粉末冶金法制备Mo-Cu合金及其性能的研究

Mo-Cu合金具有优良的导热、导电性能,与陶瓷基片良好匹配的热膨胀系数,被广泛用作热沉材料和电子封装材料。采用粉末冶金法制备了Mo-Cu合金材料,研究了烧结工艺对Mo-25Cu合金组织和性能的影响。结果表明,Mo-25Cu合金最佳烧结工艺为烧结温度1200℃和保温时间2h。合金的抗弯强度和硬度分别为554 MPa和56HRA,电阻率为3.7×10-8Ω·m,热导率为138 W·m-1·K-1。     

放电等离子烧结高合金工具钢的组织与性能

本文研究了放电等离子烧结（SPS）参数对HGSF01高合金工具钢致密度、硬度的影响规律,以及烧结态HGSF01高合金工具的显微组织、抗弯强度和摩擦磨损性能。结果表明：材料的致密度随烧结温度的升高和保温时间的延长呈上升趋势,而硬度则是先升高后降低;经SPS得到的材料晶粒细小,晶粒尺寸约为5μm,碳化物颗粒细小、均匀、弥散分布在基体上;烧结态材料的抗弯强度比电渣重熔态材料提高了一倍,耐磨性比电渣重熔态材料略有提高。     

烧结温度对WC-TiC-TaC-Co硬质合金性能的影响

采用不同温度下的低压烧结工艺制备WCTiC-TaC-Co硬质合金.结合金相显微镜、XRD及SEM等分析测试手段,研究了烧结温度对合金的微观组织和性能的影响.结果表明,低压烧结工艺下形成了WC+(WC-TiC-TaC)+γ三相合金;合金在1475℃下获得最优的综合性能,其密度、维氏硬度、抗弯强度及断裂韧性分别为:12.9...     

后续烧结对爆炸压实CuCr合金性能的影响

采用机械合金化工艺由Cu,Cr元素粉按重量比各半合成CuCr预合金粉,尔后爆炸压实工艺制坯,再加后续烧结制备了电触点材料CuCr合金,着重研究了后续烧结对爆炸实CuCr合金性能的影响,结果表明,真空烧结略微提高爆炸压实的CuCr合金的密度,而氢气烧结处理反而使其密度降低,真空烧结和氢气烧结都能显著降低CuCr合金硬度,而且氢气烧结降低得更明显,真空烧结和氢气烧结都显著提高CuCr合金的电导率,而且真空烧结提高更显著。     

烧结温度对Ni-Cr-Mo合金性能的影响

Ni-Cr-Mo合金经冷压成型于真空中以不同温度烧结.通过测定其相对密度、线收缩率、拉伸强度和硬度,研究了烧结温度对合金性能的影响.结果表明:当烧结温度不超过1330°C时,合金的相对密度、收缩率、拉伸强度和硬度随烧结温度的上升而缓慢增加;当温度上升到1360°C时,合金的这些性能指标急剧增加;当温度上升到1390°C时,烧结后的合金试样外形发生严重变形.     

激光诱导自蔓延烧结Al80-(Fe-Cr)20合金组织及性能研究

将铝粉和高碳铬铁粉末按80∶20原子比混合压制成坯,并对压坯进行激光诱导自蔓延烧结,利用金相显微镜、X射线衍射仪等设备,表征烧结合金显微组织及物相结构;采用硬度计、磨粒磨损机及电化学腐蚀仪等,表征烧结合金宏观性能。研究合金表层区、中层区和底层区组织及性能变化规律。结果表明:烧结合金物相主要有α-Al、Fe_2AlCr、Al_(13)Cr_2、Al_(13)Fe_4及Al_2O_3等,且烧结合金中层区富Al相Al_(13)Cr_2和Al_(13)Fe_4的含量最多,α-Al相含量最少。烧结合金中层区显微组织最细小均匀;硬度值最高,为817.5HV;磨损率最低,为0.08mg/mm~2;耐蚀性能最好,钝化电流最小,为115.8μA/cm~2。     

现代烧结技术在难熔金属材料中的应用

微波烧结、放电等离子体烧结、选择性激光烧结作为材料烧结致密化的新技术是活化烧结和快速烧结的有机结合,它们不仅具有升温速度快、烧结时间短、抑制晶粒长大、组织结构可控等独特的优势,而且还具有生产周期短、高效节能的巨大工业应用价值和前景,已成为当今材料领域的研究热点。难熔金属材料及其合金的烧结一直是难熔材料制备和烧结领域的难题,为了进一步探索难熔金属材料及其合金的新型烧结技术,探讨了微波烧结、放电等离子体烧结、选择性激光烧结在难熔金属材料及其合金制备中的应用现状,综述了其工作原理、特点及系统组成。     

