Fe和Si杂质对Al-Zn-Mg-Cu合金淬火敏感性的影响EI北大核心CSCD

采用光学显微镜、扫描电子显微镜和透射电子显微镜等方法,研究了Fe和Si杂质对Al-Zn-Mg-Cu合金淬火敏感性的影响。结果表明:杂质含量的增加降低了合金的淬火敏感性,用硬度表征时最大降低3.29%。随杂质Fe和Si含量的增加,Al7Cu2Fe相和Mg2Si相含量明显增加,消耗了基体中的Cu和Mg原子,合金的过饱和度降低,从而引起合金淬火敏感性的降低;同时粗大的Al7Cu2Fe相和Mg2Si相有利于再结晶核心的形成,增加了合金的再结晶晶粒和(亚)晶界数目,促进慢速淬火过程中η平衡相的析出。过饱和度对合金淬火敏感性的影响大于晶粒结构对合金淬火敏感性的影响。     

Nd对Mg-10Gd-0.5Zr合金组织和力学性能的影响

采用XRD、OM和SEM方法,通过拉伸试验、断口分析和组织观察,研究了Mg-10Gd-(0,1,2,3,4)Nd-0.5Zr合金的显微组织和25~250℃下的力学性能,结果表明:时效态MN0合金组织由α-Mg基体和Mg5Gd相组成,Mg5Gd相主要分布在晶界处。随着Nd含量的增加,产生了新相Mg12Nd,合金晶粒细化,抗拉强度和伸长率都有显著提高,同时,随着温度的升高,合金的抗拉强度具有反常的温度效应。     

磁控溅射沉积Cu-W薄膜的特征及热处理的影响

采用磁控共溅射法制备含钨1.51%~14.20%(原子分数,下同)的Cu-W合金薄膜,并用EDX、XRD、SEM、显微硬度仪和电阻仪研究了其成分、结构及性能。结果表明,添加W可显著细化Cu-W薄膜基体相晶粒,晶粒尺寸随W含量的增加而减小,Cu-W薄膜呈纳米晶结构。Cu-W薄膜中存在W在Cu中形成的fcc Cu(W)非平衡亚稳过饱和固溶体,固溶度随W含量的增加而提高,最大值为10.65%。与纯Cu膜对比发现,薄膜的显微硬度和电阻率总体上随W含量的增加而显著增大。经200℃、400℃及650℃热处理1h后,Cu-W薄膜基体相晶粒长大,EDX分析显示晶界处出现富W第二相;薄膜显微硬度降低,电阻率下降,降幅与退火温度呈正相关。添加W引起的晶粒细化效应以及退火中基体相晶粒度增大分别是Cu-W薄膜微观结构和性能形成及演变的主要原因。     

Ni50Mn38-xIn12Fex多晶合金的马氏体转变和磁转变特性

详细研究了Ni50Mn38-xIn12Fex(x=0,3,4,5,6)合金体系中Fe取代Mn对合金马氏体相变行为及磁学性能的影响.发现当x≤4时,合金表现出由B2结构的奥氏体向正交结构的马氏体转变的相变行为,而当x≥5时该相变被完全抑制.当Fe对Mn的取代超过3％时,合金的显微结构中出现y相,并发现其数量随Fe含量的增加而增加.γ相的形成改变了合金基体相成分,进而带来了基体相e/a(每原子的电子浓度)值的变化,研究结果证明合金的一系列性能改变均与基体相e/a值的变化相关.第一,基体相e/a(每原子的电子浓度)值随着Fe含量的增加而迅速减小,导致了合金马氏体相变温度、相变潜热及相变熵变的降低.第二,Fe的引入有效地增强了合金基体相的铁磁性能,提高了合金的居里转变温度和合金的磁化强度.详细阐述了Fe的引入是合金马氏体相变及磁学性能变化的本质原因.     

