Mechanical properties and potential applications of magnesium alloys

1　INTRODUCTIONDuringthefirsthalfofthetwentiethcentury ,magnesiumalloyswereusedextensivelyincivilianandmilitaryaircraftcomponents.TheneglectofmagnesiumalloysafterworldwarⅡwasrepresentedbytheslumpoftheproductionfrom 2 2 8.8kt/ain194 4to 10kt/aafterWorldWarⅡ .Themostsig nificantapplicationofmagnesiumalloysinthesecondhalfofthetwentiethcenturywasinproductionofair cooledenginesandgearboxesforVolkswagenBeetle ,whichledtheautomobileindustrytomakeavolun tarycommitmenttoachieve 30 %CO2 emissio…     

清洁高效的电镀锡线高压变频电阻软熔电源

连续电镀锡生产线软熔需要大功率单相交流电源供电。针对目前使用的三相变单相变压器可控硅调压式电阻软熔电源对电网影响较大、厂区用电效率低下等问题,采用了高压变频式电阻软熔电源。本文分析了该电源的电路结构。在多条电镀锡线上的应用证明,该电源既具有平衡负载、消除谐波和效率高等优点,而且能有效消除镀锡板的木纹缺陷。     

烧结FeSiAl磁头芯片的研制

FeSiAl材料具有优良的磁性能和耐磨、耐蚀性，但由于基脆性限制了它的应用。我们应用粉末冶金工艺直接通过压制成形烧结方法生产磁头芯片，不但节省材料而且大大简化了磁头加工工艺，使磁头的成本大幅度的降低，有利于发展FeSiAl磁头应用市场。     

塑料包覆铁粉制作的软磁复合材料

与硅钢片相比，塑料包覆铁粉制作的软磁复合材料，因其各向同性而便于设计，且通过粉末冶金生产工艺易于生产复杂的最终形状的部件，温压工艺可达到比传统铁粉压块更高的密度与生坯强度，在高频下，塑料包覆铁粉压块的总损耗低。因而塑料包覆铁粉可经济地制作高频应用的软磁材料。     

逆变电源用纳米微晶软磁铁心

介绍了一种FeNbCuSiB纳米微晶合金铁心,这种铁心具有低损耗、低乘磁和高磁导率等优良磁性能。介绍了2种能有效地散热的铁心保护装置,同时介绍了铁心的热稳定性和逆变电源变压器的设计要求。这种铁心适用于20－100kHz的各种高频大功率电源变压器。     

Investigation of Conventional- and Induction-Sintered Iron and Iron-Based Powder Metal Compacts

Induction sintering was developed as an alternative method to conventional sintering to sinter iron-based powder metal (PM) compacts. Several compositions of compact such as pure iron, 3 wt.% copper mixed iron, or 3 wt.% bronze mixed iron were sintered by using induction sintering machines with 12 kW power and 30 kHz frequency. The mechanical properties, microstructural properties, densities, and microhardness values were investigated for both processes. Iron-based PM compacts sintered at 1120°C by induction in 8.33 min (500 s) were found to be similar to those sintered conventionally in 30 min. The results were compared with the experimental studies.     

一种磁集成全桥LLC软开关焊接电源

采用绕组绕制在EE型磁芯侧柱上的方法设计高频变压器,通过适当的绕组和气隙设计,使得高频变压器励磁电感和漏感满足LLC谐振电路参数的要求,LLC谐振槽中的两个谐振电感和变压器可以集成在同一磁芯上,减少变换器磁性元件个数,磁集成变换器可以提高效率,提高了变换器功率密度;同时,LLC磁集成焊接电源在整个负载工作范围内,实现原边开关管零电压开通,副边整流管实现零电流关断,降低损耗.在此基础上,研制2.5 kW输出平特性的软开关全桥LLC磁集成焊接电源试验样机.结果表明,磁集成技术提高了系统性能.     

