热等静压Ti-6Al-4V钛合金热变形微观组织演变

采用Gleeble-1500热模拟试验机对热等静压态Ti-6Al-4V钛合金在温度950～1050℃、应变速率0.01～1 s-1条件下进行了热模拟压缩实验,研究了变形温度、应变速率对其显微组织的影响规律。结果表明:热等静压态Ti-6Al-4V钛合金在950℃以上变形后淬火组织以粗大的声晶粒与针状及板条马氏体组成,具有典型的β相区变形组织特征。β转变组织形成交错的网篮结构并具有特定的取向关系。变形过程中,发生了动态再结晶,并伴随着动态回复现象。在950℃/0.01 s-1条件下,以动态再结晶占据主导,得到均匀等轴β转变组织。随应变速率增大,以动态回复为主,β晶粒沿金属流动方向拉长,β转变组织得到细化。随温度升高,β晶粒变粗大,并仍然存在拉长变形带。同时,β转变组织有一定程度的粗化。     

Ti-6Al-4V热变形行为及利用多项耦合进行本构关系修正

采用热模拟试验机对钛合金Ti-6Al-4V进行高温压缩试验,研究其在850~1100 ℃温度下,0.001~0.1 s?1应变速率的流动应力行为。结果表明:钛合金Ti-6Al-4V具有应变速率、温度敏感性;随着温度的升高和应变速率的减小,流动应力逐渐降低,加工硬化速率与动态软化速率达到动态平衡。通过分析工艺参数对材料参数的影响,发现合金的材料参数(N、A、Q)随变形条件的变化而变化。在传统双曲正弦函数型Arrhenius方程的基础上提出一种考虑应变速率、温度和应变耦合修正的双曲正弦本构方程,并用相关系数R和平均相对误差(AARE)来评价所建立的本构模型的准确性,定量分析结果表明,修正的本构方程能够较准确地预测钛合金Ti-6Al-4V的流动应力。     

置氢Ti-6Al-4V钛合金的热压缩变形行为研究

通过热模拟压缩实验,研究了氢对Ti-6Al-4V钛合金热变形行为的影响。结果表明,置氢可以显著降低Ti-6Al-4V钛合金高温压缩时的流动应力,提高Ti-6Al-4V钛合金的热加工变形速率一个数量级以上,并且明显降低了Ti-6Al-4V钛合金的变形温度。在变形温度760℃~800℃范围内,置氢量为0.4wt%的Ti-6Al-4V钛合金的流动应力最小;在变形温度840℃~920℃范围内,置氢量0.2wt%的Ti-6Al-4V钛合金的流动应力最小。同时,置氢前后Ti-6Al-4V钛合金的变形激活能计算结果表明,置氢量为0.4wt%的Ti-6Al-4V钛合金在α+β两相区的变形激活能为208.3kJ/mol,与未置氢Ti-6Al-4V钛合金相比降低了316kJ/mol。     

铸态27SiMn钢热成形本构方程的建立

利用热模拟试验机对铸态27SiMn钢在应变速率为0.01¹0 s-1,变形温度为1 00010 s-1,变形温度为1 000¹ 150℃条件下的热成形流变应力行为进行了等温恒应变速率压缩试验。通过真应力-真应变曲线,分析了应变速率和变形温度对流变应力的影响规律。通过线性回归分析计算出铸态27SiMn钢的应变硬化指数n,变形激活能Q,获得了铸态27SiMn钢的热成形流变应力本构方程。     

石油管用Ti-6Al-4V-0.1Ru钛合金高温流变行为及预测模型研究

通过使用Gleeble-3500热模拟试验机进行等温单轴压缩试验,研究了Ti-6Al-4V-0.1Ru钛合金在温度800到1100℃,应变速率0.01到10 s-1条件下的高温流变行为。结果表明,Ti-6Al-4V-0.1Ru钛合金的峰值应力随着变形温度的降低以及变形速率的增大而增大,软化机制在950℃以下为动态回复,在950℃以上为动态再结晶。通过使用线性回归的方法建立了Ti-6Al-4V-0.1Ru钛合金的Arrhenius本构模型,计算得到该合金的热激活能为720.477 kJ/mol,应变速率敏感指数为4.809。通过引入应变对材料常数α、n、A和Q的影响,建立了考虑应变的流变应力预测模型,通过对试验值和预测值的比对,相关系数达到96.9%,说明该模型具有较好的预测精度。     

