铁基粉末冶金零件的电阻焊

本文以飞块座部件焊接为例阐述了铁基粉末冶金用凸焊法焊接的可行性，对各焊接规范参数与焊接强度的关系作了全面的分析，对焊接中相关问题作了说明，如预制焊点的制备、焊接结构的选择、被焊材料含碳量的选择、被焊材料的密度、被焊材料的清洁度、焊接工装的设计、焊接精度的保证等，在此基础上肯定了铁基粉末冶金是可以焊接的并能够获得较高的强度和精度。     

On enhancement of hypoeutectic aluminium–silicon powder metallurgy alloy

Abstract

Currently, there exists a considerable demand within the automotive industry for the development of aluminium–silicon alloys that can be processed through powder metallurgy (PM) technologies. As such, a study aimed at the development of a new hypoeutectic aluminium–silicon PM alloy (Al–6Si–4·5Cu–0·5Mg–0·2Sn) was recently undertaken. Although the preliminary data were encouraging, it was postulated that a refinement of the bulk alloy chemistry could yield additional gains. In the present work, the sintering response mechanical properties of this alloy were enhanced by making controlled adjustments in composition. The influence of the amount and raw powdered sources of copper, magnesium and tin were the principal variables investigated. Using XRD and metallographic examination, it was determined that a decrease in the copper content to 3·0 wt-% improved ductility significantly. Furthermore, the incorporation of magnesium as an elemental powder versus an Al–Mg master alloy improved sintering behaviour significantly, while tin additions up to 0·2 wt-% increased yield stress and hardness. The optimised alloy exhibited a threefold increase in ductility as well as a 25% gain in yield strength.

Présentement, il existe une grande demande dans l’industrie de l’automobile pour le développement d’alliages aluminium silicium qu’on peut obtenir par les techniques de métallurgie des poudres (PM). Ainsi, on a récemment entrepris une étude visant au développement d’un nouvel alliage hypoeutectique aluminium silicium (Al-6Si-4·5Cu-0·5Mg-0·2Sn) par PM. Bien que les données préliminaires soient encourageantes, on a postulé qu’un raffinement de la chimie de l’alliage brut pourrait produire des gains additionnels. Dans le présent travail, on a amélioré les propriétés mécaniques de la réponse au frittage de cet alliage en faisant des ajustements contrôlés de la composition. L’influence de la quantité et l’influence des sources de poudres brutes de cuivre, de magnésium et d’étain étaient les principales variables examinées. En utilisant la XRD et l’examen métallographique, on a déterminé qu’une diminution de la teneur en cuivre à une valeur de 3·0% en poids améliorait significativement la ductilité. De plus, l’incorporation du magnésium comme poudre élémentaire par rapport à un alliage maître d’Al-Mg améliorait significativement le comportement de frittage, alors que des additions d’étain jusqu’à 0·2% en poids augmentaient la limite élastique et la dureté. L’alliage optimisé exhibait une augmentation triple de la ductilité ainsi qu’un gain de 25% de la limite d’élasticité.     

On development of hypoeutectic aluminium–silicon powder metallurgy alloy

Abstract

Powder metallurgy allows for the rapid, automated and efficient production of many different types of automotive components. However, a drawback is the limited selection of readily available light alloy blends. Owing to the wide spread use of aluminium–silicon casting alloys for existing components it is logical to develop aluminium–silicon PM options. Therefore, an experimental hypoeutectic aluminium–silicon alloy was chosen for study and an optimum processing route developed. Tests were performed to determine the green strength and density as a function of compaction pressure. Sintering conditions were optimised based on sintered density, hardness and dimensional changes. Metallography, differential scanning calorimetry and energy dispersive X-ray spectroscopy analysis provided insight into post-sinter furnace cooling and heat treatment parameters. An appropriate T6 heat treatment was developed and samples were tested in tension. The alloy was able to achieve a high sintered density approaching 98% and a yield strength of 232 MPa under the T6 condition.     

