Y2O3对超细Mo复合粉末烧结性能与显微组织的影响

以仲钼酸铵(NH<,4>)<,6>Mo<,7>O<,24>·4H<,2>O和硝酸钇Y(NO<,3>)<,3>6H<,2>O为原料,采用喷雾干燥-煅烧-热还原工艺制备含Y的超细Mo复合粉末,粉末经成形、预烧和高温烧结制备细晶Mo合金,研究Y<,2>O<,3>对超细Mo复合粉末烧结性能与显微组织的影响.结果表明:热还原后稀...     

热压制备Mo-Nb-Si系新型高温金属硅化物合金

以Mo粉、Nb粉和Si粉为原料,采用机械活化/热压工艺制备(Mo1-xNbx)5Si3(x=0,0.4,0.6,1.0)型高温金属硅化物.通过XRD、SEM和EDS等分析手段对合金试样进行物相分析、显微组织观察、微区成分分析及力学性能测试.结果表明:合金试样的主要物相为Mo5Si3、α-Nb5Si3、γ-Nb5Si3及其(Mo,Nb)5Si3和β-(Nb,Mo)5Si3固溶体相,Mo有助于高温相β-Nb5Si3的相稳定;随着Nb含量的增加,硬度值呈上升趋势,合金硬度较高,达1 311.5～1 397.5HV;试样的压痕断裂韧度和抗压强度呈先增加后降低的趋势,当x=0.6时断裂韧度和抗压强度达到最大,分别为4.71 MPa·m1/2和1 637 MPa,Nb5Si3和Nbss(Nb基固溶体)有助于合金断裂韧度的提高.     

TiAl及TiAl-9Nb合金抗热腐蚀性能研究

研究了TiAl及TiAl-9Nb合金在850℃下25%NaCl+75%Na_2SO_4(质量分数)熔盐中的热腐蚀行为,采用扫描电子显微镜(SEM)、能谱分析(EDS)和X射线衍射(XRD)分析了腐蚀产物膜的结构和相组成。结果表明:TiAl和TiAl-9Nb合金的腐蚀产物均主要由TiO_2, Al_2O_3和少量的TiS组成,腐蚀产物膜结构疏松,容易剥落,对基体的保护性很差。在热腐蚀过程中, NaCl对TiAl和TiAl-9Nb合金的表面氧化膜造成了破坏,生成的Cl_2导致了表面氧化膜的开裂;继而O和S对TiAl合金中的α_2相、 TiAl-9Nb合金中的β相产生了内氧化、内硫化的选择性腐蚀。与普通TiAl合金相比, TiAl-9Nb合金具有更优异的抗热腐蚀性能,这归因于TiAl-9Nb合金中β相较高的Al含量以及β相与α_2相之间组织结构的差异。     

Nb含量对TiAl合金铸态组织的影响

利用金相显微镜(OM)、X射线衍射仪(XRD)和扫描电镜(SEM)及能谱分析(EDS)等测试方法研究Nb含量对铸造TiAl-xNb(x=1,3,5,7;原子分数,%)合金组织的影响。结果表明:Nb含量为1%时,TiAl-Nb合金铸锭组织主要为单相的γ组织;随Nb含量升高,合金组织主要为α2/γ层片组织;并在层片组织间存在2种偏析,分别是网状β相和γ相,合金的层片晶团平均尺寸逐渐增加,β相的体积分数逐渐升高;当合金中Nb的含量从1%增加到7%,层片晶团平均尺寸由89μm增加至190μm,β相的体积分数从1.9%增至12.9%;随合金中Nb含量增加,β相中Nb含量增加而Cr含量减少,γ相的偏析区域宽度变窄。     

