纳米ZrO2激光重熔涂层组织与性能分析

采用金相试验、扫描电镜试验、热震试验和显微硬度试验对不同激光重熔工艺下的Y2O3部分稳定ZrO2纳米陶瓷涂层组织与性能进行研究.重点分析了涂层重熔宽度与深度、表面形貌、显微硬度和热震性能随激光比能量的变化规律.结果表明,ZrO2纳米陶瓷涂层的重熔深度和宽度随着激光比能量的增大而增加;涂层的表面成形与激光比能量密切相关;涂层的显微硬度随激光比能量的增大而升高;激光比能量对涂层热震性能的影响十分明显,当激光比能量为37.2 J/mm2时重熔涂层的热震性能最好.     

毫米波与激光复合隐身涂料研究

利用近红外激光隐身涂料对毫米波的透明性,将其涂敷于毫米波隐身涂层表面,制备出毫米波与激光复合隐身涂层.测试结果表明激光隐身与毫米波隐身效果良好,0.93μm、1.06μm、1.54μm处反射率均小于0.5%,8mm处的雷达反射率达-10dB,并具备可见光伪装性能.     

激光热输入对钴基合金涂层组织与裂纹的影响

采用激光熔覆技术制备了钴基合金涂层,通过对该涂层进行一系列制备和测试试验,深入研究了激光热输入对钴基合金熔覆涂层尺寸、稀释率、组织、气孔数量及裂纹的影响.结果表明:激光热输入能量从66.7 J/mm2增加到120 J/mm2,该涂层高度逐渐降低,热影响深度先减小后增大,涂层的稀释率与热影响深度有相同的变化趋势,涂层搭接...     

欢迎订阅2005年《表面工程资讯》和《材料保护》

《表面工程资讯》杂志报道现代表面技术(如表面徐层技术、表面改性技术、表面薄膜技术等)的现状及未来发展趋势，涉及电镀与化学镀、腐蚀与防护、涂料与涂装、热喷涂与热喷焊、摩擦与磨损、激光表面强化、纳米涂层等专业的高新技术成果、性能评价、工艺和质量控制等，以及专利、标准、人才交流及市场行情、产品供求、会展预告等信息。     

铁基多元陶瓷涂层激光熔覆制备及优化

采用20钢为基材,激光熔覆涂层材料以YD-F625型铁基粉末为基,添加有Ti C、WC和Si C多元陶瓷增强相,通过调整多元陶瓷相中Ti C的比例来获得不同的涂层合金材料,同时选用多组激光功率、扫描速度、粉末厚度等工艺参数进行激光熔覆对比试验,以涂层表面硬度为性能指标,对激光熔覆工艺和涂层材料种类进行优化。通过激光熔覆制备多元陶瓷复合涂层可以使20钢表面的硬度显著提高,其中最优工艺组合为激光功率3000 W、扫描速度280mm/min、预置粉末厚度2.0 mm、Ti C粉末含量为20%时,涂层最高显微硬度可达1100 HV以上,出现在距涂层表面0.05 mm深度处。     

球墨铸铁凸轮轴的激光表面熔凝处理

分析了激光表面熔凝处理后球墨铸铁凸轮轴硬化层的组织和性能特点，并与其它强化方法进行了比较。结果表明，采用适当的激光表面熔凝处理工艺参数，可以在表面获得搭接均匀、表面硬度大于80HRA和厚度达1．0mm的硬化层；硬化层由熔凝层和淬硬层组成，其中熔凝层的基体组织主要为细小、均匀并且有一定方向性的亚共晶莱氏体，淬硬层主要由石墨球及其周围的硬质环、细马氏体和铁素体基体所组成。与其它铸铁凸轮轴强化方法相比，激光表面熔凝处理具有表面硬度高、组织细小均匀、零件畸变小和不影响心部性能等优点。     