钼及钼合金研究与应用进展

综述了钼单晶、钼铼合金、钼钛锆（TZM）合金、钼硅合金、稀土钼合金、钼铜合金的研究现状与应用进展，详细介绍了稀土钼合金的研究与应用，包括稀土钼的韧化作用机理、稀土掺杂钼粉的粒度控制、稀土钼合金力学性能和热发射性能研究。由于钼及钼合金具有高温性能好、热传导率高、膨胀系数低等特性，因此在航空航天、核能工业等诸多领域得到广泛应用。今后，发展新的制备工艺，提供更高性能的材料，开辟新的应用领域成为钼及钼合金发展的关键。     

铁基堆焊耐磨合金的研究现状

概述耐磨堆焊材料、方法的分类及堆焊层合金元素的性质和堆焊层中碳化物形成特点;对铁基堆焊耐磨合金的固溶强化、第二相强化(弥散强化和析出强化)、晶界强化、热处理和定向凝固等强化方法进行了论述。分析合金元素在堆焊层中的作用、磨料磨损的形貌以及铁基耐磨合金的耐磨机理。铁基堆焊具有成本低、品种多,且易于改变堆焊层强度、韧性、耐磨性、抗冲击性等优点。铁基堆焊耐磨合金是当前研究的重要方向之一,应用前景广阔。     

基于STM32的超声电源研制

介绍了一种基于STM32的超声电源,其利用DDS芯片直接合成需要的PWM驱动波形,死区时间由单稳态触发器来调节,采用最大电流反馈跟踪及锁相跟踪相结合的方式来实现频率跟踪。通过调节STM32输出PWM信号的占空比,从而控制半桥变换器,使其保持功率恒定。实验表明,本电源具有跟踪精度高、成本低、工作稳定的特点。     

New Fe-based soft magnetic amorphous alloys with high saturation magnetization and good corrosion resistance for dust core application

Fe-rich amorphous dust core alloys with minor-addition of Mo and/or Cr were synthesized because of the industrial request of mass production of high efficient low core loss Fe-based dust cores. It was found that the present Fe-(Cr, Mo)-P-B-Si-(C) amorphous alloy ribbons exhibit good soft magnetic properties of above 1.5 T for saturation magnetization, below 10 A/m for coercivity and rather good corrosion resistance in 3%NaCl aqueous solution. Besides, the amorphous alloy ribbons exhibit good bending ductility in as-spun and optimally annealed states. It is noticed that these characteristics are much superior to those for commercial Fe-Cr-Nb-P-B-Si soft magnetic dust core alloy (SENNTIX). In addition, the annealing treatment was noticed to cause the improvement of corrosion resistance without detriment to bending ductility. The new Fe-based soft magnetic alloys with good combined characteristics are expected to be used as the basic material as high-efficient soft magnetic dust cores in a high frequency range.     

粉末冶金镁基材料研究进展

镁及其合金具有密度低、比强度和比刚度高、阻尼减振和电磁屏蔽性能好、液态成型和机加工性能优良、易回收再生等优点,在航空航天、地面交通和3C产品等领域具有很好的应用前景。然而,镁合金的绝对强度偏低,耐热和耐腐蚀性能不佳,限制了其更广泛的应用。研究和工程实践显示,粉末冶金工艺在改善镁基材料力学性能和耐蚀性方面具有很大的潜力。本文综述了粉末冶金镁基材料研究的最新进展,并简要介绍了粉末冶金镁基材料在生物医学、汽车和储氢等领域的应用情况,最后,展望了粉末冶金镁基材料及工艺研究的发展方向。     

高频感应焊接逆变电源PWM和PFM软开关控制

高频感应焊接逆变电源具有体积小、效率高、加热速度快等优点,但是传统设备采用的是整流调压方式,其控制精度低、动态响应速度慢,并且逆变器功率开关管经常工作在硬开关状态,引起较大开关损耗,使效率降低.文中提出一种使用自关断器件绝缘栅极晶体管作为功率开关,采用脉冲宽度调节方式和脉冲频率调节方式混合调功方式的高频感应焊接逆变电源的软开关控制方法,详细分析了电路的控制原理和工作模式,并设计出以锁相环为核心的控制电路.结果表明,这种方法实现了全部开关器件的软开关控制,具有功率调节范围宽,软开关调整范围广的优点.     