Nb含量对铸造高铝TiAl合金室温拉伸性能的影响

研究了Nb含量对铸造高铝Ti Al合金(%,原子分数)Ti-48Al-x Nb-2.5V-1.0Cr(x=2,4,7,9),以下分别简称2Nb,4Nb,7Nb和9Nb合金)组织和室温拉伸性能的影响。组织观察发现:不同Nb含量合金宏观组织均为柱状晶组织,微观组织均为有取向层片组织。经X射线衍射(XRD)分析表明,不同Nb含量合金均由γ相、α_2相和少量的B2相组成,其中,γ相体积分数随Nb含量的增加而增多;α_2相体积分数随Nb含量的增加而减少;B2相含量由于含量较少无法定量,但从XRD谱及扫描电镜(SEM)背散射(BSE)图可定性得知,其含量随Nb含量的增加而显著增多。合金室温抗拉强度随Nb含量的增加而降低:由2Nb合金的648.2 MPa降为9Nb合金的613.8 MPa;但屈服强度却随Nb含量的增加而升高:由2Nb合金的561.1 MPa增为9Nb合金的613.5 MPa。合金室温延伸率随Nb含量的增加呈线性下降:由2Nb合金的延伸率1.2%,降为9Nb合金的0.3%。γ相的晶格常数c/a随Nb含量的增加而增大,这对合金的室温塑性有不利的影响。     

Nb对0Cr11铁素体不锈钢组织和性能的影响

 铁素体不锈钢与奥氏体不锈钢相比具有成本低、热膨胀系数低和耐应力腐蚀等优点,所以被广泛应用到汽车排气系统、家用电器和建筑等领域。研究了不同的Nb含量对铁素体不锈钢显微组织和力学性能的影响。研究结果表明：Nb有细化晶粒的作用,随着Nb含量的增加,晶粒的平均尺寸减小;由于合金元素Nb和Ti的加入,形成了TiN、NbC 和 Fe2Nb析出相,其透射电镜观察结果与Thermal calc计算结果一致;材料的抗拉强度和显微硬度随着Nb含量的增加而增加,这是由于Nb的固溶强化和析出强化共同作用的结果。     

Mo-Nb合金单晶的高温力学性能

研究了晶向为111Mo-Nb合金单晶的高温力学性能。实验结果表明,随着少量溶质原子Nb的加入,Mo-Nb合金单晶的高温强度获得了明显的提高。在1873K和Nb含量在0～6%范围内时(文中合金元素Nb含量均为质量百分比,下同),Nb含量每增大1%,材料的高温屈服强度就增加约16～25MPa,当Nb含量在0～3%范围内时,随着Nb含量的增加,塑性急剧下降,而在3%～6%范围内时其下降幅度趋于平缓;同时,随着Nb浓度的增大,更多的Nb溶质原子增大了原子间扩散阻力,使材料高温稳态蠕变率减小,大大提高了材料的高温抗蠕变性能;在1773K/10MPa时Mo-Nb合金单晶的稳态蠕变率较纯Mo单晶的降低了3～4个数量级,分析认为其蠕变机制为扩散蠕变。     

Nb对OCrll铁素体不锈钢组织和性能的影响

铁素体不锈钢与奥氏体不锈钢相比具有成本低、热膨胀系数低和耐应力腐蚀等优点,所以被广泛应用到汽车排气系统、家用电器和建筑等领域.研究了不同的Nb含量对铁素体不锈钢显微组织和力学性能的影响.研究结果表明:Nb有细化晶粒的作用,随着Nb含量的增加,晶粒的平均尺寸减小;由于合金元素Nb和Ti的加入,形成了TiN、NbC和FezNb析出相,其透射电镜观察结果与Thermal-eale计算结果一致;材料的抗拉强度和显微硬度随着Nb含量的增加而增加,这是由于Nb的固溶强化和析出强化共同作用的结果.     

微合金元素Nb对热塑性的影响

<正>在Nb、V、Ti等微合金元素中,Nb对钢的热塑性影响最大,随着钢中Nb含量的增加,面收缩率和温度曲线中的塑性凹槽加深变宽。含Nb钢在高温变形过程中,Nb主要以奥氏体晶粒内部的位错为核心形核、长大,也可以在晶界上析出。Nb(CN)沿奥氏体晶界的析出是造成钢热塑性降低的主要原因。钢中N含量减少,即抑制碳氮化     

