The Bonding Properties of Solid Steel to Liquid Aluminum

The bonding of solid steel plate to liquid aluminum was studied using rapid solidification. The relationship models of interfacial shear strength and thickness of interfacial layer of bonding plate vs bonding parameters ( such as preheat temperature of steel plate, temperature of aluminum liquid and bonding time ) were respectively established by artificial neural networks perfectly. The bonding parameters for the largest interfacial shear strength were optimized with genetic algorithm successfully. They are 226℃ for preheating temperature of steel plate, 723℃ for temperature of aluminum liquid and 15.8s for bonding time, and the largest interfacial shear strength of bonding plate is 71.6MPa. Under these conditions, the corresponding reasonable thickness of interfacial layer (10.8μm) is gotten using the relationship model established by artificial neural networks.     

铝合金板与混凝土的粘贴粘结强度研究

为了在提高加固钢筋混凝土梁承载力的同时具有很好的延性和耗能能力,特别是满足侵蚀环境及寒冷环境中加固工程的需要,采用铝合金板加固钢筋混凝土梁是一个很好的解决办法。铝合金板通过粘贴层将力传给钢筋混凝土梁,故铝合金板与混凝土的粘贴粘结性能决定了铝合金板加固钢筋混凝土梁的效果。铝合金板与混凝土的粘贴粘结强度作为铝合金板加固钢筋混凝土梁连接设计的基础,对其开展试验和理论研究。开展105个试件的铝合金板与混凝土面内单剪试验发现：对粘贴界面没有进行粗糙处理的试件发生了界面剥离破坏,其他试件均发生了混凝土层剥离破坏;界面剥离破坏的粘结性能远差于混凝土层剥离破坏,说明了对粘贴界面进行处理的必要性。通过试验得到铝合金板和混凝土连接的极限粘结荷载,根据铝合金板正应力的变化率与粘贴界面剪应力的关系,得到剪应力的分布曲线和有效粘结长度;假设剪应力沿有效粘结长度处处相等,得到了铝合金板与混凝土的粘贴试验粘结强度,并基于此讨论了界面处理、混凝土强度、铝合金板宽度、厚度和粘贴长度等因素对试验粘结强度的影响。结合试验数据的统计回归分析,提出计算铝合金板与混凝土的粘贴粘结强度的修正Niedermeier模型,得到了铝合金板与混凝土的有效粘结长度和粘贴粘结强度的理论计算公式,其理论值和试验值吻合较好,误差最大值为8.98%,平均值为0.004,标准差为0.041。研究成果为铝合金板加固钢筋混凝土梁的粘贴设计提供了理论基础。     

Flexural strength of zirconia/stainless steel functionally graded materials

Zirconia/stainless steel (ZrO₂/SUS316L) functionally graded materials (FGMs) were fabricated by tape casting and laminating. Microstructures of FGMs were observed by optical microscope. Fracture behavior of FGMs in different loading modes and influences of different gradient changes on flexural strength were investigated. The results show that ZrO₂/ SUS316L FGMs with graded components at interlayers are obtained after they are sintered in vacuum and pressureless condition at 1 350 °C. The I–II mixed mode crack creates in composite layer and grows to both sides zigzag while loading on ZrO₂ layer. Flexural strengths are 496.4, 421.7 and 387.5 MPa when gradient changes are 10%, 15% and 20%, but flexural strengths of the corresponding fracture layers are 387.1, 334.6 and 282.3 MPa since cracks of FGMs are affected by three-dimensional stress, respectively. The cracks are generated in ZrO₂ layer and extend to SUS316L layer while loading is added on SUS316L layer, flexural strength does not change with the graded components and keeps consistent basically.     

