TiAl合金气雾化制粉及热等静压成形研究进展

概述了TiAl合金气雾化制粉及热等静压成形的主要研究成果。在TiAl合金粉末制备方面,重点介绍了气雾化制粉工艺、粉末粒度控制、粉末氧含量控制和粉末组织特征。针对热等静压技术,介绍了TiAl合金粉末热等静压致密化过程及机理,总结了采用热等静压近净成形工艺制备TiAl合金转捩片的研究成果。结合粉末冶金TiAl合金研究进展,提出了未来TiAl合金粉末制备及成形技术的发展方向。     

当代金属注射成形技术

一、前言 金属注射成形(Metal Injection Molding,简称MIM)是一种从塑料注射成形行业中引伸出来的新型粉末冶金近净成形技术,其基本工艺过程为:首先是选择符合MIM要求的金属粉末和粘结剂,然后在一定温度下采用适当的方法将粉末和粘结剂混合成均匀的注射成形喂料,经制粒后在注射成形机上注射成形,获得的成形坯经过脱脂处理后烧结致密化成为最终成品。 金属注射成形技术在制备具有复杂几何形     

烧结TiH_2粉末制备钛合金的工艺及组织EI北大核心CSCD

以TiH2粉末为原料,通过组元球磨混合、压制成形和烧结工艺制备钛合金。用扫描电镜对球磨过程TiH2粉末的粒度、形貌变化以及烧结CP-Ti,Ti-6Al-4V合金的组织形貌进行了观察;采用热重分析方法研究了TiH2粉末脱氢的特性;用热膨胀技术研究了TiH2,TiH2-Al-V两种粉末压坯的烧结致密化特性。结果表明:TiH2粉末经过球磨后迅速变细,其粒度随球磨时间的延长而减小,粉末形貌由原来的不规则形状逐渐变为等轴状;TiH2粉末在烧结过程的脱氢将使α-Ti产生强烈收缩、同时因脱氢后获得的新鲜钛表面所发生的快速粘接而使烧结体迅速致密、得到相对密度大于99%的烧结坯体;TiH2-Al-V粉末压坯在烧结时因为伴随着合金元素的溶解而使其烧结致密特性不如纯TiH2粉末压坯的好;TiH2粉末经过成型、烧结脱氢工艺可获得典型的等轴状纯钛组织,TiH2-Al-V粉末经过相同工艺可获得典型的层片状α+β钛合金组织、且合金元素分布均匀。     

粉末高速钢超固相线烧结制备耐磨摇臂镶块

为解决粉末高速钢成形和烧结困难的问题,提出了添加石墨粉末改善成形性,降低烧结温度和拓宽烧结窗口的实用方法.对粉末高速钢耐磨摇臂镶块的的成分、工艺、组织和性能进行了系统的试验研究.确定了较优的化学成分为M2+0.2%G,超固相线液相烧结(SLPS)工艺为1050℃×1 h+1200℃×1.5 h+1240℃×0.25 h.制备出符合性能要求的粉末冶金摇臂镶块,其密度≥8.0 g/cm3,硬度≥50HRC.研究表明采用液相烧结的粉末高速钢摇臂镶块具有优良的性能.     