铌含量对LF9合金性能的影响

 研究了不同Nb含量的LF9合金经固溶+二次时效处理后的力学性能。结果表明,随Nb含量增加,合金的室温和高温强度提高,塑性及韧性下降。经960 ℃固溶+二次时效后,合金中的主要强化相为η相,随着Nb含量增加,η相数量增多,形态由短片状变为长片层状。经1 020 ℃固溶+二次时效后,合金中的主要强化相为(γ′+γ″),随着Nb含量增加,η相形态从微量的颗粒状变为大量的短片状,对提高合金强度起到了重要作用。经(960~1 020 ℃)固溶+二次时效后,合金中(γ′+γ″)相的尺寸主要为10~100 nm。     

Electrochemical Behavior of Bulk Amorphous Steel Fe55M2Cr12Mo10B6C13Y2（M=Ni, Cu, Nb）

 Fe55Ni2Cr12Mo10B6C13Y2,Fe55Cu2Cr12Mo10B6C13Y2 and Fe55Nb2Cr12Mo10B6C13Y2 alloys with diameter of 4mm were produced by copper mold casting. The role of alloying additions (Ni, Cu or Nb) on corrosion resistance of Fe55Nb2Cr12Mo10B6C13Y2, Fe55Ni2Cr12Mo10B6C13Y2 and Fe55Cu2Cr12Mo10B6C13Y2 alloys were studied by polarization curves and electrochemical impedance spectroscopy (EIS). The results show that Fe55Ni2Cr12Mo10B6C13Y2 and Fe55Cu2Cr12Mo10B6C13Y2 alloys can be cast into bulk metallic glasses. Fe55Ni2Cr12Mo10B6C13Y2 and     

Electrochemical Behavior of Bulk Amorphous Steel Fe55M2Cr12Mo10B5C13Y2(M=Ni,Cu,Nb)

Fe55Ni2Cr12Mo10B6C13Y2,Fe55Cu2Cr12Mo10B6C13Y2 and Fe55Nb2Cr12Mo10B6C13Y2 alloys with diameter of 4 mm were produced by copper mold casting. The effect of alloying additions (Ni,Cu or Nb) on corrosion resistance of Fe55 Ni2 Cr2Mo10 B6 C13 Y2,Fe55Ni2Cr12Mo10B6C13Y2 and Fe55 Cu2 Cr12 Mo10 B6 C13 Y2 alloys was studied by polarization curves and electrochemical impedance spectroscopy (EIS). The results show that Fe55Ni2Cr12Mo10B6C13 Y2 and Fe55Cu2Cr12Mo10B6C13 Y2 alloys can be cast to form bulk metallic glasses. Fe55Ni2Cr12Mo10B6C13 Y2 and Fe55Cu2Cr12 Mo10B6C13Y2 amorphous alloys with passive potential about 1500 mV exhibit good corrosion resistance in NaCl solution of 5 % and 1 mol/L HC1 solution. The passive current density of the alloy with Ni addition is lower than that of other alloys. EIS results only show one impedance element. Amorphous alloy Fe55 Ni2 Cr12 Mo10 B6 C13 Y2 with larger charge transfer reaction resistance indicates good corrosion resistance.     

Effect of Ti Addition and Microstructural Evolution on Toughening and Strengthening Behavior of as Cast or Annealed Nb–Si–Mo Based Hypoeutectic and Hypereutectic Alloys

Room temperature fracture toughness along with compressive deformation behavior at both room and high temperatures (900 °C, 1000 °C and 1100 °C) has been evaluated for ternary or quaternary hypoeutectic (Nb–12Si–5Mo and Nb–12Si–5Mo–20Ti) and hypereutectic (Nb–19Si–5Mo and Nb–19Si–5Mo–20Ti) Nb-silicide based intermetallic alloys to examine the effects of composition, microstructure, and annealing (100 hours at 1500 °C). On Ti-addition and annealing, the fracture toughness has increased by up to ~ 75 and ~ 63 pct, respectively with ~ 14 MPa√m being recorded for the annealed Nb–12Si–5Mo–20Ti alloy. Toughening is ascribed to formation of non-lamellar eutectic with coarse Nb_ss, which contributes to crack path tortuosity by bridging, arrest, branching and deflection of cracks. The room temperature compressive strengths are found as ~ 2200 to 2400 MPa for as-cast alloys, and ~ 1700 to 2000 MPa after annealing with the strength reduction being higher for the hypoeutectic compositions due to larger Nb_ss content. Further, the compressive ductility has varied from 5.7 to 6.5 pct. The fracture surfaces obtained from room temperature compression tests have revealed evidence of brittle failure with cleavage facets and river patterns in Nb_ss along with its decohesion at non-lamellar eutectic. The compressive yield stress decreases with increase in test temperature, with the hypoeutectic alloys exhibiting higher strength retention indicating the predominant role of solid solution strengthening of Nb_ss. The flow curves obtained from high temperature compression tests show initial work hardening, followed by a steady state regime indicating dynamic recovery involving the formation of low angle grain boundaries in the Nb_ss, as confirmed by electron backscattered diffraction of the annealed Nb–12Si–5Mo alloy compression tested at 1100 °C.

