火花等离子体放电制备高温合金细粉新技术

提出了火花等离子体放电(SPD)制备高温合金细粉新技术,并设计了样机.该方法与常用的高温合金制粉方法—等离子旋转电极法和氩气雾化法的原理不同,与之相比,该方法冷速更快,可制备粒度更细小的粉末,且设备简单.对2种高温合金进行制粉,实验表明:该方法制备的粉末粒度分布窄、球形度高、粉末颗粒表面光滑、看不到枝晶、颗粒内部是球状晶凝固组织,从而组织更均匀.

火花等离子体放电制备粉末技术

火花等离子体放电技术已经用于制备纯金属、合金、化合物、半导体和陶瓷材料粉末。该技术制备的粉末具有球形度好、无坩埚熔化、原位快速淬火、粉末细小等特点。介绍了火花等离子体放电制备粉末的机理、特点以及该技术制备高温合金粉末的现状。

电火花等离子体熔蚀制备铁超细粉末的研究

采用电火花等离子体熔蚀装置在液相电介质中制备了超细铁粉末。并利用X射线衍射(XRD)、扫描电子显微镜(SEM)等测试手段对样品的表面形貌、物相、粒度分布进行了性能表征,并对粉末产量、电源参数进行了记录和分析。结果表明:制备的铁超细粉末粒度在5μm以下,绝大多数粉末粒度<1μm,粉末呈完好的球状,产量可高达70g/h,能源利用效率估算为12%。

火花等离子体放电法制备高温合金粉末

采用火花等离子体放电法制备了高温合金粉末。通过扫描电子显微镜对在不同电介质和电流条件下制备的高温合金粉末的形貌、颗粒大小以及内部凝固组织进行了分析。结果表明,该方法制备的高温合金粉末的粒度细小、颗粒球形度高、粉末颗粒表面光滑、看不到枝晶,颗粒内部凝固组织随颗粒大小和制备工艺而异。该方法还具有冷速快且设备简单的优点。

火花放电喷射等离子体触发气体开关导通特性及工作模式分析

为理解喷射等离子体触发气体开关的导通过程和触发机理,利用高速分幅相机拍摄火花放电喷射等离子体触发气体开关的导通过程,结合开关导通时延测量,研究了该开关在10%~90%工作系数下的触发导通特性,分析了开关在高、低工作系数下的导通过程和工作模式。结果表明,火花放电喷射等离子体触发气体开关在10%~90%的极宽工作系数范围内能可靠触发导通,导通时延随工作系数提高而逐步从数十μs减小至数百ns。低工作系数时气体开关为慢导通模式,导通过程可分为喷射等离子体形成阶段、喷射等离子体快速发展阶段、喷射等离子体发展饱和阶段和主间隙放电4个阶段,其导通延时受工作系数和触发脉冲幅值的影响,为数μs至数十μs。随着开关工作系数提高,开关由慢导通模式逐步过渡到快导通模式,导通过程只包括喷射等离子体形成阶段和主间隙放电两个阶段,放电发展过程较为迅速,导通时延约为数百ns。

电火花等离子体熔蚀法制备PtRh20合金粉末

采用电火花等离子体法在超纯水中制备了铂铑合金(PtRh20)粉末,利用ICP光谱分析仪、扫描电镜(SEM)、激光粒度分析仪等对制粉过程中的杂质含量变化、成品粉末表面形貌、成分及粒度分布进行了分析。结果表明:电火花等离子体熔蚀法制备PtRh20合金粉末效率可达1000 g/h,粉末纯度较高,由成分相同的高球形度颗粒和絮状物组成,粉末粒径基本在5~60μm之间,平均粒径25μm。

用火花等离子体烧结技术制成的钛复合材料

意大利特兰托大学用火花等离子体烧结技术制成了钛复合材料，研究了颗粒强化对粉末冶金Ti6A14V合金的微结构及力学特性的影响。采用了两种颗粒增强剂——TiB2和SiC，将其与合金粉末混合后，进行烧结。火花等离子体烧结要求温度不高，而且烧结时间也比一般短，从而使基质与增强剂间的相互作用达到最小。

用火花等离子体烧结技术制成的钛复合材料

意大利特连托大学用火花等离子体烧结技术制成了钛复合材料，研究了颗粒强化对粉末冶金Ti6A14V合金的微结构及力学特性的影响。采用了两种颗粒增强剂——-TiBe2和SiC，将其与合金粉末混合后，进行烧结。火花等离子体烧结要求温度不高，而且烧结时间也比一般为短，从而使基质与增强剂间的相互作用达到最小。

低压氩气氛火花放电等离子体中铜的时间分辨发射光谱及其激发机理(英文)