Mo对Ti-Mo系合金显微组织的影响及其强化效应

对不同Mo含量β单相区锻造的Ti-Mo合金在相变点以上进行固溶处理,然后对合金进行显微组织分析和力学性能测试。结果表明:Ti-1Mo合金和Ti-2Mo合金主要由等轴的α相组成,Ti-4Mo合金主要由针状六方马氏体α′相和原始β晶界组成,当合金Mo含量超过10%(质量分数)时,合金主要由等轴的β相组成。晶粒尺寸统计结果显示:晶粒尺寸与固溶时间呈指数关系;在固溶时间一定的条件下,晶粒尺寸随固溶温度的升高而增大,随合金中Mo含量的增加而明显减小。另外Ti-Mo合金的强度随晶粒尺寸的减小而提高,但合金的塑性变化不大,最后对影响合金强化的机理进行了探讨。     

冷喷涂制备cBN-NiCrAl金属陶瓷涂层EI北大核心

采用机械合金化制备40vol%cBN-NiCrAl金属陶瓷复合结构粉末,采用冷喷涂制备了40%cBN-NiCrAl(体积分数)金属陶瓷复合结构涂层。研究了机械合金化过程对粉末的相组成、晶粒尺寸以及显微组织的影响。采用扫描电子显微镜和X射线衍射分别表征不同球磨时间下粉末以及冷喷涂涂层的显微组织和相结构。采用Scherrer公式估算不同球磨时间下粉末以及冷喷涂涂层中合金基体相的晶粒尺寸。结果表明,40vol%cBN-NiCrAl金属陶瓷粉末球磨40h后,基体的平均晶粒尺寸达到~50nm;复合结构涂层组织致密,硬质颗粒在合金基体中分布均匀。喷涂过程中,粉末相结构未发生变化,晶粒尺寸也未发生明显的长大。测试表明涂层的显微硬度约为1170HV0.3。     

微量硼对Ti-Fe-Cu-Sn-Nb合金力学性能的影响

基于细晶强化和第二相强化原理,通过在一种近β钛合金中加入微量硼(B)元素,以强化该合金.首先设计不同含硼量的Ti85 Fe6 Cu5 Sn2 Nb2合金,并用真空非自耗电弧炉制备,随后对合金在800℃下进行多道次热轧及最终淬火.通过组织观察、拉伸力学性能测试、断口观察及透射电子显微分析,考察不同硼含量对Ti85 Fe6 Cu5 Sn2 Nb2合金组织及力学性能的影响.结果表明,微量硼元素可以使合金的晶粒细化,强度明显提高,但伴随着塑性下降.添加质量分数为0.15％硼可以使合金具有较好的综合力学性能(σ0.2=1105 MPa,δb=4.5％).随着硼含量的增加,合金的强度升高,最高可达1156 MPa.硼的加入在合金中形成正交结构的TiB相,分布于β钛基体中.变形过程中,TiB断裂、TiB割裂基体及其与基体脱粘,产生裂纹源,导致合金塑性下降.     

Ce掺杂对Fe81Ga15.5A13.5合金微观结构和磁性能的影响

以Fe₈₁Ga_15.5Al_3.5合金为基体向其中掺杂Ce元素，研究(Fe₈₁Ga_15.5Al_3.5)_100-xCe_x(x=0, 0.2, 0.4, 0.6, 0.8, 1.0)合金微观结构和磁性能的变化。结果显示：Fe₈₁Ga_15.5Al_3.5合金的晶粒形状为柱状晶，加入Ce元素后，晶粒形状变为树枝晶。少量Ce元素加入时，(Fe₈₁Ga_15.5Al_3.5)_100-xCe_x合金的相结构仍以A2相为主；当x>0.8%时，合金的相结构由A2相和CeCa₂相组成。Ce元素的加入可以改变合金[100]晶向的取向性；合金的晶格常数随着Ce含量的增加而逐渐减小。在扫描电镜下，可以观察到Fe₈₁Ga     

