激光冲击强化技术在核电领域的研究进展

激光冲击强化技术属于改善金属性能的重要表面形变强化技术,因其独特的技术优势在航天及船舶领域获得广泛应用。 随着科技的发展研发出多种激光冲击强化技术,并逐渐开始在核电装备领域获得应用,然而针对该技术在核电领域的研究进展缺乏系统的综述。先通过介绍不同表面形变强化技术,叙述激光冲击强化技术的发展,阐述激光冲击强化机制,最后综述激光冲击强化技术在核电领域的应用研究进展。总结发现,激光冲击强化技术可有效改善核电领域材料力学、摩擦磨损及腐蚀性能,但传统和添加辅助手段激光冲击强化技术受约束层和吸收层影响较大,无涂激光冲击强化技术对金属易产生热效应, 飞秒激光冲击强化影响层浅且强化效果差,不同工艺技术在核电领域提升摩擦磨损性能研究较少。对不同工艺激光冲击强化机理及在核电领域材料不同性能的提升进行深入研究,为进一步提升激光冲击强化技术在核电领域材料的应用提供理论基础,可为核电领域关键装备进行强化、提升核电装备运行寿命提供参考。     

特种焊接技术在核电汽轮机部件修复及再制造方面的应用

随着自主核电技术的深入发展,我国核电装备的修复再制造领域呈现跨越式发展,一些新型特种焊接技术不断发展、创新,已成功进入百万千瓦级核电汽轮机核心部件的修复再制造市场。实践证明:以高速或超高速激光熔覆、微弧等离子焊接为主的高能束焊接技术在修复市场具有广阔的应用市场;以冷金属过渡焊接(CMT)技术为主的技术仍具有很强的适应性;以高频冷焊技术为主的瞬时过渡焊接技术在精密部件小缺陷的修复方面具有广泛优势。可以预见,以机器人3D打印技术为主要平台的高能束智能再制造技术将是未来核电修复市场的一个主流趋势。同时,核电部件修复的相应行业指导规范或标准也应随着特种焊接技术的不断发展而适时的作出升级,以促进行业技术的不断发展。     

水下激光加工技术在核电维修领域的应用现状及发展

核能是一种安全、清洁、高效的能源,发展核电将成为未来世界电力发展的主要趋势。核电站关键设备及堆内构件在长期运行于高放射性高温环境后,需进行检修及退役处理,为降低检测和维修人员受辐照的风险,相关检修工作需要在水下进行。水下激光加工由于具有热输入低、作用位置精确、可远程传输的特点,在核电领域具有广阔的应用前景。概述了水下激光焊接、冲击强化、切割等水下激光加工技术的原理及国内外研究现状,重点介绍了激光加工技术在核电水下维修领域的应用现状,同时对该技术的发展趋势进行了探讨。     

压缩机易腐蚀零部件表面损伤的覆层修复

对螺杆压缩机转子、叶轮、缸体等压缩机的金属工作部件表面的腐蚀损伤进行修复是受到业界关注的课题.根据损伤表面的状况,激光合金化技术可以用于螺杆压缩机转子和离心压缩机叶轮表面损伤的修理.这种绿色再制造技术的应用关键在于:"冷焊"用的金属修补剂的研制及其在零部件表面损伤修复方面的推广.还应增加这样的技术服务型企业:能够开展压缩机设计计算和动平衡测试,同时具备金属零部件热喷涂或激光表面合金化技术.     

激光熔覆技术在结构修复上的应用现状

激光熔覆是现代制造业中最为重要的结构修复技术之一,激光熔覆修复技术的发展对提高金属结构的可靠性和使用寿命有着重要的意义。分析了激光熔覆技术在修复结构方面的应用;讨论了不同工艺参数对修复质量的影响;对熔覆过程流场、温度场及残余应力场的数值仿真进行总结;讨论了熔覆后结构的显微组织、力学性能测试及后处理措施,展望了激光熔覆修复方法在结构中的应用前景。     

