纯氧氛围下Ag-Sn-In合金粉末压坯烧结工艺探究

采用雾化法制备Ag-Sn-In合金粉末,通过讨论工艺参数（烧结温度、烧结保温时间、压坯压力）对AgSnO2电触头材料性能的影响,确定合理实验参数：压坯压力为200MPa,烧结温度为950℃,烧结保温时间为10h。对比纯氧氛围下烧结和传统烧结工艺的材料性能和显微组织,发现纯氧氛围下更有利于高温烧结,提高了烧结效率,改善烧结坯的烧结组织,提高了材料性能。     

Preparation of plasma-sprayed coatings of ZrN under a controlled nitrogen atmosphere

Spraying of 22 — 45 μm ZrN particles was performed in a controlled-atmosphere chamber using an Ar-N₂ plasma. The power levels were varied from 20 to 45 kW. The nitrogen pressure was regulated at either 60, 150 or 700 Torr. Use of the flattening test ensured that the degree of melting of the particles could be controlled. The crystalline structure, microhardness, thermal expansion, microstructure and porosity distribution of the coatings deposited onto steel substrates were examined and compared for the different spraying conditions. The flattening test showed that spraying at 700 Torr improves the heat transfer and leads to dense deposits with good interlamellar cohesion. The microhardness of such deposits varies between 945 and 1045 HV. The sprayed layers are very sensitive to oxidation at temperatures higher than 500 °C, the oxidation modigying their structure and causing a sharp variation in their expansion coefficient (from α = 8 × 10^-6 °C^-1 below 500 °C to α = 125 × 10^-6 °C^-1 between 600 °C and 1000 °C). This phenomenon limits the use of ZrN to temperatures lower than 500 °C.     

Biological,antibacterial activities and electrochemical behavior of borided commercially pure titanium in BSA-containing PBS

The effects of boride coating on the bioactivity, antibacterial activity, and electrochemical behavior of commercially pure titanium (CP-Ti) in phosphate buffer solution (PBS) with bovine serum albumin (BSA) were studied. The grazing incidence X-ray diffraction (GIXRD) pattern confirmed the formation of a TiB/TiB₂ coating via boriding process. Scanning electron microscopy (SEM) observation indicated that the TiB₂ cross-linked particles covered the TiB whiskers. Water contact angle measurements revealed that boriding led to the formation of a surface with intermediate water affinity. Potentiodynamic polarization (PDP) assays demonstrated that the TiB/TiB₂ coating had acceptable passivation behavior in BSA-containing PBS. Electrochemical impedance spectroscopy (EIS) measurements revealed that the passivation behavior of the CP-Ti and the borided samples was improved by increasing exposure time. Based on the Mott-Schottky (M-S) tests, it was realized that the charge carriers of passive films of both samples decreased with increasing exposure time in BSA-containing PBS. The bioactivity test results in a simulated body fluid showed that the TiB/TiB₂ coating switched the CP-Ti from bioinert to bioactive material. Finally, the antibacterial activity test of the TiB/TiB₂ coating against Escherichia coli and Staphylococcus aureus indicated 99% antibacterial activity.     

On the recrystallization behavior of technically pure molybdenum

In the last decades the amount of interstitial impurities in the raw material used for powder metallurgical production of molybdenum has been reduced significantly. The quality of the production process has been adapted to the latest technological standards and, consequently, the properties of technically pure molybdenum have changed accordingly. For processing pure molybdenum and to predict the resulting mechanical properties, the recrystallization behavior, which strongly depends on the concentration of the prevailing impurities, e.g. carbon, nitrogen and oxygen, is decisive. A reliable recrystallization diagram of molybdenum was published in 1965, which does not accurately describe the recrystallization behavior of the current quality of technically pure molybdenum. Therefore, in the present investigation a diagram which reflects the static recrystallization behavior of molybdenum containing low concentrations of interstitial impurities was established. The recrystallization behavior has been monitored on differently deformed and subsequently heat-treated samples by means of hardness testing, light microscopy and scanning electron microscopy employing electron channeling contrast imaging (ECCI) and electron back scatter diffraction (EBSD). Especially ECCI and EBSD investigations offer the possibility to analyze the change of microstructure with regard to recovery and recrystallization effects, e.g. the evolution of subgrains. The quantity of the impurities was determined by standard chemical analysis methods. As a bcc metal, molybdenum exhibits a high stacking fault energy. Thus, the recrystallization behavior is strongly dominated by concurrent recovery processes, which deviate from that of fcc metals showing a comparably low stacking fault energy. A revised recrystallization diagram for technically pure powder metallurgically processed molybdenum is presented.     