Ti-45Al-8.5Nb-W-Mo-Y合金的组织转变

研究了Ti-45Al-8.5Nb-W-Mo-Y合金的相结构。该合金铸态组织大部分由α2 γ片层域团组成，同时含有少量的B2 ω相。经过1200℃，2h处理后，B2相全部转变成ω相。合金经过70%-80%热变形后，组织由等轴γ晶粒，残余高温B2 ω相，少量的变形片层域团α2 γ片层组成。变形组织再经过1280℃，2h的热处理，其中高温相大幅度减少，同时α2板条增加。挤压态组织由变曲的片层及少量的等轴γ晶粒组成。循环热处理技术细化组织。     

Sn含量对Al-Zn合金组织与溶解性能的影响

为了改善Al-Zn合金组织,有效调控合金的溶解速率,采用光学显微镜(OM)、X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)和电化学工作站等测试手段,研究了不同Sn含量对铸态Al-Zn合金微观组织和电化学性能的影响规律。结果表明:合金主要由Al基体相、Al_(0.71)-Zn_(0.29)相和Sn相组成,随着Sn含量的增加,析出相在晶界处的含量明显增加,尺寸逐渐增大,且由颗粒状逐渐转变为长条状;当Sn含量从0.1wt%增加到2wt%时,合金的平均晶粒尺寸从194.54μm减小到65.33μm,溶解速率和电化学活性不断提高; Sn含量继续增加,合金的平均晶粒尺寸逐渐增大,溶解速率和电化学活性下降。     

Al含量对含25%Ba的Si-Ba合金物相结构的影响

在含Ba量为25%的Si-Ba合金中加入不等量的Al,研究其对合金物相结构的影响规律.结果表明:含Al量大于2.5%时,其合金不再粉化,这是由于Al_Ba、(Si、Al、Fe)2等物相的生成,抑制了Si-Ba二元化合物的大量形成.     

AuPt合金的两种典型生长机理研究

分别采用晶种生长法和快速共还原法制备得到了AuPt合金。采用晶种生长法制备AuPt合金时,Au晶种的尺寸对Au-Pt双金属结构的形成有关键性影响,当用小尺寸的Au纳米颗粒(3nm)作为晶种时才会形成AuPt合金结构,当Au晶种尺寸较小时,由于颗粒内纳米尺度的原子快速扩散导致合金结构的形成。高温下油胺对Au和Pt前体的快速共还原会使Au和Pt在极短的时间内同时得到还原,避免了两相的分离,得到了AuPt合金结构。     

Structure and properties of nanoporous FePt fabricated by dealloying a melt-spun Fe_(60)Pt_(20)B_(20) alloy and subsequent annealing

A nanoporous FePt alloy has been fabricated by dealloying a melt-spun Fe(60)Pt(20)B(20)alloy composed of nanoscale amorphous and face-centered-cubic FePt(fcc-FePt)phases in H2 SO4 aqueous solution.The nanoporous alloy consists of single fcc-FePt phase with an Fe/Pt atomic ratio of about 55.3/44.7,and possesses a uniform interpenetrating ligament-channel structure with average ligament and pore sizes of 27 nm and 12 nm,respectively.The nanoporous fcc-FePt alloy shows soft magnetic characteristics with a saturation magnetization of 37.9 emu/g and better electrocatalytic activity for methanol oxidation than commercial Pt/C in acidic environment.The phase transformation from disordered fcc-Fe Pt into ordered face-centered-tetragonal FePt(L10-FePt)in the nanoporous alloy has been realized after annealing at823-943 K for 600 s.The volume fraction of the L10-FePt phase in the alloy increases with the rise of annealing temperature,which results in the enhancements of coercivity and saturation magnetization from 0.14 kOe and 38.5 emu/g to 8.42 kOe and 51.4 emu/g,respectively.The ligament size of the samples is increased after annealing.     