     

耐蚀合金G3、G3-Z和825热加工性的研究

用Thermomacmaster-Z热模拟机和TEM,SEM研究了G3(%:0.012C、46.51Ni、24.71Cr、8.88Mo、1.15W、1.72Cu、0.10Nb)、G3-Z(%:0.014C、46.53Ni、24.05Cr、6.89Mo、1.09W、1.70Cu)和825耐蚀合金(%:0.006C、43.77Ni、22.10Cr、3.24Mo、1.90Cu、0.86Ti)1 030～1 300℃、应变量(ε)0～0.8、应变速率1～2.5 s^-1的应力-应变曲线和温度对合金最大应力和断面收缩率的影响,并分析了合金发生动态再结晶的影响因素。结果表明,G3、G3-Z、825合金动态再结晶的晶粒大小随温度补偿系数Z的增大而减小;G3、G3-Z、825合金适宜的热加工温度范围分别为1 100～1 240℃、1 130～1 220℃和1 050～1 240℃。     

Studies on synthesis and microstructure evolution of multiphase in-situ composites based on Mo-Cr-Si system

This paper presents the results on in-situ synthesis of refractory metal-intermetallic composites (RMICs), Mo-16Cr-4Si and Mo-11Cr-9Si (wt.%) multiphase alloys and their characterization. The alloys were prepared from the oxides of molybdenum and chromium by their coreduction with Si as reductant. Exothermic nature of the synthesis reactions resulted in the formation of consolidated composite as a product in a single step. As-reduced alloys were remelted by arc melting and heat treatment was given. The evolution of phases and the microstructure were studied by XRD, SEM, and EDS analysis. The multiphase microstructure consist of the silicide phases (Mo,Cr)₃Si + (Mo,Cr)₅Si₃ for hypereutectic and (Mo,Cr)₃Si phase distributed in bcc matrix comprising essentially a solid solution of (Mo,Cr) for hypo-peritectic composition. Comparative studies of the synthesized alloys were also carried out to the composition, phases, microstructure, hardness and their oxidation behavior.     

Electrochemical Corrosion and Impedance Studies of Porous Ti–xNb–Ag Alloy in Physiological Solution

Porous titanium (Ti) and its alloys are promising materials for orthopedic applications due to their low elastic modulus, high strength, excellent corrosion resistance, and biocompatibility. In this study, the porous Ti–xNb–5Ag (x = 25, 30 and 35 wt%) alloys were synthesized using the powder metallurgy approach. The effects of Nb content on the porosity, mechanical properties, and electrochemical corrosion behavior of the alloys were investigated. XRD analysis revealed that the porous alloys mainly consist of α-Ti, β-Ti, intermetallic compound (Ti₄Nb), and oxides of TiO₂ and NbO phases. Porous alloys possess the porosity ranging from 57 to 65%, due to the addition of NH₄HCO₃ (45 wt%). Increase in Nb content lead to a reduction in the elastic modulus and compression strengths of the sintered porous Ti–xNb–5Ag alloys. All three developed porous Ti–xNb–5Ag alloys show the optimum combination of elastic modulus and compression strength, which is suitable for orthopedic applications. These porous alloys exhibit excellent electrochemical corrosion resistance in the simulated body fluids, and the samples having low porosity exhibit higher corrosion resistance than high-porosity samples.

