机械合金化过程中Fe-Al合金粉末的组织演变

将纯Fe粉和Al粉按原子比Fe∶Al=60∶40混合后,在行星式高能球磨机中进行机械合金化,采用X射线衍射仪、扫描电镜、透射电镜和硬度仪研究球磨过程中Fe-Al合金粉末相结构、晶粒尺寸、表面形貌、截面形貌和硬度的演变规律。结果发现,球磨24 h后,Al原子全部固溶于Fe晶格中,形成Fe(Al)过饱和固溶体,随着球磨时间的增加,晶粒尺寸呈现先快后慢的减小趋势,球磨36 h后合金粉末的晶粒尺寸小于100 nm。粉末内部组织为层状结构,且随着球磨时间延长层片厚度不断减小,球磨36 h后层状结构全部消失,获得组织均匀的纳米晶Fe-Al合金粉末。随着球磨时间延长,Fe-Al合金粉末的硬度不断增加,球磨36 h后合金粉末的硬度约为405 HV0. 025。球磨Fe(Al)固溶体合金粉末在500℃热处理转变为有序Fe Al金属间化合物。     

Ti6Al4V预合金粉末制备与研究

以乙醇为过程控制剂,采用机械球磨法制备Ti6Al4V预合金粉末,借助X射线衍射、扫描电子显微镜(SEM)和透射电镜(TEM),研究不同球磨时间的Ti6Al4V预合金粉末的相组成和微观形貌。结果表明,随着球磨时间的增加,粉末逐渐细化,晶粒尺寸变小,微应变逐渐增加;球磨60 h后粉末达到较好的细化效果以及固溶效果;球磨90h后,粉末完全合金化,粉末粒度到达纳米级别,平均粒径50 nm。     

纳米复合Al-Sn合金烧结中的组织和硬度变化

利用机械合金化制备纳米复合Al-Sn合金粉末,将其压制成型并烧结.运用X射线衍射仪、扫描电镜分析了纳米复合Al-Sn合金在烧结过程中的组织结构变化,测定了显微硬度.结果表明,随着烧结温度的升高,机械合金化制备的Al-Sn纳米复合结构长大.当烧结温度低于Al-Sn共晶温度时,Sn相分布均匀;当烧结温度超过Al-Sn共晶温度时,Sn相沿着粉末颗粒的周围呈网状分布,网状形态取决于球磨后的粉末颗粒尺寸.纳米复合Al-Sn合金的显微硬度随烧结温度的提高而降低,与传统的铸造方法相比,机械合金化方法显著强化了Al-Sn合金.     

机械合金化法制备Cu-Nb合金过程中的形变孪生特性

采用机械合金化法制备纳米Cu-10%Nb合金,通过显微硬度测量以及高分辨透射电镜观察,对该合金粉末在室温球磨过程中的微观结构演变和形变孪生特性进行研究;利用局部应力集中模型分析形变孪晶的形核机制。结果表明:随着球磨时间的增加,该合金硬度(HV)不断升高,球磨120 h后可达4.8 GPa;该合金在球磨初期以位错胞结构为主;球磨50 h后,Cu平均晶粒尺寸减小至约50 nm,部分区域出现纳米形变孪晶;继续增加球磨时间,孪晶数量增加,孪晶界强化效果显著;由于孪生将促进纳米晶粒的进一步细化,球磨120 h后,纳米晶尺寸减小到20 nm以下。     

粉末冶金超细晶医用Ti-Mo-Fe合金的制备与表征

以元素粉末为原料,采用机械合金化方法结合放电等离子烧结工艺制备了Ti-8Mo-(0~9)Fe合金材料,并探讨了制备工艺对球磨粉体及烧结态合金性能的影响规律。结果表明,当铁含量为3%~9%(质量分数)时,球磨10 h粉体经900℃烧结可获得高致密度、并具有超细晶结构的钛合金材料,其显微组织主要由β-Ti相基体及fcc-Ti颗粒组成,其晶粒尺寸为130~490 nm,这是在钛合金块体材料中首次制备出fcc结构Ti相。在机械合金化过程中,Fe元素的加入可显著提高合金体系的非晶形成能力,并随Fe含量增加体系非晶形成能力增强,粉末非晶相比例增加,经10 h高能球磨后,即可合成具有良好的热稳定性的非晶/纳米晶Ti-Mo-Fe复合粉末。     