Structure of BaO on hierarchical macro-meso-microporous alumina and its effect of interaction with Pt nanoparticle on NO2 desorption

Recently, the lean NOx trap technology using supported Pt catalyst on alumina was devised to store NOx under lean condition and to reduce into N2 and water under rich condition in lean burn engine. In this work, the effect of the Pt nanoparticle supported on hierarchical macro-meso-microporous BaO-Al2O3 on NO2 desorption has been investigated with NO2 temperature programmed desorption, TEM, SEM, TGA and hydrogen chemisorption. Crystalline BaO phase of 20-30 nm thickness were obtained on the hierarchical macro-meso-microporous Al2O3 with a simple impregnation of Ba(NO3)2 and Ba(ClO4)2. The interaction of Pt and BaO was resulted in the formation of atomically dispersed Pt nanoparticles and also decreased the desorption temperature of NO2 adsorbed on BaO at much lower temperature than that from the BaO-Al2O3 support only. This synergistic lowering of NO2 desorption temperature may be originated from the interaction between Pt and BaO.     

Microstructure and mechanical properties of Pt-added and Pd-added Zr-20Nb alloys and their metal release in 1 mass% lactic acid solution

The effects of Pt and Pd addition to a Zr-20Nb alloy on its microstructure and mechanical property, as well as the elution of metals from the alloys in lactic acid solution, were investigated. The microstructure was characterized with an X-ray diffractometer (XRD), an optical microscope (OM), and a transmission electron microscope (TEM). The mechanical properties were evaluated by a tensile test. The β phase is dominantly observed in the Zr-20Nb as well as in the Pt-added and Pd-added Zr-20Nb alloys. Needle-like microstructures are observed in equiaxed grains in all alloys. Pd addition to the Zr-20Nb alloy suppresses ω phase formation more than Pt addition does. The 0.2% offset yield strength and the ultimate tensile strength of the Pt-added and Pd-added Zr-20Nb alloys increase with the Pt and Pd concentrations. XRD analysis revealed that the lattice parameter of β-Zr in the Pt-added and Pd-added Zr-20Nb alloys decreases with the Pt and Pd concentrations. Pt and Pd solute in β-Zr as a substitutional element and contribute to the increase in the strength by solid solution hardening. The addition of 2Pt and 2Pd to the Zr-20Nb alloy also improves metal elution from the alloys in lactic acid solution.     

Ba(OH)2·8H2O/泡沫铜相变复合材料的制备及传热性能

采用SEM和X射线能谱仪分析方法研究了50次热循环后Ba(OH)₂·8H₂O与铝合金和紫铜的相容性,发现Ba(OH)₂·8H₂O对铝合金有一定的腐蚀性,与紫铜具有优良的相容性.以简单的真空吸附填充方法制备了Ba(OH)₂·8H₂O/泡沫铜相变复合材料.搭建了含和未含泡沫铜相变储能装置实验台,对Ba(OH)₂·8H₂O/泡沫铜相变复合材料进行室温下稳态和瞬态的传热实验.结果表明:Ba(OH)₂·8H₂O/泡沫铜相变复合材料比纯Ba(OH)₂·8H₂O传热速率快,导热性能好,有效地降低了Ba(OH)₂·8H₂O的过冷度.高温恒温箱的传热实验表明:Ba(OH)₂·8H₂O/泡沫铜相变复合材料的蓄热能力随外界环境温度的升高而降低,当环境温度高于材料相变点温度时,应考虑对相变复合材料采取一些保温措施.     

Synthesis and characterization of PtSn/carbon and Pt3Sn/carbon nanocomposites as methanol electrooxidation catalysts

Two Pt-Sn/vulcan carbon nanocomposites containing nanoclusters of PtSn (niggliite) and Pt3Sn highly dispersed on a carbon powder support have been prepared using Pt(SnPh2Cl)(PPh3)2(Ph) or [Pt3[mu-(PPh2)2CH2]3(mu 3-SnF3) (mu 3-CO)][PF6] as single-source precursors of metal alloy. PtP2 or Pt metal is also present as a secondary phase. Bimetallic Pt-Sn nanoclusters with an average diameter of 5-8 nm are formed at a total metal loading of ca. 15 wt%. Evaluation of both Pt-Sn/C nanocomposites as electrooxidation catalysts in a direct methanol fuel cell gives fuel cell performances comparable to that expected for Pt-Sn catalysts prepared by more conventional methods.     