Densification behaviour of pure molybdenum powder by spark plasma sintering

Pure molybdenum was sintered with SPS under various temperatures, external pressures and heating rates. The microstructure of the specimens representing the different sintering conditions was investigated by classical metallographic methods. The relative density, the microhardness and the chord length distribution were measured. Linear shrinkage, depending on time or temperature, was calculated from piston travel, which was recorded during sintering process. These results show that the main part of consolidation takes place during fast heating up. The densification behaviour is controlled mainly by sintering temperatures and applied pressure. The molybdenum powder was successfully consolidated by SPS in very short times. A relative density of 95% was reached by sintering temperatures of 1600 °C and external pressure of 67 MPa.     

气氛可控热喷涂舱的研制

在此设计并制造了一种气氛可控热喷涂舱.利用设计的法兰连接,将电孤喷涂枪和等离子喷涂枪同时连接到喷涂舱上.这样可以单独或同时对试件进行交替或分层喷涂.利用气氛可控热喷涂方法,除了可以制备致密而又极少氧化的复合涂层外,还可以制备具有反应性成分的特殊金属涂层以及某些硬质涂层.同时,该种方法为航天、航空、能源、生物医学以及其它许多领域提供特殊性能的涂层,还可以作为一种新型复合材料开发的工具.     

精确可控气氛渗氮系统的改进

介绍了用比例阀和转子流量计代替质量流量控制器对精确可控气氛渗氮系统工艺气体流量测量和控制的方法,阐述了该方法实际的应用效果。采用该方法后,避免了因为质量流量器的损坏造成的停车,提高了精确可控气氛渗氮系统的稳定性。     

一种新型炉中钎焊保护气氛--氮基可控气氛

氮基可控气氛是炉中钎焊保护气氛的最新发展,它能给钎焊提供比其它气氛有更大的适应性和更高的效率,尤其是在充分发挥炉子各种功能的情况下更是如此,它有取代液化石油燃烧气及氨分解气的趋势。本文论述了氮基可控气氛的制备,用于炉中保护气氛钎焊的优点等诸多方面的内容。它不仅具有技术之先进性,而且兼有经济实用性,应用前景非常广阔。     

控制气氛下的AgCuTi/TiAl润湿铺展动力学

采用热台原位加热法系统研究了不同保护气体流量对润湿铺展过程、润湿铺展最大半径、润湿铺展动力学以及界面组织结构的影响.保护气体为氩气,保护气体流量分别为5,10,15 mL/s;加热曲线设定最高温度为1273 K,保温时间120 s;采用扫描电镜、能谱分析、光学显微镜等分析了界面组织结构.结果表明,保护气体流量为15 mL/s时,润湿铺展等效半径最大,原始半径0.9 mm的钎料铺展半径达到约1.4 mm.各种保护条件下,AgCuTi/TiAl体系的润湿铺展动力学过程相似,铺展半径与时间之间呈n次幂关系,即rn~kt;润湿铺展中钎料熔敷/TiAl的界面结构为:残余钎料的富银相/AlCuTi三元相层(AlCu₂Ti, AlCuTi, Ti₃Al)/TiAl母材,保护条件对其影响不大.     

纯钼板坯高温塑性变形行为及本构方程

采用Gleeble?1500热模拟机,在变形温度为1 100～1 350℃、变形速率为0.01～5 s?1、变形量为60%的实验条件下,对纯钼板坯的高温塑性变形行为进行研究。结果表明:流变应力随变形温度的升高而减小,随应变速率的增大而增大;不同变形温度下流变应力之间的差值随着应变速率的增加逐渐减小;同一应变速率下,峰值应力随变形温度的升高向应变小的方向推移。采用包含Zene-Hollomon参数的双曲正弦模型,建立了纯钼板高温塑性流变应力与变形温度和应变速率之间的本构方程。依据本构方程计算出的纯钼板坯流变应力理论值与实际值的平均相对误差仅为3.68%,表明该本构方程可为纯钼热成形加工工艺的制定提供理论依据。     

Relative wear resistance of borided steels

Conclusions Among the steels investigated, the wear resistance in contact with anthracite was highest for steel 45 after boriding and heat treatment consisting of oil quenching from 850° and tempering at 180° for 2h.V. Ya. Chubar' Zaporozh'e Machine Construction Institute. Dneprovskii Electrode Factory, Zaporozh'e. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 9, pp. 70–71, September, 1976.     

