TiB2/A356复合材料航空零件的熔模铸造

研究了TiB2/A356复合材料的各热物性参数与TiB2体积分数的关系,并对ProCAST软件的数据库进行二次开发,以得到不同TiB2体积分数的TiB2/A356复合材料的热物性参数随温度变化的关系.对某航空零件进行熔模铸造的模拟和试验.结果表明,通过提高浇注温度、浇注速度以及添加保温材料,消除了该零件表面的缩松、缩孔缺陷.     

Numerical Simulation Research of Investment Casting for TiB2/A356 Aluminum Base Composite

研究了TiB2/A356铝基复合材料的某航空零件熔模精密铸造性能。根据该复合材料的各热物性参数和TiB2体积分数的关系,结合Pro CAST软件对其数据库进行二次开发,建立了体积分数为10%的TiB2/Al铝基复合材料的热物性参数随温度变化的关系。对某航空薄壁零件进行熔模铸造模拟,模拟结果显示:通过提高A356浇注温度、浇注速度和在浇口与冒孔周围添加保温材料措施,使零件表面的缩孔、缩松缺陷得到解决。     

TiB_2/A356铝基复合材料的熔模铸造数值模拟研究(英文)

研究了TiB2/A356铝基复合材料的某航空零件熔模精密铸造性能。根据该复合材料的各热物性参数和TiB2体积分数的关系,结合Pro CAST软件对其数据库进行二次开发,建立了体积分数为10%的TiB2/Al铝基复合材料的热物性参数随温度变化的关系。对某航空薄壁零件进行熔模铸造模拟,模拟结果显示:通过提高A356浇注温度、浇注速度和在浇口与冒孔周围添加保温材料措施,使零件表面的缩孔、缩松缺陷得到解决。     

铝基复合材料机器人件的熔模铸造数值模拟

熔体粘度较高和颗粒分布不均匀是影响颗粒增强金属基复合材料铸造性能的主要因素之一。本文通过熔体反应法制备了TiB2/A356复合材料,根据复合材料热物性计算公式得到其热物性参数,并利用PROCAST软件对其热物性参数进行二次开发和熔模铸造数值模拟。模拟结果显示,熔体流动性差,缩孔缩松明显。分析其产生的主要原因为熔体粘度较大,颗粒分布不均匀。为此,提出了真空浇注、提高浇注温度和模壳初始温度的改进方案。结果表明,优化方案可行,为解决颗粒增强金属基复合材料的铸造问题打下基础。     

TiB_2/A356复合材料的热物性参数计算系统开发与熔模铸造数值模拟

使用Matlab软件开发了复合材料的热物性参数计算系统,并使用该系统获取了TiB_2/A356复合材料的热物性参数,并导入PROCAST的数据库对其热物性参数进行二次开发,对铸件熔模铸造过程进行模拟。模拟结果显示,铸件缩孔、缩松严重,且空隙率较大。分析缺陷产生的原因为增强体的加入使得液体流动性变差,补缩能力较弱。最后通过正交试验法获得流动性较好的A356铝合金,并通过提高浇注温度得到浇注结果合格的铸件。     

基于神经网络的泵体铸造过程数值模拟的优化与应用

根据A356泵体铸件金属型低压铸造特点,结合生产实际,以A356泵体浇注工艺参数为研究对象,L16(45)型正交实验数据作为训练学习样本,与正交实验成分有关的前16个样本作为训练与检验,用BP神经网络进行预测和优化,结果表明神经网络优化后的模拟值最大误差很小,CPU占用时间仅为40s.人工神经网络与正交实验相结合,能大大节省时间和费用,降低CPU占用率,也证实了对A356泵体充型过程数值模拟的神经网络优化是可行的.     

原位TiB2颗粒增强铝基复合材料及其力学性能

对原位反应合成TiB2／A356铝基复合材料微观组织和力学拉伸性能进行了研究。结果表明，原位反应生成的颗粒增强相在复合材料基体中分布均匀，基体与颗粒间的界面洁净。复合材料强度随着颗粒含量的增加显著提高，与基体合金相比，TiB2质量分数为8％的TiB2／A356复合材料强度和弹性模量的提高幅度约为28％，TiB2质量分数为16％的TiB2／A356复合材料强度和弹性模量的提高幅度约为35％。复合材料的断裂主要是由于基体与颗粒界面脱粘，在拉伸应力作用下由此萌生微裂纹并扩展，导致界面处的基体撕裂，从而降低复合材料塑性。     

蛇形管浇注制备TiB_2/7075半固态浆料及数值模拟

通过原位合成法制备出TiB2/7075复合材料,研究了TiB2颗粒对7075铝合金微观组织的影响。结果表明,添加4.5%的TiB2后能有效优化α-Al晶粒形貌,但添加9%的TiB2后由于颗粒团聚、优化作用降低。使用ProCAST软件对蛇形管制备过程进行了数值模拟,得出了适宜的蛇形管温度、浇注温度及蛇形管弯道数量。在蛇形管保温温度为400℃,浇注温度为670℃时能够获得半固态浆料。根据模拟得到的工艺参数进行流变挤压铸造试验,获得了良好的球状晶组织。     

“筒壳”铸件半固态压铸过程数值模拟

采用铸造模拟软件ProCAST对腔深、壁薄的A356合金的“筒壳”铸件进行模拟分析.通过对其压铸过程中的温度场进行数值模拟、分析,预测缩孔缩松所在的位置及大小.优化出最佳工艺参数:浇注温度为590℃,压射速度为5 m/s,模具温度为220℃.在此工艺条件下A356半固态浆料充型平稳,温度场分布均匀,无飞溅卷气和浇注不足等缺陷,在实际生产中获得了质量完好的铸件,验证了该工艺参数.     

铸造用型砂热物性参数研究及校正

型砂的热物性参数对铸造凝固过程数值模拟结果有很大影响,得到准确的型砂热物性参数对提升铸造数值模拟的准确性意义重大.本文通过现场试验测得了实际铸造型砂的降温曲线,在仿真模拟软件中对型砂热物性参数进行反算优化,并与现场实测的降温曲线匹配拟合,最终确定出与现场匹配的型砂热物性参数用于今后的数值模拟计算中,提升数值模拟准确性,...     

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.     

电化学噪声数据处理方法概述

综述了常见的电化学噪声数据处理方法,介绍了直流趋势剔除、统计分析、快速傅立叶变换(FFT)法计算功率谱密度(PSD)以及小波变换处理电化学噪声信号的基本过程,并阐释了各种数学处理及所得参数的物理意义。