High temperature plastic deformation behavior of non-oriented electrical steel

High temperature plastic deformation behavior of non-orientated electrical steel was investigated by Gleeble 1500 thermo-mechanical simulator at strain rate of 0.01−10 s⁻¹ and high temperature of 500–1 200 °C. The stress level factor (a), stress exponent (n), structural factor (A) and activation energy (Q) of high temperature plastic deformation process of non-orientated electrical steel in different temperature ranges were calculated by the Arrhenius model. The results show that, with dynamic elevation of deformation temperature, phase transformation from α-Fe to γ-Fe takes place simultaneously during plastic deformation, dynamic recovery and dynamic recrystallization process, leading to an irregular change of the steady flow stress. For high temperature plastic deformation between 500 and 800°C, the calculated values of a, n, A, and Q are 0.039 0 MPa⁻¹, 7.93, 1.9×10¹⁸ s⁻¹, and 334.8 kJ/mol, respectively, and for high temperature plastic deformation between 1 050 and 1 200 °C, the calculated values of a, n, A, and Q are 0.125 8 MPa⁻¹, 5.29, 1.0×10²⁸ s⁻¹, and 769.9 kJ/mol, respectively. Foundation item: Project(2005038560) supported by the Postdoctoral Foundation of China; Project(05GK1002-2) supported by Key Program of Hunan Province     

Physical simulation of hot deformation of TiAI based alloy

In order to establish a model between the grain size and the process parameters, the hot deformation behaviors of Ti-49.5Al alloy was investigated by isothermal compressive tests at temperatures ranging from 800 to 1 100 ℃ with strain rates of 10^-3-10^-1 s^-1. Within this range, the deformation behavior obeys the power law relationship, which can be described using the kinetic rate equation. The stress exponent, n, has a value of about 5.0, and the apparent activation energy is about 320 J/mol, which fits well with the value estimated in previous investigations. The results show that, the dependence of flow stress on the recrystallized grain size can be expressed by the equation: σ = K1 drex^-0.56. The relationship between the deformed microstructure and the process control parameter can be expressed by the formula: lgdrex= -0.281 1gZ 3.908 1.     

Flow stress equation for multipass hot-rolling of aluminum alloys

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Hot deformation behavior of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy with acicular microstructure

The characteristics of hot deformation of an α+β titanium alloy Ti-6.5Al-3.5Mo-1.5Zr-0.3Si with acicular microstructure were studied using isothermal hot compressive tests in a strain rate range of 0.01-10 s-1 at 860-1 100 °C. The true stress-true strain curves of alloy hot-compressed in the α+β region exhibit a peak stress followed by continuous flow softening; whereas in the β region,the flow stress attains a steady-state regime. At a strain rate of 10 s-1 and in a wide temperature range,the alloy exhibit...     

Thermal deformation behavior and microstructure of nuclear austenitic stainless steel

Gleeble-1500D thermal simulation tester was employed in the hot-compression investigation of as-cast nuclear 304 austenitic stainless steel under conditions: deformation temperature 950―1200℃; deformations 30% and 50%; deformation rates 0.01 and 0.1 s?1. The results show that the flow stress decreases with temperature rise under the same strain rate and deformation, that the flow stress increases with deformation under the same temperature and strain rate, and that the flow stress increases with strain rate...     

Superplastic Deformation Behavior of Hot-rolled AZ31 Magnesium Alloy Sheet at Elevated Temperatures

1IntroductionAs a typical wrought magnesiumalloy,AZ31alloyhas a wide prospect for applications inthe fields of auto-mobiles,electronic appliances and aeronautic facili-ties[1,2].However,due to the hexagonal close-packed(HCP)structure of magnesium,the ductility of AZ31al-loy at roomtemperature is rather poor,which greatly re-stricts its applications in structural fields[3-5].Owing tothe activation of non-basal slip system[6],the ductility ofMg alloycan be significantlyimproved at elevatedtem…     

Deformation behavior and microstructural evolution of Al-Zn-Cu-Mg-Sc-Zr alloy during high temperature compression

The deformation behavior of a new Al-Zn-Cu-Mg-Sc-Zr alloy was investigated with compression tests in temperature range of 380–470 °C and strain rate range of 0.001–10 s⁻¹ using Gleeble 1500 system, and the associated microstructural evolutions were studied by metallographic microscopy and transmission electron microscopy. The results show that true stress—strain curves exhibit a peak stress, followed by a dynamic flow softening at low strains (ɛ<0.05). The stress decreases with increasing deformation temperature and decreasing strain rate, which can be represented by a Zener-Hollomon exponential equation with the activation energy for deformation of 157.9 kJ/mol. The substructure in the deformed specimens consists of few fine precipitates with equaixed polygonized subgrains in the elongated grains and developed serrations at the grain boundaries. The dynamic flow softening is attributed mainly to dynamic recovery and dynamic recrystallization. Foundation item: Project(2006AA03Z523) supported by the National High-Tech Research and Development Program of China     

