纳米锰方硼石粒径分布对铜基摩擦材料的影响

采用高能球磨法制备粒径小于200 nm的微细锰方硼石颗粒,将其作为摩擦填料添加到铜基摩擦材料中,利用放电等离子烧结(SPS)的方法制备出铜基摩擦材料。通过扫描电镜(SEM)、透射电镜(TEM)以及X射线衍射(XRD)研究纳米颗粒的形貌、显微结构与成分。在铜基摩擦材料中添加不同粒径的纳米锰方硼石,并通过摩擦磨损试验测试其磨损性能。结果表明:高能球磨法可以有效地细化锰方硼石;添加球磨处理的锰方硼石后所有样品的致密度均在97%以上,添加球磨50 min的纳米锰方硼石的样品致密度达到99%以上;稳定了摩擦因数(平均摩擦因数为0.187),磨损量为1.049×10-14 m3·J-1,抗压强度达到167 MPa;随着锰方硼石的细化,摩擦的样品磨损机理从剥层磨损与粘着磨损逐渐转向轻微的磨粒磨损。     

锰方硼石的摩擦性能

为了开拓锰方硼石的应用,将选矿之后粉末状锰方硼石进行高能球磨处理,得到尺寸小于10μm的粉末颗粒,采用放电等离子烧结,将得到的粉末颗粒制备成圆片状样品.使用X射线衍射仪和扫描电子显微镜对粉末状锰方硼石和摩擦片样品进行表征,证实该样品为斜方晶系的Mn₃B₇O₁₃Cl.用WTM-ZE可控气氛微型摩擦试验仪测试锰方硼石样品的摩擦性能,其摩擦因数范围为0.2~0.6,磨损量小,为1×10-9 cm3·N-1·m-1左右,表明锰方硼石在摩擦材料填料领域有应用前景.      

锰方硼石对铜基摩擦材料摩擦性能的影响

为了拓展锰方硼石的应用领域,提高铜基摩擦材料性能,将锰方硼石高能球磨处理30min后(颗粒尺寸<1μm),按照0.5%和1.0%的质量分数分别添加于铜基摩擦材料,用SPS烧结制得试样;并与不含锰方硼石的摩擦试样进行比较,分析3种样品的硬度、相对密度、摩擦系数及磨损率。结果表明:当锰方硼石的质量分数为0.5%时,摩擦试样的硬度较大,摩擦系数最平稳(平均摩擦系数为0.218)且磨损率最低;SEM分析发现其磨损机理为粘着磨损和磨料磨损。     

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。     

纳米锰方硼石的合成与结构性能表征

通过溶胶?凝胶（Sol?Gel）法成功合成了纳米锰方硼石并对其进行了稀土Eu3+掺杂。使用X射线衍射、透射电子显微镜和高分辨透射电子显微镜等表征了锰方硼石晶体结构,并通过荧光光谱测试对其发光性能进行了研究。结果表明:合成纳米锰方硼石为粒径小于50 nm的球状颗粒,与天然锰方硼石的物相结构相同,属于斜方晶系,与尖晶石类似,（010）晶面的晶面间距为0.8565 nm。在490 nm激发光激发下,天然锰方硼石、合成锰方硼石和稀土Eu3+掺杂锰方硼石晶体中的Mn2+发光,其中发绿光的Mn2+在晶体中占据四面体格位中心,发红光的Mn2+在晶体占据八面体格位中心。合成的锰方硼石随激发波长变长,产生发射光谱的红移现象,有利于实现冷暖发光转换;在稀土Eu3+掺杂的纳米锰方硼石光谱的发光强度得到了提升。      

氧化锆球体表面机械球磨涂覆钛涂层工艺研究

采用机械球磨涂覆技术在1 mm氧化锆球体上制备钛涂层, 研究了球料比、球磨时间及球磨气氛对钛涂层形成的影响, 利用扫描电子显微镜(scanning electron microscope, SEM)、X射线衍射(X-ray diffraction, XRD)及超声波对钛涂层的显微结构及物理性能进行了表征。结果表明, 钛涂层厚度随球磨时间、球料比的增加先增加后减小, 球磨30 h的涂层平均厚度最大, 约为76 μm, 球料比2.5:1.0的涂层平均厚度最大, 约为73 μm; 钛涂层结合强度随球磨时间的增加先增加后减小; 球磨过程中适当增加球料比, 可缩短涂层的形成时间; 在球磨过程中间歇性引入空气, 球磨罐中的钛粉易被氧化成TiO, 导致涂层形成困难, 故而球磨过程处于密封状态更有利于钛涂层的形成。     

