedance. A compact and uniform layer of lead dioxide was obtained at the current density of 3 mA·cm-2. A further increase in current density results in smaller particles with high porosity. EDS and XRD analyses have shown that the PbO2 deposited in alkaline conditions is highly non stoichiometric, and the PbO impurities are formed on the surface layer besides the α-PbO2 . The corrosion resistance of α-PbO2  at the low current density is superior to that of the high current density. It can be attributed to a porous layer of deposited films at high current densities. When used as anodes for oxygen evolution in aqueous Zn2+ 50~g·L-1, H2SO4 150~g·L-1, the Al/conductive coating/α-PbO2 exhibits lower potential compared to Pb electrode. Al/conductive coating/α-PbO2  electrode with the best electrocatalytic activity was obtained at current density of 1mA·cm-2. The lowest roughness factor was obtained at 1 mA·cm-2.

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Creep crack growth in a Cr-Mo-V type steel: experimental observation and prediction
Jianping TAN, Guozhen WANG, Fuzhen XUAN and Shan-Tung TU
Acta Metall Sin(English)    2011, 24 (2): 81-91.   DOI: 10.11890/1006-7191-112-81
Abstract   PDF (2474KB)  
In this study, the creep crack growth (CCG) properties and fracture mechanism of a Cr-Mo-V steel at 566℃ in compact tension (CT) specimens were investigated, and the CCG rate was predicted by using the NSW model. The results show that the CCG rate measured by CT specimens is much lower than that predicted by the NSW model under plane-strain state. This means that the NSW model prediction for the CCG rate of the steel is over-conservative. In addition, the CCG rate da/dt versus C* measured by the experiments shows the piecewise linear relation on log-log scale instead of a single linear relation predicted by the NSW model. The main reasons for these results are that the actual creep fracture mechanism of the steel and the actual creep crack tip stress field in the CT specimens have not been fully captured in the NSW model. The experimental observation shows that the creep crack propagates in a discontinuous way (step by step) at meso-scale, and the cracks at micro-scale are usually formed by the growth and coalescence of voids on grain boundaries. The NSW model based on the creep ductility exhaustion approach may not correctly describe this creep fracture process. In addition, the opening stress and triaxial stress ahead of crack tips calculated by three-dimensional finite element method is lower than those predicted by the HRR stress field which is used in the NSW model under plane-strain state. The use of the high HRR stress field will cause high CCG rates. The change in the creep fracture mechanism at micro-scale in different ranges of C* may cause the piecewise linear relation between the da/dt and C* . Therefore, it is necessary to study the actual CCG mechanism in a wide range of C* and the actual creep crack tip stress field to establish accurate CCG prediction models.
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Residual stress relaxation in typical weld joints and its effect on fatigue and crack growth
Liangbi LI,Zhengquan WAN,Zili WANG,Chunyan JI
Acta Metall Sin(English)    2009, 22 (3): 202-210.   DOI: 10.1016/S1006-7191(08)60090-3
Abstract   PDF (3482KB)  

Many factors influence the fatigue and crack growth behavior of welded joints. Some structures often undergo fairly large static loading before they enter service or variable amplitude cyclic loading when they are in service. The combined effect of both applied stress and high initial residual stress is expected to cause the residual stresses relaxation. Only a few papers seem to deal with appropriate procedures for fatigue analysis and crack growth by considering the combined effect of variable amplitude cyclic loading with residual stresses relaxation. In this article, some typical welded connections in ship-shaped structures are investigated with 3-D elastic-plastic finite element analysis. The effect of residual stress relaxation, initial residual stress, and the applied load after variable amplitude cyclic loading is revealed, and a formula for predicting the residual stress at hot spot quantitatively is proposed. Based on the formula, an improved fatigue procedure is introduced. Moreover, crack growth of typical weld joints considering residual stresses relaxation is studied.

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CORROSION BEHAVIOR OF A ZIRCONIUM-TITANIUM BASED PHOSPHONIC ACID CONVERSION COATING ON AA6061 ALUMINIUM ALLOY
S.H. Wang, C.S. Liu, F.J.Shan
Acta Metall Sin(English)    2008, 21 (4): 269-274 .  
Abstract   PDF (1282KB)  
The conversion coating was formed by dipping AA6061 in a fluorotitanate/zirconate acid and amino trimethylene phosphonic acid (ATMP) solution at room temperature. The formation process and the anti-corrosion performance of the conversion coating were investigated using electrochemical test and salt spray test (SST), respectively. The electrochemical test shows that the Zr/Ti and ATMP coating improves the corrosion resistance of AA6061 as good as the chromate (VI) coating. But the results of SST show that the corrosion resistance of Zr/Ti and ATMP coating is not as good as the chromate (VI) coating. The corrosion area is less than 2% after 72h.
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Effect of process parameters of pulsed current tungsten inert gas welding on weld pool geometry of titanium welds
M. Balasubramanian, V. Jayabalan, V. Balasubramanian
Acta Metall Sin(English)    2010, 23 (4): 312-320.   DOI: 10.11890/1006-7191-104-312
Abstract   PDF (1006KB)  

The effects of pulsing current parameters on weld pool geometry namely front height, back height, front width and back width of pulse current gas tungsten arc welded (GTAW) titanium alloy was analysed. Four factors, five levels, central composite design were used to develop empirical relationships, incorporating pulsed current parameters and weld pool geometry.

