Structural and physical properties of permalloy thin films prepared by DC magnetron sputtering at different substrate temperature

Permalloy Ni80Fe20 films have been grown on thermal oxidized Si (111) wafers by magnetron sputtering at well-controlled substrate temperatures of 300, 500, 640 and 780 K in 0.65 Pa argon pressure. The base pressure was about 1×10-4 Pa. The deposition rate was about 5 nm/min for all the films. The structure of the films was studied using X-ray diffraction, scanning electron microscopy and atomic force microscopy. The composition of the films was analyzed using scanning Auger microprobe. The resistance and magnetoresistance of the films were measured using four-point probe technique. The results show that the content of oxygen in the films decreases gradually with raising substrate temperature. In addition, the surface morphology of the films presents notable change with the increasing of the substrate temperature; the residual gases and defects decrease and the grains have coalesced evidently, and then the grains have grown up obviously and the texture of (111) orientation develops gradually in the grow     

Si和316L基片上TiN薄膜微观结构和应力的对比分析

目的 比较Si和316L基片上TiN薄膜的微观结构和应力,分析基片材料和基片初始曲率对薄膜应力的影响.方法 采用电弧离子镀技术在Si基片和316L基片上制备了TiN薄膜,实测了薄膜应力,通过XRD、SEM、TEM等方法对薄膜的微观结构进行了分析.运用有限元分析技术,以结构力学为原理,分别对不同初始曲率的Si基片和316...     

金刚石粒径对金刚石/Cu-B合金复合材料热物理性能的影响

采用Cu-B合金为基体,选用粒径分别为110、230、550 μm的金刚石颗粒作为增强体,利用气压熔渗工艺在1 100 ℃、10 MPa气体压力下制备金刚石/Cu-B合金复合材料,研究金刚石颗粒粒径对复合材料组织结构、界面相分布及热物理性能的影响。结果表明,随着金刚石粒径的增大,复合材料热导率上升,热膨胀系数减小,复合材料界面处硼碳化合物含量增加,界面结合情况得到改善。由金刚石颗粒粒径为550 μm时,复合材料热导率最高,可达680.3 W/(m·K) ,热膨胀系数最小,为4.905 × 10⁻⁶ K⁻¹,符合高效热管理器件对金刚石/金属基复合材料的热物理性能要求,在电子产品散热器件方面具有良好的应用前景。     

Effect of Substrate Temperature on Deposition Behavior of Copper Particles on Substrate Surfaces in the Cold Spray Process

The deposition behavior of sprayed individual metallic particles on the substrate surface in the cold spray process was fundamentally investigated. As a preliminary experiment, pure copper (Cu) particles were sprayed on mirror-polished stainless steel and aluminum (Al) alloy substrate surfaces. Process parameters that changed systematically were particle diameter, working gas, gas pressure, gas temperature, and substrate temperature, and the effect of these parameters on the flattening or adhesive behavior of an individual particle was precisely investigated. Deposition ratio on the substrate surface was also evaluated using these parameters. From the results obtained, it was quite noticeable that the higher substrate temperature brought about a higher deposition rate of Cu particles, even under the condition where particles were kept at room temperature. This tendency was promoted more effectively using helium instead of air or nitrogen as a working gas. Both higher velocity and temperature of the particles sprayed are the necessary conditions for the higher deposition ratio in the cold spraying. However, instead of particle heating, substrate heating may bring about the equivalent effect for particle deposition. This article is an invited paper selected from presentations at the 2007 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Global Coating Solutions, Proceedings of the 2007 International Thermal Spray Conference, Beijing, China, May 14-16, 2007, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2007.     

气压熔渗法制备高导热金刚石/Cu–B合金复合材料

以硼质量分数为0.5%的Cu–B合金为金属基体以及平均粒径为500 μm的金刚石颗粒为增强体,采用气压熔渗法制备金刚石/Cu–B合金复合材料,研究气压参数对其组织结构和热物理性能的影响规律。结果表明：随着气压升高,金刚石与Cu–B合金之间的界面结合效果、导热性能均增强,热膨胀系数减小;当气压为10 MPa时,其界面结合效果最优,界面处生成的碳化物层将金刚石完全覆盖,且100 ℃时的样品热导率为680.3 W/(m·K),热膨胀系数为5.038×10⁻⁶ K⁻¹,满足电子封装材料的热膨胀系数要求。     

