机械合金化工艺对Fe_(33)Si_(67)合金微观组织结构的影响

以Fe33Si67(原子分数)为研究对象,采用机械合金化方法制备β-FeSi2热电材料。用X射线衍射(XRD)和扫描电子显微镜(SEM)研究了球磨机转速、球料比及球磨时间等工艺参数对生成物物相和显微形貌的影响,着重研究了机械合金化引起的Fe-Si合金相变过程。研究表明,随球磨时间的延长,合金粉末依次析出ε-FeSi、α-FeSi2和β-FeSi2相,随后β-FeSi2、α-FeSi2相消失,合金粉末转化为单一相ε-FeSi;在球磨机转速为450r/min、球料比为10∶1、球磨时间为35～50h时,所得合金粉末中β-FeSi2相的质量分数约为50%。     

机械合金化能量转换与Ni50Ti50非晶合金的形成

本文报道了球磨转速，装球量对Ｎｉ５０Ｔｉ５０单质混合粉机械合金化的影响，并建立模型用于计算工艺条件对球磨能量转换的影响，进而讨论了它与机械合金化相变反应方式的关系。粉末在每次碰撞的变形能过高时，可能形成金属间化合物，而粉末经长时间球磨获得的总能量超这一定值将引起非晶的晶化。     

机械合金化制备NiAl(Cr,Nb)粉体

采用机械合金化的方法制备NiAl(Cr,Nb)金属间化合物粉末。以Ni、Al、Cr和Nb的粉末为原料,按原子分数Ni-38Al-5Nb-5Cr配比,研究其机械合金化过程,并采用XRD,SEM,DSC等分析手段对粉末的结构、颗粒形貌及热稳定性能等进行表征。结果表明:复合粉末在球磨10h后初步合成了NiAl(Cr,Nb),随球磨时间的延长,粉末有细化的趋势,最终产物多为规则的近球形。     

高能球磨法制备Fe_3Si合金粉末

采用高能球磨法研究了原子配比Fe75Si25的混合粉末在不同的球磨条件下的机械合金化,用X射线衍射(XRD)仪、扫描电子显微镜(SEM)表征样品的物相、晶体结构、晶粒尺寸和点阵常数,分析了Fe75Si25粉末的机械合金化机理。研究表明,球磨时间、球料比和球磨机转速对机械合金化(MA)进程有重要影响。MA 55h后可达到完全合金化,Si溶入Fe中形成α-Fe(Si)饱和固溶体,晶粒尺寸减小至7～8nm。     

(FeAl)_(1-x)Ni_x和(FeAl_3)_(1-x)Ni_x机械合金化研究

为了研究按摩尔分数(FeAl)1-xNix(x=0.4,0.6)和(FeAl3)1-xNi(x=0.1,0.3)配比的粉体在机械合金化过程中的结构演变,采用X射线衍射(XRD)对球磨样品进行分析。结果表明:球磨50h后的产物主要由Fe和Al的原子比来决定,Ni的成分含量大小对主要产物基本没有影响。     

Cu-Cr机械合金化工艺研究进展

综述了机械合金化工艺制备Cu-Cr合金的研究进展。主要包括Cu-Cr机械合金化的基本原理;Cu-Cr粉末机械合金化过程的影响因素,包括球磨时间、球料比,填充率、球磨机转速、过程控制剂、球磨温度等;Cu-Cr合金机械合金化过程的缺陷。简要讨论了机械合金化方法生产Cu-Cr合金粉末的发展前景。     

球磨参数对ODS奥氏体不锈钢机械合金化效果的影响

为了研究球磨参数对ODS奥氏体不锈钢机械合金化效果的影响,以Fe、Cr、Ni、W、Ti纯金属元素粉末和纳米Y2O3为原料进行混合(配比为Fe-18Cr-8Ni-2W-1Ti-0.35Y2O3,质量分数),通过高能球磨的方式实现混合粉末的机械合金化.研究球磨时间、转速的变化对粉末粒度、成分均匀度和固溶程度的影响.结果表明,在真空环境下,球料比为10∶1、转速为380r/min、球磨时间60h时,粉末达到了很好的机械合金化效果,成分分布均匀;当球磨时间延长到100h时,粉末颗粒达到最细,继续球磨,粉末将出现明显的团聚.对最优机械合金化工艺参数获得的粉末进行热压致密化研究表明,随着温度的升高,试样的密度随之升高,维氏硬度随之降低.     

