铸造铅合金曲面工件X射线检测工艺研究

针对铸造铅合金曲面工件的内部质量检测问题，通过研究射线检测工艺，优化射线检测参数和研制孔型像质计，实现了铅铸件的射线检测和检测过程质量控制。结果表明可检出工件内部小至Ф3mm的缺陷，且缺陷主要为疏松和渣孔。     

薄壁圆环激光焊缝X射线实时成像检测应用

利用射线照相的替代技术——X射线实时成像检测技术，对某薄壁圆环的焊缝进行了实时成像检测，结果表明该技术可以检测出试环焊缝中最小为0．4mm的孔型缺陷，像质计测定的检测灵敏度优于2％。     

中等厚度铅合金铸件的超声波检测

对铅合金铸件声学特征参数测试发现,铅合金的纵波声速较低,衰减系数较大,为超声的强衰减材料。对不同孔径的平底孔试样检测结果表明,目前采用超声水浸和直接接触法,均可较好地检出10mm厚板材内的1mm人工缺陷。因此采用超声方法检测中等厚度的铅合金铸件是可行的,重点是选取恰当的检测方法,以实现最佳的检测灵敏度。     

射线实时成象检验技术

射线实时成象检验系统得到的图象是电视系统的扫描光栅图象,与胶片射线照相的图象相比,它具有完全不同的结构.常规胶片射线照相图象,由于胶片乳剂的颗粒很小,在一般情况下清晰度不会成为影响图象质量的重要因素.常用的测定胶片射线照相灵敏度的象质计(丝型、孔型),主要反映的是图象对比度.射线实时成象检验系统的图象由象素构成,图象常常可以达到较高的对比度,但不能达到较好的清晰度.这种情况表朗,采用常规的象质计,不能准确测定射线实时成象检验系统图象的质量.美国ASTM E1411—91“射线实时成象检验系统鉴定方法”规定,对射线实时成象检验系统的综合性能应从三方面评定:①空间分辨力(或简称为分辨力).②对比度灵敏度.③IQI灵敏度.     

射线检测缺陷检出灵敏度研究与实际应用

简要评述射线检测缺陷检出灵敏度与像质计灵敏度的关系以及实际应用。     

高温合金闭式叶轮的工业CT检测

高温合金闭式叶轮为多层、薄壁、曲面流道的内腔与较大直径轴颈相连的整体复杂结构,使用透照电压不高于450kV的传统X射线照相方法对其进行检测时,存在X射线无法穿透叶轮厚大区域以及无法实现缺陷定位的问题,为此采用高能X射线工业计算机断层扫描(CT)方法对其进行检测。为了验证CT检测方法的缺陷检出能力,在高温合金闭式叶轮上加工已知尺寸的人工孔并进行检测,证明可检出φ0.5mm的孔。最后,对闭式叶轮的实际缺陷进行检测,可实现其内部气孔、缩孔等缺陷的检测和定位。     

FLOW-3D在薄壁圆筒类铸件压铸模拟中的应用

采用Flow3D软件对薄壁圆筒类铸件压铸过程中铝液的填充过程进行模拟,采用最佳进浇方式减小铸件内部孔洞类缺陷,提高铸件的合格率.     

细长薄壁类铸件的铸造技术

针对汽车空调HOWO气室铸件在采用顶注浇注系统、可倾转重力铸造时产生的缺陷,分析了缺陷产生原因,提出了改进方案.通过试生产的结果表明,采用阶梯式浇注系统作为批生产的工艺,可以大大减少汽车空调某气室铸件内夹渣、气孔和缩松的缺陷,提高了铸件的合格率.改进后的工艺方案已成功地应用到其他数十类气室类薄壁铸件的生产中.     

超声相控阵检测缺陷的灵敏度试验

为模拟实际焊缝中裂纹、气孔等常见缺陷,设计了一个具有不同孔径、深度、和倾斜角度的通孔型试块,来实现仪器探伤灵敏度的标定。通过对试块上四组缺陷的检测,发现超声相控阵对不同缺陷的检出灵敏度表现出一定的规律性,且通过合理的焦距设置可以改善仪器的检测效果。试验结果对实际焊缝和钢材内部缺陷检测具有一定的参考价值。     

薄壁涡旋铸铁件CIVA超声检测模拟

以薄壁涡旋铸铁件为例,在对材质声学特性进行分析的基础上,运用CIVA软件对超声检测工艺参数进行模拟仿真。结果表明,优化超声检测工艺参数,选择合适的检测频率和探头晶片尺寸,能够保证缺陷检出的灵敏度,对于8 mm薄壁铸件而言,直径12 mm探头检测效果优于8 mm,频率5 MHz的探头优于2 MHz。     

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。