Dy对Pr2Fe17合金微波吸收特性的影响

采用电弧熔炼及高能球磨工艺制备出 DyxPr2-xFe17 (x =0.0, 0.1, 0.2, 0.3, 0.4) 合金微粉,借助XRD、SEM、振动样品磁强计和网络矢量分析仪等仪器分别对合金微粉的结构、形貌、磁性能及其微波吸收性能进行了研究。研究发现, 随着Dy含量的增加,DyxPr2-xFe17微粉的饱和磁化强度降低。DyxPr2-xFe17合金的最小反射峰频率随Dy含量的增加往高频方向移动,最小反射损耗呈先增大后减小的变化趋势;其中Dy0.3Pr1.7Fe17合金具有最好的吸波效果,在最佳匹配厚度2.5 mm下,Dy0.3Pr1.7Fe17合金的最小反射损耗在5.04 GHz处达到-42.38 dB左右,反射损耗小于-10 dB的频带宽度达到了1.20 GHz。     

节能节材、绿色低碳、清洁环保的直流焊接电源

通过对直流电焊机发展历程的回顾,逐一分析了传统旋转式直流焊机、硅整流直流焊接电源、电子式的晶闸管直流焊接电源和逆变式直流焊接电源,总结出"高效、节能节材、绿色低碳、清洁环保"是直流焊接电源今后发展的必然方向。通过分析逆变焊机电源主电路中的电源噪声滤波电路、一次侧工频整流电路和中频逆变电路等拓扑结构,归纳出"高效、节能节材、绿色低碳、清洁环保"电源的具体技术方案是:逆变式直流焊接电源加装电磁骚扰滤波器以之降低电磁骚扰信号幅度,使电源清洁环保;采用具有功率因素校正电路的一次侧工频整流电路替代一般的工频整流滤波电路提高功率因素,降低电源对电网的谐波干扰;采用合适的软开关逆变技术降低开关损耗,提高电源的效率。     

热处理对水雾化Fe74Cr2Mo2Sn2P10C2Si4B4非晶磁粉芯性能的影响

采用水雾化Fe74Cr2Mo2Sn2P10C2Si4B4非晶磁粉制备出了高频特性较好的磁粉芯。研究了去应力退火和磁场退火对磁粉芯磁性能的影响。结果表明:非晶磁粉芯压制后的去应力退火处理能有效提高磁导率和品质因数。过高热处理温度使非晶粉末晶化,析出导电性较差的非铁磁相,恶化磁性能。最佳退火温度为400℃,最佳的磁性能为:在3500 kHz的频率下,μ=40.5,Q=225。磁场退火对Fe74Cr2Mo2Sn2P10C2Si4B4非晶磁粉芯磁导率影响较小。纵向磁场退火能增大非晶磁粉芯的损耗,横向磁场退火能降低非晶磁粉芯的损耗,磁粉芯总损耗变化主要来源于磁滞损耗。     

热等静压对铁基非晶纳米晶合金软磁性能的影响

在铁基非晶纳米晶合金,普通氮气热处理最佳退火温度的基础上,将热等静压工艺引入到非晶带材磁芯的退火工艺中,探究热等静压工艺对Fe基非晶纳米晶合金软磁性能的影响。用X射线衍射仪、精密磁性元件测试仪和软磁交流设备测量了铁基非晶带材的晶体结构、磁芯的电感L和磁损耗P_s等。结果表明,在频率100 kHz和工作磁感应强度B_m=0.1 T时,普通氮气保护退火样品的矫顽力和磁损耗为2.04 A/m、10.10 W/kg,而热等静压样品则为1.33 A/m、6.58 W/kg,分别降低了53.4%、34.9%;普通氮气保护退火样品的有效磁导率和品质因数为11 579、0.46,而热等静压则为15 980、0.70,分别增加了38.0%、52.2%。     

