球磨时间对W-30Cu复合粉末中W晶粒度及烧结致密化行为的影响

研究了高能球磨时间对W-30Cu复合粉末晶粒度及烧结行为的影响.结果表明,当球磨时间从16h提高到33h时,复合粉的晶粒度由25nm减小到10nm,并发生机械合金化现象;在温度为1275℃烧结60min,经18h高能球磨的复合粉末烧结就可以达到全致密.研究还发现,高能球磨W-30Cu复合粉末具有较好的热稳定性,经950℃退火处理,晶粒尺寸没有发生异常长大现象;经烧结材料的硬度明显高于普通的W-30Cu复合材料.经1 275℃烧结30 min后合金其晶粒尺寸在300～550 nm.     

球磨工艺对Co-Cr-W合金粉末性能的影响

采用球磨法制备Co-Cr-W合金粉末,研究球磨时间(0,5,10,15,20,25 h)对该合金粉末性能的影响。利用XRD和SEM等方法对不同球磨时间合金粉末的晶粒尺寸、微观应变和微观形貌进行分析,并测定烧结后合金的密度、硬度和抗弯强度变化。结果表明:在球磨转速为300 r/min,球料质量比为10:1的条件下,在球磨初期粉末颗粒明显细化,粉末出现片状形貌;随球磨时间继续增加,粉末粒度先增大后减小,晶粒尺寸不断减小,并在球磨20 h后这种变化趋于平稳。随球磨时间延长,微观应变和合金硬度也明显提高。     

球磨时间对ZrC-FeCrAl粉末特性及合金力学性能的影响

为进一步提高FeCrAl合金的力学性能，采用机械球磨和放电等离子烧结（spark plasma sintering,SPS）技术制备了纳米ZrC颗粒弥散强化FeCrAl(ZrC-FeCrAl)合金，通过扫描电子显微镜（scanning electron microscope,SEM）、透射电子显微镜（transmission electron microscope,TEM）、氧含量分析、粒度分析、X射线衍射（X-ray diffraction,XRD）分析、硬度测试、拉伸性能测试等方法，研究了球磨时间对粉末特性及合金力学性能的影响。结果表明，延长球磨时间有利于粉末颗粒细化，但氧含量过高会导致烧结材料力学性能恶化。当球磨时间为30 h时，粉末平均粒径为72.88μm，氧含量最低，为0.14%（质量分数）；球磨30 h的ZrC-FeCrAl合金具有较好的力学性能，其放电等离子烧结样品的极限抗拉强度、延伸率和维氏硬度分别为1046 MPa、12.1%和HV 349.9。结果证实，添加纳米ZrC可以有效强化FeCrAl合金，为其在耐事故燃料包壳材料中的应用提供了数据支撑。     

纳米氧化物弥散强化铁素体合金的制备

以氢化钛、氢化钇、氧化铁和Fe-Cr-W气雾化预合金粉末为原料,通过球磨得到Fe-14Cr-3W-0.5Ti-0.31Y-0.22O合金粉末,经压制、烧结制备出纳米氧化物弥散强化铁素体合金。采用激光粒度仪、XRD、SEM和TEM表征粉末和预烧坯的显微结构。研究结果表明,粉末粒径随球磨时间增加呈先增大后下降,冷焊主导变形机制向破碎主导机制的转变点发生在球磨24h。XRD谱显示氢化物和氧化铁均已溶解于铁素体基体,48h球磨粉末没有发现第二相粒子的存在。球磨48h后过饱和的Y、Ti、O铁素体固溶体在随后的加热过程中析出尺寸为5nm左右的弥散相颗粒,这种第二相粒子非常稳定,即使1200℃保温8h仍不发生明显长大,起着强烈钉扎位错的作用。     

