泡沫铝芯填充合金的制造工艺技术研究

介绍了熔体发泡法制备泡沫铝的工艺方法,分析了增粘剂加入量、TiH2加入量和保温发泡时间对泡沫孔结构的影响.得出了制备具有均匀孔结构泡沫铝的工艺参数.     

用可溶石膏型预制块制备低密度开孔泡沫铝

研究了用可溶石膏型预制块制备低密度开孔泡沫铝的工艺及其压缩性能。采用聚氨酯网状海绵为母体材料制备可溶石膏型预制块,并分析了MgSO4和铝矾土的加入量对石膏型预制块可溶性和抗压强度的影响。采用预制块加压渗流的方法制备低密度开孔泡沫铝,研究了渗流工艺参数的控制方法,并对制备的泡沫铝进行了压缩试验,研究了其压缩力学行为,结果表明,所制备的低密度开孔泡沫铝压缩过程表现出3个明显的阶段,即弹性段、塑性坍塌段和密实段,而且应力-应变曲线在塑性坍塌段表现出明显的波动特征。     

开孔泡沫铝导电性的研究

本文采用加压渗流方法制备开孔结构的泡沫铝,并通过调整工艺参数改变泡沫铝的孔径和相对密度.采用“直流四端电极”法测量了不同参数泡沫铝的电阻,研究开孔泡沫铝的导电性随其相对密度和孔径的变化规律.实验结果表明：随着相对密度的提高,开孔泡沫铝的电导率增大,且电导率随相对密度的改变呈指数关系变化;当相对密度参数基本相同时,随着泡沫铝孔径的减小,由于在制备过程中产生的结构缺陷增多,其电导性下降.     

搅拌摩擦加工制备的闭孔泡沫铝的组织及性能

为避免传统方法制备大面积闭孔泡沫铝工艺过程的局限性，采用搅拌摩擦加工技术结合加热工艺制备闭孔泡沫铝复合材料。采用有限元软件对搅拌摩擦加工制备预制体过程的温度场进行了模拟仿真，研究了制备工艺参数对泡沫铝预制体质量的影响规律。利用光学金相显微镜对不同加工工艺参数及发泡时间条件下制备的泡沫铝孔隙率和形貌进行了分析。同时，对闭孔泡沫铝进行了准静态压缩性能试验，研究了不同孔隙率下泡沫铝的压缩性能。结果表明，与搅拌针移动速度相比，不同旋转速度对闭孔泡沫铝预制体的形貌影响更大。当搅拌针移动速度50 mm·min^-1、旋转速度2000 r·min^-1时，焊核区金属和夹层中的混合粉末发生了充分的塑性变形，粉末圈分布连续且均匀。模拟结果表明：搅拌摩擦加工时最高温度区域出现在搅拌针附近，呈“碗状”分布，此时温度达到最大值491℃,焊核区金属和夹层中的混合粉末发生充分塑性变形和流动，模拟结果与试验结果一致。经过680℃发泡后，泡沫铝最大孔隙率为69.3%,平均泡孔直径为Φ130μm,屈服应力为3.2 MPa,平台应力值为2.9 MPa。     

石膏型渗流法制备低密度开孔泡沫铝工艺研究

研究用可溶石膏型预制块制备低密度开孔泡沫铝的工艺。采用不同孔径的聚氨酯网状海绵为母体材料,用石膏粉、硫酸镁、铝矾土和水为配方制备石膏型预制块,并分析了硫酸镁和铝矾土的加入量对石膏型预制块可溶性和抗压强度的影响。通过加压渗流的方法制备出低密度的开孔泡沫铝,并对渗流参数的选择做出总结。结果表明：利用石膏型渗流法制得的开孔泡沫铝相对密度在0．1以下。     

泡沫铝合金显微组织和压缩力学性能的研究

采用Si、Mg及Cu元素进行合金化处理，制备了几种不同力学性能的开孔泡沫铝，并通过准静态压缩实验，研究合金化对泡沫铝压缩力学行为与吸能特征的影响。实验结果表明：采用Si、Mg及Cu元素合金化处理显著改变了泡沫铝的应力-应变行为与吸能特征，使泡沫铝的屈服强度提高，吸能性大幅度上升。另外，还研究了渗流法制备工艺对泡沫铝微观组织和性能的影响，结果显示由于渗流法制备过程特殊的凝固条件，使得泡沫铝的微观组织比相同成分的铸造铝合金的组织明显粗大。     

铝熔体泡沫化过程中孔结构的控制

在大量试验研究的基础上，探索了铝熔体泡沫过程中控制泡沫铝孔径、孔隙率等结构参数的工艺方法，研究了发泡剂加入量，搅拌及保温时间等对孔结构的影响。     

熔体发泡法批量制备泡沫铝板材关键技术的研究

采用熔体发泡工艺,实现了A356合金500 mm×1000 mm×X不同厚度泡沫铝板材的批量制备.对该工艺方法的増粘、发泡剂加入,泡沫均匀性控制等关键技术进行了系统研究.获得了工厂条件下A356合金泡沫铝块体和板材的优化制备工艺参数.对欠、过发泡,中心大孔,裂纹等缺陷的产生原因进行分析,提出了解决方法.     

粉末冶金法浸入式发泡制作泡沫铝的试验研究

研究了浸入法制备泡沫铝的发泡新工艺以及工艺参数对发泡效果的影响，得出以工业纯铝粉和而H2粉为原料，制备气泡均匀、孔隙可控的泡沫铝的工艺参数为：浸入温度为680～760℃，浸入时间为10～30s，保温发泡时间为10～60s。研究结果表明，粉末冶金法浸入式发泡制备泡沫铝的效果好、结构均匀、TiH2利用率高，是一种有较好开发前景的新制备方法。     

添加造孔剂法制备开孔泡沫铝及其性能研究

以球形尿素颗粒为造孔剂,采用传统的粉末冶金工艺制备开孔泡沫铝并研究了其性能.结果表明,添加造孔剂法制备的泡沫铝可以任意控制孔隙率及孔径的大小,且孔结构良好,保持了造孔剂的形状;高的烧结温度使泡沫铝的压缩强度提高,但过高的温度将导致孔壁熔化.本试验制成的泡沫铝其压缩曲线和泡沫金属典型压缩曲线相似,且抗压强度和经典理论计算结果一致.     

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.     

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.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.     

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.