镁合金细径薄壁管材加工组织与性能研究

对AZ31管材进行了不同变形量的冷轧试验,冷轧过程中,由于孪生与滑移的相互协调,可以提高镁合金的塑性变形能力,控制变形量ε在11%~15%左右,可以得到最佳的表面质量及管材性能。研究发现,400℃,保温5~120 min的热处理工艺能有效消除加工过程中产生的内应力,同时起到细化晶粒、均匀组织的作用。     

轴向取向组织BFe10-1-1管材冷轧加工过程中组织、织构与力学性能的变化

采用热冷组合铸型(HCCM)水平连铸技术制备具有轴向取向组织的BFe10-1-1管材,对管材进行冷轧加工,研究管材的组织、织构与性能的变化。结果表明:HCCM水平连铸管材不需铣面便可直接冷轧加工;无中间退火的累积冷轧变形量可达80%以上;冷轧管表面质量好,轧制过程中无裂纹、裂口和飞边等缺陷;随着变形量的增加,取向组织晶粒内一次枝晶主干间距逐渐减小,由铸态的100~200μm减小到变形量60%时的10~20μm;当冷变形量为60%时,组织中可观察到剪切带,当冷变形量为80%时,组织呈波浪状,枝晶、晶界很难辨认;冷轧过程中管材由铸造织构(主要取向{012}<61>)、经过渡型织构{012}<100>(变形量为20%)和{057}<3■2>(变形量为40%),转变为变形量为60%时的Cube织构,当变形量为80%时转变为G织构;随着变形量的增加,冷轧管的抗拉强度和硬度分别由铸态的234 MPa和70HV增加至变形量80%时的372 MPa和152HV,伸长率由铸态的46.5%降低至80%变形量时的13%。     

Ti-0.3Mo-0.8Ni合金管材冷轧开裂原因研究

研究了润滑剂、冷轧道次加工率和冷轧送进量对Ti-0.3Mo-0.8Ni合金管材开裂比率的影响。结果表明，冷轧时不同的润滑剂对应着不同的金属变形温度，使用使金属变形温度保持在150～200℃之间的B润滑剂，可使Ti-0.3Mo-0.8Ni合金管材开裂比率比较低，为5％左右；而两辊冷轧道次加工率为40％，多辊冷轧道次加工率为30％和25％。冷轧送进量选为中等大小，可有效地控制Ti-0.3Mo-0.8Ni合金管材的开裂比率在较低的范围内波动，从而提高了Ti-0.3Mo-0.8Ni合金管材冷轧成品率。     

冷轧TA18管材变形过程中微观组织及织构

采用SEM、TEM、XRD及EBSD技术,研究TA18合金管材冷轧过程中微观组织及织构的演变。结果表明,TA18合金管材冷轧组织为典型的纤维状组织,滑移变形为主要的变形机制。其中,轧制初始阶段,TA18变形主要以{10-10}棱柱滑移为主;随着变形量的增大,{0001}基面滑移代替棱柱滑移,成为管材中主要变形方式,同时棱锥滑移逐渐开动;当变形量进一步增大时,棱锥滑移代替基面滑移,成为管材中主要的变形方式,织构主要以{10-12}、{10-13}、{10-14}、{11-23}、{11-24}棱锥织构为主。     

皮尔格冷轧无缝钢管成形工艺参数及力学研究

皮尔格冷轧无缝钢管工艺参数基本依靠经验选取,其选择不当会导致管材产生缺陷。基于此,本文选取304不锈钢冷轧重要工艺参数——送进量、回转角度和Q(变形压下段和精整段长度的比例)值,通过全流程数值仿真分析了成形过程中管材的力学及成品尺寸的变化规律。结果表明,皮尔格冷轧过程中轧制力、管材等效应力、残余应力以及外径回弹量均随着送进量和回转角度的增大而增大,随着Q值的减小而增大。     

