管材外高压成型工艺研究现状及应用

管材液压成型是一种生产中空轴类零件的成型技术,其在汽车和航空领域有广泛的应用前景.本文介绍了一种新的液压成型工艺--管材外高压成型;并综述了外高压成型(EHF)的基本原理、外高压成型优点、研究现状、应用范围、适用材料.     

电弧喷涂铝青铜复合涂层的抗高温氧化作用与机理

采用铝青铜底层,外加厚度为0.1～0.2 mm的纯铝涂层可进一步地提高涂层体系的抗氧化性能.900 ℃加热12 h的10次循环氧化试验结果表明,纯铝层的应用有助于提高铝青铜涂层的自封孔能力,在涂层表面形成的增厚富铝氧化膜以及在涂层基体界面上形成的富铝氧化层都对钢铁基体的防护有利.复合涂层体系与试件基体结合可靠,没有早期失效迹象,是一种有希望的高温防护涂层体系.     

The Microstructure and Mechanical Properties of the Low Carbon Microalloy Steel by High Voltage Electropulse Heating

The low carbon microalloy steel samples were heated to different temperatures by high voltage electropulse discharge heating method. The temperature of sample increases with the discharge current density. Microstructures were observed by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results show that coexist microstructure of ultrafine ferrite grain and martensite can be obtained by proper high voltage electropulse discharge heating process parameter. The tensile testing indicate that better mechanical properties were obtained, including 758MPa yield strength, 796MPa ultimate strength and 12% total elongation.     

铍的焊接缺陷及其控制技术研究

加填充材料焊接铍是防止铍焊缝开裂的技术措施之一,但加填充材料对铍进行高能束焊接可使焊缝形成钎接焊.介绍了铍焊接时生成的缺陷,主要有焊接裂纹、气孔、夹杂、未焊透和热影响区的晶粒长大等,全面系统地总结了铍焊接形成的各类缺陷,减轻和消除焊接缺陷的各种试验技术.在焊接参数试验的过程中,避开对焊接裂纹敏感的脉冲焊和深熔焊接工艺参数,可使铍的焊接缺陷（特别是焊接裂纹）明显地减少.     

16Co14Ni10Cr2Mo钢制飞机零件真空热处理工艺

１６Ｃｏ１４Ｎｉ１０Ｃｒ２Ｍｏ钢是国外广泛地用于制造飞机重要受力构件的一种经双真空冶炼的新型超高强度结构钢。作者经过试验优选了该钢的真空热处理工艺并用于生产。试验证明：该钢经真空热处理后，表面光亮，无氧化脱碳，且基本上不变形，工艺重现性好。     

激光熔覆用高硬度铁基合金的研究与应用

研究了激光熔覆Fe-Ni-Cr—B—Si合金粉末时粉末中的碳含量对于熔覆层组织、开裂敏感性、硬度和硬度均匀性的影响。结果表明，粉末含碳量的微小变化能显著改变熔覆层的组织和性能；在相同工艺条件下，粉末含碳量在一定范围内可显著提高熔覆层的硬度、降低熔覆层开裂敏感性，从而获得高硬度无裂纹的熔覆层；碳含量的增加可提高熔覆层的硬度均匀性。本文还报道了用自制Fe基合金粉末成功修复大型轧辊的实例。     

High-temperature oxidation of pure titanium in CO2 and Ar-10%CO2 atmospheres

The oxidation behavior of pure titanium has been investigated in the temperature range of 1000 K to 1300 K in CO₂ or Ar-10%CO₂. Optical microscopy, electron probe microanalyses, and X-ray measurements on the oxide scales formed during oxidation indicate that their structures are nearly independent of temperature and the corrosion atmosphere. The scales consisted of two layers, an external one and an internal one, having a rutile (TiO₂) structure. The parabolic rate law was confirmed for growth of the external scale and the permeation depth of oxygen in titanium with apparent activation energies of 266 and 226 kJ/mol, respectively. The rate-determining diffusion species in the oxidation processes are discussed.     

MICROSTRUCTURAL EVOLUTION OF HIGHLY UNDERCOOLED EUTECTIC Ni78.6Si21.4 ALLOY

A large undercooling level up to 550K （0.386Te） was achieved in eutectic Ni78.6Si21.4melt by the combination of molten-glass and cyclic superheating. A microcrystaUine structure is obtained at large undercooling. Surprisingly, the morphology of ct（Ni） phase transits from the non-faceted phaseto faceted phase at large undercooling of 390K. Based on the classical nucleation theory and transient nucleation theory, the process of microstructure evolution and competitive nucleation was analyzed, and the refinement of crystal structure is determined by the high nucleation rate under large undercooling.     

钻井工具的MAG焊接工艺

在对钻井工具的焊接特点、MAG焊接缺陷进行分析的基础上，通过选择合适的焊接材料、优选焊接工艺参数、采用合理的环缝焊接操作技术，克服了MAG焊易出现的气孔、熔化区开裂缺陷，焊缝金相组织为回火索氏体，成功的将MAG焊应用到了钻井工具制造领域，提高了焊接效率、降低了焊接成本。     

高强铝合金沿晶断裂声发射研究

高强度铝合金沿晶界断裂过程中的声发射信号特征反映了材料沿轧制方向的宏观性能。在带有预制裂纹的双悬臂梁(DCB)试样中，裂纹失稳扩展前，先有一短距离的韧窝状穿晶撕裂的稳态裂纹扩展。稳态裂纹扩展起始于K1C并发射出许多幅值超过阈值35dB的信号。当稳态裂纹扩展至Kmax时，便出现失稳的沿晶开裂。对稳态及失稳的裂纹扩展两种情况，其累计声发射能量均与宏观断裂能呈线性关系。