抽真空充氩激发条件下,测定了Cu元素的单次火花脉冲放电时的几种原子线和离子线的放电强度随着氩气气氛压力变化的情况。它的原子谱线和离子谱线的放电信号随时间变化的峰形有很大差异。原子共振线CuⅠ324.75 nm的峰宽要大于离子线CuⅡ213.60 nm的峰宽。对于CuⅠ324.75 nm谱线,其单次放电寿命几乎与氩气压力无关,在随时间变化的峰形中包含一个初始峰和一个较大的后端拖尾峰,在氩气压力增大时拖尾峰更加明显。对于CuⅡ213.60 nm谱线,其单次放电寿命在不同氩气压力条件下有一定变化,在随时间变化的峰形中包含一个初始峰和一个小的后端拖尾峰。在每一次火花脉冲放电中,激发机理是随时间变化而变化的,因此上述现象就可以从它们的激发机理的不同得以解释。

Synthesis and spark plasma sintering of Al-Mg-Zr alloys

Although casting is commonly used to process aluminum alloys, powder metallurgy remains a promising technique to develop aluminum based materials for structural and functional applications. The possibility to synthesize Al-Mg-Zr alloys through mechanical alloying and spark plasma sintering techniques was explored. Al-10Mg-5Zr and Al-5Mg-1Zr alloyed powders were synthesized through wet ball milling the appropriate amount of elemental powders. The dried milled powders were spark plasma sintered through passing constant pulsed electric current with fixed pulse duration at a pressure of 35 MPa. The samples were vacuum sintered at 450, 500, 550, 600 and 620℃ for 10, 15 and 20 min. The Al-10Mg-5Zr alloy displays poor densification at lower sintering temperatures of 450, 500, 550 and 600℃. Its sinterability is improved at a temperature of 620℃ whereas sintering temperatures higher than 620℃ leads to partial melting of the alloy. It is possible to sinter the Al-5Mg-1Zr alloy at 450, 500 and 550℃. The increase of sintering temperature improves its densification and increases its hardness. The Al-5Mg-1Zr alloy displays better densification and hardness compared to Al-10Mg-5Zr alloys.

SiC whisker reinforced MoSi_2 composite prepared by spark plasma sintering from COSHS-ed powder

SiC whisker reinforced MoSi2 composite powder was synthesized by a novel process, referred to the literature as chemical oven self-propagating high temperature synthesis(COSHS). The as-prepared SiCw/MoSi2 composite powder was rapidly sintered by spark plasma sintering(SPS) process. The sintering temperature and pressure were 1 723 K at heating rate of 100 K/min and 40 MPa, respectively. The microstructure and mechanical properties of the composite were investigated. Relative densities of the monolithic material and composite are 95% and 99.3%, respectively. SEM micrographs of SiCw/MoSi2 composite show that SiC whiskers homogeneously distribute in MoSi2 matrix. The composite containing SiC whisker has higher Vicker hardness than monolithic MoSi2. Especially the room-temperature fracture toughness of the composite is higher than that of MoSi2, from 3.6 MPa·m1/2 for MoSi2 to 7.7 MPa·m1/2 for composite with 15% SiC(volume fraction), increased by 113.9%. The morphology of propagation of crack and fractured surface of composite reveal the mechnaism to improve fracture toughness of MoSi2 matrix. The results show that the in-situ SiCw/MoSi2 composite powder prepared by COSHS technique can be successfully sinterded through SPS process and significant improvement of low temperature fracture toughness can be achieved.

Synthesis of Ti_3SiC_2 by spark plasma sintering(SPS) of elemental powders

Ti 3SiC 2 materials have been fabricated by spark plasma sintering of the elemental powders with the addition of Al. At the heating rate of 80 ℃/min and under the pressure of 30 MPa, the ideal synthesis temperature of Ti 3SiC 2 is in the range of 1 1501 250 ℃. The addition of Al is in favor of the formation of Ti 3SiC 2. The synthesized compound has the molecular of Ti 3Si 0.8Al 0.2C 2 and lattice parameters of a=0.306 9 nm, c=1.767 0 nm. Its grain is plane-shape with a size of about 50 μm in the elongated dimension. The prepared material has Vickers hardness of 3.55.5 GPa(at 1 N and 15 s) and is as readily machinable as graphite’s.