超细晶钛铝基合金的高温压缩性能研究

采用高能球磨及真空热压烧结的方法制备超细晶/纳米晶双相γ-TiAl基合金,将名义成分为Ti-45Al-7Nb(%,原子分数)的混合粉末经40 h高能球磨后,粉末达到纳米级。球磨后的混合粉末经真空热压烧结(烧结温度1200℃,压力30 MPa,保温保压1 h)。研究该合金在温度为1000,1050和1100℃,应变速率为1×10^-4,1×10^-3和1×10^-2s^-1 3个变形速率条件下的高温压缩组织、流变行为和本构关系。研究结果表明：经过高能球磨及真空热压烧结原位合成的组织为超细晶α₂-Ti₃Al及γ-TiAl双相等轴状合金组织,晶粒尺寸小于5μm。合金为热敏感型和应变速率敏感型合金,合金压缩流变应力随应变速率的降低和温度的升高而下降。高温热压缩时,合金组织由规整等轴状被压变形为长条形,形变主要发生在γ-TiAl相中,晶界和γ相晶内可见位错及孪晶,孪晶及位错为主要的形变机制。在1000,1050和1100℃,1×10^-4,1×10     

高能球磨对锆钛酸铅镧粉末性能的影响

以Pb3O4、ZrO2、La2O3和TiO2为原料,通过高能球磨制备锆钛酸铅镧（Pb0.92La0.08（Zr0.65Ti0.35）0.98O3,简称PLZT）粉末,并研究球磨工艺对合成粉末物相、颗粒形貌及烧结性能的影响,以期优化球磨工艺,加速开发PLZT陶瓷的低温烧结致密化新工艺。结果表明：随球磨转速提高,粉末形貌由层片叠加状转变为不规则小颗粒状。在160r／min、58h条件下球磨后粉末没有合成PLZT相,粉末体系处于部分非晶化状态;而在400r／min、16h条件下球磨后粉末中出现钙钛矿结构的PLZT相。合金化的球磨（400r／min,58h）粉末在1100℃烧结后密度为6．29g／cm^3,而在同样烧结条件下,未合金化的球磨（160r／min,58h）粉末烧结后密度达到7．02g／cm^3。借助MAGINI能量模型及相关球磨理论,分析球磨工艺参数对该粉末体系物相、形貌及粉末烧结性能的影响。     

高能球磨工艺对钨铜复合材料组织的影响

采用机械合金化方法将W-15%Cu混合粉末在行星式高能球磨机中球磨,研究了不同球磨时间对钨铜复合材料组织的影响,利用XRD及SEM分析了不同球磨时间的粉末和烧结后的样品,结果表明,随着球磨时间的延长,粉末的晶粒尺寸不断减小,烧结后样品的相对密度不断提高.球磨60h的混合粉末在1350℃烧结后的相对密度达到98.8%.     

高能球磨及烧结制备含氮不锈钢的研究

在流动氮气氛下,采用高能球磨法制备出了含氮不锈钢粉末,随后利用冷压及烧结工艺获得了含氮不锈钢材料,研究了粉末随球磨时间的增加其物相、粒度、形貌、氮含量的变化及烧结体的显微组织.结果表明:随球磨时间的延长,粉末不断细化,氮含量也呈增加趋势,但球磨超过4h后,粉末不再发生细化,氮含量的增长也变得极其缓慢.烧结体为奥氏体-铁素体双相组织,相对密度达到97%,最终氮含量为(质量分数)0.27%,其拉伸性能优于高压熔炼法制得的含氮不锈钢.     

球磨对制备钨钛封垫的原料粉末的影响

通过粉末冶金方法制备适合于高压封垫材料的W-Ti合金,其中选择W以及Ti或TiH_2为原始粉末,采用行星球磨机球磨,然后经成形和真空烧结得到最终W-Ti合金。利用激光粒度仪、X射线衍射仪(XRD)、扫描电镜(SEM)、能谱仪(EDS)等手段,研究W-Ti和W-TiH_2体系在球磨过程中粉末的形貌、粒度、粒度分布、合金化程度及其对合金组织的影响。结果表明,两个体系混合粉末球磨12.0 h后,W-TiH_2混合粉末的中位径达到1.31μm,约为W-Ti混合粉末的中位径(13.01μm)的10%,因为细小而硬的W粉颗粒促进粗而脆的TiH_2粉末的破碎,使整体粉末粒度变细,呈等轴颗粒状,但对粗而软的Ti粉的破碎没有作用,反而嵌在片状Ti粉上使整体粒度变粗;W-TiH_2混合粉末球磨12.0 h后,中位径由原始的10.87μm急剧降低到1.31μm,再延长球磨时间中位径变化缓慢;随着球磨时间延长到22.0 h,W-TiH_2混合粉末中TiH_2分解与W形成Ti_xW_(1-x)固溶体,同时TiH_2粉与Ti_xW_(1-x)固溶体向纳米级细化,烧结后更容易得到均匀细小的合金组织。     