MA法制备Fe83Nb7B9Cu1纳米晶粉末及其热稳定性

利用高能球磨法在Fe Nb B Cu体系中获得纳米晶粉末 ,研究了机械球磨过程中产物的组织结构、α Fe相平均晶粒尺寸及其热稳定性。结果表明 :采用Fe 2 0B中间合金粉末代替B粉并未明显影响机械合金化动力学过程 ;球磨至 5h时 ,即可获得平均晶粒尺寸约 18nm的α Fe单相过饱和固溶体 ,其后延长球磨时间 ,晶粒尺寸缓慢减小 ,至 45h后 ,平均晶粒尺寸减小到 9nm。退火处理后的XRD分析表明 ,α Fe过饱和固溶体从 10 0℃开始发生结构弛豫现象 ,738.8℃后则发生了相转变 :α Fe过饱和固溶体→α Fe固溶体 Fe3 B FeB ,在 5 5 0℃以内退火 ,纳米晶粒长大不明显 ,在 770～ 95 0℃范围内退火 ,晶粒开始明显长大 ,但晶粒尺寸仍处于纳米级范围。     

低温高能球磨Ti/Al复合粉显微组织结构演化

采用低温高能球磨法制备了两种Ti/Al复合粉末,粉末组成为Ti-47Al(at%),Ti-45Al-2Cr_2Nb-1B-0.5Ta(at%).研究两种粉末在球磨过程中显微组织结构演化、形貌变化.结果表明,降低球磨温度能够有效控制球磨颗粒尺寸,低温条件及合金元素共同作用可以获得高质量的细晶均匀化复合结构粉末.在低温(-140-5)℃不加过程控制剂条件下球磨12 h,Ti-45Al-2Cr-2Nb-1B-0.5Ta(at%)粉末粒度得到有效细化,表现出精细均匀化复合结构粉末,Ti与Al晶粒尺寸分别约为16 nm,9 nm.在相同条件成分为Ti-47Al(at%)球磨5.2 h,Ti与Al元素没有很好复合及成分均匀化,两种成分球磨条件下均未有新相生成.在不加过程控制剂条件下,低温环境球磨和合金元素添加对机械合金化过程具有十分重要影响.     

机械合金化对Cr-W粉末及烧结材料组织的影响

通过机械球磨法制备原子比为4:1的Cr-W预合金粉末,对球磨后的Cr-W粉末进行XRD、SEM、TEM分析,探讨球磨时间对Cr-W粉末形貌、晶粒大小、组织结构及烧结Cr-W合金固溶度的影响。结果表明：采用机械合金化法,可以制备纳米级的Cr-W预合金粉末;球磨初期,晶粒尺寸、微应变变化较大,48 h后趋于稳定获得小于30 nm的纳米晶粉末;经72 h球磨后,粉末中有固溶体形成;球磨过程伴随着晶格常数的变化;球磨时间越长的粉末,烧结后各相分布越均匀,固溶程度越高     

双步球磨法制备纳米晶结构TiAl基合金粉末的研究

以元素粉末为起始粉末,采用双步球磨法(球磨+热处理+球磨)制备TiAl基纳米晶多相结构粉末(粉末成分为Ti-47Al(at%)、Ti-45Al-2Cr-2Nb-1B-0.5Ta(at%)).采用xRD、SEM、EDs、DTA、粒度分布仪对两种粉末颗粒在球磨和热处理过程中的特性进行了表征和分析.结果表明,采用双步球磨法制备的多相结构纳米晶粉末杂质含量低,粒度分布均匀,合金元素弥散分布.一步球磨6 h获得Ti/Al均匀复合结构及实现Ti(Al)部分固溶;700℃,2 h热处理获得Ti3Al、Ti、Al3Ti、TiAl相,Al相已经消失;二步球磨实现晶粒尺寸、颗粒尺寸进一步细化.     