Zr-Sn-Nb-Fe合金管材冷轧变形过程中织构演变

文章通过电子背散射衍射技术（EBSD）对Zr-Sn-Nb-Fe合金管材轧制变形锥体不同变形位置的微观晶粒取向进行分析,研究了Zr-Sn-Nb-Fe合金管材冷轧变形过程中织构演变。研究表明:Zr-Sn-Nb-Fe合金管材冷轧变形相对减壁量与相对减径量的比值（Q值）约为1.20时,主要形成<0001>//周向（TD）的晶粒取向,<0001>//径向（RD）的织构含量较少;随着冷轧变形量的增加,<11-20>//轧向（AD）的织构含量急剧减少,<10-10>//轧向（AD）的织构明显增强,<11-20>//轧向（AD）的晶粒逐渐转向<10-10>//轧向（AD）。     

多道次轧制不同变形量对铜镍合金管材组织和性能的影响

采用电子背散射衍射（EBSD）技术对冷轧后铜镍合金管材的组织进行分析。通过对第二道次冷轧不同变形量（3.19%、9.57%、19.37%、23.97%、31.78%）的C71500铜镍合金在管材轧制后的显微硬度、抗拉伸性能、微观组织、织构及其含量变化的研究,揭示该合金织构的变化规律。通过对铜镍合金管材晶界、织构的变化及晶粒尺寸进行分析,揭示了变形量与变形储存能的量化关系,这种关系可以通过小角度晶界的比例更直观地体现出来。随着加工率的增加,铜镍合金的屈服强度、抗拉伸强度和维氏显微硬度均呈现上升的趋势,而合金的塑性则呈现下降的趋势。研究结果为合理选择变形量以及形成特殊晶界的热力学提供依据,同时为后续铜镍合金管材的变形加工提供理论依据。     

冷轧变形量对N06600合金管材组织及性能的影响

对N06600合金管材进行了40%、50%、55%、60%、65%变形量的冷轧,再进行了1000、1050℃退火,研究了冷轧变形量对管材组织与性能的影响。结果表明:经1000℃/3 min退火,随着变形量的增加,显微组织发生再结晶,强度逐渐下降,伸长率上升;1050℃/3 min退火后,各变形量显微组织均发生完全再结晶,且随着变形量的增加晶粒度尺寸变小,力学性能稳定。     

基于DOE的锆合金包壳管冷轧质量分析及改善

为了提高锆合金包壳管的冷轧质量,通过统计过程控制技术和工序能力分析研究了锆合金包壳管冷轧后的壁厚偏差问题,并基于试验设计(design of experiment, DOE)技术对皮格尔冷轧工艺进行了优化。包壳管冷轧质量分析和工艺优化试验的结果表明,轧制前管材的壁厚偏差和送进量对轧制后的管材壁厚偏差有显著影响;当轧制前管材壁厚偏差<0.3 mm、壁厚变形量为65%、送进量为1.0 mm/次时,轧制后的管材壁厚偏差最小;通过轧制工艺优化后,反映壁厚偏差离散性的极差平均值由0.036减小到0.018,极差波动也明显减小,轧制质量显著提高;当轧制管材壁厚变形量一定时,对轧制前壁厚偏差较大的管材,采用小送进量轧制,可减小轧制后管材的壁厚偏差,达到提高锆合金包壳管材质量的目的。     

异型钢管生产知识(二)

<正> 2 用冷轧冷拔法生产异型钢管用冷轧冷拔法除可以生产精密、薄壁和高强度钢管外,还可以生产黑色、有色金属及合金异型管材。 2.1 冷轧冷拔法的特点尽管冷轧、冷拔法的生产工艺差别不大,但各有特点。一般地说,冷轧具有道次变形量大、轧制时钢管受力状态好的优点,因而用冷轧法可以生产D/S比大于100的薄壁钢管,并且轧出的管材尺寸精度高,内外表表质量好,但缺点是设备结构复杂,工具制造难度大,因工艺限制产品不能多样     

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。