车用铝材分流模挤压过程温度场分析

为了对汽车用铝材分流模挤压过程的温度场分布进行分析,根据刚塑性有限元基本原理,利用数值模拟技术对其进行评估.分析了挤压速度及摩擦因子对坯料截面不同方向(平行及垂直挤压方向)的温度场分布的影响,选取特征点对焊合区域的温度场分布进行研究.对数值模拟结果进行分析可知,当坯料初始温度为450℃,摩擦因子为0.3时,挤压速度由1增至3mm·s-1时,温度最大值与最小值的差值在X方向上由7℃增至8℃、在Y方向上由9℃增加到10℃;通过对温度场的分析发现:具有良好散热条件的挤压筒壁附近的特征点温度出现一定程度的下降,而一些位于内部的特征点热损失很小,而且与坯料间具有不同程度的热交换,因此温度下降幅度小,在某些点上甚至出现了反常升高.     

9Cr马氏体耐热钢膨胀-温度曲线上的斜率变化研究

9Cr马氏体耐热钢在发生α→γ相变前的升温过程中其膨胀-温度曲线的斜率发生了偏折,偏折点处的温度为660 ℃左右.采用相同的升温速率将该钢样品升温至600、660和750℃三个温度,保温15 min后水淬,利用金相显微镜和扫描电镜分析各样品中组织的差异.研究结果表明,9Cr钢加热至660 ℃和750℃的样品中析出相的数量较600℃明显增加,因此钢中碳氮化物在偏折点温度处的大量析出是膨胀曲线斜率发生明显改变的原因.     

固溶温度对特超级双相不锈钢S33207组织及成分分布的影响

通过对特超级双相不锈钢S33207进行不同温度的固溶处理,采用SEM对S33207进行组织观察及奥氏体与铁素体两相中成分分布的分析,以及各自点蚀抗力当量(PREN)值的测算。结果表明:特超级双相不锈钢S33207在1100℃固溶处理时其σ相完全溶解,此时两相比例较为理想,接近1∶1。当温度为1130℃时,两相各自PREN值达到理想水平,此时材料具有较佳的耐点腐蚀性能。建议工业生产中选择1100~1130℃温度范围对此钢进行固溶处理。     

单双面焊接结构的温度场

针对T型板单、双面两种焊接结构的焊接温度场分布的异同问题,建立了两种焊接结构的有限元模型,利用焊接热过程分析理论,通过SYSWELD分析比较两者的温度场云图和焊趾线上温度热循环曲线。结果表明,焊接过程中双面焊熔池的最高温度比单面焊熔池的最高温度高约150℃。单面焊焊趾线上选取点的最高温度达到1 460℃~1 500℃;对于双面焊,由于第一道焊缝焊接时对第二道焊缝的预热作用,使得在第二道焊缝未焊接时E2~H2点的最高温度就达到约550℃,且选取点的最高温度为1 700℃~1 750℃。此研究结果可指导实际生产中焊接结构的选择。     

焊接热循环峰值温度对10CrMo910钢硬度的影响

利用自行设计的焊接热循环测试系统,通过分别实时测试两块试板的三个不同位置点在不同焊接参数下的温度信号,研究焊接热循环峰值温度对10CrMo910耐热钢的硬度变化的影响规律.结果表明,焊接热循环峰值温度对10CrMo910耐热钢硬度值影响较大,当峰值温度小于1 150℃时,随着峰值温度的增高,硬度值增大;当峰值温度大于1 150 ℃时,随着峰值温度的增高,硬度值反而有所减小.     

淬火温度对Co40.5Ni34Al25.5合金相变和磁性的影响

用金相显微分析、DSC和VSM方法研究了Co40.5Ni34Al25.5合金马氏体相变和Curie点随淬火温度的变化,通过三点弯曲试验研究其形状记忆效果.结果发现该合金马氏体相变温度和Curie点与淬火温度成正比关系.马氏体相变的4种温度,即Ms,Mf,As和Af基本平行变化,淬火温度每升高10℃,马氏体相变温度和Curie点升高8℃～9℃.β相中Al的含量随淬火温度升高而降低,因而使马氏体相变温度和Curie点升高.1320℃淬火的Co40.5Ni34Al25.5合金的弯曲强度约为450 MPa,弯曲试验表明Co40.5Ni34Al25.5合金有双向形状记忆特性.     

重复热处理次数对CD3MN双相不锈钢性能的影响

多个标准中规定材料的重复热处理数不得超过两次。对CD3MN双相不锈钢在1080℃及1120℃分别进行了4次重复固溶处理试验,检测试块的力学性能、金相组织、耐点腐蚀性能。结果表明:CD3MN双相不锈钢在同一温度下经过4次固溶处理后,力学性能变化不大,均满足标准要求;耐点腐蚀性能变化不大;固溶处理温度从1080℃升高到1120℃,铁素体含量从30%提高到45%,力学性能和耐点蚀性能略有提高。     

聚脲施工质量保证

温度检测：喷涂聚脲施工时要进行温度控制。首先检测原料桶的温度，应保持在19℃以上。先不连接喷枪，测量加热软管输出末端，这可以通过用泵抽出一些原料放在两个分开的，如纸杯之类的容器内用温度计测量，温度应该在60—70℃之间，并且两个组分温度应该一致。     

Mo对Ti(C,N)基金属陶瓷包覆相结构与性能的影响

研究了不同Mo含量对高镍Ti(C,N)基金属陶瓷包覆相的组织结构与性能的影响。在Ti(C,N)基金属陶瓷中添加3%～15%不同含量的Mo,分别于1420℃、1430℃、1440℃温度下,进行真空烧结制备试样,通过扫描电镜观察组织结构与断口形貌,用三点弯曲法测试抗弯强度,用洛氏硬度计测得试样硬度。结果表明:当Mo含量为9%时材料的组织均匀,形成的包覆相厚度适中;在1430℃真空烧结时,比在1420℃及1440℃烧结时材料的力学性能好;当真空烧结温度为1430℃、Mo含量为9%时,试样的综合性能最好。     

TA15钛合金相变温度与锻造温度符合性确认

针对TA15钛合金相变温度与两相区（α+β）锻造加热温度符合性问题,对TA15钛合金棒料及锻件进行了多批次对比性的工艺验证,结果表明：TA15棒料相变点测定有效区间在992～996℃,根据相变点选取原则,将两相区（α+β）锻造加热温度（955±5）℃进行固化并进行试验,锻件形状、尺寸、力学性能、高低倍组织、超声检测等全部达到了规定的技术要求。     

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.