CuNiBeZrRE合金强化工艺研究

对用于发电机转子槽楔的CuNiBeZrRE合金进行了一系列的热处理强化工艺研究.结果表明:该合金经940℃×1 h固溶+40%的冷变形+490℃×3 h时效后,其硬度为248 HB,导电率为50%IACS,抗拉强度为860 MPa,屈服强度为720 MPa,伸长率为14%,软化温度为550℃;其力学件能和物理性能均能满足服役条件苛刻的汽轮发电机组转子槽楔的要求.     

新型CuNiCrSiZr合金的热处理工艺

对新型发电机槽楔用CuNiCrSiZr合金进行了不同的固溶、冷变形、时效等工艺试验,利用光学显微镜、扫描电镜和能谱仪等手段研究了不同热处理工艺及冷变形对CuNiCrSiZr合金的组织与性能的影响。结果表明,经930℃×1 h固溶+45%冷变形+480℃×3 h时效处理后,CuNiCrSiZr合金的硬度和导电率分别可达242 HB和30%IACS,具有良好的综合使用性能,满足发电机槽楔的技术要求。     

CuNiCoCrBeZr合金强化工艺与组织性能研究

对CuNiCoCrBeZr合金进行了一系列的热处理强化工艺试验.结果表明,该合金经940℃×1.5 h固溶+30%冷变形+490℃×3 h时效处理后,其硬度为253 HB,导电率为57.76%IACS,室温下抗托强度903 MPa,屈服强度861 MPa,伸长率16.24%,其物理性能和力学性能均能满足服役条件苛刻的超(超)临界汽轮发电机转子槽楔的使用要求.     

热处理工艺对CuNiCrBeTi合金组织和性能的影响

对用于汽轮发电机转子槽楔材料Cu-Ni-Cr-Be-Ti铜合金进行了一系列的热处理强化工艺试验.试验结果表明,该合金经(950±10)℃×1.5 h固溶 25%～35%的冷变形 (520±10)℃×2 h时效处理后,其硬度为256HB,导电率为47.23%IACS,室温下抗拉强度775 MPa,屈服强度678 MPa,伸长率20%,其物理性能和力学性能均能满足服役条件苛刻的汽轮发电机转子槽楔的使用要求,对于研究开发槽楔合金材料具有重要意义.     

新型CuNiCrSiZr合金的热处理工艺及组织与性能

对新型发电机槽楔用CuNiCrSiZr合金进行了不同的固溶、冷变形、时效等工艺试验,利用光学显微镜、扫描电镜和能谱仪等手段研究了不同热处理工艺及冷变形对CuNiCrSiZr合金的组织与性能的影响。结果表明,经930 ℃×1 h固溶+45%冷变形+ 480 ℃×3 h时效处理后,CuNiCrSiZr合金的硬度和导电率分别可达242 HB和30%IACS,具有良好的综合使用性能,满足发电机槽楔的技术要求。     

槽楔用CuNiCrBeTi铜合金的热处理工艺及其组织与性能

对槽楔CuNiCrBeTi合金开展了大量系统的热处理试验,研究其强化工艺。研究表明,该CuNiCrBeTi合金经950℃×1.5 h固溶+25%的冷变形+520℃×2 h时效处理后,其硬度可达到244 HBS、导电率47.23%IACS,室温下抗拉强度R_m=775 MPa,规定塑性延伸强度R_(p0.2)=678 MPa,伸长率A_5=18%,均达到了槽楔对材料的技术指标要求。     

多级形变时效对Cu-Cr-Zr合金组织和性能的影响

采用力学性能和电导率测试及透射电镜观察等方法,研究了不同时效工艺对Cu-1.0Cr-0.2Zr合金组织和性能的影响.结果表明:合金在一级时效工艺(960℃固溶2h+60%冷变形+450℃时效4h)下有很强的时效强化效应,抗拉强度和屈服强度分别为527.0MPa和487.0MPa,伸长率为12.3%,导电率为82.0%IACS,软化温度为520℃;采用二级时效工艺(960℃固溶2h+60%冷变形+450℃时效4h+60%冷变形+450℃时效5h),合金保持较高的电导率的同时,合金的强度及软化温度得到较大提高,抗拉强度和屈服强度分别为565.4MPa和524.1MPa,伸长率为9.8%,电导率为80.1%IACS,软化温度为560℃.显微组织分析表明,高强度主要来源于预冷变形引起的亚结构强化和弥散相的析出强化.二级时效工艺细化了析出相的尺寸,析出的弥散质点对基体的回复和再结晶阻碍作用强烈,使合金具有很高的软化温度.     

CuNiCoBe合金冷变形时效特性

采用真空感应熔炼技术浇铸CuNiCoBe合金,利用光学显微镜、硬度计、电导仪,研究固溶、冷变形和时效处理工艺对CuNiCoBe合金组织和性能的影响.结果表明,CuNiCoBe合金较为合适的固溶温度为960℃;时效前冷变形有利于加快时效进程、缩短时效时间;冷变形量越大,合金时效后的室温硬度越高,达到时效硬化峰值的时间越短,峰值后硬度下降的幅度越大;总体说来冷,预冷变形亦有利于提高合金时效后的电导率,提高幅度平均约为10%.经960℃保温1.5 h固溶处理+60%冷变形+490℃保温2.5 h时效处理后的CuNiCoBe合金的硬度可达377 HV30,比未冷变形时提高了124%.     

热处理对QBe2合金组织和性能的影响

研究了固溶处理、时效处理、形变时效等对QBe2合金显微组织及性能的影响.结果表明,QBe2合金最佳固溶处理工艺为780℃×10 min水淬,时效工艺为320℃×2 h空冷,经此工艺处理后合金的抗拉强度达到1257MPa,电阻率为0.0677Ω·mm2/m;时效前的冷变形对晶界的不连续析出有抑制作用,使沉淀相沿晶内滑移线析出显著,形变时效可以使合金强度达到1390MPa,与一般软态峰值时效相比,强度提高10.3%.     

热处理对CuNiCrSi合金组织和性能的影响

研究了不同热处理工艺和预冷变形对汽轮发电机转子CuNiCrSi槽楔合金的显微组织和性能的影响。结果表明,CuNiCrSi合金最佳固溶处理工艺为 925℃×1 5h水冷, 40%预冷变形后再经 480℃×2h时效,其硬度可达到 249HV0 03,导电率为 48%IACS。     

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.     

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.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.