WC颗粒增强Fe基粉末冶金复合材料研究进展

介绍了WC颗粒增强Fe基粉末冶金复合材料,讨论了WC颗粒增强Fe基粉末冶金复合材料的WC含量、组织结构、制备工艺、WC颗粒形貌及强韧化机理,并指出研发一种短流程、低成本的高性能WC颗粒增强Fe基粉末冶金复合材料及其制备工艺是Fe基复合材料未来发展的趋势之一。     

粉末短流程成形固结技术的研究及展望

针对粉末冶金行业最新发展的几种短流程成形固结新技术,结合华南理工大学近十多年来在粉末材料-工艺-装备-零件一体化方面开展的研究,重点阐述了粉末冶金温压成形、高速压制成形、喷射成形、多场作用下粉末成形与烧结一体化技术的研究进展及应用情况。指出在粉末冶金成形固结研究领域,合理拓展现有粉末冶金技术规范的空间,有望给传统粉末冶金成形固结技术注入新的活力。粉末冶金成形固结新技术的不断出现,必将促进先进制造业和高技术产业的快速发展,也必将给材料工程和制造业带来更加光明的前景。     

Metallography of powder metallurgy materials

The primary distinction between the microstructure of an ingot metallurgy/wrought material and one fabricated by the powder metallurgy route of pressing followed by sintering is the presence of porosity in the latter. In its various morphologies, porosity affects the mechanical, physical, chemical, electrical and thermal properties of the material. Thus, it is important to be able to characterize quantitatively the microstructure of powder metallurgy parts and components. Metallographic procedures necessary for the reliable characterization of microstructures in powder metallurgy materials are reviewed, with emphasis on the intrinsic challenges presented by the presence of porosity. To illustrate the utility of these techniques, five case studies are presented involving powder metallurgy materials. These case studies demonstrate problem solving via metallography in diverse situations: failure of a tungsten carbide-coated precipitation hardening stainless steel, failure of a steel pump gear, quantification of the degree of sinter (DOS), simulation of performance of a porous filter using automated image analysis, and analysis of failure in a sinter brazed part assembly.     

Induktive Erwärmung von partikelverstärkten Stahlpresslingen in den thixotropen Temperaturbereich

The producers of powder metallurgy components are constantly making efforts to improve manufacturing processes and to extend the present ranges of their applications. One way to increase the complexity of powder metallurgy components is the combination of powder metallurgy and thixoforging. In contrast to the conventional process route, the powder‐pressed raw parts are heated up to the thixotropic temperature range in order to realise complex components in one process step. Additionally, the powder metallurgy combined with ceramic particles allows to produce Metal Matrix Composite (MMC) materials with improved mechanical properties compared to conventional materials. In this work basic experiments of the pressing and inductive heating of particle‐reinforced steel parts are examined.     

Aluminium powder metallurgy technology for high-strength applications

A literature survey of aluminium powder metallurgy (PM) for high-strength applications was undertaken. Improvements in aluminium—base alloys made via ingot metallurgy (IM) are reaching the point of diminishing returns. PM offers an alternative technology, capable of producing alloys having improved fatigue, corrosion, and stress-corrosion resistance, as well as improved strength and toughness at room or elevated temperatures. The steps involved in powder metallurgy: powder manufacture, powder processing, de-gassing, and consolidation, are described. The merits and deficiencies of the various processes for each step are compared. The key to successful application of Al powder metallurgy alloys appears to be the de-gassing and consolidation of the powder. The properties of several new PM alloys are compared, with particular emphasis on highstrength, corrosion-resistant alloys and alloys developed for use at elevated temperatures.     

粉末冶金钛合金的应用现状

简要介绍了粉末冶金钛合金的特性,从应用的角度总结了粉末冶金钛合金的材料体系,主要技术和产品的发展现状和趋势,回顾了粉末冶金钛合金在航空、航天、航海、汽车工业、医疗及生物、储氢合金等方面的应用。最后针对国内粉末冶金钛合金的市场发展和需求,讨论分析了国内粉末冶金钛合金材料的发展重点和方向。     

粉末冶金曲轴主轴承盖的研制

分析了汽车发动机曲轴主轴承盖473QB的结构和性能特点,采用粉末冶金材料取代铸铁或球墨铸铁,降低了生产成本。制定了合理的开发方案,确定了材料配方、生产工艺流程,并设计了模具。通过试制进行产品金相分析,改进了粉末冶金工艺和模具结构,成功研制出了符合要求的可承受复杂载荷的粉末冶金曲轴主轴承盖。     