不同电介质对制备TiAl合金粉末的影响

以Ti-46.2%Al-8%Ta为实验材料,选用不同的电介质,通过电火花等离子体放电法制备了TiAl基合金粉末。结果表明:电介质为无水乙醇时,所制备粉末的成分是TiC和Al_(2)O_(3),粉末球形度非常低,且氧含量非常高;电介质为液氮时,所制备粉末的成分是TiN和AlN,粉末中的氮含量非常高;电介质为液氩时,所制备粉末成分是TiAl,粉末质量较高,但粉末产量非常低。在后续的研究中,可以采用液氩为电介质,不断优化工艺参数,在保证粉末质量的同时,进一步提高粉末的产量。

Microstructure and properties of p-type (Bi_(0.25)Sb_(0.75))_2Te_3 fabricated by spark plasma sintering

P-type thermoelectric material(Bi0.25Sb0.75)2Te3 was sintered by spark plasma sintering(SPS) process in the temperature range of 320-420 ℃. The microstructures of sintered materials were found to be well aligned,particularly when sintered at lower sintering temperatures. The electrical conductivity of the material became larger as the sintering temperature increased. The Seebeck coefficient showed a general decreasing tendency with an increase in sintering temperature. In terms of the power factor,the optimum sintering temperature was found to be 380 ℃ for a maximum value of around 2.6 mW/K.

Fabrication and mechanical properties of WC-Co-Al_2O_3 nanocomposites by spark plasma sintering

Small amounts of nanocrystalline Al2O3 particles were doped in WC-Co nanocrystalline powders to study their reinforcing effects, and spark plasma sintering technique was used to fabricate the WC-Co-Al2O3 nanocomposites. Experimental results show that the use of Al2O3 nanoparticles as dispersions to reinforce WC-Co composites can increase the hardness, especially the transverse rupture strength of the WC-Co hardmetal. With addition of （0.5%）（mass fraction） Al2O3 nanoparticles, the spark plasma sintered WC-7Co-0.5Al2O3 nanocomposites exhibit hardness of 21.22 GPa and transverse rupture strength of 3 548 MPa. The fracture surface of the WC-7Co-（0.5Al2O3） nanocomposites mainly fracture with transcrystalline rupture mode. The reinforcing mechanism is maybe related to the hindrance effect of microcracks propagation and the pinning effect for the dislocations movement, as well as the residual compressive strength due to the Al2O3 nanoparticles doped.

Mechanical alloying and characteristics of spark plasma sintering of Ti-Al composite powders

The mechanical alloying process of Ti-Al composite powders were carried out by use of high energy ball-milling machine. Structure variations of powder mixtures during mechanical alloying and characteristic of spark plasma sintering were investigated. The results show that during milling,TiAl,Ti3Al and Ti2Al phase intermetallic compounds are formed,simultaneously with powder refinement for the(TiH2-45Al-0.2Si-5Nb) and(TiH2-45Al-0.2Si-7Nb) mixtures. The particle sizes of two powder mixtures are less than 300 nm after milling for 30 h. Sintering process of the milled powder can be completed in a short time by spark plasma sintering,and the sintering microstructure is composed of fine and homogeneous TiAl and Ti3Al phase.

高温合金粉末还原过程的研究

针对火花等离子体放电法制得粉末中的氧含量高的现状,对高温合金粉末的还原过程进行了探索性研究。结果表明:火花等离子体放电法制得的氧含量较高的镍基高温合金粉末使用CaH2作为脱氧剂,在常压氩气保护下550℃的低温下即可将原始粉末中的氧含量由9.26%(质量分数,下同)降至1.52%,最终粉末中的氧含量主要取决于CaO的去除情况。

A bulk metal/ceramic composite material with a cellular structure

A bulk metal/ceramic composite material with a honeycomb-like micro-cell structure has been prepared by sintering the spherical Al90Mn9Ce1 alloy powders clad by Al2O3 nano-powder with the spark plasma sintering (SPS) technique. The as-prepared material consists of Al90Mn9Ce1 alloy cell and closed Al2O3 ceramic cell wall. The diameter of the cells is about 20―40 μm, while a thickness of the cell wall is about 1―2 μm. The ultimate compressive strength of the as-sintered materials is about 514 MPa, while its fracture strain is up to about 0.65 %. This composite material might possess good anti-corrosion, thermal endurance and other potential properties due to its unique microstructure. The result shows that the Al90Mn9Ce1/Al2O3 composite powders can be sintered by spark plasma sintering technique despite the large difference in their sintering temperature. This work offers a way of designing and preparing metal/ceramic composite material with functional property.

Preparation and mechanism study of bulk pure rare-earth metals with amorphous and nanocrystalline structures

The preparation and the mechanism study of bulk pure rare-earth metals with amorphous and nanocrystalline structures, which were produced by spark plasma sintering (SPS), were carried out in this paper. With different processing parameters, the amorphous, two phases of amorphous and nanocrystalline, and complete nanocrystalline microstructures have been obtained. The nano-grain sizes in the bulk nanocrystalline materials are found smaller than the original powder particles sizes, which may change the conventional viewpoint that the grains in the sintered bulk are generally coarser than the raw powder particles. The technique developed in the present work can be extended to the preparation of many other nano bulk metal materials, and thus enables the studies of the nano-size effects on the physical, chemical and mechanical properties of bulk nano materials.