1Cr18Ni9Ti的流变浆料制备和直接轧制试验

利用自行设计装置进行1Cr18Ni9Ti不锈钢的半固态流变浆料制备和半固态流变浆料的直接轧制试验。结果表明：在本试验条件下制备的1Cr18Ni9Ti不锈钢半固态流变组织中先结晶的奥氏体呈近球状，尺寸在100－200μm，半固态流变浆料的固相率为50%-60%；该流变浆料具有较好的流动性，在半固态直接轧制成形过程中会产生液相偏析和一定程度的固相颗粒塑性变形。     

制浆-成形分离式铝合金流变成形技术

采用自主研制的双向多级速电磁搅拌装置、浆料转移工具和涂料、阶梯板流变性能试件和半固态合金压铸模具,开发出一种半固态合金浆料制备系统与工件成形系统分离的铝合金流变成形技术。结果表明:该技术可在20～25 s内制备出形状因子为0.85左右,晶粒尺寸为70～80μm(空冷尺寸)的A356合金半固态浆料,实现制浆设备与成形设备“一对一”配套;可在浆料温度下降不超过3℃的情况下,实现合金浆料从制备系统到压铸机压室的平稳输送;试件的抗拉强度和伸长率分别比液态压铸提高11.6%～18.2%和42.5%～50%;该流变成形技术与传统的成形技术衔接简便。     

制浆-成形分离式铝合金变成形技术

采用自主研制的双向多级速电磁搅拌装置、浆料转移工具和涂料、阶梯板流变性能试件和半固态合金压铸模具,开发出一种半固态合金浆料制备系统与工件成形系统分离的铝合金流变成形技术.结果表明:该技术可在20～25 s内制备出形状因子为0.85左右,晶粒尺寸为70～80 μm(空冷尺寸)的A356合金半固态浆料,实现制浆设备与成形设备"一对一"配套;可在浆料温度下降不超过3℃的情况下,实现合金浆料从制备系统到压铸机压室的平稳输送:试件的抗拉强度和伸长率分别比液态压铸提高11.6%～18.2%和42.5%～50%;该流变成形技术与传统的成形技术衔接简便.     

1Cr18Ni9Ti的流变浆料制备和直接轧制试验

利用自行设计装置进行 1Cr18Ni9Ti不锈钢的半固态流变浆料制备和半固态流变浆料的直接轧制试验。结果表明 :在本试验条件下制备的 1Cr18Ni9Ti不锈钢半固态流变组织中先结晶的奥氏体呈近球状 ,尺寸在 10 0～ 2 0 0 μm ,半固态流变浆料的固相率为 5 0 %～ 60 % ;该流变浆料具有较好的流动性 ,在半固态直接轧制成形过程中会产生液相偏析和一定程度的固相颗粒塑性变形     

钢铁半固态流变浆料制备与输送装置的研制

没计了一套适合于制备高熔点钢铁材料半固态流变浆料的装置，这种装置不仅能制备含非枝晶状初生固相的半固态流变浆料，而且能将这种半固态浆料输送出来，满足后续的钢铁材料半固态浆料流变轧制的需要。本装置主要由电磁搅拌器、搅拌坩埚预热和保温系统、半固态浆料输送系统和其他辅助结构组成。采用电阻丝加热方法对搅拌坩埚进行预热和保温，控制钢水或铁水在坩埚中的冷却速度；采用旋转磁场型电磁搅拌器对搅拌坩埚中的金属液体进行连续的电磁搅拌，制备出初生相或先析出相为球状或近球状的半固态流变浆料；采用底漏式坩埚和塞杆及其提升机构对半固态流变浆料进行输送，半固态浆料在重力作用下经过搅拌坩埚底部的水口流出。     

镁合金半固态流变压铸成形关键技术与装备通过湖北省科技厅组织的成果鉴定

由华中科技大学承担 ,武汉正华镁合金技术有限责任公司为合作单位的湖北省重点科技发展计划项目《镁合金半固态流变压铸成形关键技术与装备》业已完成 ,并达到了预定的技术指标。 2 0 0 1年 1 1月 2 1日 ,通过湖北省科技厅成果鉴定。该项目研制的超高剪切速率镁合金半固态浆料制备装置 ,采用特殊的机械搅拌方式 ,运转平稳 ,温度控制精确 ,剪切速率可达 2 0 0 0～ 2 0 0 0 0ｓ- 1 ,并制备出初生晶粒细小的半固态浆料(固相率可达 1 5 %～ 50 % ;晶粒平均直径为 30～ 50μｍ)。采用无毒的气体保护和高温镁液的定量封闭输送技术 ,很好地解决了镁…     

倾斜冷却法浆料制备研究现状

介绍了倾斜冷却法制备半固态合金浆料的实验装置、实验方法,以及采用这些实验装置所进行的研究内容,简述了倾斜板法在半固态连铸、半固态挤压、半固态轧制、半固态压铸和半固态锻造中的工业应用研究现状,提出了倾斜冷却法制备浆料的发展前景。     

模糊控制在半固态浆料制备装置中的应用

介绍了低转速输送管半固态浆料制备装置的原理和组成，采用模糊控制技术改进了该装置的温度控制系统，并详细介绍了该控制系统的总体设计及软硬件方案。试验证明，模糊控制技术的应用提高了该装置的温度控制效果，实现了良好稳定的铝金属半固态浆料微观组织控制作用。     

搅拌工艺参数对SIMA法半固态AZ91D镁合金组织的影响

采用自行设计制造的半固态镁合金机械搅拌装置，制备了镁合金半固态浆料，研究了搅拌工艺参数对半固态镁合金组织的影响。结果表明：镁合金半固态等温搅拌温度在570～580℃，搅拌时间为6～9min时，获得的组织均匀细小。搅拌时间过长，晶粒尺寸反而有所增大。搅拌温度影响固相率，从而也影响到固相晶粒的圆整度。     

AZ91D半固态流变压铸成形的研究

采用双螺杆机械搅拌方式制备半固态浆料；研究了AZ91D镁合金半固态浆料的流变压铸成形工艺。结果表明：压射压力在40～50MPa，压射充型速度在10～15m／s内，固相率在10％～60％的浆料都能流变压铸成薄壁圆形铸件；半固态流变压铸成形比液态压铸成形的强度、伸长率分别提高37％、44％，并可施以热处理，进一步提高性能，易于实现“净近成形”。     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Quantitative Analysis of the Crystallographic Orientation Relationship Between the Martensite and Austenite in Quenching–Partitioning–Tempering Steels

The orientation relationships(ORs)between the martensite and the retained austenite in low-and medium-carbon steels after quenching–partitioning–tempering process were studied in this work.The ORs in the studied steels are identified by selected-area electron diffraction(SAED)as either K–S or N–W ORs.Meanwhile,the ORs were also studied based on numerical fitting of electron backscatter diffraction data method suggested by Miyamoto.The simulated K–S and N–W ORs in the low-index directions generally do not well coincide with the experimental pole figure,which may be attributed to both the orientation spread from the ideal variant orientations and high symmetry of the low-index directions.However,the simulated results coincide well with experimental pole figures in the high-index directions{123}_(bcc).A modified method with simplicity based on Miyamoto’s work was proposed.The results indicate that the ORs determined by modified method are similar to those determined by Miyamoto’method,that is,the OR is near K–S OR for the low-carbon Q–P–T steel,and with the increase of carbon content,the OR is closer to N–W OR in medium-carbon Q–P–T steel.     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.