TiH_2/SiC粉末搅拌球磨及真空烧结制备超细晶钛

对TiH2/SiC混合粉末进行搅拌球磨,然后通过压制与真空烧结制备金属钛,研究球料比、球磨转速及球磨时间等工艺参数对球磨粉末粒度与显微组织的影响,并通过对烧结钛的组织观察与分析,研究此工艺制备超细晶钛的可行性。结果表明:适度提高转速或延长球磨时间有利于TiH2粉末的高效细化并提高粉末粒度分布的集中度;在球磨过程中没有发现TiH2分解和形成其他新相的现象;随球磨粉末的中位径D50和粒度跨度值ψ减小,烧结金属钛的晶粒度变得更小、更均匀。在600r/min转速下搅拌球磨8h后的TiH2/SiC粉末,在1050℃/3h条件下高真空烧结后得到平均晶粒度在5μm以下的超细晶钛。     

Mo_5Si_3-Al_2O_3复合材料的制备及抗氧化性能研究

采用机械化学还原法结合热压烧结制备了Mo_5Si_3-Al_2O_3复合材料,并对复合材料在600℃下的氧化行为进行了研究。结果表明:以MoO_3粉、Mo粉、Si粉和Al粉为原料,机械球磨10h,可获得具有纳米晶结构的Mo_5Si_3-Al_2O_3复合粉体;相比纯Mo5Si3试样,Mo_5Si_3-Al_2O_3复合材料的烧结相对密度和硬度提高,分别达97.2%和1350HV;Al_2O_3的引入可有效防止Mo_5Si_3的低温"粉化"现象,使Mo_5Si_3-Al_2O_3复合材料的抗氧化性明显提高,其氧化动力学曲线呈近似抛物线规律。     

An analysis of the microstructure of rapidly solidified Al-8 wt pct Fe powder

Rapidly solidified powders of Al-8 wt pct Fe exhibit four distinct microstructures with increasing particle diameter in the size range of 5 μm to 45 μm: microcellular α-Al; cellular α-Al; a-Al + Al₆Fe eutectic; and Al₃Fe primary intermetallic structure. Small powder particles (~10 μm or less) undercool significantly prior to solidification and typically exhibit a two-zone microcellular-cellular structure in individual powder particles. In the two-zone microstructure, there is a transition from solidification dominated by internal heat flow during recalescence with high growth rates (microcellular) to solidification dominated by external heat flow and slower growth rates (cellular). The origin of the two-zone microstructure from an initially cellular or dendritic structure is interpreted on the basis of growth controlled primarily by solute redistribution. Larger particles experience little or no initial undercooling prior to solidification and do not exhibit the two-zone structure. The larger particles contain cellular, eutectic, or primary intermetallic structures that are consistent with growth rates controlled by heat extraction through the particle surface (external heat flow).     

粉末热锻制备9Cr-ODS钢的微观组织和力学性能研究

摘要：ODS钢因其优异的高温力学性能和抗辐照能力被认为是新一代核反应堆最具潜力的结构材料之一。在机械合金化后,通过粉末热锻成型的方法制备了一种低活化9Cr-ODS钢。采用SEM、XRD、TEM及拉伸实验等研究了粉末形貌和粒度随球磨时间的变化规律,以及热处理后9Cr-ODS钢的微观组织及力学性能。实验结果表明,球磨至50 h后,粉末的粒度、晶粒尺寸和晶格畸变趋于稳态。热处理后的9Cr ODS钢成功获得了具有高密度位错的回火马氏体组织,晶粒细小,析出相为M23C6碳化物及Y-Ti-O型氧化物。氧化物颗粒的平均直径为10.2nm,数密度约为1.3×1022m-3。粉末热锻成型的9Cr-ODS钢的致密度达到了99.4%,并具有优良的强塑性,其室温抗拉强度和屈服强度分别为910MPa和750MPa,700℃时分别为200MPa和160MPa。     