激光合金化掺杂TiC对等离子喷涂8YSZ热障涂层热腐蚀行为的影响*

传统的等离子喷涂热障涂层在高温环境下服役易受熔融腐蚀盐渗透而过早剥落失效，研究激光合金化掺杂自愈合材料 TiC 对热障涂层热腐蚀行为的影响具有重要意义。采用大气等离子喷涂技术（Atmospheric plasma spray，APS）在 Inconel 718 镍基高温合金表面制备 NiCrAlY 粘结层，采用大气等离子喷涂技术在 NiCrAlY 粘结层上制备 8 wt.%氧化钇部分稳定的氧化锆（8 wt.% yttria partially stabilized zirconia，8YSZ）陶瓷层，构建典型双层结构热障涂层体系。采用 1 kW 光纤耦合激光器将自愈合材料 TiC 熔于 8YSZ 热障涂表层，并考察其在 900 ℃下 25%NaCl+75%Na₂SO₄混合熔盐中保温 4 h 的热腐蚀行为。结果表明，与等离子喷涂涂层相比，激光合金化改性热障涂层表面更加光滑，分布有网状裂纹，且结构致密。等离子喷涂涂层的热腐蚀产物主要是针状颗粒 Y₂(SO₄)₃ 和 m-ZrO₂，但仅有较少的热腐蚀盐渗透至激光合金化改性热障涂层内部，其热腐蚀产物为 Y₂(SO₄)₃ 和少量的 TiO₂。激光合金化改性热障涂层的抗热腐蚀性能较等离子喷涂态热障涂层提升 55.5%，一方面激光合金化改性层组织致密，可阻止热腐蚀盐渗透至涂层内部，另一方面，激光合金化改性热障涂层表面粗糙度更低，能减少与热腐蚀盐的接触面积。此外，自愈合材料 TiC 在高温下发生氧化反应引起体积膨胀，实现裂纹的部分自愈合效应，进一步阻止了热腐蚀反应的发生。采用激光表面改性技术将自愈合材料 TiC 引入热障涂层，激光合金化改性热障涂层不仅具有光滑的表面形貌，还具有致密的微观组织结构；同时自愈合材料 TiC 在高温环境下的裂纹自愈合效应有助于抑制热腐蚀盐的渗透， 最终提高热障涂层的抗热腐蚀性能。     

飞秒激光刻蚀对纳米金刚石薄膜表面微观特性的影响

利用飞秒激光对纳米金刚石涂层进行刻蚀试验,通过改变激光的重复频率,输出功率以及焦点扫描速度,研究不同的激光加工参数对金刚石涂层烧蚀结果的影响。利用白光干涉仪器、SEM、拉曼光谱仪研究了飞秒激光刻蚀后涂层表面微观粗糙度、微观形貌以及碳相结构变化。采用面积推算法计算出扫描速度1 mm/s,有效脉冲数为90时的烧蚀阈值。结果表明：金刚石涂层表面飞秒激光诱导的条纹状结构周期（LIPSS）接近飞秒激光波长,改变飞秒激光重复频率对涂层表面形貌修饰影响不大;由于烧蚀饱和作用,飞秒激光功率增加至80 mW过程中涂层表面微观粗糙度持续减小随后维持在325 nm左右;激光扫描速度的增大可使LIPSS特征消失,当扫描速度增加至1.4 mm/s后,涂层表面微观粗糙度不再继续降低而是随着速度的增大而增大。激光诱导的金刚石涂层表面石墨化程度越高,涂层表面微观粗糙度则越低;当有效脉冲数为90时纳米金刚石薄膜的飞秒激光烧蚀阈值为0.138 J/cm²。     

氧化锆热障涂层在液芯大压下轧机轧辊上的应用

利用有限元软件ABAQUS对热力耦合作用下热障涂层对液芯轧机轧辊应力场、温度场的影响进行分析;采用等离子喷涂方法在轧辊材料H13钢表面制备厚度0.5mm的氧化锆热障涂层,并对其进行激光重熔处理,研究等离子喷涂热障涂层和激光重熔涂层的硬度、抗热冲击性能。结果表明,热障涂层能有效降低轧辊表面温度和等效应力,缓解热冲击效应,延长轧辊使用寿命;相对于等离子喷涂涂层,激光重熔涂层具有更大的硬度和更好的抗热冲击性能,在提高轧辊使用寿命方面有着更好的前景。     

激光冲击处理对304不锈钢力学性能的影响

选用不同涂层对304不锈钢板材激光冲击处理,研究了自主研制的硅酸乙脂涂层与几种常用吸收涂层对304不锈钢的硬度和表面残余应力等冲击力学性能的影响.结果表明,在激光冲击过程中,黑漆涂层、铝箔涂层和硅酸乙脂黑漆涂层都能有效提高激光冲击试样的表面硬度,激光连续冲击后,在304不锈钢试件表面能形成1mm厚的硬化层,其表面硬度最大到240HV;随着激光功率密度的增强,其表面硬度逐渐增强;其表面残余应力也随着激光功率密度的增加而逐渐增大.     

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.