The Influence of Preheat Temperature of Steel Plate on Steel-mushy Cu-graphite Bonding

The pressing bonding of steel plate to QTi3.5-3.5 graphite slurry was conducted. Under the conditions of 530 ℃ for the preheat temperature of dies, 45% for the solid fraction of QTi3.5- 3.5 graphite slurry, 50 MPa for the pressure and 2 min for the pressing time, the relationship between the preheat temperature of steel plate and interfacial mechanical property of bonding plate was studied. The results show that when the preheat temperature of steel plate is lower titan 618 ℃ , the interfacial shear strength of bonding plate increases with the increasing of the preheat temperature of steel plate. When the preheat temperature of steel plate is higher than 618 ℃ , the interfacial shear strength decreases with the increasing of the preheat temperature of steel plate. When the preheat temperature of steel plate is 618 ℃ , the highest interfacial shear strength of bonding plate of 127.8 MPa can be got.     

不锈钢复铝板结合强度和延伸率的实验研究

实验研究了N2 气保护下加热轧制复合和辊板轧制工艺对不锈钢和铝复合板材界面结合强度及复合板深加工性能的影响。结果表明 ,N2 气保护下加热轧制复合和辊板轧制可有效提高复合板界面结合强度 ,同时使达到界面良好结合的临界变形率明显降低 ;这两种轧制工艺不仅在小变形的条件下即可实现不锈钢和铝复合界面的良好结合 ,而且能明显降低复合过程中不锈钢的变形率分配 ,有利于改善复合板的深加工性能     

Effect of carbon fibre on properties of TiB2/C composite cathode coating for aluminum electrolysis

The tensile strength, compressive strength and electrical resistivity of TiB₂/C composite cathode coating were measured with a hydraulic pressure universal test machine and an electrical resistivity test device, and the effects of carbon fibre content and carbon fibre length on tensile strength, compressive strength and electrical resistivity were investigated. The results show that the tensile strength of coating increases at the beginning and then reduces with the increase of carbon fibre content when the carbon fibre (length of 3 mm) content ranges from 0 to 4.0%; at the carbon fibre content of 1.5%, the tensile strength of coating reaches the maximum, 25.6 MPa. For the coating with carbon fibre content of 1.5%, the carbon fibre length has a great influence on tensile strength and compressive strength of coating; when the carbon fibre length is 6 mm, the tensile strength and compressive strength of coating reach the maximum, 27.6 MPa and 39.2 MPa, respectively. The electrical resistivity of coating reduces with the rise of temperature and the length of carbon fibre, and the influence of carbon fibre length on electrical resistivity of coating at low temperature (30–200 °C) is more obvious than that at high temperature (960 °C). Foundation item: Project(2005CB623703) supported by the Major State Basic Research Development Program of China     

The stamping formability of AZ31 magnesium alloy sheet improved by equal-channel angular pressing

Equal channel angular pressing (ECAP) processing and annealing were applied to the AZ31 magnesium alloy sheets to evaluate the potential improvement in the mechanical properties and formability. The ECAP experiment was conducted at 300 °C in a die having an included angle of 90° between two channels by the B_CZ route with the sheets rotated by 90° about the normal axis of plate plane. The tensile tests and conical cup tests were conducted at various temperatures from 20 to 250 °C. The experimental results indicated that improving the working temperatures could lead to the soft in the material and the enhancement of ductility. Comparatively, the ECAPed AZ31 alloy sheets showed the lower yield strength and smaller conical cup value (CCV) than the unECAPed counterpart in the room temperature. The difference in yield strength between them became small in the elevated temperature, but the ECAPed samples still had the smaller CCV value, implying the improved formability. The texture of the AZ31 alloy sheets could be modified by ECAP and the decrease in the yield strength and more uniform deformation realized in the material, so the formability of AZ31 alloy sheets was improved.     

真空热轧不锈钢复合板界面结合行为的研究

为了研究真空热轧不锈钢复合板的结合行为,本文以热轧304不锈钢／Q345低碳钢复合板为研究对象,通过剪切试验及组织分析等手段研究了变形量及真空度对不锈钢复合板结合性能的影响规律．结果表明,轧制总变形量从35％增加到75％之后复合板的剪切强度大约可增加100MPa．真空度降低会导致结合界面氧化程度增加,进而降低复合板的结合性能,当真空由0.1Pa变为20Pa时,界面氧化物的比例由约10％提高到约50％,剪切强度由440MPa降低到了350MPa左右．最后根据试验结果提出了热轧不锈钢复合板的结合行为．     

Influence of aluminum solid fraction on property of steel-mushy aluminum bonding plate

The interfacial shear property of steel-mushy aluminum bonding plate was studied, and the relationship between aluminum solid fraction and the interfacial shear strength of bonding plate was determined. The results showed that when aluminum solid fraction is 34.3 %, the maximum interfacial shear strength of bonding plate is 71 .0 MPa.     