Effects of Mg content on aging behavior of Al4CuXMg PM alloy

Starting with elemental (pre-mixed) powders for producing shaped powder metallurgy alloys provides some advantages over a pre-alloyed system. The premixed powders are softer than prealloyed powders and therefore by using premixed powders it is possible to have higher compact densities and within a longer die life. In this research work, elemental aluminum powder was mixed with copper and magnesium in various ratios. They were compacted, sintered and heat treated in order to produce light but strong Al-based powder metallurgy alloys. The main focus of this paper is on the effects of micro to macro scale addition of magnesium on the aging response of Al4Cu alloys. Four per cent Cu gives Al powder metallurgy alloy a good control of sintering and a large space for solution treatment. Minor addition of Mg with little amount of Fe, comes from the based Al and Cu powders, enhances the hardness values of Al4Cu powder metallurgy alloys. Highest hardness value was 118 HB obtained from 24 h aged Al4Cu2Mg alloy.     

Study of the properties of low-cost powder metallurgy titanium alloys by 430 stainless steel addition

Titanium is a lightweight metal with an outstanding combination of properties which make it the material of choice for many different applications. Nonetheless, its employment at industrial level is not widespread due to higher production costs with respect to competitor metals like steel and aluminium. In this work the production of low-cost titanium alloys is attempted by combining the utilisation of a powder metallurgy process and cheap alloying elements (i.e. commercial 430 stainless steel powder optimised for the powder metallurgy industry). Low-cost titanium alloys are fabricated by blending elemental titanium with stainless steel. The behaviour of the powders as well as that of the sintered materials are analysed and compared to that of a master alloy addition Ti6Al4V alloy. The produced low-cost titanium alloys show comparable properties to both wrought and powder metallurgy titanium alloys and, therefore, they are proposed as an alternative to obtain structural component made out of titanium alloys.     

混合元素法PM钛合金的研究进展

混合元素法PM钛合金在汽车工业中具有广阔的应用前景，以显微组织及力学性能为基准，综述了混合元素法Ti-6Al-4V合金的研究进展，提出了今后研究走向的几点思考。     

Preparation of nano-structured pure rare-earth bulks by combining inert-gas condensation with SPS

A number of techniques have been developed to synthesize nanocrystalline bulk materials,including inert-gas condensation and consolidation,electrodeposition,severe plastic deformation,crystallization of amorphous solid,surface mechanical attrition,and powder metallurgy.However,it is hard to produce the bulk with controllable nanostructures,especially with the grain sizes controllable in a wide range below 100 nm.In the conventional powder metallurgy,due to the fact that rapid coarsening of the particles ...     

Novel processing and characterization of Cu/CNF nanocomposite for high thermal conductivity applications

Enhancing the thermal conductivity and reducing the thermal expansion for electronic packaging applications can be achieved by compositing carbon nanofibers in copper-matrices. Though achieving these optimal thermal properties is theoretically possible, such composites are currently not available due to many unresolved practical problems. Conventional compositing processes are incapable of obtaining the desired fiber distribution while controlling the fiber–matrix interfaces for effective heat and load transfers. In this paper, three different powder metallurgy based processes are presented; two based on conventional techniques and the third a relatively new method. The first method is basically the conventional powder metallurgy process. The second and the third methods are also powder metallurgy processes with different ways of modifying the surface of the fibers using either electroless coating or the novel salt decomposition method. It is shown that the salt decomposition method is capable of achieving the desired high thermal conductivity values while the thermal expansion values remain the same in all the three processes.     

载流摩擦用铜碳粉末冶金材料概述

铜碳载流摩擦材料运用广泛,随着科技的发展,对其要求越来越高。铜碳载流摩擦材料常用的成形工艺是粉末冶金工艺。铜碳粉末冶金载流摩擦材料是载流摩擦材料的重要研究领域。综述了铜碳粉末冶金载流摩擦材料的成分设计、碳增强体的表面处理及粉末冶金工艺的研究情况。并指出了铜碳载流摩擦材料的发展方向。     

Investigation on the Fe-based PM materials reinforced by In Situ synthesized TiC particulates

Atomized iron powder, carbonyl nickel powder, molybdenum powder, electrolytic copper powder, titanium powder and graphite powder were used as experimental materials; the titanium and graphite powders were added by an atomic ratio of Ti/C = 1:1 (the addition of Ti was 0 ～ 4 wt%) to Fe-2Ni-0.5Mo-2Cu-0.3C powder, and the iron-based powder metallurgy materials reinforced by in situ-synthesized TiC particulates were prepared by a powder metallurgy technique. The results show that the microstructures of sintered samples are mainly pearlite, ferrite and bainite. The amount of pearlite increases with the increase of Ti content, whereas the ferrite and bainite decrease. TiC particles sized 0.3 µm distribute mainly near the grain boundary of pearlite. The apparent hardness of sintered samples increases, while the sintered density and flexural strength decrease with the increase of Ti content. The fracture morphology of the sintered materials is brittle type.     