过共析Ti-Cr合金的机械合金化

以钛、铬元素粉为原料研究了Ti-20％Cr(质量分数)和Ti-30％Cr 2种合金的MA规律。研究结果表明,在球磨初期的2 h内会发生钛的(011)主衍射峰强度迅速降低,(010)第二衍射峰强度提高并成为了最强峰,以及铬的衍射峰强度提高的现象。随着球磨时间的增加,钛和铬的X射线衍射峰都发生宽化、强度下降和衍射角左移减小。当球磨时间为30～40 h时,钛逐步非晶化。但是,在本试验条件下铬没有发生非晶化。MA的前10 h是粉末晶拉细化、晶格应变和合金化进行得最迅速的时期,经过该阶段球磨后铬的晶粒度可达20 nm;进一步球磨有利于获得过饱和固溶的合金粉末。2种合金在超过100 h的MA过程中均未发现在固相合成Laves相TiCr_2。根据试验结果制备纳米晶或者非晶过饱和固溶Ti-Cr合金粉末的合理球磨时间为30～40 h。     

高能球磨雾化铁基合金粉末的组织与性能

采用气雾化技术制备无氧铁基合金粉末,通过在500℃空气中氧化的方式给粉末加氧,然后进行高能球磨。通过氧含量测定、X射线衍射（XRD）、扫描电镜（SEM）分析及显微硬度测定,研究高能球磨后粉末组织与性能的变化。结果表明：球磨后粉末氧含量变化不明显,显微硬度大幅度提高;随球磨时间的延长,衍射峰逐渐宽化;通过球磨获得了晶粒细小、晶粒度分布较均匀的粉末颗粒,尤其是在球磨24 h、交替运行30 min条件下获得的粉末颗粒,不仅晶粒细小而且氧含量分布均匀。     

Mo-Si-B基超高温合金粉体的机械合金化

采用XRD,SEM和EPMA等方法分析Mo-12Si-10B-3Zr-0.3Y(原子分数)混合粉末在500 r/min转速下进行球磨时的机械合金化行为。结果表明:球磨后在混合粉末中并未形成Mo3Si和Mo5SiB2化合物相,而仅形成了合金元素在Mo中的过饱和固溶体Moss和弥散分布于其中的亚微米级B颗粒。随球磨时间延长,Moss的晶粒尺寸不断减小,其微观应变不断增加,球磨30 h后两者分别约为47 nm和0.53%;从XRD谱可知,球磨2 h后有少量的α-MoSi2生成,但球磨30 h后其衍射峰消失。球磨5 h后混合粉末由层片状的复合颗粒组成,球磨10 h后层片状复合颗粒破裂并转变为等轴状,球磨30 h后混合粉末由平均粒径约1μm的球状团聚体颗粒组成。     

高能球磨工艺参数对氢化钛粉和镁粉性能的影响

采用氢化钛粉代替钛粉,与镁粉混合高能球磨,研究球磨工艺参数对粉末性能的影响。采用机械合金化法这种非平衡态的粉末冶金方法,通过高能球磨粉末,提高Mg在Ti中的固溶度。利用激光粒度仪、X线衍射仪、扫描电镜等测试分析仪器表征粉末的性能。研究发现,随球磨时间延长,混合粉末的粒径逐渐变小,确定16 h为最佳球磨时间。Mg的衍射峰随球磨时间增加而逐渐减弱,球磨8 h后基本消失,表明球磨过程可促使Ti和Mg原子的合金化。选取4%(质量分数)的硬脂酸作为过程控制剂,能有助于减小颗粒尺寸且能有效防止粉末冷焊,粉末的收得率提高至73.3%。     

Ball-milling-induced crystallization and ball-milling effect on thermal crystallization kinetics in an amorphous FeMoSiB alloy

Microstructure evolution in a melt-spun amorphous Fe_77.2Mo_0.8Si₉B₁₃ alloy subjected to high-energy ball milling was investigated by means of X-ray diffraction (XRD), a transmission electron microscope (TEM), and a differential scanning calorimeter (DSC). It was found that during ball milling, crystallization occurs in the amorphous ribbon sample with precipitation of an α-Fe solid solution, and the amorphous sample crystallizes completely into a single α-Fe nanostructure (rather than α-Fe and borides as in the usual thermal crystallization products) when the milling time exceeds 135 hours. The volume fraction of material crystallized was found to be approximately proportional to the milling time. The fully crystallized sample with a single α-Fe nanophase exhibits an intrinsic thermal stability against phase separation upon annealing at high temperatures. The ball-milling effect on the subsequent thermal crystallization of the amorphous phase in an as-milled sample was studied by comparison of the crystallization products and kinetic parameters between the as-quenched amorphous sample and the as-milled partially crystallized samples. The crystallization temperatures and activation energies for the crystallization processes of the residual amorphous phase were considerably decreased due to ball milling, indicating that ball milling has a significant effect on the depression of thermal stability of the residual amorphous phase.     