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Thermodynamic analysis of the simple microstructure of  AlCrFeNiCu high-entropy alloy with multi-principal elements
Anmin LI,Xiyan ZHANG
Acta Metall Sin(English)    2009, 22 (3): 219-224.   DOI: 10.1016/S1006-7191(08)60092-7
Abstract   PDF (402KB)  

AlCrFeNiCu high-entropy alloy (THA) was synthesized by the arc melting and casting method. The alloy exhibits simple FCC and BCC solid solution phases rather than intermetallic compounds. The reason is that the Gibbs free energy of mixing of the equimolar AlCrFeNiCu alloy is smaller than that of inter-metallic compounds by calculation according to the Miedema model.

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Some Aspects of High Manganese Twinning-Induced Plasticity (TWIP) Steel, A Review
Liqing CHEN, Yang ZHAO and Xiaomei QIN
Acta Metallurgica Sinica(English letters)    2013, 26 (1): 1-15.   DOI: 10.1007/s40195-012-0501-x
Abstract   PDF (1803KB)  

High manganese twinning-induced plasticity (TWIP) steel is a new kind of structural material and possesses both high strength and superior plasticity and can meet the weight-lightening requirement for manufacturing vehicle body. The excellent formability of the TWIP steel comes from the extraordinary strain hardening effect during plastic deformation. The reduction of specific weight by aluminum alloying and strain hardening effect can lead to an effective weight reduction of the steel components, and provide a better choice for materials in vehicle body design. The TWIP effect in high Mn steels is generally associated with the successive work-hardening generated by twins and influenced by some factors, such as Mn content, Al addition revealed by stacking fault energy (SFE), grain size, deformation temperature and strain rate. The present review introduces some aspects of the TWIP steels relating to their physical metallurgy, influencing factors associated with their deformation mechanisms, and a prospect for the future investigation is also described. Moreover, as a potential candidate for replacing Ni-Cr austenitic stainless steel, researches on the oxidation behavior and corrosion resistance of Fe-Mn-Al-C system steels are also reviewed.

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Microstructure and Mechanical Properties of X80 Pipeline Steels in Different Cooling Schedules
Min ZHOU
Acta Metall Sin(English)    2010, 23 (3): 171-175.   DOI: 10.11890/1006-7191-103-171
Abstract   PDF (1129KB)  
The microstructures and mechanical properties of three X80 pipeline steel plates were investigated in this study. The plates were hot rolled by two stages, and cooled by three different cooling schedules to obtain different microstructures and mechanical properties. Transmission electron microscope (TEM) was used to observe the microstructural details in the steel. The results indicate that the amount of polygonal ferrite (PF) and quasi-polygonal ferrite (QPF) decrease with decrease of finish cooling temperature (FCT), while the amount and size of M-A islands are larger. Relaxation promotes the Charpy V notch(CVN) property at -20℃, but not the drop weight tear testing(DWTT) property at -15℃, and decreases the strength of the steel.
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Chemical composition and Mott-Schottky analysis of passive film formed on G3 alloy in bicarbonate/carbonate buffer solution
Dangguo LI, Darong CHEN, Jiadao WANG and Haosheng CHEN
Acta Metall Sin(English)    2010, 23 (6): 461-472.   DOI: 10.11890/1006-7191-106-461
Abstract   PDF (940KB)  
The chemical composition and semi-conductive properties of passive film on nickel-based alloy (G3 alloy) in bicarbonate/carbonate buffer solution were investigated by Auger spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectra (EIS) and Mott-Schottky plot. AES and XPS results showed that the passive film appeared double-layer, in which the inner film was composed of nickel oxide, the mixed nickel-chromium-molybdenum-manganese oxides were the major component of the outer film. The electrochemical results revealed that the factors including frequency, potential, time, temperature and pH value can affect the semi-conductive property, the doping densities decreased with increasing potential and pH value, prolonging time, and decreasing temperature. According to the above results, it can be concluded that the film protection on the substrate enhanced with increasing potential and pH value, prolonging time, and decreasing temperature.
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Influence of Strain Rate on Tensile Characteristics of SUS304 Metastable Austenitic Stainless Steel
Xifeng LI, Jun CHEN, Liyan YE, Wei DING, Pengchao SONG
Acta Metallurgica Sinica(English letters)    DOI: 10.1007/s40195-013-0206-9
Improvement of Mechanical Properties of Martensitic Stainless Steel by Plasma Nitriding at Low Temperature
Y.T. Xi, D.X. Liu, D. Han, Z.F. Han
Acta Metall Sin(English)    2008, 21 (1): 21-29 .  
Abstract   PDF (494KB)  
A series of experiments were carried out to study the influence of low temperature plasma nitriding on the mechanical properties of AISI 420 martensitic stainless steel. Plasma nitriding experiments were carried out for 15 hours at 350℃ by means of DC-pulsed plasma with 25%N2+75%H2 gas. The microstructure, phase composition and residual stresses profiles of the nitriding layers were determined by optical microscopy and X-ray diffraction. The microhardness profiles of the nitriding surfaces were also studied. The fatigue life, sliding wear and erosion wear loss of the untreated specimens and plasma nitriding specimens were determined on the basis of a rotating bending fatigue tester, a ball-disk wear tester and a solid particle erosion tester. The results show that the 350℃ nitriding surface is dominated by -Fe3N and , which is supersaturated nitrogen solid solution. They have high hardness and chemical stabilities. So the low temperature plasma nitriding not only increases the surface hardness values but also improves the wear and erosion resistance. In addition, The fatigue limit of AISI 420 steel can also be improved by plasma nitriding at 350℃, because plasma nitriding produces residual compressive stress inside the modified layer.
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Effect of process parameters on SPRC35 spot welded automotive panels
M. Balasubramanian,V.Balasubramanian
Acta Metall Sin(English)    2010, 23 (3): 185-190.   DOI: 10.11890/1006-7191-103-185
Abstract   PDF (660KB)  
This paper presents an experimental study on the resistance spot weldability of SPRC35 (steel plate re-phosphorised cold rolled) sheets. The sheets were joined by using resistance spot welding as lap joint. The weld nugget diameter and tensile shear force were investigated. Tensile-shear tests were applied to the welded specimens to understand the tensile shear force that the joint can withstand. Mathematical models were developed for both nugget diameter and tensile shear force. Use of automatic mode, will increase the dependence on the use of equations to predict the nugget diameter. The developed models have been checked for their adequacy and significance by the F test and t test respectively. The results obtained from the mathematical models have been optimized and also tested using conformity test runs.
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Parameter optimization of dissimilar resistance spot welding on ultra-high strength hot-stamped steel and mild steel by numerical simulation
Wen ZHENG,Min WANG,Liang KONG,Xuanting CHENG,Ming LEI
Acta Metallurgica Sinica(English letters)    2012, 25 (6): 487-498.   DOI: 10.11890/1006-7191-126-487
Abstract   PDF (1855KB)  