氮化硅陶瓷磨削表面残余应力的测试与计算

利用X射线衍射应力分析的sin2 ψ法测量、计算出氮化硅陶瓷试样的残余应力。分析表明 ,经平面磨磨削后的气压烧结氮化硅陶瓷试样表面存在的残余应力为拉应力 ,而再经过表面抛光处理 ,则可以适当地降低表面残余应力。     

焊接速度对核压力容器焊接残余应力的影响

采用ANSYS有限元分析法,并利用热-结构耦合及生死单元技术,模拟不同焊接速度对核压力容器上马鞍形焊缝焊后残余应力的影响。通过分析焊后温度场和应力场,发现焊缝中心的残余应力最大,随着距焊缝中心距离的增加,应力逐渐变小。其中焊接速度为450 mm/min和400 mm/min时焊后等效应力变化趋势基本吻合,而420 mm/min时焊后的应力值略高于其他两种。     

Quenching stress in plasma sprayed coatings and its correlation with the deposit microstructure

Quenching stress arises within a thermally sprayed splat as its thermal contraction after solidification is constrained by the underlying solid. Dependence of the quenching stress in plasma-sprayed deposits of Ni-20Cr alloy and alumina on the substrate temperature during spraying was discussed in conjunction with the change in the nature of the interlamellar contact between splats. It was found by mercury intrusion porosimetry and observation of cross sections of impregnated deposits that the interlamellar contact is improved significantly by raising the substrate temperature during deposition from 200 to 600 °C. The positive dependence of the quenching stress on the substrate temperature in this temperature range was attributed to a stronger constraint against thermal contraction of sprayed splats after solidification due to the improved contact.     

QFP器件不同引线材料对焊点可靠性影响的有限元分析

采用有限元方法对QFP器件三种引线材料焊点的残余应力进行了数值模拟计算分析.结果表明,焊点应力集中的部位均在焊点最内侧的尖角处,该处是整个焊点最易发生破坏的部位.分析比较合金-42、铜合金、可伐合金三种引线材料的模拟结果,焊点的应力应变曲线图显示,应力应变是随着时间做周期变化,同时具有累积迭加的趋势.同时可以看出合金-42引线焊点的应力应变最小,可伐合金引线焊点的应力应变居中,铜合金引线焊点的应力应变最大,研究结果可为QFP器件引线材料的选用提供理论指导.     

灯丝／基体距离对金刚石涂层质量的影响

热丝CVD法金刚石膜生长中基体温度对金刚石薄膜的质量有很大的影响,而基体与灯丝的距离决定着基体沉积温度的高低。本实验采用单一变量法,在其它工艺参数不变的情况下,研究不同基体与灯丝距离对CVD金刚石涂层的质量的影响。采用扫描电镜、Raman光谱、洛氏硬度计对试样的表面形貌、成分和涂层与基体的结合力进行泓定。结果表明,当采用两步法基体预处理,在碳源体积浓度为2％、沉积气压为3kPa、反应功率为4kW时,得到最优金刚石涂层质量的热丝与基体的距离为5mm。     

30Cr1Mo1V高中压转子残余应力分析与讨论

为了详细了解30Cr1Mo1V高中压转子最终热处理工艺对表面残余应力的控制水平,分别利用环芯法和盲孔法对转子进行多处表面残余应力测试,重点分析了转子轴身残余应力的分布规律,并对比了两种残余应力检测方法的优缺点。     

缝隙腐蚀研究进展及核电材料的缝隙腐蚀问题

综述了缝隙腐蚀的主要机理、模拟研究技术及影响因素,介绍了核电材料在实际服役过程中的缝隙腐蚀问题,讨论了高温高压水环境下缝隙腐蚀研究存在的主要问题以及进一步的研究方向。     

Stress distributions of welding joints in titanium–steel composite pressure vessel under working conditions

Abstract

Titanium–steel composite plate finds its application to constructing large pressure vessels normally used for storage and processing petrochemicals. The present study aims to calculate the stress–strain distributions in different types of welding joints possibly used in a pressure vessel which is built with a TA2/16MnR composite plate. A finite element numerical investigation has been preformed. In this work, influences on stress–strain distributions caused by various factors such as work temperatures, working loads and joint structures, were studied, taking into consideration the welding residual stress caused by the welding process. It is found that working temperatures are the main factors that would cause a great effect on the final stress distribution. As to the different types of welding joints, the stress peaks and distributions present various patterns due to the different structures of the joints. Based on the simulation result, suitable welded joint types under different working conditions are proposed.     