     

逆变焊机用Fe_(73.5)Cu_1Mo_3Si_(15.5)B_7超微晶合金的软磁性能

对比了Fe73.5Cu1Mo3Si15.5B7超微晶合金和目前逆变焊机主变压器普遍采用的Fe73.5Cu1Nb3Si15.5B7铁芯的静态和动态磁性能。重点研究了两种材料铁芯的饱和磁致伸缩系数、10~40kHz范围内的高频性能和脉冲性能、-40~140℃间的损耗及磁导率变化。研究结果表明,Fe73.5Cu1Mo3Si15.5B7铁芯可获得低的高频损耗、高磁导率、较低的饱和磁致伸缩系数及良好的温度稳定性,满足逆变焊机主变压器对铁芯材料的要求,同时,Fe73.5Cu1Mo3Si15.5B7带材韧性更高,可改善材料制备的工艺性能和快淬带材的力学性能,提高成材率。     

铌硅基高温合金定向凝固铸造温度场模拟计算

以铌硅基高温合金定向凝固铸造过程为对象,通过实验测试和反求法确定了铌硅基高温合金和型壳的热物性参数,以及凝固过程各界面换热系数等边界条件;利用ProCAST软件对不同抽拉速率下铌硅基高温合金凝固过程温度场进行了模拟。结果表明,随着抽拉速率由5 mm·min?1增加到10 mm·min?1,固/液界面离液态金属锡表面的距离由12.1 mm下降到8.2 mm;平均糊状区宽度逐渐变窄,由11.5 mm减小到10.4 mm。针对抽拉速率为5 mm·min?1的实验结果表明,数值模拟结果与实际定向凝固实验获得的一次枝晶间距差异在6%以内,从一个方面验证了温度场模拟结果的正确性,相关结果可为铌硅基高温合金叶片定向凝固铸造参数的确定提供参考。      

Effects of Pb and Cu additives on microstructure and wear corrosion resistance behaviour of PM Al–Si alloys

Abstract

The wear and wear corrosion resistance of Al–20Si–XPb–YCu (X=0–10 wt-%, Y=0–3 wt-%) alloys fabricated using powder metallurgy technique and subsequent heat treatments were evaluated using a block on ring tribotest. The microstructures of all aluminium alloys were observed using an optical microscope, a scanning electron microscope and an X-ray energy dispersive spectroscope. The evaluation studied the effects of applied potential and environments of dry air and 3·5 wt-%NaCl aqueous solution. The microstructural analysis showed that Pb was bimodally distributed in Pb containing alloys, and Cu particles formed the intermetallic phase CuAl₂. Additionally, the hardness of both Pb and Cu containing alloys increased significantly. The wear and corrosion results showed that the addition of both lead (Pb) and copper (Cu) increased the wear resistance and the corrosion rate, while heat treatments reduced the corrosion rate of most alloys except the Al–Si alloy. Furthermore, comparison of all alloys following heat treatment shows that the wear corrosion resistance of Al–Si alloy is inferior to that of the other alloys. Therefore, addition of Pb and Cu further improved the wear corrosion resistance. Additionally, at anodic potential, the wear corrosion rate and current density of both Al–Si and Al–Si–Cu alloys containing particle Pb were significantly lower than those of alloys containing no Pb, because the layer produced by corrosion comprised Al, O and Pb elements.     

Nanocrystallization of Amorphous Fe73. 5 Cu1 Nb3 Si13. 5 B9 Irradiated by Laser

The surface nanocrystallization of amorphous Fe73.5 Cu1Nb3Si13.5B9 radiated by CO2 laser was studied by means of M（oe）ssbauer spectroscopy, transmission electro iroscope and X-ray diffraction. The result shows that under certain technical conditions, nanocrystalline is fiound on the surface of amorphous Fe73.5 Cu1Nb3Si13.5B9 radiated by laser; the crystallization phase is α-Fe（Si） crystalline, and its size is about 10-20 nm; the nanocrystalline is uniformly distributed on amorphous base to keep the amorphous and crystallized phase in balance; the a mount of crystallization reaches 23% when the laser power is 300 W, the diameter of light spot is 20 mm, and the radiation speed is 20 mm/s. The phase balance can be controlled by adjusting the laser technology parameter. Laser radiation on the amorphous Fe73.5 Cu1Nb3Si13.5B9 alloy is an important technique for surface nanocrystallization of the amorphous alloys.