等离子喷涂过程中纳米粒子生长分析

为了研究等离子喷涂过程中纳米粒子的生长情况,从而为喷涂工艺参数优化提供参考,在B rook晶粒生长经典理论基础上,计算了等离子喷涂纳米ZrO2-7%Y2O3粉末过程中纳米粒子尺寸变化,分析了不同温度历程及纳米粒子初始尺寸对其生长的影响.同时,对纳米团聚体粉末进行等离子喷涂试验.结果表明,纳米结构涂层是由一定比例完全熔化...     

等离子喷涂纳米复合陶瓷涂层的组织结构及其形成机理

以Al2O3-13%TiO2(质量分数)团聚体复合陶瓷粉末为材料,采用等离子喷涂工艺在TiAl合金表面制备纳米结构陶瓷涂层.用扫描电镜(SEM)和X射线衍射仪(XRD)分析粉末和涂层形貌、微观结构及相组成,讨论涂层的微观组织形成机理.结果表明:纳米结构复合陶瓷涂层由部分熔化区以及与常规等离子喷涂类似的片层状完全熔化区组成;根据组织结构的不同,部分熔化区又分为液相烧结区(亚微米Al2O3粒子镶嵌在TiO2基质相的三维网状或骨骼状结构)和固相烧结区(经过一定程度长大但仍保持在纳米尺度的残留纳米粒子);等离子喷涂使部分α-Al2O3以及全部θ-Al2O3转变为亚稳态γ-Al2O3;纳米结构复合陶瓷涂层中的完全熔化区、液相烧结区及固相烧结区分别由等离子喷涂过程中纳米团聚体粉末中温度高于Al2O3熔点、介于TiO2熔点到Al2O3熔点之间以及低于TiO2熔点区域沉积获得,纳米结构涂层中不同部分熔化组织源于复合陶瓷粉末中Al2O3与TiO2之间的熔点差异.     

等离子喷涂纳米Al2O3-13TiO2陶瓷涂层研究

以常规和纳米团聚体Al2O3-13TiO2(ω/%,下同)复合陶瓷粉末为原料,采用等离子喷涂工艺在TiAl合金表面制备常规和纳米结构陶瓷涂层.用扫描电镜(SEM)和X射线衍射(XRD)仪分析粉末和涂层形貌、微观结构及相组成,同时对纳米结构涂层的微观组织形成机制进行了讨论.结果表明:常规复合陶瓷涂层呈典型的等离子喷涂层状堆积特征;纳米结构复合陶瓷涂层由部分熔化区以及与常规等离子喷涂类似的片层状完全熔化区组成.根据组织结构的不同,部分熔化区又分为亚微米A12O3粒子镶嵌在TiO2基质相的三维网状或骨骼状结构的液相烧结区和经过一定长大但仍保持在纳米尺度的残留纳米粒子的固相烧结区,不同的部分熔化组织源于复合陶瓷粉末中A12O3与TiO2之间的熔点差异.由于等离子喷涂过程中涂层沉积时的快速凝固作用,不管是常规还是纳米涂层都以亚稳相γ-A12O3为主.     

材料结构与制备工艺对热障涂层显微组织的影响

以常规和纳米团聚体ZrO2-7%Y2O3陶瓷粉末为原料,采用等离子喷涂和等离子喷涂+激光重熔复合工艺在TiAl合金表面制备了常规和纳米结构热障涂层。用扫描电镜(SEM)分析了粉末结构及制备工艺对涂层显微组织的影响。结果表明:用常规等离子喷涂法制备的陶瓷涂层为典型的层状堆积特征;而用等离子喷涂法制备的纳米结构涂层则由纳米颗粒完全熔化区和部分熔化区组成,呈两相结构。由于受到激光功率、能量密度、激光作用区温度场分布、陶瓷导热系数和涂层厚度等因素的综合影响,经激光重熔后,涂层呈现出明显的分层结构特征:上部为致密的柱状晶重熔区,下部为残余等离子喷涂区。由于激光重熔纳米结构涂层重熔区中残余纳米粒子的增韧作用,其晶界强度较高,从而导致断口有相当数量的穿晶断裂,而激光重熔常规涂层重熔区的断口基本是沿晶断裂。     