On the oxidation resistance of a powder metallurgy nickel-based superalloy

Abstract

To evaluate the influence of reactive minor elements on oxidation resistance of a nickel-based superalloy, 0?5w/o Si, and/or 0?1w/o Y were added in various combinations to a quaternary powder metallurgy alloy that consisted of a ternary master alloy, Ni–12Cr–9Fe+6w/o Al (w/o). The processing included production of transverse rupture strength (TRS) bars by uniaxial pressing followed by sintering to 1300°C and Gleeble thermo-mechanical deformation to reduce porosity. Sectioned TRS bars were then oxidised (static) at 900°C in air for times up to 1000 h and the influence of the Si/Y additions on oxidation resistance was determined via a combination of weight gain data and microstructural examination. It was found that the addition of 0?5w/o Si to the quaternary Ni–Cr–Fe–Al powder metallurgy system provided a measureable improvement in oxidation resistance both in terms of thickness of oxide layer and in overall weight gain. Conversely, 0?1w/o Y provided little benefit when added with the Si and was shown to be detrimental in the absence of Si. Interestingly, little difference was noted in final microstructures. Specifically, variation in %γ′ between samples was minimal (58?3–61?7 v/o) and a distinct precipitate free zone was always present between the oxide and the γ+γ′ matrix.

Afin d’évaluer l’influence des oligoéléments réactifs sur la résistance à l’oxydation d’un superalliage à base de nickel, on a ajouté 0?5% en poids de Si et/ou 0?1% en poids d’Y en combinaisons variées à un alliage quaternaire de la métallurgie des poudres qui consistait en un alliage ternaire maître, Ni–12Cr–9Fe+6% en poids d’Al. Le traitement incluait la production de barres de résistance à la rupture transversale par pressage uniaxe, suivi par le frittage à 1300°C et par la déformation thermomécanique de Gleeble pour réduire la porosité. Les barres sectionnées de TRS étaient ensuite oxydées (en statique) à 900°C à l’air jusqu’à 1000 h et l’influence des additions de Si/Y sur la résistance à l’oxydation était déterminée par l’intermédiaire d’une combinaison de données de gain de poids et d’examen de la microstructure. On a trouvé que l’addition de 0?5% en poids de Si au système quaternaire Ni–Cr–Fe–Al améliorait de façon mesurable la résistance à l’oxydation, tant en termes de l’épaisseur de la couche d’oxyde que de son gain global en poids. Réciproquement, 0?1% en poids d’Y avait peu de bénéfices lorsque ajouté avec le Si et l’on a montré qu’il était nuisible en absence de Si. De façon intéressante, on notait peu de différence dans les microstructures finales. Spécifiquement, la variation entre les échantillons du% de γ′ était minime (58?3 à 61?7% en volume) et une zone distincte sans précipités était toujours présente entre l’oxyde et la matrice de γ+γ′.     

粉末冶金内涵百年演变

近代粉末冶金诞生迄今已届百年,在此其间,粉末冶金技术取得令人瞩目的发展,其内涵随之拓展和延伸.粉末冶金技术不断提供各种关键性材料和制品,在人类经历的4次技术革命所形成的全部产业中均有应用,甚至促使某些工业分支产生重大变革,引发相关技术的更新换代.粉末冶金技术属于先进的材料制备和成形加工技术.现代粉末冶金技术凭借发展高性能金属材料和复合材料的卓越成果,将金属材料科学与工程提高到新的高度.笔者试图通过分析粉末冶金百年来的重大成就,认识其内涵的演变.     

粉末冶金法制备AZ91镁合金的组织及热性能

采用粉末冶金方法制备了AZ91镁合金,研究了烧结温度对合金的致密度和热导率的影响规律,并对烧结样品的物相和显微组织进行了分析.研究发现,AZ91镁合金的最佳烧结温度为610℃,致密度可以达到97.4%,实验条件下所获得的最高热导率可达到63.1W·m^-1·K^-1.X射线衍射和扫描电子显微镜结果分析表明,烧结合金组织主要由α-Mg固溶体和β-Mg₁₇Al₁₂相两相组成,其中β-Mg₁₇Al₁₂相表现出离异共晶β相和非连续析出β相两种主要存在形态.     