Age-hardening by miscibility limit of Au–Pt and Ag–Cu systems in an Au–Ag–Cu–Pt alloy

The age-hardening by miscibility limit of Au–Pt and Ag–Cu systems in an Au–Ag–Cu–Pt alloy was examined by characterizing the hardening behavior, phase transformations and changes in microstructure, and elemental distribution during aging. The hardness increased by the transformation of the parent α₀ phase into the α₁ and metastable AuCu I′ phases, but not by the further transformation of the metastable AuCu I′ phase into the stable AuCu I phase due to the simultaneously initiated lamellar-forming grain boundary reaction. The replacing ratio of matrix by lamellar structure was not directly proportional to the AuCu I phase formation. The relatively high Pt content caused the severe exclusion of Au from the Cu-rich layer of the lamellar structure due to the overlapped miscibility limit of both Au–Pt and Ag–Cu systems.     

(Ba(x)La(1-x)(2))In(2)O(5+x) (0.4 < or = x < or = 0.6) electrolyte-supported mixed-potential CO sensors

The dense (Ba(x)La(1-x)(2))In(2)O(5+x) electrolytes with different compositions (x = 0.4, 0.5, 0.6) were synthesized by Pechini method. The obtained sintered (Ba(x)La(1-x)(2))In(2)O(5+x) electrolytes showed a high relative density of approximately 98%, and the major phase of three electrolyte compositions was indexed as a cubic phase. The CO sensing properties of as-fabricated planar-type (Ba(x)La(1-x)(2))In(2)O(5+x)-based sensors coupled with ITO and Pt as the sensing electrode and reference electrode, respectively, were investigated. The effects of factors such as gas flow rate, chemical compositions, and density of the electrolytes on the sensing performance were investigated. The sensors showed good sensitivity to different concentrations of CO from approximately 100 to approximately 500 ppm and excellent selectivity over low concentrations of methane (<500 ppm). Linear relationships between emf of the sensors and CO gas concentrations from approximately 100 to approximately 400 ppm were observed. However, the sensors indicated more sluggish response compared with the sensors coupled with a corresponding porous electrolyte. The probable reason has been discussed. The long-term stability of the sensor for the detection of CO was also investigated, which indicated a reasonably stable sensor signal after an initial decline during the incubation period.     

Tuning the perpendicular magnetic anisotropy of co-based layers in multilayered systems

The combination of Pt with Co either in alloy or in multilayer form is widely studied among the potential magnetic media for ultrahigh density magnetic recording. On the other hand the combination of Co with Cr in alloy form is currently providing commercial magnetic media. In an effort to further exploit and benefit from both systems, we fabricated Co(1-x)Cr(x)/Pt multilayers with two adjustable parameters. The first one is the Cr concentration on CoCr layer (x = 0, 5, 30), which modulates segregation effects on Co grains, thus tunes macroscopic magnetic features such as saturation magnetization and coercive field. The second one is the small layer thickness (< or = 0.6 nm) that affects interlayer coupling, perpendicular magnetic anisotropy and magnetization enhancement through spin polarization of Pt atoms in a ferromagnetic environment. The X-ray diffraction patterns verified the existence of multilayered structures following a preferable face-centered-cubic stacking. The Pt thickness and Cr concentration are found to significantly affect the macroscopic magnetic behavior. It is remarkable the fact that, samples present perpendicular anisotropy that scales with Pt thickness and temperature, even in the case of significant Cr concentration (30% in the alloy) when ferromagnetic behavior is expected to diminish according to relevant studies in alloys and in bulk films. Such an effect may be attributed to spin-polarization of Pt interlayers and was evidenced by X-ray magnetic circular dichroism. The spin-polarization of Pt is also the drive for the strong magneto-optic enhancement in the ultra-violet region between 4.5 and 5 eV shown by magnetooptic Kerr spectroscopy.