纳米Fe-Cu粉末的制备及其对铁基压坯烧结行为的影响

以化学共沉淀法制备出纳米Fe-Cu复合粉末并对其性能进行了表征,分别以此纳米Fe-Cu粉末和电解Cu粉与铁粉进行混合获得铁基粉末混合料,成形压坯在H2气氛中不同温度下进行烧结,测定基加入不同形态Cu(合金）粉末铁基烧结坯的烧结性能,结果表明,在相同的Cu添加量及烧结条件下,添加纳米Fe-Cu粉末较加入电解Cu粉于铁基压坯中可以明显地提高压坯烧结后的密度,硬度及强度等性能,而添加纳米Fe-Cu粉末压坯在较低温度下烧结可达到添加电解Cu粉压坯在较高温度下烧结后的性能水平,说明采用纳米Fe-Cu粉末形式向铁基压坯中引入Cu有利于制备高密度,高性能的铁基烧结材料。     

微波烧结Fe-2Cu-0.6C合金的保温时间对组织与性能的影响

对微波烧结Fe-2Cu-0.6C粉末冶金材料进行了1150℃不同保温时间下的性能和显微组织研究,并与常规烧结试样进行了对比.结果表明:微波烧结保温时间由5min增加至15min,试样的各项性能达到最佳:密度为7.22g/cm3,硬度HRB为78,抗拉强度为416.8MPa,延伸率为5.5%;保温时间延长至20min对试样性能影响不大.微波烧结的性能较常规烧结高.通过金相显微分析表明:微波烧结有着良好的微观结构,即小的、近圆形且均匀分布的孔隙结构,从而也有利于获得细小的晶粒和高的致密度;微波烧结较常规烧结有着更多片状和粒状珠光体,能显著改善其性能.由断口分析可知,常规烧结样品属于脆性穿晶断裂,而微波烧结样品为脆性穿晶断裂和韧窝型的穿晶韧性断裂的混合型断裂.     

低压烧结温度对Ti(C,N)基金属陶瓷显微结构和力学性能的影响

采用低压烧结技术制备了Ti(C,N)基金属陶瓷,通过SEM与XRD观察了不同烧结温度下合金的显微结构和物相组成,并对比了合金的力学性能。结果表明,合金的显微结构以黑芯/白环结构为主,物相中仅存在(Ti、W、Mo、Ta)(C,N)和Ni/Co固溶体;随着烧结温度的提高,合金组织逐渐均匀化,抗弯强度和硬度呈现先增大后减小的趋势。1450℃时,合金综合性能最佳,抗弯强度为1774MPa,维氏硬度为1682MPa。     

Enhancement of work‐hardening behavior of dual phase steel by heat treatment

The work‐hardening response and mechanical properties of dual phase steels originated from different initial microstructures under low and high martensite volume fractions were investigated using a typical carbon‐manganese steel. The modified Crussard‐Jaoul analysis was used for studying the work‐hardening stages and the deformation behavior of ferrite and martensite. It was revealed that the initial martensitic microstructure before intercritical annealing is much better than the full annealed banded ferritic‐pearlitic and spheroidized microstructures in terms of work‐hardening capacity and strength‐ductility trade off. By increasing the amount of martensite, via intercritical annealing at higher temperatures, the ductility decreased but the tensile toughness of dual phase steels increased toward reaching the domain of extra‐advanced high‐strength steels due to the enhancement of work‐hardening rate.     

Surface Hardened Corrosion Resistant Rolling Element Bearings

Through hardening bearing steels with low alloy content are sometimes surface hardened by induction hardening to implement compressive residual stresses into the surface. This method is not regularly applied for steels with high alloy content especially not for applications in the aerospace and space industry. Here carburizing grades are used if compressive residual stresses are required. For a protection against corrosion chromium plating is applied or a through hardening chromium steel is chosen which offers no compressive residual stresses. This work deals with the evaluation of surface hardening and corrosion resistant bearing components. For this the steels AISI 440C and Cronidur30 were investigated.     

铜在高强度合金钢及焊缝金属中的作用

评述了铜对高强度低合金钢及焊缝性能的影响 ,详细阐述了铜在钢中的溶解特性和沉淀强化机理。并对今后的研究工作提出了建议     

Tensile and work hardening properties of low carbon dual phase strip steels at high strain rates

Abstract

As a result of their unique combination of strength and ductility dual phase steels play an important role in reducing weight in automobile components and improving crashworthiness. The purpose of this paper is to quantify the crash performance of dual phase steels, as defined by the influence of low and high strain deformation rates (0·001 s^-1 and 100 s^-1 respectively), on the tensile and work hardening properties of a range of commercial dual phase products. The objective is to establish whether dual phase steels maintain their desirable mechanical property characteristics of low yield strength, high tensile strength and high work hardening rates during plastic deformation under the application of a high strain rate loading. The results confirmed that the yield/proof strength and tensile strength increased with increasing volume fraction of second phase constituents and increasing strain rate. In particular, a dual phase steel with a microstructure consisting of a significant volume fraction (>10–15%) of additional second phase material (bainite) is shown to display superior energy absorption properties. However, this is accompanied by poor ductility and work hardening characteristics.     