Ti-575钛合金热变形行为及微观组织演变

本文以Ti-575钛合金为研究对象，分别对魏氏组织和双态组织Ti-575钛合金进行热模拟压缩实验，分析不同热变形条件下的真应力-应变曲线，构建了其在α+β相区的热变形本构方程，并分别探究了变形温度和应变速率对微观组织的影响。结果表明，流变应力值随着变形温度的升高而降低，随着应变速率的升高而升高；当应变速率为0.1 s-1及以上时，随着变形温度的升高流变曲线出现了不连续屈服现象。根据两种组织Ti-575钛合金流变曲线的峰值应力，分别计算出其在α+β相区的变形激活能，构建Arrhenius型热变形本构方程。在不同的热变形条件下，随着变形温度的升高，魏氏组织Ti-575钛合金动态再结晶的程度越来越大，而双态组织Ti-575钛合金等轴αp相体积分数和尺寸逐渐降低；随着应变速率的降低，魏氏组织Ti-575钛合金动态再结晶的程度逐渐增大，而双态组织Ti-575钛合金等轴αp相体积分数先减少后增加；双态组织Ti-575钛合金在830℃或1 s-1应变速率下热压缩时，显微组织中残留少量的粗片层α相没有发生相变，βt基体中会有硅化物析出。     

Ti-6Al-2Zr-1Mo-1V合金β锻动态再结晶(英文)

通过热压缩实验研究Ti-6Al-2Zr-1Mo-1V钛合金在变形温度为1000～1100°C,应变速率为10-3～1.0s-1的条件下的动态再结晶行为。结果表明:在变形温度高于1050°C、应变速率低于0.01s-1时,合金的动态再结晶机制以不连续动态再结晶为主;在变形温度低于1050°C、应变速率高于0.01s-1时,合金的动态再结晶机制以连续动态再结晶为主,同时存在少量的不连续动态再结晶。此外,降低应变速率和升高变形温度均能促进动态再结晶进程并使β变形晶粒细化。     

电子束冷床熔铸TC4合金的多道次热变形行为

利用Gleeble-3500热模拟试验机,对电子束冷床熔铸制备的Ti-6Al-4V(TC4)钛合金在变形温度为850～1000℃、应变速率为0.01～1 s~(-1)和总变形量为50%条件下进行多道次热压缩模拟实验,研究铸态合金的多道次压缩热变形行为及微观组织演变规律。结果表明:合金的流变应力随变形温度的升高和应变速率的降低均呈降低趋势;不同变形温度下随应变速率的降低,合金的软化率逐渐升高,且变形温度越高,各道次间软化率趋于稳定;在变形温度950～1000℃、应变速率0.01～0.1 s~(-1)范围内合金的组织均得到不同程度的细化和均匀化,并发生动态回复与再结晶现象,此变形参数下合金的热加工性能稳定,可为电子束冷床熔铸TC4合金的铸态直接多道次热轧成形提供指导。     

应用智能方法建立Ti-6Al-2Zr-1Mo-1V合金的本构关系(英文)

利用Thermecmastor-Z热模拟机进行Ti-6Al-2Zr-1Mo-1V钛合金在不同工艺参数(变形温度800,850,900,1000,1050°C,应变速率0.01,0.1,1,10s-1)条件下的热模拟压缩试验,研究变形温度和应变速率对Ti-6Al-2Zr-1Mo-1V钛合金流变应力的影响。以试验数据为基础,应用BP神经网络算法原理,建立该合金的高温流动应力与变形温度、应变和应变速率对应关系的高温本构关系预测模型。结果表明,运用神经网络方法建立的Ti-6Al-2Zr-1Mo-1V钛合金本构关系模型具有较高的预测精度,与试验结果吻合良好。此外,运用Visual Basic可视化编程语言设计并开发了具有神经网络功能的用户界面。     

新型Ti-V-Mo系钛合金热变形行为及热加工图研究

通过高温热压缩试验研究Ti-555钛合金热变形过程中变形温度、应变速率对流变应力的影响,采用Arrhenius双曲正弦函数模型推导出Ti-555本构方程,并依据动态材料模型建立了ε=0.6时的热加工图。结果表明,Ti-555钛合金流变应力对应变速率和变形温度较为敏感,热变形时随变形温度的升高或应变速率的降低,流变应力下降。根据热加工图确定了2个热加工安全区参数为:(1)变形温度为850～950℃、应变速率为0.6～10 s-1;(2)变形温度为950～1150℃、应变速率为0.36～0.9 s-1。     

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。