粉末冶金发展状况

随着全球工业化的快速发展,粉末冶金技术已广泛应用到各个领域。粉末冶金具有原材料利用率高,制造成本低,废料损耗少,材料综合性能好,产品尺寸精度高且稳定等优点。此外,粉末冶金可用于制备传统方法无法制备的材料和难以加工的零件,因此,研究粉末冶金的发展越来越具有重要的意义。粉末冶金产品已能满足现中国国民经济建设的基本需求,更重要的是粉末冶金科学为中国的国防建设提供了新材料,为重点军事工程建设做出了重要贡献。主要论述了粉末冶金演变历史,北美、欧洲、日本、中国及其他国家粉末冶金产业的发展状况,粉末冶金新技术和新材料的发展及应用;并分析了中国在此行业中存在的不足;针对中国粉末冶金产业和技术发展,提出几点建议。     

粉末冶金法制备CrFeNiCuMoCo高熵合金的组织与性能

利用粉末冶金法制备CrFeNiCuMoCo高熵合金,用带有能谱的扫描电子显微镜(SEM/EDS)、X射线衍射仪、显微/维氏硬度计、电化学工作站、材料试验机等对CrFeNiCuMoCo高熵合金组织结构进行分析并测试其硬度、耐蚀性和压缩性能.结果表明:CrFeNiCuMoCo高熵合金组织形貌简单;物相主要由FCC和BCC两相组成,Mo元素和Cu元素在合金中存在偏析现象;合金的耐蚀性能优异,与304不锈钢相比,自腐蚀电流密度减小1个数量级;组元间原子半径的差异导致较大的晶格畸变,阻碍位错的运动,使得固溶强化效应增强;Mo元素起到细化晶粒作用,使该合金具有较高的硬度和抗压强度,合金硬度为485 HV,抗压强度约为1 385MPa;断裂类型为脆性解理断裂.     

Cu含量对粉末冶金AlCuMgSi合金性能的影响

用金属Al粉、Cu粉、Mg粉和Al-Si粉为原料,采用液相烧结法制备Cu含量(质量分数,下同)为0~6.0%的AlCuMgSi合金,研究Cu含量对AlCuMgSi合金组织与力学性能的影响,采用国外的Al-3.8Cu-1.0Mg-0.75Si粉末为原料,用相同的工艺制备Al-3.8Cu-1.0Mg-0.75Si合金作为性能对比试样。结果表明:在铝合金中添加Cu元素后,组织致密均匀,密度、硬度和抗拉强度等均显著提高。当Cu含量为4.0%时材料的性能最优,密度为2.72g/cm3,致密度达到98.9%,硬度HB为64,抗拉强度为207MPa,伸长率为2.1%,与采用国外的Al-3.8Cu-1.0Mg-0.75Si粉末制备的材料性能相当。     

粉末冶金表面滚压致密化链轮工艺的开发

粉末冶金零件以其近终成形、成本低、效率高的优势在汽车行业得到了广泛的应用。但是由于粉末冶金零件表面存在大量的空隙,严重影响了其强度、硬度和耐磨性等性能,使其在某些重载工况中达不到要求,从而限制了其在汽车行业的应用。本文论述了一种粉末冶滚压金表面致密化链轮工艺,通过将粉末冶金技术和滚压致密化技术结合在一起,减小粉末冶金零件表面的空隙,在零件表面形成一层均匀的致密层,而提高其强度、硬度和耐磨性等性能,从而扩大其应用范围。     

Contemporary powder metallurgy: Achievements and problems

The world’s production and use of powders is discussed. Factors that influence the development of powder metallurgy and measures that will promote wider application of powder products are considered. Estimates for the development of powder metallurgy up to 2011 and some developments that won awards of the Metal Powder International Federation (MPIF) in 2005 are presented. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 3–4 (454), pp. 122–126, 2007.     