Effects of Ag on microstructure and mechanical properties of 2519 aluminum alloy

The effects of Ag on the microstructure and mechanical properties of 2519 aluminum alloy were investigated by means of tensile test, micro-hardness test, transmission electron microscope and scanning electron microscope. The results show that the addition of 0.3 % （mass fraction） Ag accelerates 2519 aluminum alloy＇s age-hardening, increases its peak hardness and reduces 4 h of peak aged time at 180 ℃. The addition of 0. 3% （mass fraction） Ag increses the tensile strength at room temperature and elevated temperature. This increment at room temperature and 200 ℃ is 24 MPa and 78 MPa, respectively. In contrast, the elongation of 2519 aluminum alloy is decreased with Ag addition. The increase of tensile strength of 2519 aluminum alloy with Ag addition is attributed to the high volume fraction of Ω phase.     

Microstructure and mechanical property of 2024／3003 gradient aluminum alloy

2024/3003 gradient aluminum alloy was prepared by semi-continuous casting using double-stream-pou-ring technique. The microstructures of the as-cast, pressed and heat-treated alloys were analyzed by scanning elec-tron microscope and transmission electron microscope. And the mechanical properties of the alloy in pressed and heat-treated states were studied. The results show that the ingots with diameter of 65 mm and external thickness about 5.5 mm are obtained when the temperatures of the melt in the internal and external ladles are 1 023 and 1 003 K, respectively, and the nozzle diameter is 2.0 mm. The microstructures of the as-cast alloy consist of α(AI) θ(CuAl2)q S(Al2CuMg) in the internal region and α(Al) MnAl6 in the external region. The phases found in the internal and external layers coexist in the transition zone. The transition layer is maintained after plastic deformation and heat treatment of the alloy. The tensile strength, yield strength and elongation of the alloy are 300 MPa,132 MPa and 16.0%, respectively, after T6 treatment. The tensile and yield strength are increased by 150.0% and 94.1%, respectively, compared with that of 3003 aluminum alloy. The maximum hardness in the internal region of 2024/3003 gradient aluminum alloy can be increased from HRF 55 in the pressed state to HRF 70 in the heat-treated state.     

Structural characteristics and properties of polyurethane modified TDE-85/MeTHPA epoxy resin with interpenetrating polymer networks

Diglycidyl-4,5-epoxycyclohexane-1,2-dicarboxylate（TDE-85）/methyl tetrahydrophthalic anhydride （MeTHPA） epoxy resin was modified with polyurethane（PU） and the interpenetrating polymer networks（IPNs） of PU-modified TDE-85/MeTHPA resin were prepared. The structural characteristics and properties of PU-modified TDE-85/MeTHPA resin were investigated by Fourier transform infrared（FTIR） spectrum,emission scanning electron microscopy（SEM） and thermogravimetry（TG）. The results indicate that epoxy polymer network （Ⅰ） and polyurethane polymer network （Ⅱ） of the modified resin can be obtained and the networks （Ⅰ） and （Ⅱ） interpenetrate and tangle highly each other at the phase interface. The micro morphology presents heterogeneous structure. The integrative properties of PU-modified TDE-85/MeTHPA epoxy resin are improved obviously. The PU-modified TDE-85/ MeTHPA resin’s tensile strength reaches 69.39 MPa,the impact strength reaches 23.56 kJ/m,the temperature for the system to lose 1% mass （t1%） is 300 ℃,and that for the system to lose 50% mass （t50%） is 378 ℃. Compared with those of TDE-85/MeTHPA resin,the tensile strength,impact strength,t1% and t50% of the PU-modified resin increases by 48%,115%,30 ℃,11 ℃,respectively. The PU-modified TDE-85/MeTHPA resin has the structure characteristics and properties of interpenetrating polymer networks.     