粉末钛合金热等静压近净成形技术及发展现状

粉末钛合金热等静压(HIP)近净成形技术作为一种理想的钛合金构件制备工艺之一,可以通过整体近净成形产品来提高材料利用率,降低钛合金产品的生产成本和生产周期,因此越来越受到武器装备等军工领域的关注。自该工艺出现以来,材料学者从原材料粉末的制备、包套设计、近净成形过程到材料的后处理都做了系统的研究,以了解该工艺的技术原理和材料性能影响因素,进而获得更高性能的产品,并进一步降低生产成本。研究表明,原材料粉末和包套设计是影响粉末钛合金近净成形产品质量和成本最重要的两个因素。球形度高、流动性好的钛合金粉末具有好的填充性和高的松装密度,能增加产品的成形精度。与此同时,作为控制粉末冶金制品中组织结构、孔洞和杂质元素的关键因素,高质量钛合金粉末的使用还可以获得力学性能更加优异的产品,但此种粉末的价格较高,增加了粉末冶金的生产成本,所以高质量、低成本钛合金粉末的制备是钛合金粉末冶金未来发展的重要方向之一。包套作为钛合金HIP近净成形技术的主要成本构成之一,合适的材料选择和结构设计既可以提高产品的成形精度又可以改善产品的表面质量,而通过计算机仿真模拟技术来设计包套和模拟近净成形过程,可以进一步提高成形精度和降低构件的研发成本,因此计算机仿真模拟是钛合金HIP近净成形未来发展的重点。通过选择合适的原材料粉末、设计合理的成形包套以及精确控制的成形过程,目前HIP近净成形获得的钛合金构件显示出与锻件相当的力学性能,而成本相对铸锻件节约了1/3以上。近年来,粉末钛合金热等静压近净成形技术在国外的航空航天等军工领域都已经得到了广泛的应用,并显现出理想的减重和降低成本的效果;国内则主要以航天领域的应用为主,而对其疲劳性能的质疑是限制其在国内航空领域广泛应用的主要原因。本文对粉末钛合金HIP近净成形技术进行了全面综述,对工艺过程中的影响因素,粉末致密化过程、力学性能及其影响因素等分别进行了阐述,同时介绍了计算机仿真模拟技术在粉末钛合金HIP近净成形技术上的应用。最后对该技术在国内外的应用情况进行了简要总结,并展望了该技术未来的发展趋势。     

纳米晶钨基重合金粉末的注射成型与固相烧浇

采用高能球磨技术制备了90W-7Ni-3Fe(质量分数,%)纳米晶钨基重合金粉末,研究了该粉末的注射成型和烧结行为,并与传统混合粉末进行了比较.结果表明,机械球磨可以有效地增加粉末喂料的固体粉末含量,改善粉末料的均匀性,并可促进固相烧结的致密化.纳米粉末注射成形坯在1300～1450℃进行固相烧结后,可得到近全致密(＞99%),晶粒细(3～5μm)、拉伸强度高(≥1130MPa)和几乎无变形的重合金样品.     

纳米晶钨基重合金粉末的注射成型与固相烧结

采用高能球磨技术制备了９０Ｗ－７Ｎｉ－３Ｆｅ（质量分数,％）纳米晶钨基重合金粉末,研究了该粉末的注射成型和烧结行为,并与传统混合粉末进行了比较,结果表明,机械球磨可以有效地增加粉末喂料的固体粉末含量,改善粉末料的均匀性,并可促进团相烧结的致密化,纳米粉末注射成形坯在 １３００～１４５０℃进行固相烧结后,可得到近全致密（＞９９％）、晶粒细（３～５μｍ）、拉伸强度高（≥１１３０ＭＰａ）和几乎无变形的重合金样品     

活化烧结制备TiC-Ni金属陶瓷复合材料及其性能

采用球磨法制备TiC/Ni金属陶瓷复合材料粉末,粉末在3000kg/cm2压力下压制成形,在1340℃进行真空液相烧结.对活化粉末进行XRD分析和TEM分析,采用普通金相显微镜对烧结体的微观组织进行分析,用三点弯曲试验测试其抗弯强度,在硬度测试仪上测试其硬度.结果表明:TiC/Ni金属陶瓷复合材料可在1340℃进行烧结制备,球磨初期粉末烧结体的微观组织随着粉体球磨时间的延长逐渐得到改善;过分延长球磨时间,则由于粉末中引入大量的缺陷和严重加工硬化而导致粉末压缩性能下降,进而抑制了材料的烧结致密化能力,使得烧结体的孔隙率急剧上升,力学性能相应下降.     

金属粉末塑性变形致密化过程的试验研究

本文提出的金属粉末致密化工艺与传统的压实烧结致密;冷热等静压致密:粉末模锻的致密化工艺不同。它是采用粉末包套无烧结的大塑性变形的致密化方法,即粉末包套自由锻造工艺。通过对高速钢粉末包套自由锻工艺试验,证实此方法是切实可行的。本文重点研究了塑性变形致密化过程的基本规律。该致密化方法的主要特点是只要采用优质粉末和利用现行的锻压设备,就可生产出高性能的粉末金属材料和制件坯料,其工艺简便稳定,适于多品种小批量生产,有良好的经济效益。     

粉末冶金制备大块非晶合金研究进展

粉末冶金作为制备大块非晶合金的主要方法之一,与快速冷凝相比,该方法可以在更广的合金系、更宽的成分范围内制备出尺寸更大、形状复杂、近净成形的大块非晶合金材料,因此粉末冶金是一种极具前景的大块非晶合金的制备方法.简要介绍了粉末冶金制备大块非晶合金的基本过程,详细阐述了各种成形技术的特点、原理、优缺点以及制备大块非晶合金的研究进展,期望为非晶、纳米晶粉末的致密化研究和制备大块非晶合金提供技术指导.     