In this study, a coupled axisymmetric finite element model (FEM) was built to sim­ulate the resistance spot welding (RSW) process between ultra-high strength hot-stamped (UHSS) and mild steel by SORPAS software. Via simulating this process, the temperature distribution and dynamic temperature curves of the welding area were studied, and welding spatter phenomena were predicted and validated by com­paring them with experimental results. By adjusting the welding parameters in nu­merical simulation, appropriate welding parameters were achieved. Moreover, the mechanical properties of the welding joints under the optimized conditions were also compared with those of not optimized. The study results have already been applied in a manufacturing production. It can also provide guidance for the RSW on UHSS and mild steel.

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Reduction treatment of low-grade manganese ore by biomass roasting
Jingjing Song,Guocai Zhu,Yuna Zhao,Ping Zhang
Acta Metall Sin(English)    2010, 23 (3): 223-229.   DOI: 10.11890/1006-7191-103-223
Abstract   PDF (357KB)  
The reduction of manganese dioxide in low-grade manganese ore by biomass roasting process was investigated for extracting manganese from poor manganese ore more effectively. In this study,the cinder of ore fines and sawdust was further leached by sulphuric acid to obtain MnSO4. Over 97% manganese in ores can be converted into MnSO4. Effects of the mass ratio of manganese ore to sawdust, roasting temperature and time, leaching temperature and time, leaching agent concentration and liquid-solid ratio were studied. The manganese recovery achieved 97.71% under the conditions: the mass ratio of manganese ore to sawdust of 5:1, roasting temperature 500℃ for 40min, leaching temperature 60℃ for 40min, sulphuric acid concentration of 1mol/L and liquid-solid ratio of 10:1. This technology can be suitable for extraction of Mn in low-grade manganese ore.
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Deformation Behavior Of Aa6063 Aluminium Alloy After Removing Friction Effect Under Hot Working Conditions
Z.Y. Chen, S.Q. Xu, X.H. Dong
Acta Metall Sin(English)    2008, 21 (6): 451-458 .  
Abstract   PDF (629KB)  
The hot deformation behavior of AA6063 aluminium alloy has been investigated by means of compression tests at temperatures between 400 and 520℃, and strain rates ranging from 2.5 to 10 s-1. Owing to the barreling, the theoretical model on the basis of Hill's general method is used to calculate the flow stress of a cylindrical specimen under uniaxial simple compression so as to consider the friction effect at the die-specimen interface. A method of evaluating the friction coefficient by combining compression tests with the finite element method is presented. The real flow behavior of AA6063 aluminium alloy can be described with sinh-Arrhenius equation. The hot deformation activation energy Q derived from the corrected stress and strain data is 232.350 kJ/mol.
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CN: 21-1315/TG
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