Joining processes for powder metallurgy parts: a review

Abstract

Powder metallurgy (PM) processes have high productivity and are ideal for making near net-shape parts of complex geometries from a range of materials, which maximises material utilisation, and minimises or eliminates secondary operations such as machining. The secondary operations that are common for components made via liquid metal processing may result in additional manufacturing steps with substantial cost and waste implications. Despite this obvious advantage of PM components, including powder metal injection moulded (MIM) parts, the joining of sintered powder materials has been associated with difficulties related to their inherent characteristics, such as porosity, contamination and inclusions, at levels which tend to influence the properties of a welded joint. A critical review of the current state of the art of welding PM components is presented. The intention is to identify preferred joining processes and identify technology gaps in joining of PM parts, in terms of initial processing and attendant materials issues, with an emphasis on offering solutions to welding problems. Brazing, diffusion bonding and shrink fitting are briefly considered in addition to welding.     

粉末冶金铝合金烧结致密化过程

以纯Al粉为主要原料,添加Cu单质粉末以及Al-Mg、Al-Si中间合金粉,利用粉末冶金压制烧结方法制备出相对密度98%以上的Al-Mg-Si-Cu系铝合金.研究表明,烧结致密化过程主要分为3个阶段:初始阶段(室温~460℃),坯体内首先形成Al-Mg合金液相,液相中的Mg原子分别扩散至Al或Al-Si粉末中,与Al₂O₃反应并破除氧化膜,形成Al-Mg-O等化合物;同时,Al-Cu发生互扩散,形成Al₂Cu等金属间化合物.第二阶段(460~560℃),Al-Cu、Al-Si液相快速填充颗粒缝隙或孔洞,坯体相对密度显著提高;此阶段的致密化机制主要是毛细管力引起的颗粒重排,以及溶解析出导致的晶界平直化.第三阶段(560~600℃),随温度的升高,液相润湿性提高,晶粒快速长大,使得大尺寸孔洞填充,烧结体基本实现全致密,此阶段的致密化主要由填隙机制控制.在铝合金晶界处发现了MgAl₂O₄和MgAlCuO氧化物的存在,推测Al粉表面氧化膜的破除机制与合金成分有关.由于Al-Cu液相在Al表面的润湿速率远高于AlN的生长速率,因为在本体系中未发现AlN的存在.     

Pb在快凝Al-Si基减摩材料中的作用

研究AJ-Si基减摩材料中Pb含量与材料力学性能和摩擦磨损特性的关系，分析了材料的微观组织，结果表明，Pb能够提高减摩性能，改善材料的摩擦磨损特性。     

粉末冶金Ti-1.5Fe-2.25Mo钛合金的热变形本构方程

采用元素粉末法制备Ti-1.5Fe-2.25Mo合金,在Thermec-Master Z热模拟机上对该合金进行等温压缩试验。实验温度为650～900℃,变形速率0.01～10 s-1。以经典的双曲正弦形式的模型为基础,对热模拟真应力-真应变曲线进行计算和分析,建立粉末冶金Ti-1.5Fe-2.25Mo合金高温本构方程。研究表明,β相区等温压缩时,合金流变应力快速达到峰值然后进入稳态流变变形阶段,应力指数n=4.24,应变激活能Q=378.01 kJ/mol。而在α+β两相区等温压缩时,合金在较低应变速率(≤0.1 s-1)下,曲线经过应力峰后出现不同程度的加工软化现象;在应变速率≥1 s-1条件下,呈现出1种稳态变形,热变形的应力指数n=6.77,应变激活能Q=257.73 kJ/mol。所得结果为粉末冶金钛合金锻造成形提供了一定的理论依据。     