精密可控气氛渗氮技术及其设备

气体渗氮是重要的热处理表面强化工艺,适用于汽车、能源等动力机械、有色金属型材、电子资讯产品、家用电器、医疗器械、家具、五金制品和各种机械设备等制造业的热处理生产。但传统气体渗氮工艺,无法对氮势与渗氮层组织实现精确控制,     

Thin film metallization by magnetron sputtering from highly pure molybdenum targets

Both vacuum and powder metallurgy methods of preparation of molybdenum for magnetron-sputtering targets were studied. It is found that a combination of multiple-electron-beam melting and electric arc vacuum melting is an optimal metallurgical method to obtain highly pure molybdenum polycrystalline ingots for massive magnetron targets. Highly sensitive methods of analysis were used to characterize the molybdenum target. The specific resistivity of deposited thin molybdenum films was found to be strongly dependent on both the sputtering conditions and the initial target purity.     

Initial corrosion behavior of pure zinc in simulated tropical marine atmosphere

The initial corrosion behavior of pure zinc in a simulated tropical marine atmosphere was investigated using gravimetric method, scanning electron microscope combined with energy dispersive spectroscopy (SEM-EDS), X-ray diffractometry (XRD), Fourier transform infrared spectrometry (FTIR) and electrochemical impedance spectroscopy (EIS). The kinetics of corrosion process is a decelerating process following the empirical equation D=Atⁿ (n<1). The protectiveness of the corrosion product layer could be attributed to the formation of simonkolleite, Zn₅(OH)₈Cl₂·H₂O, which could inhibit the rate determining step, namely charge transfer step, of the electrochemical corrosion process. A model of the evolution process of the product layers formed on zinc was proposed. In addition, the regularity of the corrosion rate of zinc as a function of the NaCl deposition rate can be described by a power function.     

Creep microstructures and creep behaviors of pure molybdenum sheet at 0.7 Tm

The creep behavior of high purity molybdenum (99.995 wt.%) is investigated at temperatures of 1600 to 2000 °C (0.61–0.77 T_m) by direct ohmic heating. The stress and temperature dependency of creep strain and rupture time are described through optical microstructure observations. Under low load and low temperature conditions, coarse secondary recrystallized grains caused by dynamic recrystallization are observed far from the crack tip. In contrast, under high load and high temperature conditions, coarse secondary recrystallized grains are only fully formed near the crack tip, while coarse secondary recrystallized grains and small primary recrystallized grains coexisted further away from the tip. The recrystallized grain size of the Mo-B sheet is smaller than that of the Mo-A sheet, and small primary and large secondary recrystallized grains are mixed throughout whole specimens of the Mo-B sheet. Mo-A sheet shows elongated ductile fracture, but Mo-B sheet shows irregular brittle fracture under the same conditions. The steady-state creep strain rate at 1800 °C is found to be 7.34 × 10^− 6, 2.83 × 10^− 5 and 1.53 × 10^− 4 s^− 1 under a constant stress of 5, 10 and 20 MPa, respectively. The stress exponent is estimated to be 3.85–3.98 and the strain activation energy for steady state creep is 362–413 kJ/mol.     

Heat treatment of molybdenum under vacuum conditions

Oxide coverage of molybdenum plays an important role in several applications, for example in lighting industry. Surface conditioning procedures were simulated in an XPS instrument by in situ heat treatments while monitoring the surface composition and changes in the chemical states of molybdenum. Heat treatments have been made at different temperatures between 435 and 690 °C under vacuum conditions. It has been observed that during heating the molybdenum test samples the native MoO₃ layer on the surface dissociates, and a layer of suboxides forms on the surface. This layer hinders the further reduction of the surface, thus reaction speed decreases after the initial phase. It has been established that in the second phase of the heat treatment the activation energy of the process is 1.1 ± 0.2 eV. Reduction of MoO₃ to elemental molybdenum runs through two intermediate states: Mo⁶⁺ → Mo⁵⁺ → Mo⁴⁺ → Mo⁰.