Effect of matrix composition on physical properties of Al<Subscript>3</Subscript>CON in-situ reaction reinforced corundum composite

60% white corundum used for aggregate, 5% aluminium powder for fixed additions and 35% various additives for matrix were prepared for specimens 1#,2#,3#. They were mixed uniformly with the suitable resin as a binder and pressed under pressure of 315 ton forging press, then dried at 200℃ for 24 h. Effects of various additives on 1500 ℃×2 h creep properties of Al3CON reinforced corundum composite were researched. The experimenal results show that creep coefficients of specimens 1#,2#,3# at 1500 ℃×2 h are 1.4×10^- 4, -9.4×10^-4, -22.6×10^-4, respectively. Crushing strength of the slide plate added with suitable additive A after fired at 1500 ℃ ×3 h reaches to 225 MPa, the creep rate is positive all the time from 0% to 0.014% at 1500 ℃ for 2 h. The microstructure result analysis shows that reinforced phases of Al3CON fiber composite have been formed after fired with Al powder in coke at high temperatures for specimen 1#, and the strength of the composite is increased. The hot modulus of rupture is up to 59 MPa at 1400 ℃ and the RUL is obviously higher than that at 1700 ℃. Its service life is two times as that of Al2O3-C slide plate when used in the process of pouring steel. The mechanism of creep rate resistance of the composites can be discovered by means of SEM and EDAX analysis. It is concluded that the active Al3CON and Al2O3 multiphases that were formed by N2 in gas, C, Al and Al2O3 inside the matrix of the composites during in-situ reaction,which gives the composites outstanding creep rate resistance for the dense zone resuiting from Al3CON oxidation that inhibits contraction at the high temperature. Besides, the matrix will turn into the multiphase with high refractoriness, N content and its Al3CON reinforced fiber will further increase accordingly. In addition, Al3CON formed by Al2O3 and C, Al in the matrix with N2 in gas will inhibit the creep rate and also greatly improve the creep rate resistance of the composites.     

热处理对2524铝合金显微组织及力学性能影响

在400℃下对铸态2524铝合金进行轧制成形,总变形量为90%,采用光学金相显微镜、拉伸试验机等设备检测轧制板材显微组织及力学性能.研究结果表明：随着固溶温度的升高,Al2Cu,Al2CuMg等第二相粒子数量逐渐减少,在490℃～500℃下基本固溶进铝基体中,其显微硬度值随着固溶温度的升高逐渐增大,当固溶温度为490℃时其显微硬度值为131.4 HV;2524铝合金轧制板材经490℃/20 min＋190℃/22 h处理后,其抗拉强度为485 MPa,延伸率为13.5%.     

Fabrication of high strength carbon nanotube/7055Al composite by powder metallurgy combined with subsequent hot extrusion

Bimodal carbon nanotube reinforced 7055Al(CNT/7055Al) composites containing coarse grain bands and ultra-fine grain zones were fabricated by high energy ball milling, vacuum hot pressing followed by hot extrusion. The effect of extrusion temperature varied from 320℃ to 420℃ on the microstructure evolution and tensile properties were investigated. Microstructure observation indicates that the elongated coarse grain bands aligned along the extrusion direction after extrusion. The width of the coarse grain bands increased, and the length of the coarse grain bands increased firstly and then decreased with the increase of extrusion temperature. The grain size of the ultra-fine grain zones changed little after hot extrusion, but the ultra-fine grains coarsened after subsequent heat treatment, especially for the composite extruded at low temperature of 320℃. By observing the CNT distribution, it was found that the higher temperature extrusion was beneficial to the CNT orientation along the extrusion direction.Furthermore, a precipitated free zone formed at the boundary between the coarse grain band and the ultra-fine grain zone as the composite extruded at high temperature of 420℃. As the result of the comprehensive influence of the above microstructure, the tensile strength of the composite extruded at moderate temperature of 370℃ reached the highest of 826 MPa.     