新型纳米强化超高强度钢的研究与进展

随着资源、能源和环境压力日益加大,超高强度钢的开发越来越受到世界各国的极大重视。传统的超高强度钢大都是依赖提高碳含量或合金元素含量而获得较高强度的马氏体或贝氏体钢,此种钢存在着焊接性能差、塑韧性低、钢材尺寸受限制和成本昂贵等问题,严重制约了经济的快速发展和现代国防的建设,因此,开发综合性能良好、成本低廉的新型超高强度钢刻不容缓。结合当前纳米科技的发展,介绍了新型纳米强化超高强度钢的设计理念,阐述了以纳米相析出强化为主、多种强化方式结合的强韧化理论,并总结了纳米析出强化超高强度钢在合金设计和工艺优化等方面的初步研究进展,最后探讨了新型纳米强化超高强度钢亟待解决的问题。     

Effect of intercritical temperature on the strain hardening of dual-phase bainite/ferrite steel

Medium-carbon dual-phase bainite/ferrite steels with different bainite and carbide volume fractions were prepared via intercritical annealing and austempering. Bainite dominated the microstructure at high intercritical temperatures, and carbides and ferrite phase dominated at low temperatures. Carbides existed in two types, undissolved alloy–cementite and vanadium carbide. The ferrite grain size was reduced to 1.22?±?0.7 µm at 790°C. Modified Crussard–Jaoul (MC–J) model was used to analyse the strain hardening process, and the highest strain hardening rate was obtained at 755°C. The high carbide fraction at 755°C increased the ferrite dislocation density and enhanced the ferrite phase strength. The high dislocation density in ferrite and the small strength difference in bainite and ferrite enhanced the strain hardening rate at 755°C.     

Controllable fabrication of a carbide-containing FeCoCrNiMn high-entropy alloy: microstructure and mechanical properties

Previous studies have reported that high carbon contents in FeCoCrNiMn high-entropy alloys lead to carbides precipitating from the alloys. Typically, carbides are used to improve the strength of alloys but also lead to decreased ductility. However, the strength and ductility of alloys can be improved when carbides shape, size and distribution are carefully controlled. Therefore, a carbide-containing FeCoCrNiMn alloy with 2?at.-% carbon was prepared by arc melting, and its microstructure and mechanical properties were further tuned by cold rolling with subsequent annealing treatment. The yield strength and uniform elongation of the resultant alloy were excellent, reaching 581?MPa and 25%, respectively, due to the additive combination of various strengthening mechanisms, such as solid-solution hardening, grain-boundary hardening and precipitation hardening.     

轧制工艺对低碳中锰钢微观组织和力学行为的影响

目的 研究热轧和温轧两种轧制工艺对低碳中锰钢的微观组织演变和力学性能的影响规律,阐明两种轧制工艺对马氏体转变和应变硬化行为的影响.方法 通过对热轧和温轧两种轧制工艺得到的实验钢进行拉伸性能测试,分析温轧后实验钢强塑性同步提升的现象,通过EBSD数据分析,测量热轧和温轧实验钢中马氏体的转变量,并对两种轧制工艺拉伸后实验钢...     

Einsatzhärten mit Stickstoff für nichtrostende Wälzlager und Werkzeuge

Case hardening of stainless bearings and tools using nitrogen Case hardening of low alloy steels is widely used for bearings, tools, gear wheels etc. Carburizing of high alloy stainless steels, however, leads to the precipitation of carbides and lowers the corrosion resistance. This may be avoided by case hardening with nitrogen instead of carbon. Dissolved nitrogen increases the hardness, the corrosion resistance and the compressive residual stresses of the martensitic case. Secondary hardening during tempering allows for service temperatures up to about 350°C with only little loss of corrosion resistance. The new heat treatment, which is quite different from nitriding, may be applied e. g. to advanced bearings for aircraft or tools for processing aggressive polymers.     

New developments in carbon and alloy steels

Recent developments in carbon and alloy steels outlined in this paper include those pertaining to low-carbon mild steels, high-strength low-alloy (HSLA) steels, dual-phase steels, low-carbon bainitic steels, ultrahigh strength steels and ferritic stainless steels. The factors that improve the cold-forming characteristics of low carbon sheets and strips are outlined. The physical metallurgy principles governing the ferrite grain refinement in HSLA steels are discussed, pointing out how it can be achieved by the controlled rolling process. The importance of sulphide shape control in imparting the necessary through-thickness ductility in HSLA steels is discussed and the various methods available for inclusion shape control are outlined. Improved formability coupled with adequate strength characterizes the dualphase steels. Among the ultrahigh strength steels, two recent developments,viz. TRIP steels and maraging steels are outlined. It is pointed out how the improved formability of ferritic stainless steels is making them compete with the more expensive austenitic stainless steels. The scope for future developments in these steels is discussed at the end.