无润滑挤压铝合金管材时铸锭长度的确定

根据对穿孔针所受拉力的计算,得出如何确定无润滑挤压铝合金管材时合理的铸锭长度,以减少挤压时的断针现象.     

用固定式和随动式穿孔针正向挤压铝管时冷却穿孔针的影响(Ⅱ)

3.挤压力和摩擦力挤压时测获的轴向力分布与所采用冷却的或未冷却的穿孔针的挤压法之间的关系如图11所示.令人注目的是冷却的穿孔针对挤压开始阶段出现的最大力竟无影响.这对于挤压筒、铸锭与穿孔针之间的摩擦力以及作用于模具的变形力都是如此.用穿孔针挤压铝管时所需总的挤压力与穿孔针的冷却程度     

无润滑热挤压铝合金厚壁管材工艺研究总结

一、前言国民经济的不断发展,对热挤压铝合金厚壁管材的内表面质量提出了新的严格的要求.本文扼要地分析了热挤压铝合金厚壁管材的生产方法及其特点,在总结生产实践经验的基础上提出了能显著改善厚壁管材内表面质量的空心铸锭无润滑热挤压铝合金厚壁管材新工艺.并详细地阐述了这种工艺的参数、特点、优越性,以及工艺操作中可能出     

第七讲 空心铝型材挤压模具优化设计（1）

第七讲空心铝型材挤压模具优化设计（１）沈阳新光模具制造公司赵云路西南铝加工厂刘静安１无缝圆管挤压模具设计这类模具主要是指借助于穿孔针用空心铸锭或实心铸锭穿孔来挤压管材用的模子和针尖。由于穿孔针必须置于挤压机的中心线上，所以，只能进行单孔挤压，因而模孔...     

6061铝合金异形管材分流挤压模拟研究与优化

基于刚粘塑性有限元理论,采用DEFORM-3D有限元软件,对6061铝合金异形管材分流挤压工艺过程进行了数值模拟,揭示了挤压力的变化规律和坯料金属温度的分布规律.通过虚拟正交试验,获得了影响挤压力峰值的因素主次顺序为:工作带长度L＞焊合角θ＞焊合室深度h.以降低挤压力峰值为优化目标,获得了该规格6061铝合金异型管材分流挤压工艺最优水平组合为焊合室深度h=20mm,焊合角θ=35°,工作带长度L=5mm.     

挤压工艺参数对Mg-6Al合金显微组织的影响

以Mg-6Al合金为研究对象,采用小型挤压模具及电子万能试验机对其进行热挤压,研究了挤压工艺参数对Mg-6Al合金显微组织和挤压力的影响。结果表明,均匀化态Mg-6Al合金经不同条件热挤压后发生了不完全动态再结晶,部分原始组织保留下来,且再结晶晶粒多数在原始晶界和孪晶处形核。随着挤压温度升高,挤压过程中的挤压力峰值及稳态挤压力均降低。随着挤压速度增大,挤压力峰值与稳态挤压力之间的差值增大。此外,增大挤压比,挤压力峰值及稳态挤压力随之增大。     

2A12合金的无润滑管材挤压工艺实验研究

为了在国产35 MN挤压机上实现2A12合金管材的无润滑挤压,减少废品的产生,通过分析2A12合金的材料性能及国产35 MN挤压机的结构特点,对挤压机的穿孔针系统结构进行改造,并在该挤压机上进行了2A12合金的无润滑管材挤压实验.实验结果表明,在合理控制挤压速度、挤压温度、铸锭加热温度等工艺参数的条件下,可以实现2A12合金的无润滑管材挤压;挤压产品的内表面质量好,偏心度得到很大改善.     

铝合金管材反向挤压技术（2）

铝合金管材反向挤压技术（２）西北铝加工厂郭士安４管材反向挤压工艺制订原则与挤压力计算本节述及的反向挤压工艺主要指挤压系数、铸锭长度、残料厚度、模子规格范围、挤压针规格、挤压针尖规格范围、挤压温度和速度的选择。这些工艺参数除了取决于所生产的合金之外，都...     

7075铝合金管材挤压成形及对性能影响

对7075铝合金管材挤压成形进行了实验研究，测试了管材挤压成形时挤压力变化规律和变形程度对挤压后管材力学性能的影响规律，指出，7075铝合金管材挤压成形时必须严格控制坯料温度，模具预温度，润滑方式，挤压速度，挤压比等工艺参数。     

铝合金挤压管材内擦伤的分析

介绍了铝合金挤压管材内擦伤的分类、形成原因，以及挤压温度、挤压速度、工艺润滑、铸锭冶金质量、铸锭表面加工质量等对管材内擦伤的影响。     

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。