Microstructural Characteristic of Montmorillonite and Its Thermal Treatment Products

The montmorillonite was studied by different methods, such as chemical analysis, DAT, TG, XRD, IR, AFM and MAS NMR. The experimental results show that the hydroxyl in octahedra sheets beans dehydrating when the thermal treatment temperature reaches 659℃, but the layer structure remavins the same, and the corresponding Al ( Ⅳ ) is turned into Al ( Ⅳ ) in octahedra sheets. When the temperature reaches 900℃ , the layer structure of montmorillontite is destrtoyed, and the new mineral phase μ-cordierite is found. When the temperature reaches 1200℃, the μ-cordierite phase loses its stability, and decomposes into cristobalite phase and mullite phase. Meanwhile, the recrystallization phenomenon in thermal treatment products is obvious. There is a small quantity of Al Ⅳ signal in MAS NMR spectrum, corresponding to Al of mullite. When the temperature reaches 1350℃ , the cristobalite and mullite phases reduce sligluly, and more Fe-cordierite phase appears, corresponding to Fe-cordierite spectrum in XRD and MAS NMR.     

Effect of annealing on microstructure and properties of Si_3N_4-AlN composite ceramics

Aiming at developing novel microwave-transparent ceramics with low dielectric loss,high thermal conductivity and high strength,Si3N4-AlN(30%,mass fraction) composite ceramics with La2O3 as sintering additive were prepared by hot-pressing at 1 800 °C and subsequently annealed at 1 450 °C and 1 850 °C for 2 h and 4 h,respectively.The materials were characterized by XRD and SEM.The effect of annealing process on the phase composition,sintering performance,microstructure,bending strength,dielectric loss and the...     

Influence of sulfur content in raw materials on oxidized pellets

The influence of sulfur content in raw materials on oxidized pellets was studied. The results show that most sulfur exists in the form of elementary sulfur in pyrite cinder, and over 95% sulfur is removed in producing pyrite cinder oxidized pellets. The compressive strength of fired pellets drops from 3 186 N to 2 405 N when the ratio of pyrite cinder increases from 40% to 70% under the conditions of preheating at 900 °C for 9 min and firing at 1 230 °C for 15 min. The porosity and microstructures of fired pellets prove that the higher ratio of pyrite cinder is given, and the more holes and cracks are achieved, leading to the better reducibility index (RI) and reduction swelling index (RSI), and the lower compressive strength of fired pellets and the worse reduction degradation index (RDI).     

Prediction of antifreeze critical strength of infant age concrete

The rule of infant age concrete strength development under low temperature and complex affecting factors is researched. An efficient and reliable mathematical forecast model is set up to predict the infant age concrete antifreeze critical strength under low temperature at construction site. On the basis of the revision of concrete equivalent coefficient under complex influencing factors, least-squares curve-fitting method is applied to approximate the concrete strength under standard curing and the forecast formula of concrete compressive strength could be obtained under natural temperature condition by various effects. When the amounts of double-doped are 10% fly ashes and 4% silica fumes as coment replacement, the antifreeze critical strength changes form 3.5-4.1MPa under different low temperature curing. The equivalent coefficient correction formula of concrete under low temperature affected by various factors could be obtained. The obtained equivalent coefficient is suitable for calculating the strength which is between 10% to 40% of standard strength and the curing temperature from 5-20 ℃. The forecast value of concrete antifreeze critical strength under low temperature could be achieved by combining the concrete antifreeze critical strength value with the compressive strength forecast of infant age concrete under low temperature. Then the theory for construction quality control under low temperature is provided.     

Effect of metallic content on mechanical property of Ni/（10NiO-NiFe2O4 ） cermets

1 INTRODUCTIONThe use of inert or non-consumable anodes forreplacement of consumable carbon anodes in Hall-H啨roult electrolysis cells for the production of alu-minum has been a technical and commercial goalfor many decades .In the present process ,consumable carbon an-odes are used,andthe anode product is CO2. Withaninert anode ,the cell reaction will be :Al2O3=2Al +23O2(1)The basic requirements for aninert anode are :1) to exhibit a lowcorrosion rate in the high tem-perature melts an…