高度稳定化β型Ti40阻燃钛合金的动态再结晶行为

采用热压缩试验方法,对高度稳定化的β型Ti40阻燃钛合金的动态再结晶行为进行了研究.结果表明,Ti40合金的动态再结晶形核机制为亚晶形核、晶界弓出形核和位错塞积形核等多种机制;Ti40合金高温塑性变形后,空冷及850 ℃退火的再结晶晶粒呈现混晶现象;1000 ℃退火,再结晶晶粒充分长大,是完全再结晶的结构特征.     

GH4169合金非均匀组织在加热过程中的演化机理

通过对第二相状态、晶界取向差及晶粒尺寸演化的分析,研究了GH4169合金不均匀组织在加热过程中的演化机理.结果表明,GH4169合金中d相的体积分数在低温下随温度的升高和时间的延长而增加;在高温时随温度的升高而降低,随时间的延长先增加后降低至恒定值.第二相的钉扎作用表现为:晶内析出的d相和g"相阻碍位错的运动,沿晶界析出的d相阻碍再结晶晶粒的形核和长大,碳化物阻碍晶粒长大.小角度晶界的体积分数随加热温度的升高和时间的延长而降低;高温下,退火孪晶的生长使得小角度晶界含量增加.GH4169合金的组织演化机理主要包括:亚晶长大、再结晶晶粒的长大和退火孪晶的长大.新的再结晶晶粒主要通过亚晶长大过程获得,亚晶长大过程主要通过小角度晶界的转动和位错的迁移完成.晶粒长大过程受到抑制时,合金通过退火孪晶的形核及长大耗散其吸收的热量.     

多道次热轧模拟过程中Al-Zn-Mg-Cu-Zr合金的再结晶特征（英文）

采用Gleeble-1500D热模拟试验机根据设计的轧制工艺对7055合金进行多道次热压缩试验,模拟其企业热轧过程,采用电子背散射衍射和透射电镜研究了再结晶特征。在不同变形条件下,表现出不同的再结晶机制,主要动态再结晶机制有连续动态再结晶和几何动态再结晶。前者的形核机制主要为原始晶界弓出形核和亚晶合并形核;后者归因于严重的不均匀变形。在道次间的间隙期间,静态再结晶发生。另外,尺寸大于1μm的第二相也促进再结晶。     

多道次热轧模拟过程中Al-Zn-Mg-Cu-Zr合金的再结晶特征

采用Gleeble-1500D热模拟实验机根据设计的轧制工艺对7055合金进行多道次热压缩试验,模拟其企业热轧过程,采用电子背散射衍射和透射电镜研究了再结晶特征。在不同变形条件下,表现出不同的再结晶机制,主要动态再结晶机制有连续动态再结晶和几何动态再结晶。前者的形核机制主要为,原始晶界弓出形核和亚晶合并形核;后者归因于严重的不均匀变形。在道次间的间隙期间,静态再结晶发生。另外,尺寸大于1 μm的第二相也促进再结晶。     

GH625镍基高温合金动态再结晶模型研究

在Gleeble热模拟机上对GH625合金进行了等温热压缩试验,获得了不同变形条件下该合金的真应力-真应变曲线,并对热压缩试样的微观组织进行了分析。通过对实验数据的计算,获得了GH625合金发生动态再结晶所需的临界变形量与变形温度和应变速率的函数关系;建立了合金动态再结晶的运动学方程,用该方程预测的动态再结晶体积分数与实测值吻合较好,误差的平均值为13%;构建了GH625合金的晶粒长大模型,用该模型预测的晶粒尺寸值与实测值之间的误差平均值为7.52%。GH625合金动态再结晶的形核方式主要为晶界弓出形核和亚晶合并长大形核。     

含钪Al-Cu-Li-Zr合金高温压缩变形组织的研究

含钪Al-Cu-Li-Zr合金在高温压缩实验中,会发生动态回复;在一定条件下会发生动态再结晶;并且温度越高、应变速率越低,该合金越易发生动态再结晶。再结晶的形核机制是亚晶合并和亚晶长大。     

含钪Al-Cu-Li-Zr合金的热变形行为及组织演化

在实验温度范围为380～500℃、应变速率范围为0.001～10.0 s-1,采用Gleeble-1500热模拟机,对含钪Al-Cu-Li-Zr合金的高温热变形行为进行研究,采用金相显微镜和透射电镜观察合金在压缩变形时的组织变化.结果表明:变形温度和应变速率的变化强烈影响合金的流变应力,合金的流变应力随变形速率的增加而增大,随变形温度的升高而降低,可用包含Arrhenius项的Zener-Hollomon参数描述合金在高温压缩变形时的流变应力行为.当合金在温度低于440℃变形时,合金中主要形成亚晶组织,仅发生动态回复;在ln Z≤36.7变形时,合金发生部分动态再结晶,其动态再结晶形核机制主要为晶界弓出和亚晶合并形核.     

Ti-5553合金高温变形时动态再结晶行为

采用热压缩试验方法,对Ti-5553钛合金的动态再结晶行为进行研究。结果表明,在温度800～860℃、应变速率0.01～10s-1的范围内,Ti-5553合金在高温、低应变速率变形时,晶界弓出形核是其主要的动态再结晶形核机制;在低温、高应变速率、大变形量变形时,位错塞积形核是主要的动态再结晶形核机制。在非均匀变形的条件下材料产生绝热剪切现象,其形核主要以亚晶吞并长大形核机制进行。     

Incoloy 028合金不连续动态再结晶中链状组织形成机理研究

利用热力模拟、EBSD和TEM等方法,研究了Incoloy 028合金在1000~1150℃和0.001~1 s-1应变速率条件下的不连续动态再结晶(DDRX)行为,分析了DDRX过程中链状组织的形成机理。结果表明,随着变形温度降低或应变速率升高,体系发生传统型向链状型DDRX转变,其中传统型DDRX过程由晶粒长大主导,主要在三叉晶界处形核;链状型DDRX发生多层形核长大,其第一层形核机制为孪晶界辅助的原始晶界弓出形核,后续层为亚晶扭转与三叉晶界形核;孪晶界在辅助形核后消失以提高界面移动性,晶粒长大时再次形成以降低体系能量。     

TA15钛合金β热变形中的动态再结晶形核

利用Thermecmaster-Z型热模拟试验机在β相区对TA15钛合金进行了热压缩试验,采用金相显微镜及EBSD取向差分析技术,研究了TA15钛合金β热变形中动态再结晶形核.结果表明,随内、外界条件的不同,TA15钛合金存在两类典型的动态再结晶形核地点,即晶界周围及变形带.相应地,随应变速率增大,存在两种动态再结晶形核机制,在较低应变速率下,晶界弓弯形核是动态再结晶的主要形核机制,晶界、三岔界是主要形核地点;在高应变速率下,动态再结晶不仅可以在晶界、三岔界附近形核,还可以借助变形带形核.此时的动态再结晶形核为晶界弓弯与亚晶旋转机制共同作用.     

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).     

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.     

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.     

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。