Effect of distribution of B4C on the mechanical behaviour of Al-6061/B4C composite

In this work, the effect of mixing parameters on the distribution of B₄C in 6061-Al alloy and its correlation with mechanical behaviour was studied. 6061-Al alloy powder was mixed with 10 mass-% B₄C powder in a ball mill and powder rotator mixer by varying mixing time from 1 to 5?h. Mixing was performed in both wet and dry conditions in a ball mill while only dry condition was used in the powder rotator mixer. The green compacts were sintered at 630°C. The quadrat method was used to quantify the distribution of B₄C particles in the microstructures of sintered Al/B₄C composite. The results showed that the distribution was improved with mixing time but the density, hardness and compression strength of Al/B₄C composites were reduced with time during ball milling. On the other hand, the distribution of reinforcement, density, hardness and compressive strength of Al/B₄C composites was improved with mixing time in the powder rotator mixer.     

机械合金化制备Fe-Co系非晶合金

在高纯氩气保护下采用高能球磨法对原子组成为Fe44Co44Zr3.5Nb3.5B4Cu1的混合粉末进行机械合金化(MA)实验,成功地制取了非晶合金粉末.利用X射线衍射(XRD)、扫描电镜(SEM)、差热分析(DTA)对其进行测试,结果表明:Fe-Co系的混合粉末在MA过程中,通过原子之间的相互固溶、扩散可形成非晶态.此非晶合金的形成是晶粒细化、球磨过程中的缺陷、应力和致密堆垛结构等多种因素综合作用的结果,这与机械合金化的合成机理之一的扩散型机制相吻合.用非晶化的热力学条件判据和动力学条件判据对此合金进行计算,其结果也表明此合金已非晶化.     

Fe-C-Ti机械合金化粉末的电子显微试样制备及分析

论述了用扫描电镜和透射电镜研究Ｆｅ－Ｃ－Ｔｉ机械合金化粉末的制样方法，分析了该合金粉末的形态和组织结构。结果指出，合金粉末的尺寸随球磨时间增加先增大后减小，其形态由球形先变为纺锤形，后又成为球形。将最终得到的复合粉末进行真空热处理，ＴｉＣ弥散析出，而且层间界面处的ＴｉＣ尺寸较大。     

Extrusion, Properties, and Failure of Spray-Formed Hypereutectic Al-Si Alloys Based on the Optimization of Fe-Bearing Phase

Based on the densification of the spray-formed hypereutectic Al-Si (hyper-AS) alloys, the microstructural evolution, mechanical properties, as well as the failure are studied in this investigation. The appropriate process and parameters for the densification of the deposits are gained from the thermomechanical simulation. Besides of the spray-formed Al-25Si-5Fe-3Cu (3C) alloy, the microstructures of other spray-formed alloys with Mn/Cr addition are stable without coarsening of the refined α-Al(Fe,TM)Si (TM = Mn/Cr/(Mn+Cr)) particles, which can improve the heat resistance. Especially, a great number of the submicrosized α-Al(Fe,TM)Si phases are observed in the hot-extruded TM-containing alloys. The critical ranges of the major parameter TM/Fe mass ratios that can affect the formation of the α-Al(Fe,TM)Si phases in the cast or spray-formed hyper-AS alloys are severally determined. The structure and lattice constant of the refined α-Al(Fe,TM)Si phases also are characterized. The mechanical properties of the current extruded hyper-AS alloys at room or elevated temperatures are close to or higher than some commercial alloys or other published results. Therefore, the hyper-AS alloys can be proposed as new lightweight, heat-resistant, and high-strength alloys, which can be used in the complex working conditions, such as advanced engine systems. The main reason for the enhanced properties would be the formation of a large quantity of microsized/submicrosized α-Al(Fe,TM)Si phases and abundant dislocations, which can greatly reinforce the matrix and transform the brittle fracture of the needle-like Fe-bearing phases into ductile fracture.     