An estimation of factors influencing residual stress characteristics of fillet welded lap joints

The residual stress behaviours in fillet welded lap joints of sheet metal have been researched in a systematic testing procedure with varied steel types, steel thicknesses and welding wires having different transformation points. Consequently, under the simulated fabrication welding conditions (with a constant amount of deposited metal), the transverse residual stress at the weld toe, which is deemed critical in fatigue strength, has been found almost invariable to a change in steel type and thickness, but it has been clarified to become compressive to a greater extent as the wire’s transformation point is lower. Moreover, as for the residual stress inside the weld metal, the compressive residual stress area has been found to expand as the welding wire’s transformation point reduces, from the results of the thermo-elastic-plastic analysis.     

镀铝温度对渗铝层/基体界面空洞生长动力学的影响

采用不同的镀铝温度在20碳钢上制备了不同厚度的热浸镀铝层,通过测量热浸镀铝层厚度以及高温氧化后渗铝层/基体界面空洞平均直径和形核数量随氧化时间的变化,研究了镀铝温度对渗铝层/基体界面空洞生长的影响。结果表明:随镀铝温度升高,镀铝后的表面层厚度减小,合金层厚度增加;在高温氧化期间,渗铝层/基体界面空洞的生长速度随镀铝温度的升高而减小,其变化规律与热浸镀铝后表面层厚度随镀铝温度的变化规律相一致;界面空洞平均深度随镀铝温度升高而增加,其变化规律与热浸镀铝后合金层厚度随镀铝温度的变化规律相一致;界面空洞增量随氧化时间的延长先增加而后逐步减少,且镀铝温度越高,空洞形核速度越小。分析了镀铝温度对界面空洞生长的影响机制。     

NbTi / Cu 超导材料清洗废酸负压蒸发再生系统研制

目的研究超导材料清洗过程中产生的废酸的处理和回收技术,实现废酸提纯回用,达到废酸液零排放的目标。方法向废酸液中配入工业浓硫酸,以提供适量浓度的环境,然后在25 kPa真空环境下进行蒸发,酸蒸气通过换热器冷凝再生,浓缩后获得的金属硫酸盐溶液进行常温下冷却结晶回收。按照配酸、蒸发、冷凝、结晶等工艺要求,设计、制作废酸再生回用的耐腐蚀过程设备,调试组成废酸再生系统,验证并优化工艺细节。结果研制的负压蒸发再生系统日处理废酸量达到9~15 t,再生酸经浓度调整后直接回用,从浓缩液中得到的硫酸盐结晶物可作为其它化工原料。结论成功实现了清洗超导材料用硝酸和氢氟酸的再生,整个环节没有污染物排放,同时设备具备造价低、运行稳定可靠、维护量小等优点。     

基体预热温度对涂层表面形貌及残余应力影响的数值模拟

目的为了更好地研究分析不同的基体预热温度对所制备涂层质量的影响。方法采用求解热传导和能量方程,运用有限体积FVM法、流体体积跟踪法VOF追踪熔滴自由表面,建立熔滴撞击基体的三维几何模型,模拟了层片形成过程,分析不同基体预热温度对层片表面形貌的影响以及熔滴内部液滴形态变化的过程,在上述基础上,继续模拟第2个熔滴撞击在已凝固层片,从而形成涂层,进一步分析了不同基体预热温度对涂层表面形貌和残余应力的影响规律。结果随着基体预热温度的提高,沉积物与基体之间的温度梯度减少,有利于熔滴的铺展,铺展时间变长,气体的排放更顺畅,层片中的孔隙率降低,且层片铺展厚度随温度的提高而逐渐降低,而铺展半径逐渐增大,沉积物形貌更接近圆盘状。随着基体预热温度的提高,最终涂层形貌都是边缘厚、中间薄,但涂层中央的致密程度不断提高,且组织中的孔隙量越来越低。结论基体预热温度需处在一个范围,涂层的残余应力才会有一个最优值,使得涂层与基体有比较好的结合强度。     

四柱液压机自动化监测和控制改造

主要介绍四柱式液压机在非金属复合材料模压成型时的温度、压力、时间以及工艺参数的优化,实现了自动监测与控制。