纳米ZrC粉末的制备研究

探讨了采用机械合金化结合高温烧结法,以氧化锆为锆源、炭黑为碳源、镁粉为还原剂制备ZrC超微粉的可行性,采用XRD、SEM对ZrC的成分和形貌进行了观察和分析,并对采用氧化物制备难熔相进行了热力学分析对比.球磨过程中原料粉末不断细化,有助于氧化物与还原剂的紧密结合;随后的烧结过程中,可降低ZrC的生成温度,与其伴生的MgO有助于抑制ZrC颗粒的生长.以ZrO2为锆源,利用机械合金化和高温烧结可得到纯度较高且粒度为纳米级的ZrC粉末.     

Development of robust processing routes for powder metallurgy high speed steels

Abstract

This paper reviews progress made in understanding the factors which control the supersolidus liquid phase sintering of high speed steel powders to full density. The correlation between alloy composition and sintering behaviour is discussed for a number of alloy systems. Realising that for complete densification it is necessary for sintering to take place in the liquid +γ+M₆C+MC (or MX) phase region, two approaches have been developed to extend this critical phase field. This enables a scientific development of alloys that are more robust to process variations than currently sintered high speed steels of standard (for wrought materials) compositions. The new alloy systems possess wider process or sintering windows and have lower optimum sintering temperatures. The first approach relies on computer aided alloy design: vacuum sintering windows extending to 30–40 K at temperatures of 1170–1200°C have been achieved for novel Fe–C–4Cr–14Mo(–8Co)systems. The second approach involves sintering vanadium enriched high speed steels (HSSs) in nitrogen rich atmospheres. Such processing promotes the formation of MX carbonitrides in place of the more massive MC carbides. The solidus is lowered and sintering windows of ～30 K at temperatures of 1140–1150°C have been achieved. Compared with wrought HSSs, directly sintered materials have uniform, coarser microstructures. The low levels of residual porosity achieved enable attainment of metal and wood cutting properties comparable to those achieved with wrought and hipped HSSs of similar compositions.     

粉末高速钢SLPS的研究进展

粉末高速钢的个关键参数,包括合金元素、烧结窗、C含量和C(TE)点,阐明了化学成分、烧结温度和烧结气氛对显微组织的影响,最后指出了粉末高速钢研究的发展方向.     

放电等离子烧结Ti-Al系金属间化合物

用机械合金化法(MA)制备了Ti-45% Al纳米晶合金粉末,并对其进行放电等离子烧结(SPS),烧结时间仅为5min.用D-maxIIA型X射线衍射仪、JEM-2000EX型透射电子显微镜对粉末和烧结块体的微观组织及机械性能进行了研究.研究表明:Ti和Al的粉末随着球磨时间的延长,粉末有明显的细化趋势,球磨5h即有非晶产生,球磨20h后得到接近完全非晶相;采用SPS烧结技术,在1200℃下能够制备出较高硬度的TiAl金属间化合物块体材料.     

Development of high performance powder metallurgy steels by high-energy milling

High-energy milling is considered to be one of the most efficient techniques for producing materials that have a well-controlled chemical composition and microstructural features that are difficult to obtain using other synthesis routes. In this study, the mechanical alloying technique (MA) was used to develop special powder metallurgy (PM) steels with two different types of properties. The use of this technique is essential for obtaining the target microstructure, which ensures the desired performance of the resulting material. Oxide dispersion strengthened (ODS) ferritic steels were produced using MA based on the prealloyed grade Fe–20Cr–5Al and Fe–14Cr–5Al–3 W steels with the addition of Ti and Y₂O₃ as reinforcements. The incorporation of Y₂O₃ enables a homogeneous dispersion of nano-oxides and nano-clusters in a submicron-grained structure that should enhance the mechanical properties up to 600 °C. In addition, the base alloying system, Fe–Cr–Al (Ti), should enable the development of protective oxide layers through high-temperature treatments, which improves the compatibility with the environment, avoids liquid–metal embrittlement and contributes to the increase of the mechanical response up to 600 °C. Furthermore, microalloyed powders can be obtained using MA and consolidated with a pressure-assisted sintering process in an attempt to control the final grain size, to achieve microalloyed steels, and to achieve an extraordinary balance of properties.     