球磨时间对镍基ODS合金拉伸性能的影响

研究了球磨时间对Y2O3氧化物弥散强化(ODS)镍基高温合金机械合金化和拉伸性能的影响.镍基高温合金采用机械合金化和热压烧结方法制备.镍基ODS高温合金粉末是在行星式球磨机上进行球磨.采用扫描电镜及X射线衍射分析了球磨时间对镍基ODS合金粉末形貌和物相的影响.研究结果表明,Y2O3氧化物弥散强化镍基高温合金机械合金化粉末尺寸随研磨时间的增加先增大后减小,8h粉末颗粒尺寸达到最大,之后粉末颗粒尺寸逐渐减小,28h后,镍基ODS合金粉末尺寸稳定且均匀.拉伸结果表明,采用研磨28h的合金粉末制备的镍基ODS合金具有最高的抗拉强度(1300MPa).     

机械合金化制备FeSiAl合金粉末的研究

采用机械合金化的方法制备了FeSiAl合金粉末样品。以硅钢粉和铝粉为原料,按摩尔分数Fe3Si0.4Al0.6配比,研究其机械合金化过程,并对机械合金化的机制进行探讨。用激光粒度仪、X射线衍射(XRD)和扫描电子显微镜分析材料的粒度、形貌和结构。研究表明,Fe3Si0.4Al0.6混合粉末球磨30h后,粉末粒径可达18μm;Fe3Si0.4Al0.6混合粉末经高能球磨20h后,形成具有bcc结构的α固溶体;球磨继续进行,合金化的粉末和晶粒不断细化。     

机械合金化纳米晶合金Ni50Bi50的结构和磁性

研究了Ｎｉ５０Ｂｉ５混合粉末在机械合金化过程中结构和磁性的变化。Ｘ射线衍射、差示扫描量热分析和比饱和磁化强度的测量结果表明：混合粉末的晶粒尺寸随球磨时间的增加而减小。球磨２００ｈ时，样品的晶粒尺寸为１５ｎｍ。机械合金化可以提高Ｂｉ在Ｎｉ中的固溶渡。     

Mechanical Alloying of Ti50Al50 Powders and Their Consolidated Properties

Elemental powder mixtures of 50Ti-50Al (at.%) were mechanically alloyed via various ball milling methods. The microstructural evolution during the milling indicates that the mechanical alloying behavior is strongly affected by milling methods, and horizontal ball milling is most effective for producing homogeneous metastable powders. The mechanically alloyed powders were consolidated by vacuum hot pressing followed by homogeneous annealing. Compression testing results showed that the annealed specimens still retain fine grains and have a good combination of fracture strength and ductility, as compared to cast specimens of the same alloy.     

Sub-micron sized Al2TiO5 powders prepared by high-energy ball milling

High energy ball milling to obtain ultrafine aluminium titanate particles has been investigated. Tempered steel has been selected as material for the containers and balls because the desirable properties of aluminium titanate are not degraded by small amounts of Fe₂O₃. The starting powders have been milled during different periods (1–60 h) and the evolution of the morphology and crystallinity of the treated powders as well as the extent of contamination from the milling media have been characterised. Different experimental techniques, X-ray diffraction, BET-analysis, chemical analysis, scanning electron microscopy and low and high resolution transmission electron microscopy have been used. High energy ball milling has been proved to be an efficient route to obtain submicron sized (50–100 nm) aluminium titanate powders, but further milling of the powders is accompanied by contamination from the milling media and the formation of hard agglomerates.     

分子动力学模拟Pb_(20)Au_(80)和Pb_(50)Au_(50)合金热力学性质的研究

采用分子动力学方法模拟了Pb20Au80和Pb50Au50合金体系的热力学性质,计算了不同温度下合金体系的生成焓、生成自由能、过剩自由能和结合能,从宏观和微观热力学角度分析了二元合金原子间的相互作用,得到的计算结果与实验数据很吻合。     

Fabrication of ultrafine W – Cu powders by mechanical alloying

Abstract

Ultrafine composite powders of W – 15 wt-%Cu, W – 25 wt-%Cu, and W – 35 wt-%Cu have been fabricated by mechanical alloying. The effects of type of mill, process control agent, temperature of milling, and ball/powder ratio on the final products have been evaluated. The results show that the planetary ball mill possesses a higher impact energy intensity than that of the vibratory ball mill. The optimum milling time is confirmed by the formation of a nanocrystalline microstructure in the planetary ball mill after optimisation of the milling parameters. A steady state between cold welding and fracture is attained with a milling time of up to 25 h in the planetary ball mill under optimised conditions. Crystallites with sizes of 7 – 8 nm for W – Cu composite powders have been obtained after 25 h of ball milling. The powders obtained after mechanical alloying have been characterised in terms of their size, shape, phase constitution, and microstructural features using X-ray diffraction and scanning electron microscopy.     