机械合金化制备Ta-10%Al纳米晶过饱和固溶体

利用机械合金化的方式制备了组成为Ta-10%Al(质量比)的纳米晶过饱和固溶体。以XRD和SEM为表征手段,研究了球磨时间对Ta-10%Al纳米晶过饱和固溶体产生的影响,并对Ta-10%Al纳米晶过饱和固溶体形成的热力学机理进行了研究。结果表明,随球磨时间增加,Al逐渐溶入Ta中。当球磨时间达到48 h后,Al完全固溶进Ta中形成Ta-10%Al纳米晶过饱和固溶体,晶粒尺寸和微观应力分别为84.3 nm和0.285%。延长球磨时间导致Ta-10%Al纳米晶过饱和固溶体晶粒细化且微观应力增加,过长的球磨时间可能引发合金粉末的团聚。以Miedema半经验模型为依据,建立了机械合金化过程中的热力学模型,计算结果显示,以机械合金化为手段制备Ta-10%Al纳米晶过饱和固溶体的主要驱动力来源于热力学驱动。     

Fe基非晶及纳米晶合金的制备和电化学腐蚀行为

分别采用单辊甩带法和非晶晶化退火法制备出非晶及纳米晶合金Fe73.5Si13.5B9Nb3Cu1;利用DSC、XRD和TEM对该非晶合金的晶化行为进行了分析;并用电化学极化曲线的方法和电化学阻抗技术研究了该非晶合金经不同温度退火后在1mol/LHCl溶液里的电化学腐蚀行为。结果表明,该非晶合金的晶化过程出现2个阶段。当退火温度为500℃时,合金尚未晶化,仍保持非晶态;当温度达到550℃时,出现了晶化衍射峰,晶粒平均直径约13nm;当温度达到600℃时,晶粒平均直径约为15nm。经过退火得到的纳米晶合金的腐蚀电位大于未退火的非晶,且阳极电流密度变得更低,表明纳米晶状态时的耐腐蚀性能比非晶状态的更好。该非晶合金未退火、550℃退火和600℃退火时的EIS均由单一容抗弧构成,具有一时间常数;且随着退火温度升高,电化学反应电荷转移电阻在增大。     

Effect of Sn on synthesis of nanocrystalline Ti-based alloy with fcc structure

The effect of the amount of Sn on the formation of fcc phase in Ti−13Ta−xSn (x=3, 6, 9 and 12, at.%) alloys was studied. The alloys were synthesized by mechanical alloying using a planetary mill, jar and balls of stabilized yttrium. Using Rietveld refinement, it was found that the obtained fcc phase has crystallite size smaller than 10 nm and microstrain larger than 10⁻³. Both conditions are required to form an fcc phase in Ti-based alloys. For all samples, the microstructure of the fcc phase consists of equiaxial crystallites with sizes smaller than 10 nm. The largest presence of fcc phase in the studied Ti alloy was found with 6 at.% Sn, because this alloy exhibits the largest microstrain (1.5×10⁻²) and crystallite size of 6.5 nm. Experimental data reveal that a solid solution and an amorphous phase were formed during milling. The necessary conditions to promote the formation of solid solution and amorphous phases were determined using thermodynamic calculations. When the amount of Sn increases, the energy required to form an amorphous phase varies from approximately 10 to approximately −5 kJ/mol for 3 and 12 at.% Sn, respectively. The thermodynamic calculations are in agreement with XRD patterns analysis and HRTEM results.     