核电领域激光焊接技术的研究与应用现状

核电厂的建造与运行是一个极其复杂的系统，焊接是其设备制造、装配、检修等过程中必不可少的重要工艺之一，焊缝质量的好坏直接关系到核电厂设备的可靠性和运行状态。相较于传统焊接工艺，使用激光焊接不仅能改善焊接质量，减少变形和残余应力，还能够提高效率，缩短工期。但目前在核电领域，激光焊接技术的应用并不多。为推广激光焊接技术在核电领域的应用，介绍了近年来激光焊接核级材料的研究现状。包括对常见的Zr合金、不锈钢以及新型材料等的激光焊接性能研究；分析其在核电厂设备的维修以及制造等领域的应用与研究现状。在此基础上，对目前核电厂激光焊接技术应用较少的原因进行分析，并对其将来的研究方向进行展望。     

激光熔覆在零部件修复中的应用现状

激光熔覆修复技术用于修复形状复杂和加工费用高的零部件,特别是修复层与基体呈冶金结合.从零部件失效、激光熔覆材料选择、熔覆工艺优化三个方面阐述了激光熔覆修复技术的优点,结合激光熔覆修复技术在叶片、辊轴、模具等零部件修复中的大量实例,从激光熔覆修复技术的基本原理和工作特点出发,对其进行总结和分类.并论述目前激光熔覆修复技术在国内外各种零部件修复中的研究、开发和应用,为进一步提高各种零部件的使用寿命提供了一个有效的途径.探讨了激光熔覆修复技术在未来工业中应用的发展趋势和广阔前景.     

激光立体成形高性能金属零件研究进展

激光立体成形技术是从20世纪80年代初期发展起来的一项先进制造技术,能够实现高性能复杂结构金属零件的无模具、快速、全致密近净成形。该技术可以用于承受强大力学载荷的三维实体金属零件的快速制造,也可应用于具有较复杂形状和较大体积制造缺陷、误加工损伤或服役损伤零件的修复。主要围绕激光立体成形技术在追逐高力学性能方面的研究工作,综述了激光立体成形研究和应用的主要进展情况。对多种合金的大量研究工作表明：激光立体成形金属零件的综合力学性能同锻件相当,导致这样优越的力学性能的主要原因在于其材料组织致密、细小、均匀,可以通过优化成形工艺和热处理工艺而获得基本上没有冶金缺陷的状态。激光立体成形技术的主要应用对象是兼顾高性能和复杂结构的金属零件的制造和修复。实现高性能修复是激光立体成形技术最近的一个引人注目的研究进展,修复零件的力学性能可以仅在简单的退火热处理状态下即达到锻件力学性能标准,这使得过去认为不可修复的高性能重要金属零件具备了现实的修复技术途径,这必将是激光立体成形技术最有前景的应用方向之一。     

乏燃料贮存格架激光焊接问题分析及改进措施

激光焊具有能量高度集中、热影响区小、工件变形小、焊接效率高、焊接质量好、自动化程度高等特点,目前已经在很多领域得到广泛应用,但尚未在核电设备制造中进行推广应用.文中提到的激光焊焊接工艺,是在国内同类设备中首次采用,对前期项目核电机组水下燃料储存格架贮存套筒焊接质量问题及激光焊应用中发生的焊接质量问题进行梳理和总结,分析原因,并从焊接参数优化、焊缝变形控制、引弧板和收弧板的应用、清洁度控制等方面提出了技术改进措施,取得了良好效果,为激光焊在核电乏燃料储存格架贮存套筒焊接的应用提供借鉴经验.     

核电机组Overlay堆焊修复技术的典型应用分析

随着核电机组运行时间的延长,核电材料性能劣化和部件失效的几率随之增加。Overlay堆焊修复技术作为一种可实现无需去除缺陷金属的在线维修方法,已广泛应用于国内外核电设备及管道的纠正性维修和预防性维修。针对Overlay堆焊修复技术,分析技术原理并进行残余应力有限元模拟验证,研究了Overlay堆焊修复应用于核领域的标准规范要求,提出了基于失效模式及工况条件进行堆焊材料和堆焊方法的选择原则,梳理了Overlay堆焊修复技术在CRDMΩ焊缝和接管安全端异种金属焊缝维修中的应用情况,分析了堆焊结构和堆焊工艺的关键技术要求,研究了残余应力和结构完整性分析的相关结论,提出了后续Overlay堆焊修复技术的研究建议。研究表明,Overlay堆焊修复可实现结构补强和薄弱区域残余应力状态及分布的改善,堆焊后结构可满足长寿期服役安全要求。     

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.     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

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.     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

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.