Investigation of Nanocrystalline Fe-Cu-Nb-Mo-Si-B Alloy

The soft magnetic properties are reported for newly-developed nanocrystalline Fe72.7Cu1Nb1.8-Mo2Si13B9.5 and Fe73Cu1Nb1.5Mo2Si13B9.5. The high frequency core losses of the new alloys are as follows: P3/100K=473 kW·m-3, P2/200K=750 kW·m-3, P2/500K=3400 kW·m-3,P0.5/1000K=680 kW·m-3, which are clearly lower than those of the early-developed Fe-Cu-Nb-Si-B nanocrystalline alloys and the superior power MnZn ferrite H7.4. The dependences ofcore loss on frequency and amplitude magnetic flux density have been analysed. The temperature relations of initial susceptibility have been examined for as-quenched and different annealedFe72.7Cu1Nb1.8Mo2Si13B9.5 alloy and interpreted by using the phenomenological theory.     

Density of Liquid Ni-Cr Alloy

The density of liquid Ni-Cr alloy was measured by a modified sessile drop methold.The density of liquid Ni-Cr alloy was found to decrease with increasing temperature and Cr concentration in the alloy,The molar volume of liquid Ni-Cr alloy increases with increasing the Cr concentration in the alloy ,The molar volume of Ni-Cr alloy determined in the present work shows a positive deviation from the linear molar volume.     

Functionally Graded Ti-50.5Ni Alloy

Transformation behavior and shape memory characteristics of a temperature gradient annealing（TGA） treated Ti-50.5Ni （at%） alloy have been investigated by means of differential scanning calorimetry（DSC） and thermal cycling tests under constant load. By annealing the specimen under the temperature gradient from 823 K to 658 K after solution treatment, the B19＇ martensitic transformation start temperature changed by 60 K along the length of sample （150mm）. Temperature dependence of transformation elongation （dc./dT） of the TGA treated wire was found to be O. 16 %/K. By annealing the specimen under the temperature gradient from 823 K to 658 K after 47 % cold working without solution treatment, the B19＇ martensitic transformation start temperature changed by 61K along the length of sample （150ram）. Temperature dependence of transformation elongation （dJdT） of the TGA treated wire was found to be 0.04 %/K. The large decrease in de/dT by cold working effect suggested that an introduction of dislocation was more effective than precipitates for lowering de/dT,     

Quasicrystalline Phase in As-cast Mg-Zn-Y-Zr Alloy

An icosahedral phase in as-cast Mg 5. 78Zn-0.89Y-0.48Zr (wt-%) alloy has been identified with transmission electron microscope (TPM) The selected area diffraction patterns (SADP) from the phase show a five-fold symmetry of a quasicrystalline structure. The energy dispersive X-ray spectra (EDXS) indicate that the quaternary phase has a chemical composition of 67.6Zn-1 9.4Mg-8,1 Y-4 9Zr in at -%     

Annealing Embrittlement in Fe-Mo-Si-B Amorphous Alloy

Annealing at Ta=200℃ or so, the enhancement in the average tensile fracture strength of as-quenched (Fe0.99Mo0.01)78Si9B13 metallic glass increases about 7～8%. The origin of the annealing embrittlement at 244℃ in the metallic glass (Fe0.99 Mo0.01)78Si9B13 was revealed that due to the formation of nanoscale granular with bcc structure resulting in the stress localization.The temperature of annealing embrittlement was in agreement with the calculated value from Tbcc=0.637Tc (Tc is the crystallized temperature), based on micromechanism of crystallization of metallic glass.     

Microstructures of Thermomechanically Treated Eutectoid Zn-Al Alloy

A continuously cast eutectoid Zn-Al alloy was extruded at about 250℃ and the complex microstructures of three phases (α. ε and η'E) were observed in the extruded eutectoid Zn-Al alloy.The fcc Al-rich α phase appeared as isolated particles with clear boundaries instead of the α phase occurring with diffuse boundary within the dendrites of the as-cast structure. A new unstable phase η'E was determined to have hexagonal close packed crystal structure. The decomposed β's, phase comprised the matrix. The new phase η'E decompoeed and a four phase transformation α+ε T'+η occurred afterwards during the isothermal holding. The extruded alloy tended to be stable after these two phase transformations. The early shrinkage and the following increase in dimension were related to the decomposition of the new phase η'E and the four phase transformation.     

Age Hardening in Rapidly Solidified Al-V-Zr Alloy

Rapidly solidified Al-3.9V-0.1 Zr alloy is a single sol-id solution.The metastable limited solid solubility ofsolute V in Al reaches 3.9 wt-% under about 10~6 K/scooling rate.A strong age hardening response have beenobserved in this alloy.A large amount of dislocation linesand loops were observed in the alloy aged at 100-150℃:and an age peak occurs at 450℃,the hardness value in-creases by a factor of 2.The precipitate which is responsi-ble for age hardening is identified to be Al_V(Al).     

Laser Welding of TC-1 Titanium Alloy

The technology of CO2 laser welding and joint properties of titanium alloy were investigated. The problem of molten pool protection was resolved by designing a shielding trailer and a special clamp. Joints with silvery appearance were obtained, which have no pore and crack. In addition, the welding speed could reach 3 m/rain for the plate of 1.5 mm thickness being penetrated. The reason of the porosity formation in partial penetration joints is that the keyholes can be easily cut apart in the radial direction, which makes the gas enclosed in the molten pool. The surface oxide of specimens can not affect the porosity formation in welds directly.     