The correlation of microstructural development and thermal stability of mechanically alloyed multicomponent Fe-Co-Ni-Zr-B alloys

The microstructural evolution of multicomponent Fe_70-x-yCo_xNi_yZr₁₀B₂₀ (x = 0, 7, 21; y = 7, 14, 21, 28) alloys during mechanical alloying (MA) has been studied using XRD, SEM and TEM. Mixtures of elemental and pre-alloyed powders have been transformed initially into the single supersaturated bcc α-Fe solid solution phase for the alloys investigated. Subsequently, an amorphous phase has been obtained in Co-free alloys and Co-containing alloys with high Ni/Co ratios of 1 and 3. However, no amorphous phase was detected in another Co-containing alloy with a lower Ni/Co ratio (e.g. 0.33). The thermal stability of the as-milled powders has been investigated by a combination of DSC and the Pendulum magnetometer experiments. The DSC studies provide information on the thermodynamics and kinetics of crystallization of amorphous structure as a function of alloying contents. The Pendulum magnetometer studies reveal the phase transformation from nanocrystalline bcc α-Fe solid solution to amorphous structure during MA and the thermomagnetization behavior of the as-milled powder.     

Effects of rare earth La on the microstructure and melting property of（Ag-Cu28）-30Sn alloys prepared by mechanical alloying

To obtain novel intermediate temperature alloy solders with a melting temperature of 400-600°C,nominal(Ag-Cu28)-30Sn alloys without or with a trace addition(0.5 or 1.0 wt.%) of rare earth(RE) element La were prepared by mechanical alloying.The aim of this research is to investigate the effects of the addition of La on the microstructures,alloying process and melting properties of(Ag-Cu28)-30Sn alloys.The results show that the addition of La produces no new phase.A trace amount of La addition can effectively refine the grain size,but the excessive addition of 1.0 wt.% La inhibits the alloying process.The influence of La on the melting temperatures of solder alloys is negligible.However,the trace addition of 0.5 wt.% La can distinctly reduce the fusion zone and improve the melting property of(Ag-Cu28)-30Sn alloys.     

Ag-Sn-La合金粉末的氧化组织研究

采用X射线衍射仪、金相显微镜和扫描电镜,研究了Ag-Sn-La合金粉末的氧化组织。结果表明:Ag-Sn-La系合金粉末氧化后主要由Ag、SnO2和La2Sn2O73种相组成;合金元素含量不同,Ag-Sn-La合金粉末具有不同的氧化动力学特征、氧化组织和氧化机制。Ag-5.2Sn-3.4La合金粉末的起始氧化温度为350℃,氧化速度较快,元素La和Sn发生原位氧化,但柱状晶上La的快速优先氧化使得合金内部出现条状的氧化物;Ag-6.87Sn-1.28La合金粉末从加热一开始便发生缓慢氧化,在300℃以后开始快速氧化,元素La和Sn发生原位氧化,原位生成的氧化物颗粒弥散分布在银基体上;Ag-9.26Sn-0.44La合金粉末的起始氧化温度为567℃且氧化速度较慢,元素La发生原位氧化,而部分Sn在浓度梯度的驱动下向外扩散,生成的氧化锡颗粒主要分布在粉末边界,而La的氧化物则弥散分布在银基体上。     

Structure and properties of composites prepared from partially amorphous ZrCuNiTi and nanocrystalline silver

Alloys of composition Zr40Cu40Ni10Ti10 and Zr48,5Cu32.5Ni9Ti10 (in at.%) were ball milled for 40 h starting from elemental powders or melt spun from cast ingots. In both cases amorphous structure was obtained, however in the case of ribbons, larger crystals of Cu₁₀Zr₇ or Ni₇Zr₂ phases of size of a few hundred nm were observed. In the case of milled alloys much finer intermetallic phases such as Zr₂Cu or Cu₁₀Zr₇ were identified within the amorphous matrix using X-ray diffraction or HRTEM. In both alloys DSC studies have shown higher crystallization temperature for the powder, than for the ribbon. It was explained by a different structure of preexisting intermetallic nuclei crystallizing in milled powders. The milled amorphous powder was also used as a matrix for composites containing 20% or 50% of nanocrystalline silver powder, prepared from silver powder by ball milling. The composites hot pressed at the same temperature as the amorphous samples show in some places very narrow transition phase enriched in silver containing also other elements of the amorphous phase. Composites containing more silver show lower hardness and strength, but exhibit a few percent of plastic deformation in the compression test. Scanning electron studies of deformed composite samples show crack initiation within the amorphous phase, not at the components interfaces.     