等离子喷涂Al2O3-13％TiO2涂层微观组织形貌分析

采用微米粉末和纳米粉末,分别在45钢表面等离子喷涂Al2O3-13%TiO2涂层,测定了涂层的显微硬度和孔隙率,分析了涂层的显微组织。结果表明;微米尺寸粉末制备的Al2O3-13%TiO2涂层具有明显的层状结构;纳米尺寸粉末制备的Al2O3-13%TiO2涂层中有大量的未熔和半熔化粒子,粒子间结合紧密,涂层孔隙率小。     

等离子喷涂纳米ZrO2复合陶瓷涂层冲蚀行为

以常规和纳米团聚体ZrO3-7wt%Y2O3复合陶瓷粉末为材料,采用等离子喷涂工艺在TC4钛合金表面制备了常规和纳米结构陶瓷涂层,并对其进行冲蚀实验,研究了涂层微观组织和性能对涂层抗冲蚀性能的影响,以及不同工艺参数下涂层冲蚀性能.用扫描电镜(SEM)和XRD分析了涂层组分和微观结构,同时利用显微硬度计对涂层的硬度进行了测试.结果表明,等离子喷涂纳米ZrO2涂层抗冲蚀性能明显高于常规ZrO2涂层.当冲蚀角为90°时冲蚀失重最大,表现为脆性冲蚀,随着速度的增大冲蚀失重也随之增加.等离子喷涂纳米ZrO2涂层由熔化区和部分熔化区组成,部分熔化区属微纳米结构,熔化区在沉积急冷和冲击应力的作用下会形成细晶,微纳米结构与细晶共同作用下的纳米陶瓷涂层的平均粒度将远远小于常规陶瓷涂层的平均粒度,使其硬度增加;微纳米区域在涂层中其局部晶界的强度特别高,裂纹难以沿着晶界扩展,起到了良好的增韧的作用,硬度和韧性的提高使涂层的抗冲蚀性能增强.     

环氧富Zn-Al-Mg-Ce合金涂层耐腐蚀性能

采用悬浮液等离子喷涂(SPS)和常规等离子喷涂(CPS)2种工艺制备纳米结构ZrO2/Y2O3涂层。利用XRD和SEM分析涂层的物相和微观组织,同时使用韦伯分布函数对涂层的显微硬度进行了统计分析。研究结果表明:在试验条件下,SPS制备的纳米结构ZrO2/Y2O3涂层为粒状结构,涂层致密且没有观察到显微裂纹。单个层片直径在0.3～4μm之间,平均晶粒尺寸51.8nm。CPS制备的纳米结构ZrO2/Y2O3涂层由部分熔化区和全熔区组成,部分熔化区保持纳米结构。2种方法制备的涂层物相均为亚稳四方相。CPS纳米结构涂层的显微硬度韦伯图呈双态分布,其中全熔区显微硬度较高,离散性大,而部分熔化区显微硬度低,离散性较小。SPS涂层显微硬度离散性比CPS全熔区小,表明SPS涂层组织更为均匀。     

喷涂用MoSi2粉末的制备及其在等离子弧中的熔化特性

采用喷雾干燥和真空烧结技术制备MoSi2团聚颗粒,以MoSi2团聚粉末为原料,通过大气等离子喷涂法制备二硅化钼涂层,借助XRD、扫描电镜及能谱对团聚体粉末在等离子焰流中的熔化特性和涂层的组织结构进行研究.结果表明:团聚粉末在1200℃真空热处理1 h后,粉末的流动性和松装密度分别提高55.6%和42.0%,适合等离子喷涂用.MoSi2颗粒经过高温等离子焰流后,粉末熔化充分,大多数团聚体粉末发生烧结过程,颗粒的平均粒度减小,形成较致密的球形颗粒.在喷涂过程中,部分四方相MoSi2(t)转变为六方相MoSi2(h)或氧化形成了少量的Mo<,5>Si3相,涂层中的富钼相呈"网状"组织结构.     