The dislocation sub-structure evolution during hot compressive deformation of Ti-6Al-2Zr-1Mo-1V alloy at 800 °C

Hot compressive behaviors of Ti-6Al-2Zr-1Mo-1V alloy at 800 °C, as well as the evolution of microstructure during deformation process, were investigated. The experimental results show that flow stress increases to a peak stress followed by a decease with increasing strain, and finally forms a stable stage. Dislocations are generated at the interface of α/β phase, and the phase interface and dislocation loops play an important role in impeding the movement of dislocation. As strain increasing, micro-deformation bands with high-density dislocation are formed, and dynamic recrystallizaton occurs finally. XRD Fourier analysis reveals that dislocation density increases followed by a decrease during compressive deformation, and falls into the range from 10¹⁰ to 10¹¹ cm⁻².     

Effect of ECAP on the microstructure and mechanical properties of a high-Mg<Subscript>2</Subscript>Si content Al-Mg-Si alloy

A high-Mg₂Si content Al alloy was extruded by equal channel angular pressing (ECAP) for 8 passes at 250 °C and an ultrafine-grained structure with an average grain size of about 1.5 μm was achieved. The coarse skeleton-shaped Mg₂Si phase presenting in the as-cast alloy are significantly fragmented into fine rod-shaped as well as equiaxed particles mostly less than about 230 nm and become relatively dispersed. The tensile strength 192.8 MPa and the elongation up to 31.3% at ambient temperature are attained in the 8-pass ECAPed alloy versus 163.3 MPa and 9.1% in the as-cast alloy. High-temperature creep test at 250 °C reveals that the ECAPed sample exhibits a high elongation close to 100% at a relatively high creep rate 7.64×10⁻⁵ s⁻¹, compared to the elongation 56% at a low strain rate 1.74×10⁻⁷ s⁻¹ in the as-cast alloy.     

Microstructure and flow stress of Mg-12Gd-3Y-0.5Zr magnesium alloy

The microstructure and flow stress of the Mg-12Gd-3Y-0.5Zr magnesium alloy was investigated by compression test at temperatures ranging from 350 to 500 ℃ and the strain rates ranging from 0.01 to 20 s-1. The flow stress of the magnesium alloy increased with strain rate and decreased with deformation temperature. Flow stress can be expressed in terms of the Zener-Hollomon parameter Z, which describes the combined influence of the strain rate and temperature using an Arrhenius function.The values of the deformation activation energy were estimated to be 245.9 and 171.5 kJ/mol at deformation temperatures below 400 ℃ and above 400 ℃, respectively. Two constitutive equations were developed to quantify the effect of the deformation conditions on the flow stress of the magnesium alloy. The effects of deformation temperature and strain rate on the microstructure of the magnesium alloy were also examined and quantified by measuring the volume fraction of dynamically recrystallized grain Xd. Xd increased with increasing of deformation temperature. When the deformation temperature was below 475 ℃, Xd decreased with strain rate until it reached 0.15 s-1, then it increased again. When the deformation temperature was above 475 ℃, Xd increased with strain rate.     

Parameter fitting of constitutive model and FEM analysis of solder joint thermal cycle reliability for lead-free solder Sn-3.5Ag

The experimental tests of tensile for lead-free solder Sn-3.5Ag were performed for the general work temperatures range from 11 to 90 °C and strain rate range from 5×10⁻⁵ to 2×10⁻² s⁻¹, and its stress—strain curves were compared to those of solder Sn-37Pb. The parameters in Anand model for solder Sn-3.5Ag were fitted based on experimental data and nonlinear fitting method, and its validity was checked by means of experimental data. Furthermore, the Anand model was used in the FEM analysis to evaluate solder joint thermal cycle reliability. The results show that solder Sn-3.5Ag has a better creep resistance than solder Sn-37Pb. The maximum stress is located at the upper right corner of the outmost solder joint from the symmetric center, and thermal fatigue life is predicted to be 3.796×10⁴ cycles under the calculated conditions. Foundation item: Project(50376076) supported by the National Natural Science Foundation of China     

Adsorption of Pb^2＋ on macroporous weak acid adsorbent resin from aqueous solutions： Batch and column studies

