【作者】 张涛；

【导师】 张兴国； 张伟；

【作者基本信息】 大连理工大学 ， 材料加工工程， 2011， 博士

【摘要】 非晶合金具有完全不同于晶体合金的原子排列,这使得非晶合金相比晶体合金具有高的强度、硬度、耐腐蚀性、良好的磁性能、超塑成形和微纳米成形等特点。非晶合金制备及其改性技术的研究对扩大非晶合金的研究和应用范围具有十分重要意义。随着非晶合金研究不断深入,其应用范围也越来越广,高效率低成本的连续制备技术的开发已迫在眉睫。本文提出了复合铸型双室差压非晶合金连续铸造方法并建立了连铸装置,以高纯铝验证连铸装置的实用性,并探索出了合理的非晶合金连续铸造工艺。利用金相显微镜、X射线衍射仪、DSC热分析仪、振动样品磁场计、电子探针、透射电镜、ShiMaDzu电液伺服疲劳试验机和MTS实验机对连铸制备的大块非晶合金棒材的组织、热物理性能和力学性能进行了分析。本文还研究了放电等离子烧结制备非晶合金、非晶合金磁性材料强磁场热处理等非晶合金制备和改性技术,对磁性非晶合金的强磁场处理结果进行评价。论文的主要研究结果如下：非晶合金连铸时,选用高纯石墨制备熔化坩埚。非晶合金普遍具有较低熔点便于电阻丝加热熔化。非晶合金的低凝固收缩特性可简化铸型锥度设计。设计并制作出复合铸型双室差压非晶合金连铸设备。该连铸设备真空腔体由分隔板分成两部分,复合铸型通过隔板相连,并可以实现抽真空和气体压差的控制。复合铸型采用高纯石墨和纯铜复合。复合铸型能够充分发挥石墨的高温润滑性和水冷铜模的大冷却强度特点。采用高纯铝对复合铸型双室差压非晶合金连铸装置进行调试并成功制备出高质量的高纯铝杆。表明该设备可以方便的实现连铸工艺参数的有效控制,能够有效避免杂质元素对金属液的污染和控制氢含量,达到了非晶合金连铸所需要基本条件。同时还分析了拉速对连铸高纯铝杆组织和性能的影响。研究了非晶合金的连铸工艺,采用复合铸型双室差压非晶合金连铸法成功制备出直径10mm,长度接近400mm的Zr48Cu36Ag8Al8非晶合金棒材,其连铸工艺参数是：浇铸温度950-1000℃,冷却水量15-40L/min,气体压力0.02-0.05Mpa,采用拉停循环模式,拉坯速度为2mm/s,拉坯时间为5s,停留时间为2s。拉停循环方式导致连铸非晶棒材表面出现圆环形痕迹,并且相邻痕迹之间的距离与拉速有直接对应关系,圆环形痕迹不影响样品的非晶性。连铸所制备的非晶合金棒材的力学性能与铜模铸造法制备的非晶合金相当。放电等离子烧结法制备出的Fe67Co9.5Nd3Dyo.5B20大块非晶合金磁性材料是各向同性的软磁性材料。烧结过程中Nd1.1Fe4B4相的出现使得材料的矫顽力变大。由于交换耦合作用,样品在650℃下保温10min热处理后可获得较好硬磁性。强磁场热处理恶化了Fe67Co9.5Nd3Dy0.5B20的磁性能,磁场强度越大,所得材料的硬磁性越差。非晶合金Fe56.25Pt18.75B25在783K温度热处理时,强磁场能够提高合金中铁磁性相Fe2B析出的形核率,起到细化晶粒作用。更多还原

【Abstract】 Glassy alloy has short range order atomic structure, which is different from crystalline alloy. Metallic glasses have lots of special properties, such as high strength, high hardness, high corrosion resistance, good magnetic properties, superplastic forming, micromolding and so on. The research on preparation and modification of metallic glasses are very important for the widely development and applications. Continuous manufacturing techniques of glassy alloys, which have high efficiency and low cost, are strongly demanded for industrial application.A Part of the dissertation is about spark plasma sintering of bulk metallic glasses and modification of amorphous alloys by high magnetic field. The key part of the dissertation are about continuous casting of bulk metallic glass, which contain the theoretical analysis of continuous casting technology for metallic glasses, the design, establishment and debugging by high pure aluminum of vacuum multi-mold continuous casting system, and developing of the metallic glasses continuous casting technology. The microstucture and thermal, magnetic and mechanical properties are investigated by MEF-4A Metallographic Microscope, XRD-6000 diffractometer, DSC822/TGA/SDTA851 thermal analyzer, JDM-13 vibrating sample magnetometer, EPMA-1600 Electron Probe microanalyser, TG220S-Twin JEM-100CxⅡTransmission Electron Microscope, SHIMADZU EHF and MTS NEW-810 Materias Test System. The results of the study are showed bellow:High pure graphite is adopted to make the crucible for continuous casting of bulk metallic glass. The glassy alloy can be melt by electric resistance heating for its relatively low melting temperature and the mould design can be easy for the low solidification shrinkage of glassy alloy.The multi-mold two chamber vacuum pressure continuous casting machine is established. The vacuum chamber is divided into two parts by a panel for the pressure control. The multi-mold is composed of heated graphite mold and water cooling copper mold, which is fixed on that panel. Two different kinds of multi-mold are designed, which could endure high temperature, provide lubrication and large cooling speed.High pure aluminum is used to debug the vacuum multi-mold continuous casting system and aluminum rods are also produced. Contamination from impurities and Hydrogen can be effectively controlled by the vacuum pressure multi-mold continuous casting system. The effect of drawing speed on microstructure and properties of high pure aluminum rods are also discussed.A Zr48Cu36Ag8Al8 glassy alloy rod with a diameter of 10mm and length of 400mm is produced by the two multi-mold continuous casting method. The suitable parameters for multi-mold continuous casting are 950～1000℃,40L/min,0.02～0.05Mpa,2mm/s,5s and 2s for casting temperature, cooling water, Ar pressure, drawing speed, withdraw period and pausing period, respectively. Annular trace is found on the surface of the glassy alloy rods with intermittent drawing speed mode and the distance between two nearest traces changes with the drawing speeds. The glassy alloy rod produced by the multi-mold continuous casting method nearly has the same mechanical properties as the sample fabricated by copper mold casting technology.Fe67Co9.5Nd3Dy0.5B20 bulk metallic glasses produced by spark plasma sintering technique are isotropicaly soft magnetic property. The precipitation of Nd1.1Fe4B4 phase enhanced the coercivity of sintered samples. The good hard magnetic properties for the exchange-coupling effect are obtained when the sample are anneald at 650℃for 15min. The magnetic properties of Fe67Co9.5Nd3Dy0.5B20 glassy alloys are deterioration when the samples are heated in high magnetic field. The crystalline grain size of the Fe56.25Pt18.75B25 amorphous alloy are largely reduced when the sample annealed at temperature above 783K in high magnetic field.更多还原