节约型高强韧不锈钢及其薄带连铸制备技术

双辊薄带连铸技术自上世纪80年代至今已有近40年,但在常规不锈钢的工业化生产方面一直未取得成功。究其原因,主要归因于生产消耗、产品利润与产能之间的不匹配。近年来,国际国内开始将薄带连铸应用于制备节约型高强韧不锈钢,从而简化了热轧生产工艺,解决了因热塑性差而造成的钢板边裂和中裂等缺陷,大大提高了成材率。韩国浦项制铁采用薄带连铸技术生产出节约型双相不锈钢,耐腐蚀性能与SUS304奥氏体不锈钢相当,而抗拉强度可提高1倍,产品主要用于取代材料成本过高的奥氏体不锈钢。我国东北大学开发出高强韧节约型不锈钢的成分体系及其薄带连铸技术,制备出0.30~15 mm厚薄带,其强塑积高达62 000 MPa·%且其耐腐蚀性能较SUS304高出10%~15%,可以应用于核电、石化、铁路交通及汽车结构等领域。本文就薄带连铸高强韧不锈钢的现状、应用及未来发展趋势进行了综述和分析。     

Selective laser melting of aluminium components

Previous work has shown that the processing of aluminium alloys by selective laser melting (SLM) is difficult, with reasonable components only being produced with high laser powers (minimum 150 W) and slow laser scanning speeds. The high laser power is a significant problem as it is higher than that used in many SLM machines. Also, the combination of high power and low speed creates a large melt pool that is difficult to control, leading to balling of the melt and possible damage to the powder distribution system. Even when processing is carried out successfully, the high power and slow scan speed significantly increase build time and the manufacturing costs.This paper considers the changes that can be made to the SLM process so as to reduce the laser power required and increase the laser scanning rates, while still producing components with a high relative density. It also considers why aluminium and its alloys are much more difficult to process than stainless steels and commercially pure titanium. Two MCP Realizer machines were used to process 6061 and AlSi12 alloys, one processing at 50 W and the other 100 W laser power. Even with an optimum combination of process parameters a maximum relative density of only 89.5% was possible (achieved with 100 W). The major confounding factor for processing aluminium and its alloys was found to be oxidation due to the presence of oxygen within the build chamber. This formed thin oxide films on both the solid and molten materials. It was observed that the oxide on the top of the melt pool vaporised under the laser creating a fume of oxide particles, while melt pool stirring, probably due to Marangoni forces, tended to break the oxide at the base of the melt pool allowing fusion to the underlying tracks. However, the oxides at the sides of the melt pool remained intact creating regions of weakness and porosity, as the melt pool failed to wet the surrounding material. Therefore, if 100% dense aluminium components are to be produced by SLM, using low laser powers, methods need to be developed that can either disrupt these oxide films or avoid their formation.     

串联谐振式高频感应焊接逆变电源

传统的高频感应加热电源通过改变逆变器的工作频率来调节输出功率，逆变器的输出功率因数很低，而且逆变器开关管工作在硬开关状态，开关损耗大，效率低。按照大功率发电机、变压器铜排绕组焊接工艺和不同规格铜排的焊接要求，这种设备不适合这类应用。作者研究了新型频率跟踪电路，控制逆变器工作在谐振状态，负载等效阻抗呈电阻性，逆变器的输出功率因数接近1，大大减小了开关器件的功率损耗，提高了整机的效率。功率调节采用直流斩波调压实现。设计并制作了20kHz／30kw串联谐振式高频感应焊接逆变电源，改变了传统的焊接工艺，具有体积小、效率高、加热速度快等优点。