稀土La对粉末冶金钛合金组织和力学性能的影响

在Ti-Fe-Mo合金中以LaH2和LaB6两种形式引入稀土La,制备含La的粉末冶金钛合金,研究La的添加量对钛合金烧结行为以及组织与力学性能的影响,探讨合金中La的存在形式及其在烧结过程中的作用机理。结果表明,钛合金相对密度随LaH2添加量(质量分数)的增加而升高,当LaH2的添加量达到0.6%后,钛合金的相对密度不再发生明显变化;但随着LaB6添加量的增加先升高后降低,在LaB6添加量为0.15%时出现峰值。添加LaH2的钛合金中,稀土元素主要以La2O3颗粒的形式存在,随La含量增加,颗粒发生长大;而在添加LaB6的合金中,烧结反应产物主要是纤维状的TiB、具有规则外形的La2O3颗粒以及含Ti和O的富La絮状颗粒。随LaH2和LaB6的添加量增加,合金的室温抗拉强度和伸长率均先升高后降低。LaH2的添加量达到0.6%时出现强度峰值,添加量达到0.3%时出现伸长率的峰值;而LaB6的添加量达到0.15%时抗拉强度和伸长率均出现峰值。     

Density evaluation of powder metallurgy compacts using in situ X-ray radiography

Abstract

The measurement of density in porous materials during mass production process is one of the most important factors in industry. The existing methods for measuring density such as hydrostatic weighing and microscopic examinations have some limitations and some inherent problems associated with them. Recently, processes based on radiography have emerged. This paper deals with the in situ measurement of density of porous materials using X-ray techniques. For this purpose, experiments have been performed at various density levels of powder metallurgy compacts. In situ X-ray radiography was then carried out on samples. A correlation has been made between the film density of radiographic film and the surface density of the compacts. A mathematical relationship was derived between the absorbed X-ray, the film intensity and the compact density. The comparison of values of the experimental data and mathematical relationship reveals 1·6% average discrepancies.     

Ultrasound-assisted drilling of copper and pre-alloyed powder metallurgy steels

Powder metallurgy (PM) steel components are generally considered ‘difficult’ to machine when compared with their wrought counterparts. Thus, efficient and cost effective machining strategies have to be devised. This paper summarises the results obtained by utilising ultrasounds to improve the machining behaviour of copper and sinter-hardenable PM steels. The effect of ultrasonic assisted drilling on tool life with and without admixed MnS is discussed as well. These results are compared to conventional machining methods and show that, for FC-0208 PM copper steels, tool life is increased by 180% and can be several thousand per cents higher if used in combination with admixed MnS. At the same time, the use of ultrasounds permitted to increase productivity by 86%, owing to the possibility of using higher feed rates. Similarly, for FLNC-4408 pre-alloyed PM steels, tool life was increased by 130% and productivity was 60% higher than when no ultrasounds were used.     

微细Cr-Fe合金粉对粉末冶金钢组织与性能的影响

在Fe-0.5Mo预合金粉末中加入平均粒径为4.65μm的Fe Cr55C600高碳Cr-Fe合金粉末,于1 200℃,采用烧结硬化工艺制备Fe-Cr-Mo粉末冶金合金钢。结果表明:随着Cr-Fe合金粉末量的增加,合金烧结试样的硬度增加,强度增加,合金的显微组织以贝氏体为主。当添加微细颗粒的Cr-Fe合金粉末,使Cr质量分数达到1.7%时,合金烧结试样的综合性能达到最优,抗拉强度为1 210 MPa,硬度为30 HRC,显微组织主要为细小的下贝氏体和马氏体,此时合金中Cr/C质量比约为1.54。     

Integrated product and process development of powder metallurgy hub for automotive clutch

ABSTRACT

With the development of new near-net shape forming process, powder metallurgy has been widely used in the manufacturing of automobiles and their parts. This paper proposes a novel integrated product and process development (IPPD) methodology for clutch hub via powder metallurgy, and the manufacturing-oriented design is carried out. The three-dimensional model of the hub is established and simulated by ANSYS. A Fe–C-Cu–Ni–Mo material system for the powder metallurgy clutch hub is created, and a corresponding process scheme is developed. Through material metallographic analysis and experimental verification, the results show that the powder metallurgy clutch hub developed by the IPPD technology can meet the requirements of automotive applications in terms of strength and durability. The IPPD methodology and new near-net shape forming technology can be widely applied to automotive parts such as gear flanges.