Influence of processing parameters on grinding mechanism in planetary mill by employing discrete element method

Evaluation of process parameters and performance of planetary mills is considered an important issue in optimization of their predicted efficiencies. The current research deals with a computer simulation based on discrete element method (DEM) employed to evaluate the grinding mechanism of a planetary mill. The effect of rotational speed, the volume percentage of the balls and powders on impact energy, the frequency of the impacts, the abrasion of the balls and the dissipated energy have been investigated. It was realized that by increasing the rotational speed, the impact energy and the number of impacts of ball–ball, ball–container, ball–powder, powder–powder and dissipated energy were increased. By increasing the balls filling ratio, the impact energy value of ball–ball remained almost constant after a critical point while those of ball–powder impact energy and the dissipated energy were slightly increased. With an increase in powders filing ratio, a maximum value was observed for the ball–powder impact energy; however, the ball–ball impact energy remained almost constant and the dissipated energy indicates a reduction in rate.     

Mechanical Alloying of Fe_(100-x)B_x

The formation of nonequilibrium phase by mechanical alloying (MA) of Fe and B powders in a high energy vibration ball mill has been made for Fe100-xBx system with x=15. 30, 35, 45,55 and 70. By using the X-ray diffraction, magnetic measurement and M6ssbauer spectrummethods, it was revealed that the structure of the MA product varies with milling time and B contents.     

Synthesis of nanocrystalline M50 steel powders by cryomilling

The present paper reports on a study of the synthesis of nanocrystalline high speed tool steel M50 powders (4.5% Mo, 4.0% Cr, 1.0% V, 0.8% C, balance Fe) by cryogenic high energy ball milling (cryomilling). Pre-alloyed M50 steel is spray atomized, and subsequently cryomilled in liquid nitrogen for 25 hours. Elemental Al powder is added prior to cryomilling to promote the formation of nanoscale Al₂O₃ and AlN dispersoids to improve the thermal stability of the nanocrystalline M50 steel. High resolution transmission electron microscopy (HRTEM) reveals the formation of various carbides (V₈C₇, Fe₃C, and FeC), oxides (Al₂O₃, MoO₃, and V₃O₇), and a nitride phase (AlN) during cryomilling. Following one hour of heat treatment at 1373 K (0.77 T_m), an average grain size of 70 nm was retained for the M50 steel powders.     

Mechanochemical synthesis of the low-temperature (B20) phase of FeGe

We have investigated solid-state reactions in an equiatomic mixture of Fe and Ge powders during ball milling in a water-cooled high-energy mill under an argon atmosphere. The mechanical alloying products have been characterized by x-ray diffraction, Mössbauer spectroscopy, and calorimetry. The observed sequence of phase formation correlates with the thermodynamic properties of the iron germanides involved. The alloy prepared by ball milling for 2 h consists entirely of nanocrystallites (?15 nm) of the low-temperature, stable, cubic (B20) phase of FeGe.     

Microstructure evolution and interface structure of Al-40 wt% Si composites produced by high-energy ball milling

High silicon content Al-Si composites with a composition of Al-40 wt% Si were fabricated via a highenergy ball milling method. The microstructure evolution of Al-40 wt% Si milled powders and sintered composites has been thoroughly studied by scanning electron microscopy, X-ray diffraction, energydispersive spectrometry and high-resolution transmission electron microscopy. The mechanism of ball milling Al-40 wt% Si powders has been disclosed in detail: fracture mechanism dominating in the early stages, followed by the agglomeration mechanism, finally reaching the balance between the fragments and the agglomerates. It has been found that the average particle sizes of mixed Al-Si powders can be refined to the nanoscale, and the crystallite sizes of Al and Si have been reduced to 10nm and 62nm upon milling for 2h–50h, respectively. The finally formed Al-Si interfaces after ball milling for 50h are wellcohesive. A dense and homogenous Al-40 wt% Si composite have been achieved by solid-state sintering at550?C. The results thus provide an effective support for producing bulk nanostructured Al-Si composites.     

球磨条件对Ni－Ti粉末结构转变及机械合金化速度的影响

用ＸＲＤ分析研究了搅拌式球磨过程中球磨条件对Ｎｉ－Ｔｉ单质混合粉末结构演化的影响．定量测定了球磨粉末微观应变、微晶尺寸、镍的晶格常数及衍射峰相对微射强度与球磨转速及装球量的关系．研究了球磨功率对球磨温升、粉末微晶尺寸，层片状结构转变的影响，确定了非晶化所需时时间与工艺条件的关系，结果表明球磨功率成粉末塑性变形能增加，微晶尺寸减小．层片组织细化，同时微观应变大，晶格常数变化快，非晶化所需时间减小．