The adsorption properties of a novel macroporous weak acid resin (D152) for Pb²⁺ were investigated with chemical methods. The optimal adsorption condition of D152 resin for Pb²⁺ is at pH 6.00 in HAc-NaAc medium. The statically saturated adsorption capacity is 527 mg/g at 298 K. Pb²⁺ adsorbed on D152 resin can be eluted with 0.05 mol/L HCl quantitatively. The adsorption rate constants determined under various temperatures are k _{288 K}=2.22×10⁻⁵ s^t-1, k _{298 K}=2.51×10⁻⁵ s⁻¹, and k _{308 K}= 2.95×10⁻⁵ s⁻¹, respectively. The apparent activation energy, E _a is 10.5 kJ/mol, and the adsorption parameters of thermodynamics are ΔH ^Θ=13.3 kJ/mol, ΔS ^Θ=119 J/(mol·K), and ΔG ^Θ 298 K =−22.2 kJ/mol, respectively. The adsorption behavior of D152 resin for Pb²⁺ follows Langmuir model. Foundation item: Project(2008F70059) supported by the Scientific and Technological Research Planning of Zhejiang Province, China     

Superplasticity of Mg-5.8Zn-1Y-Zr alloy sheet fabricated by combination of extrusion and hot-rolling processes

Superplastic behaviors of quasicrystal phase containing Mg-5.8Zn-1Y-0.48Zr alloy sheets fabricated by combination of extrusion and hot-rolling processes have been investigated at temperature ranging from 623 to 753 K and at the strain rates ranging from 10-4 to 10-2 s-1 by uniaxial tensile tests. An excellent superplasticity with the maximum elongation to failure of 1020% was obtained at 753 K and the strain rate of 1.04×10-3 s-1 and its strain rate sensitivity, m, is as high as up to 0.75. The microstructure was stable during superplastic deformation due to the uniformly distributed fine quasicrystal particles. In addition, micro-cavities and their coalescences were observed in the superplastic deformation of the ZW61 magnesium alloy. Grain boundary sliding (GBS) was considered to be the main deformation mechanism during the superplastic deformation. Dislocation creep controlled by atom diffusion through grain boundaries or interior grains is suggested mainly to accommodate the GBS in super-plastic deformation.     

Synthesis and characterization of arsenate antimonic acid AAAc(1 : 1)

The AAAc(1 : 1) was synthesized in water by As₂O₃ and Sb₂O₃ with molar ratio of 1 : 1. AAAc(1 : 1) was characterized by Raman, IR, TG/DTG, DSC, XPS and XRD. The results show that there are four peaks to v _s of As-OH, As-O-Sb, Sb-OH and Sb-O-Sb in Raman spectra of AAAc(1 : 1) at 100 – 1 000 cm⁻¹. The solution of AAAc(1 : 1) was also titrated with KOH solution. The titration results show that AAAc(1 : 1) is a hexabasic acid with dissociation constants of k ₁=3.62 × 10⁻², k ₂=3.05 × 10⁻³, k ₃=6.43 × 10⁻⁶, k ₄ =9.78 × 10⁻⁸, k ₅=1.32 × 10⁻¹¹, k ₆=3.87 × 10⁻¹². AAAc(1 : 1) has a good solubility and stability in water, its solid obtained by free volatilizing water from its solution under air at ambient temperature is amorphous. Chemical and thermal analysis show that the composition of AAAc(1 : 1) is As₂O₅ · Sb₂O₅ · 8H₂O in air at 25 °C. AAAc(1 : 1) has the structure of AsO(OH)₂-OH-Sb(OH)₄-O-Sb(OH)₄-OH-AsO(OH)₂ or As(OH)₃-O-Sb(OH)₄-O-Sb(OH)₄-O-As(OH)₃ (isomerism) through experimental determination and geometry optimization. Foundation item: Project(50274075) supported by the National Natural Science Foundation of China     

Simulation of dynamic recrystallization for aluminium alloy 7050 using cellular automaton

The prediction of microstructure evolution plays an important role in the design of forging process. In the present work, the cellular automaton (CA) program was developed to simulate the process of dynamic recrystallization (DRX) for aluminium alloy 7050. The material constants in CA models, including dislocation density, nucleation rate and grain growth, were determined by the isothermal compress tests on Gleeble 1500 machine. The model of dislocation density was obtained by linear regression method based on the experimental results. The influences of the deformation parameters on the percentage of DRX and the mean grain size for aluminium alloy 7050 were investigated in details by means of CA simulation. The simulation results show that, as temperature increases from 350 to 450 °C at a strain rate of 0.01 s⁻¹, the percentage of DRX also increases greatly and the mean grain size decreases from 50 to 39.3 μm. The mean size of the recrystallied grains (R-grains) mainly depends on the Zener-Hollomon parameter. To obtain fine grain, the desired deformation temperature is determined from 400 to 450 °C. Foundation item: Project(2005CB724105) supported by the Major State Basic Research Program of China; Project(IRT0549) supported by Program for Changjiang Scholars and Innovative Research Team in University     

The Effect of Bi2O3 on the Structure and Microwave Dielectric Properties of Ba6-3xNd8＋2xTi18O54 System（x=2/3）