机械合金化制备纳米晶Ti-6Al-4V合金

采用机械合金化制备Ti-6Al-4V粉末。结果表明:采用机械合金化可以制备纳米晶Ti-6Al-4V合金粉,其反应机理以扩散为主,该固态反应是缺陷能和碰撞能共同作用的结果;随球磨时间延长,部分V固溶于Ti中形成置换固溶体Ti(V),球磨过程中没有中间相生成。球磨40 h后都能获得纳米晶,60 h的粉末为纳米晶和非晶的混合物,晶粒尺寸小于60 nm;60 h后晶粒尺寸变化缓慢。球磨后Ti、Al、V的原子比近似为90:6:4,与Ti-6Al-4V元素成分一致。     

机械合金化制备Ni-B-Si合金粉末

本实验选取成分为92%Ni-4%B-4%Si的混合粉末进行机械合金化,并每隔一定时间定量取粉进行SEM、XRD及DSC分析。实验结果表明,当球磨至30 h时,粉末形貌趋于球状,微量元素B和Si已经完全向镍中固溶,此时起始熔化温度降至1038℃;继续延长球磨时间粉末发生团聚,并在球磨至80 h时,趋于非晶化转变;将球磨40 h的合金粉末与松装镍粉在1100℃进行熔渗烧结时,发现其与镍粉发生冶金结合并形成致密的烧结体。     

放电等离子烧结制备Fe75Zr3Si13B9磁性材料

采用机械合金化技术制备Fe75Zr3Si13B9非晶合金粉体,利用SPS放电等离子烧结技术在不同烧结温度下将非晶合金粉体制备成d20 mm×7 mm的块体非晶纳米晶合金。采用XRD和DSC分析了Fe75Zr3Si13B9非晶合金粉体的相组成、玻璃转变温度Tg、开始晶化温度Tx和晶化峰温度Tp。然后利用XRD、SEM、Gleeble3500、VSM分析不同烧结温度下块体的相转变、微观形貌、力学性能和磁性能。研究表明,在500 MPa的烧结压力下,随着烧结温度的升高,非晶相开始晶化形成非晶纳米晶双相结构,同时,样品的致密度、抗压强度、微观硬度、饱和磁化强度均显著提高。最后在500 MPa的烧结压力和863.15 K的烧结温度下,获得密度6.9325 g/cm3、抗压强度1140.28 MPa、饱和磁化强度1.28 T的非晶纳米晶磁性材料。     

Sn-6Bi-2Ag(Cu, Sb)无铅钎料合金微观组织分析

利用差示扫描量热计 (DSC)测定了Sn 6Bi 2Ag ,Sn 6Bi 2Ag 0 .5Cu ,Sn 6Bi 2Ag 2 .5Sb三种新无铅钎料合金的熔化温度。结果表明 ,少量Cu的加入能降低Sn Bi Ag系无铅钎料合金的熔化温度 ,而Sb的加入使合金的熔化温度升高。利用光学显微镜 (OM )、扫描电子显微镜 (SEM )、能谱分析 (EDX)对合金的微观组织进行了分析与比较 ,钎料合金的微观组织与冷却条件和合金元素的含量有关 ,Sb的加入使析出相的尺寸细化。硬度测定表明Sn Bi Ag(Cu ,Sb)无铅钎料合金的硬度远大于纯Sn的硬度 ,加入少量的Cu(0 .5 % ) ,Sb(2 .5 % )对Sn Bi Ag系钎料合金的硬度影响较小