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.     

反应高能球磨制备纳米WC/MgO复合粉末

将WO3、C和Mg粉末按摩尔比为1:1:3混合,在室温下用高能球磨法对其进行球磨,经XRD、SEM 和TEM分析表明, 在球磨到4.7 h时,WO3、石墨和镁之间发生氧化还原反应直接生成了WC和MgO粉末,之后随球磨时间的延长,粉末不断细化.球磨50 h后,得到WC晶粒度和颗粒度分别约为25 nm和100 nm的WC/MgO复合粉末.实验结果和热动力学分析表明,WC/MgO的合成是一个自蔓延反应过程,此反应可以在很短的时间内完成.     

Comparison between ultrafine-grained WC–Co and WC–HEA-cemented carbides

The AlFeCoNiCrTi high-entropy alloy (HEA) powders were prepared by high-energy ball milling. The ultrafine-grained WC–HEA and WC–Co-cemented carbides were fabricated through planetary ball milling and heat-pressure sintering. The microstructures and properties of the sintered alloys were compared using scanning electron microscope, X-ray diffraction, mechanical property testing and electrochemical testing. It has been shown that the AlFeCoNiCrTi HEA can be used as a binder for the ultrafine-grained WC-based cemented carbide. The WC–HEA-cemented carbide has better performances than the WC–Co-cemented carbide. The suitable contents of HEA can inhibit the WC grain growth and improve the mechanical properties and corrosion resistance of cemented carbides.     

铌-铝化合物的机械合金化制备及机理

研究高能球磨制备Nb/Al化合物的工艺,探索在高能球磨过程中Nb、Al形成化合物的机理.结果表明,通过高能球磨可获得Al在Nb中的固溶体,固溶度与球磨转速和球磨时间成正比,并发现选用硬脂酸作为添加剂有利于Nb/Al的机械合金化.对高能球磨中机械合金化的机理进行了讨论,指出高能球磨产生的高比表面能和高密度晶体缺陷大大降低...     

Investigation of the electrochemical corrosion properties of high-energy milled Ti6Al4V alloy in simulated body fluid environment

In this study, the electrochemical corrosion properties of high-energy milled Ti6Al4V alloy are investigated. The Ti6Al4V alloy is produced by high-energy milling at different milling times in mechanical milling device as 15–120?min. Produced alloy powders are cold-pressed under 620?MPa pressure and sintered at 1300°C temperature and characterised by scanning electron microscopy (SEM), X-ray diffraction, hardness and density measurements. Corrosion tests are conducted in simulated body fluid at 37°C body temperature. Results showed that the average particle size of the powder is reduced, and the hardness of the alloy is increased with the increasing milling time. It is determined that the corrosion properties of the alloys change by the high-energy milling time, and the corrosion rate increases by the decreasing particle size of the powder. SEM examination of the corroded surfaces after potentiodynamic polarisation tests revealed that pitting formation tendency of the alloys on the alloy surface increases by the increasing high-energy milling time.     

Microstructures and Properties of Nanocrystalline NiFe Alloy With and Without Particulate TiC Reinforcement by Mechanical Alloying

In the current study, Ni₅₀Fe₅₀ alloy powders were prepared using a high-energy planetary ball mill. The effects of TiC addition (0, 5, 10, 20, and 30 wt pct) and milling time on the sequence of alloy formation, the microstructure, and microhardness of the product were studied. The structure of solid solution phase, the lattice parameter, lattice strain, and grain size were identified by X-ray diffraction analysis. The correlation between the apparent densities and the milling time is explained by the morphologic evolution of the powder particles occurring during the high-energy milling process. The powder morphology was examined using scanning electron microscopy. It was found that FCC γ (Fe–Ni) solid solution was formed after 10 hours of milling, and this time was reduced to 7 hours when TiC was added. Therefore, brittle particles (TiC) accelerate the milling process by increasing crystal defects leading to a shorter diffusion path. Observations of polished cross section showed uniform distribution of the reinforcement particles. The apparent density increases with the increasing TiC content. It was also found that the higher TiC amount leads to larger lattice parameter, higher internal strain, and lower grain size of the alloy.     

Effects of mechanical activation on physicochemical properties and alkaline leaching of hemimorphite

Effects of mechanical activation on physicochemical properties and alkaline leaching of hemimorphite from Lanping, Yunnan province were studied. The results showed that both dry milling and mechano-chemical milling could enhance zinc extraction rate and shorten the leaching time. Scanning electron microscope (SEM), particle size distribution (PSD), X-ray diffraction (XRD) analysis demonstrated that different milling times and modes could form different morphologies, particle size distributions and crystal structures, thus influence zinc recovery differently.