Microstructure and properties of Al2O3-Al(Si) and Al2O3-Al(Si)-Si composites formed byin situ reaction of Al with aluminosilicate ceramics

Al₂O₃-Al(Si) and Al₂O₃-Al(Si)-Si composites have been formed byin situ reaction of molten Al with aluminosilicate ceramics. This reactive metal penetration (RMP) process is driven by a strongly negative Gibbs energy for reaction. In the Al/mullite system, Al reduces mullite to produce α-Al₂O₃ and elemental Si. With excess Al (i.e., x > 0), a composite of α-Al₂O₃, Al(Si) alloy, and Si can be formed. Ceramic-metal composites containing up to 30 vol pct Al(Si) were prepared by reacting molten Al with dense, aluminosilicate ceramic preforms or by reactively hot pressing Al and mullite powder mixtures. Both reactive metal-forming techniques produce ceramic composite bodies consisting of a fine-grained alumina skeleton with an interpenetrating Al(Si) metal phase. The rigid alumina ceramic skeletal structure dominates composite physical properties such as the Young’s modulus, hardness, and the coefficient of thermal expansion, while the interpenetrating ductile Al(Si) metal phase contributes to composite fracture toughness. Microstructural analysis of composite fracture surfaces shows evidence of ductile metal failure of Al(Si) ligaments. Al₂O₃-Al(Si) and Al₂O₃-Al(Si)-Si composites produced byin situ reaction of aluminum with mullite have improved mechanical properties and increased stiffness relative to dense mullite, and composite fracture toughness increases with increasing Al(Si) content. This article is based on a presentation made in the “In Situ Reactions for Synthesis of Composites, Ceramics, and Intermetallics” symposium, held February 12–16, 1995, at the TMS Annual Meeting in Las Vegas, Nevada, under the auspices of SMD and ASM-MSD (the ASM/TMS Composites and TMS Powder Materials Committees).     

合金元素对机械合金化和放电等离子烧结Ti-Nb基合金显微组织的影响

β-Ti型结构的钛基材料在生物材料领域具有广泛的应用前景。本文采用机械合金化法和放电等离子烧结制备β-Ti型Ti-Nb基合金,研究不同Nb,Fe含量对合金显微组织及力学性能的影响。利用扫描电镜(SEM)、X射线衍射仪(XRD)和透射电镜(TEM)等手段分析合金的显微组织变化情况。结果表明:机械合金化过程中,粉末的平均粒度减小,当球磨时间超过60 h时粉末易发生团聚。当球磨转速为300 r/min,球料比为12:1,Ti和Nb的质量分数分别为64%和24%时,球磨100 h后制备的粉体材料中具有一定体积的非晶相。该粉末在1 000℃下通过放电等离子烧结(SPS)制备具有均匀细小的球状晶粒组织的Ti-Nb合金,其强度、伸长率和弹性模量分别为2 180MPa,6.7%和55 GPa。通过控制Nb,Fe的含量,可以促进β-Ti相形成,获得高强度和低杨氏模量的Ti-Nb合金。     

Crystallization and Microstructure Evolution of Amorphous Al85 Y4 Nd4 Fe7 Alloy

A rapidly solidified Al85Y4Nd4Fe7(%, in nominal atomic fraction) alloy was prepared by melt spinning. Asquenched and as-annealed microstructures were studied by differential scanning calorimetry (DSC), X-ray diffraction(XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). Fully amorphous structure could be obtained in the rapidly solidified Al85Y4Nd4Fe7 alloy ribbons. The temperature of first crystallization exceeds 300℃. Crystallization of as-annealed Al85Y4Nd4Fe7 alloy is shown to occur in two stages : ( 1 ) primary crystallization of α-Al; (2) formation of Al3Y, Al13Fe4 and unknown crystalline phases.