SiC_P/Al复合材料焊接方法及其填充材料研究进展

综述了碳化硅颗粒增强铝基复合材料焊接的研究进展,重点阐述了碳化硅颗粒增强铝基复合材料的熔化焊、扩散焊、搅拌摩擦焊和钎焊等焊接方法及其焊接过程中所采用的填充材料,其中熔化焊包括钨极氩弧焊、激光焊和等离子弧焊。     

先进航空材料和复杂构件的钎焊与扩散焊技术

描述了先进航空材料和复杂构件的钎焊与扩散焊技术领域的一些研究结果与进展,其中包括已经获得实际应用的钎焊扩散焊技术以及相关有价值的探索研究结果.主要内容:定向凝固高温合金、单晶合金、定向凝固Ni3Al基高温合金、钛铝金属间化合物材料、陶瓷及陶瓷基复合材料等高温结构材料的钎焊与扩散焊,高温合金钎焊技术在航空发动杌涡轮部件修复中的应用,Al-Si钎料对钛铝金属间化合物材料的表面改性研究,铝合金真空钎焊用中温钎料的研制,铝合金缝阵天线等复杂结构的精密钎焊技术.     

陶瓷基复合材料/金属焊接研究现状

由于用粒子、晶须或纤维增韧的陶瓷基复合材料具有良好的耐磨和耐腐蚀性,是目前备受重视的新型结构材料,用焊接的方法将其与金属焊接制成复合构件可推广应用.介绍了陶瓷/金属常用焊接方法的特点及连接机理,着重讨论了钎焊和扩散焊方法,并对陶瓷基复合材料/金属的焊接研究现状进行了分析.     

焊接结构与设计

20093211先进航空高温结构材料的钎焊与扩散焊技术/李晓红//焊接.-2008(11):9~18概述了在先进航空高温结构材料的钎焊与扩散焊技术领域的一些研究结果与进展,其中包括已经获得实际应用的钎焊、扩散焊技术以及相关有价值的探索性研究结果。主要内容:定向凝固高温合金、单晶合金、定向凝固Ni3Al基高温合金、ODS合金、钛合金、钛铝金属间化合物材料、钛基复合材料等高温结构材料的钎焊与扩散焊技术。图14表11参32焊接结构与设计     

焊接结构与设计

20093211先进航空高温结构材料的钎焊与扩散焊技术/李晓红//焊接.-2008(11):9~18概述了在先进航空高温结构材料的钎焊与扩散焊技术领域的一些研究结果与进展,其中包括已经获得实际应用的钎焊、扩散焊技术以及相关有价值的探索性研究结果。主要内容:定向凝固高温合金、单晶合金、定向凝固Ni3Al基高温合金、ODS合金、钛合金、钛铝金属间化合物材料、钛基复合材料等高温结构材料的钎焊与扩散焊技术。图14表11参32焊接结构与设计     

SiC颗粒增强铝基复合材料连接研究进展

论述SiC颗粒增强铝基复合材料焊接的研究现状,分析熔化焊、电阻焊、高能束焊、搅拌摩擦焊、钎焊、瞬间液相连接在焊接SiC铝基复合材料中存在的问题以及相应的解决方案。铝基复合材料连接目前仍处于试验阶段,要进行工程应用在连接方法和机理方面需要进一步的研究。     

先进航空高温结构材料的钎焊与扩散焊技术

概述了在先进航空高温结构材料的钎焊与扩散焊技术领域的一些研究结果与进展,其中包括已经获得实际应用的钎焊、扩散焊技术以及相关有价值的探索性研究结果.主要内容:定向凝固高温合金、单晶合金、定向凝固Ni3Al基高温合金、ODS合金、钛合金、钛铝金属间化合物材料、钛基复合材料等高温结构材料的钎焊与扩散焊技术.     

SiC增强铝基复合材料焊接特性及其储能焊

分析了SiC增强铝基复合材料的焊接特性。讨论了SiC增强铝基复合材料熔化焊、钎焊和固相焊的研究现状。结合试验,重点探讨了SiC增强铝基复合材料储能焊,分析了储能焊焊接接头的金相组织,其焊接接头由熔核区、熔合区及热影响区组成。由于大的冷却速率使得熔核组织显著细化,具有快速凝固组织特征,表明储能焊可实现铝基复合材料的焊接,且具有独特的优点。     

航空航天焊接专题：先进航空高温结构材料的钎焊与扩散焊技术

概述了在先进航空高温结构材料的钎焊与扩散焊技术领域的一些研究结果与进展,其中包括已经获得实际应用的钎焊、扩散焊技术以及相关有价值的探索性研究结果。主要内容：定向凝同高温合金、单晶合金、定向凝固Ni3Al基高温合金、ODS合金、钛合金、钛铝金属间化合物材料、钛基复合材料等高温结构材料的钎焊与扩散焊技术。     

亚微米级Al2O3p/6061Al铝基复合材料扩散焊接工艺

以亚微米级Al2O3p/6061 Al铝基复合材料为对象,研究了直接扩散焊与采用中间层扩散焊两种工艺焊接铝基复合材料的特点、机理,分析了中间层对接头强度的影响规律.结果表明,在铝基复合材料液、固温度区间,存在"临界温度区域",在此温度区域进行直接扩散焊接时,通过液相基体金属的浸润,使得在扩散接合面中增强相-增强相接触转化为增强相-基体-增强相的有机结合,获得高质量焊接接头;进一步研究发现,在扩散接合面上采用合适的基体中间层同样可以将增强相-增强相接触转化为增强相-基体-增强相的有机结合,同时增大"临界温度区域"范围,接头性能更加稳定,接头变形量进一步减小(＜2%).     

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.