Mo-8wt%Cu纳米复合粉末的制备和烧结

采用机械合金化法制备出Mo-8wt%Cu超细复合粉末,并对由该复合粉末所制得的压坯进行了液相烧结,利用SEM、XRD等分析手段对复合粉末的特性和烧结体的组织进行了表征和观察,实验结果表明,该方法制备的Mo-8wt%Cu超细复合粉末颗粒细小,平均粒径在300nm左右,高能球磨后的复合粉末由Mo-Cu过饱和固溶体相和Cu相组成,而且两相的晶粒度达到纳米级,其中Mo-Cu过饱和固溶体相的晶粒约为106nm,复合粉末具有很高的烧结特性,经高温烧结后合金致密度达到98.5%以上,而且金相组织分布均匀。     

机械合金化法合成金属间化合物NiAl粉末

由于NiAl基金属间化合物的一些优异性能,长期以来作为高温结构的候选材料而得到了广泛的关注。本文中用机械合金化法合成了NiAl金属间化合物粉末,详细介绍了球磨工艺,对NiAl金属间化合物粉末的形貌和物相进行表征。结果表明,金属Ni和Al的粉末在球磨机内仅球磨5h就可以使大部分金属粉末转化为NiAl金属间化合物,随着球磨时间的延长,金属间化合物有细化的趋势。     

Fatigue of sintered steels (Fe-1.5 Mo-3 Mn-0.7 C)

The powder metallurgy process is ideally suited to the mass production of structural parts of complicated shape and with tight tolerances without appreciable loss of material. Because of its unique attributes such as reducing weight and production cost, powder metallurgy has made very significant in roads as a substitution technology in automotive parts, such as cams and gears in this process, we can improve the mechanical properties such as fatigue resistance of PM materials by changing of manufacturing parameters, for example, density, sintering temperature, sintering time, etc. In this research, the fatigue behaviour of sintered steel (Fe-1.5 Mo-3 Mn-0.7 C) was investigated with varying of density and sintering temperature. The results showed that in this steel, increase of porosity plays an important role in the fatigue limit of specimens also with sintering at high temperature which results in more spherical pores, the fatigue strength was improved. In this research, SEM fractography was also used to determine the mechanism of fatigue fracture.     

Injection Molding of W-Ni-Fe Nanocomposite Powder Prepared by Mechanical Alloying

［1］R.M.German: Powder Injection Molding, 1990, MPIF,Princeton, NJ. ［2］R.M.German: Advances in Powder Metallurgy, 1991,4, 183. ［3］Xuanhui QU, Jinglian FAN, Yimin LI and Baiyun HUANG: Trans.of Nonferrous Metals Society of China, 2000, 10(2), 32. ［4］Jinglian FAN, Baiyun HUANG and Xuanhui QU:Trans. of Nonferrous Metals Society of China, 1999,9(1), 93. ［5］Xuanhui QU, Jinglian FAN, Yimin LI and Baiyun HUANG: Acta Metall. Sin. (English Letters), 2000,13(3), 917.     

Strengthening of ultrafine PM aluminium using nano-sized oxycarbonitride dispersoids

Composites consisting of ultrafine aluminium, mainly reinforced by in situ nano-sized oxycarbonitride dispersoids, were prepared by mechanical alloying followed by a simple press and sintering method. The mechanical alloying process was performed under atmospheres with different amounts of ammonia. Even when small amounts of ammonia were used, the gas was able to decompose at room temperature, with N incorporated into the aluminium powder. The sintered compact properties were strongly influenced by the amount of N incorporated into the powders during milling, with an almost linear trend for some of these properties.