The structures and dielectric properties of Ba6-3xNd8＋2xTi18O54 system（x=2/3） doped with different contents of Bi2O3, whose final molecular formula is Ba6-3x（Nd1-yBiy）8＋2xTi18O54 were investigated. It is indicated that the dielectric constant increases greatly whereas Q value（f0=4 GHz） decreases with the increase of Bi2O3 content. However, the temperature coefficient could be controlled below 0±30×10^-6/℃ in the experiment. These phenomena are related to the appearance of a new phase, Bi4Ti3O12, which has high dielectric constant. Also, that Bi^3＋（0.13 nm） substitutes for Nd^3＋（0.099 5 nm） will increase the unit cell volume, which will lead to the enlargement of the octahedron B site occupied by Ti^4＋. So the spontaneous polarization of Ti^4＋ ions will be strengthened. Besides, Bi^3＋ will fill up some vacancies which Ba^2＋ or Nd^3＋ ions leave in two A1 sites and four A2 sites. More positive ions polarize, which also contributes to higher dielectric constant. The samples got with the optimium properties are sintered at 1 200 ℃ for 4 h, when y=0.25, ε≈110, Q≈5 400（f0=4 GHz）, TCC=-4.7×10^-6/℃; When y=0.3, ε≈120, Q≈5 000（f0=4 GHz）, TCC=-24×10^-6/℃.     

Dynamic recrystallization behavior of 35CrMo structural steel

1　ＩＮＴＲＯＤＵＣＴＩＯＮＤｕｒｉｎｇｈｏｔｗｏｒｋｉｎｇ ,ｓｅｖｅｒａｌｍｅｔａｌｌｕｒｇｉｃａｌｐｈｅｎｏｍｅｎａｓｕｃｈａｓｗｏｒｋ ｈａｒｄｅｎｉｎｇ (ＷＨ ) ,ｄｙｎａｍｉｃｒｅｃｏｖｅｒｙ (ＤＲＶ) ,ａｎｄｄｙｎａｍｉｃｒｅ ｃｒｙｓｔａｌｌｉｚａｉｔｏｎ (ＤＲＸ )ｏｃｃｕｒｓｉｍｕｌｔａｎｅｏｕｓ ｌｙ[1 5 ] .Ｅｓｐｅｃｉａｌｌｙ ,ｔｈｅｏｃｃｕｒｒｅｎｃｅｏｆＤＲＸ ,ｃａｎｒｅｆｉｎｅｇｒａｉｎａｎｄｒｅｄｕｃｅｄｅｆｏｒｍａｔｉｏｎｒｅｓｉｓｔａｎｃｅｉｎｐｒａｃｔｉｃａｌｈｏｔ ｗ…     

Influence of Temperature on Electrochemical Performances of Rare Earth Based Hydrogen Storage Material

1 IntroductionRare earth-based hydrogenstorage alloys ofAB5typehave beenthe most major electrode material for small-sizeNi/MHbatteries because of their high discharge capacity,superior highrate capability andfavorable ratio of pricetoperformance. But their electrochemical performances be-come worse when the alloys are applied to large-size Ni/MHbatteries of electric vehicles .Thisfact may be due tothe rising of temperature inside the large batteries causedbythe high electric current of char…     

Selective leaching of chromium-containing slag by HCl

A batch of column experiments was carried out to investigate the change of Cr（Ⅵ） concentration leached out from chromium-containing slag with HCI as leaching agent, and to study influences of pH, ratio of solid mass to solution volume, flow velocity and temperature on Cr（Ⅵ） leaching. The optimal parameters were obtained for Cr（Ⅵ） leaching and a fitting model was established to describe the procedure of Cr（Ⅵ） leaching. The results show that Cr（Ⅵ） concentration in leachate increases with decreasing pH and increasing flow velocity and temperature. Moreover, Cr（Ⅵ） leaching percentage increases with increasing ratio of solid mass to solution volume. The optimal parameters for Cr（Ⅵ） selective leaching are as follows： pH=3.0, 1：5 of ratio of solid mass to solution volume, 180 mL/min of flow velocity and 40 ℃ of temperature. The procedure of Cr（Ⅵ） leaching fits well with the model： v= 1.87t^-0.54, indicating that the leaching rate of Cr（Ⅵ） declines in an exponential order of-0.54.     

Water permeability parameters of dermal fibroblast employed in tissue engineering in subzero temperatures

In the construction of the tissue engineered dermal equivalent, the dermal fibroblast plays a crucial role[1]. While the fibroblasts need time to proliferate, synthesize, and se-crete extracellular matrix in the three-dimensional scaffold postseeding, a degradablescaffold commences disintegration over time. This may lead to an unusable product, if proper preservation does not conduct. Cryopreservation could solve this problem. The possibility of the long-term banking of cells and tissues would…