等离子喷涂中纳米团聚体粉末温度场数值模拟

在纳米粒子排布方式理想化假设及热物性参数换算基础上,对纳米团聚体Al2O3-13%TiO2粉末等离子喷涂过程中的温度场进行数值模拟,分析粉末直径、喷涂距离及喷嘴出口处等离子焰流温度对粉末熔化状态的影响,并通过试验研究粉末在喷涂过程中的熔化特性.结果表明,要想获得适当且比较均匀的熔化状态,粉末粒度大小范围不宜分布过宽,同...     

纳米ZrO2-Y2O3-La2O3热障涂层的结构与性能研究

采用喷雾造粒工艺在纳米ZrO2-8wt％Y2O3(8YSZ)基体中添加了纳米La2O3,并进行团聚、热处理,作为喷涂喂料.NiCrAlY(Ni-25Cr-5Al-0.5Y,wt％)作为粘结层材料,采用等离子喷涂技术制备热障涂层.对涂层的组织结构和性能进行了表征与分析.结果表明:喷涂后涂层相组成只有稳定的t相;涂层具有典型的等离子喷涂结构;添加纳米LaO3能够降低涂层的热导率,且涂层的结合强度随掺杂量的增多而提高.     

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.     

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.     

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.     

An Easy Way to Quantify the Adhesion Energy of Nanostructured Cu/X(X=Cr,Ta,Mo,Nb,Zr) Multilayer Films Adherent to Polyimide Substrates

An approach based on film buckling under simple uniaxial tensile testing was utilized in this paper to quantitatively estimate the interfacial energy of the nanostructured multilayer films(NMFs) adherent to flexible substrates. The interfacial energies of polyimide-supported NMFs are determined to be *5.0 J/m2 for Cu/Cr, *4.1 J/m2 for Cu/Ta,*2.8 J/m2 for Cu/Mo, *1.1 J/m2 for Cu/Nb, and *1.2 J/m2 for Cu/Zr NMFs. Furthermore, a linear relationship between the adhesion energy and the interfacial shear strength is clearly demonstrated for the Cu-based NMFs, which is highly indicative of the applicability and reliability of the modified models.     

High-Speed Friction Stir Welding of SiC_p/Al–Mg–Si–Cu Composite

A 17 vol% SiCp/Al–Mg–Si–Cu composite plate with a thickness of 3 mm was successfully friction stir welded(FSWed) at a very high welding speed of 2000 mm/min for the first time. Microstructural observation indicated that the coarsening of the precipitates was greatly inhibited in the heat-affected zone of the FSW joint at high welding speed, due to the significantly reduced peak temperature and duration at high temperature. Therefore, prominent enhancement of the hardness was achieved at the lowest hardness zone of the FSW joint at this high welding speed, which was similar to that of the nugget zone. Furthermore, the ultimate tensile strength of the joint was as high as 369 MPa, which was much higher than that obtained at low welding speed of 100 mm/min(298 MPa). This study provides an effective method to weld aluminum matrix composite with superior quality and high welding efficiency.     

A STUDY OF TEMPERATURE-DEPENDENT VALENCE BOND STRUCTURE OF TITANIUM

On the basis of energy and shape method for the determination of the valence bond (VB) structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole temperature range of 0-1943K. The outer shell electronic distribution of Ti is e_c~(2.9907) · (s_c~(0.4980) d_c~(2.4927)) ef1.0093 in crystal. The temperature dependences of the VB structures of hcp and bcc phases are the same. The VB structures of hcp and bcc phases monotonically increase or decrease with the increase in temperature, but show discontinuous changes at the phase-transformation temperature 1155K.     

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。