Alloy Model for the Stacking Fault Energy

An accurate and simple model of stacking fault energy for alloys (solid solutions) has beendeveloped based on the embedded-atom method. The calculated value of stacking fault energy35 mJ/m2 for 304 austenitic stainless steel, is in a good agreement with the experimental one,30 mJ/m2. In the present model we find that the Hirth's empirical relationship is also suitablefor alloy.     

Calculation of Point Defects in NiAl Alloy

The potential functions of the F-S model for ordered high-temperature intermetallic compound NiAl with a B2 structure are constructed. Using the potential, the point defects properties were studied by molecuIar dynamics method, the results are in good agreement with that by EAM method and the experiment values. Meanwhile, the results clarify the experiments of two recovery stages in quenched NiAl alloy, and indicate that the two stages are corresponding to the recovery of Ni vacancies and of Al vacancies     

Diffusion of Hydrogen in Amorphous NiCrFeSiB Alloy

The diffusion of hydrogen in amorphous NiCrFeSiB alloy has been studied by electrochemicalmethod. In the temperature range of 20~50℃, diffusion coefficient of hydrogen in the alloy fol-lows the equation' D(cm2/s)= 9.27x10-8exp(-53.4 kJ/RT). At room temperature the diffusion.coefficient D and the solubility Co are 6.125x 10-12 cm2/s and 0.007 mol/cm3, respectively.When As2O3 is added into the cathodic solution or the charging current density is increased, thediffusion coefficient and solubility increase, and the difFusion activation energy decreases. Theinfluence of amorphous structure on diffusion and solution of hydrogen is discussed.     

Development of Biomedical Superelastic β Titanium Alloy

新型β钛合金具有良好的耐磨性和力学性能、高抗腐蚀性以及优良的生物相容性,因而在生物医学领域得到了越来越广泛的应用.综述了钛合金的发展阶段及新型超弹性β钛合金的研究发展状况和最新进展,探讨了几种热处理工艺对钛合金超弹性的影响,介绍了几种钛合金表面改性方法,结合我国研究现状提出了新型超弹性β钛合金存在的问题,展望了其研究发展方向.     

Oxidation of Hastelloy-XR Alloy for Corrosion-Resistant Glass-Coating

The oxidation behavior of Hastelloy-XR alloy was investigated to obtain the optimum surface condition for corrosion-resistant glass-coatings. The surface morphology of oxide scales changed significantly with variation of temperatureand oxygen partial pressure (po2 ). The oxidation kinetics was mainly parabolic independent of oxidation conditions.The oxide scales were consisted of inner Cr2O3 and outer spinel layers. The phase component of spinel layers wereMn1.5Cr1.5O4 and (Mn,Ni)(Cr,Fe)2O4 for the oxygen partial pressures po2<10 kPa and po2>10 kPa, respectively.The optimum oxidation condition to obtain an oxide scale for well-adhered glass-coating to the substrate was 1248 Kand po2 =0.01 kPa for the oxidation time of 43 ks.     

Microstructure and Mechanical Properties of TiAl-based Alloy

Two phases gamma titanium aluminide alloy,Ti-46.5Al-2.5V-1Cr.was investigated to characterizemicrostructures and to define the microstructure/mechanical property relationship.Many kinds ofmicrostructure of gamma and α_2 phases were obtained by heat treatments in the α+γ,α_2+γ and αfields.The effects of microstructure on tensile properties,fracture toughness and J-R resistancecurve at room temperature,were systematically studied.The experimental results showed that themicrostructure had a strong effect on mechanical properties,The duplex microstructure produced byheat treatment at 1250℃×4 h with controlled cooling resulted in the highest ductility of 4.8% tensileelongation,low fracture toughness and crack growth resistance.The fully lamellar microstructureproduced by heat treatment in the α field having large grain sizes resulted in the highest fracturetoughness but the lowest ductility.     

Diffusion Bonding of Ti_3Al Base Alloy

: The effects of diffusion bonding temperature and holding time on the joint strength of Ti3Al base alloy has been investigated in this paper. The shear strength of Ti-14Al-21Nb-3Mo-V alloy diffusion bonding joint under pressure of 12 MPa at 990℃ for 70 min was obtained to 797.6 MPa which approaches the base material strength. In addition, a short-time diffosion bonding process was studied in order to decrease the bonding cost. With the deformation of the specimens of 2.5% and the bonding temperature of 990℃ for 15 min, the bonding strength could reach 801 MPa.     

Density of Ni-Cr Alloy in the Mushy State

The density of Ni-Cr alloy in the mushy state has been measured using the modified sessile drop method. The density of Ni-Cr alloy in the mushy state was found to decrease with increasing temperature and Cr concentration in alloy. The molar volume of Ni-Cr alloy in the mushy state therefore increases with increasing the Cr concentration in alloy.The ratio of the difference of density divided by the temperature difference between liquidus and solidus temperatures decreases with increasing Cr concentration. The density of the alloy increased with the precipitation of a solid phase in alloy during the solidification process. The temperature dependence of the density of alloy in the mushy state was not linear but biquadratic.     

Technique of Aluminum Alloy Composite by Inversion Casting

The influence of the temperature of liquid aluminum alloy,the dipping time in liquid alloy and the thickness of base strips on the solidified layer was studied during the process of producing aluminum alloy composite strips used in automobile radizator with inversion casting.It is concluded that there is welding as well as diffusion of alloying elements between the base strip and the coating.Experiments proved that the interface has a good bonding.