粉末高温合金的低周疲劳研究进展

参考了前人对粉末高温合金低周疲劳的研究成果,回顾了基于缺陷的裂纹萌生和扩展的研究情况,介绍了针对粉末高温合金的喷丸强化机理和作用,总结了几种寿命模型,其中修正Mitchell模型最适合粉末高温合金的寿命预测;得出了需加强粉末高温合金低周疲劳寿命模型及喷丸强化研究的结论。     

喷射成形技术及其在钢铁材料上的应用

喷射成形是近年来发展非常迅速的一种近终成形先进冶金工艺技术。与传统铸造工艺及粉末冶金工艺相比,喷射成形设备、工艺简单,能生产偏析小、晶粒细、致密度高的材料。喷射成形技术在铝基合金、铁基合金、高温合金、铜合金及复合材料等方面都得到了广泛的应用。主要介绍该技术的原理及其在钢铁材料方面的应用情况,并讨论了它在钢铁领域的发展趋势,指出喷射成形工艺是一种有望替代粉末冶金工艺生产高合金钢材及一些特殊钢材的崭新工艺。     

粉末冶金航空刹车材料磨屑的形成机理研究

研究了粉末冶金航空刹车材料在摩擦磨损过程中产生的各类磨屑,探讨了各类磨屑的形成机理,并分析了磨屑在粉末冶金航空刹车副监控中的功用。研究表明,粉末航空刹车材料在摩擦磨损过程中可产生四类磨屑：片状磨屑比较常见,是表面裂纹扩展形成的;块状磨屑主要是由内外裂纹传播造成的;条状磨屑主要是犁削作用造成的;球形磨屑包括实心和空心两种,形成温度较高。磨屑在航空刹车副监控中常用来作为无分解状态下材料的使用状态和安全性判据之一。     

Ti-Mo吸气材料的性能特征研究

为了研究Ti-Mo吸气材料的性能特征,采用粉末冶金工艺制备了Ti-Mo7.5%(质量比)吸气材料。研究了该材料的结构特征,在不同激活温度、不同工作温度下的吸氢性能特征,对比了该材料对H2,N2,CO的吸收性能。结果表明,当激活温度从500℃提高到750℃时,多孔结构材料的室温吸气性能逐渐提高,但继续提高激活温度到800℃,性能基本维持恒定;工作温度越高,吸气性能越好,但作为一个特殊的性能特征,该材料的工作温度最好不要超过300℃;该材料具有优良的吸收H2,N2,CO性能,室温条件下对H2的吸收性能优于对N2和CO的吸收性能。     

粉末注射成形技术及其在难熔钨合金等材料中的应用

粉末注射成形技术是将现代塑料注射成形技术引入粉末冶金领域而形成的一门近净形成形的新技术,有着巨大的发展前景。本文阐述了粉末注射成形技术及其特点,以及在难熔钨合金和硬质合金及其它材料中的应用。     

Effect of temperature on the strength and conductivity of a deformation processed Cu-20%Fe composite

The high temperature (22–600 °C) properties were evaluated for a Cu-20%Fe composite deformation processed from a powder metallurgy compact. The ultimate tensile strengths decreased with increasing temperature but were appreciably better than those of similarly processed Cu at temperatures up to 450 °C. At 600 °C, the strength of Cu-20%Fe was only slightly better than that of Cu as a result of the pronounced coarsening of the Fe filaments. However, at temperatures of 300 and 450 °C, the strength of Cu-20%Fe is about seven and six times greater, respectively, than that of Cu, as compared to about a two fold advantage at room temperature. Therefore, Cu-20%Fe composites made by deformation processing of powder metallurgy compacts have mechanical properties much superior to those of similarly processed Cu at room temperature and at temperatures up to 450 °C. The pronounced decrease in electrical conductivity of deformation processed Cu-20%Fe as compared to Cu is attributed to the appreciable dissolution of Fe into the Cu matrix which occurred during the fabrication of the starting compacts where temperatures up to 675 °C were used. While the powder metallurgy compacts used for the starting material for deformation processing in this study did not lead to a high conductivity composite, the powder metallurgy approach should still be a viable one if processing temperatures can be reduced further to prevent the dissolution of Fe into the Cu matrix.