The float zone melting directional solidification device with super high temperature gradient has been used to prepare the TbDyFe magnetostrictive alloy and samples of 110 and 113 preferred orientations were obtained. The preferred orientation, microstructure and magnetostriction of TbDyFe alloy have been investigated. Under a 20MPa compressive stress, typical magnetostriction values of 110-oriented and 113-oriented grain-aligned rods are respectively 1.8×l0-3 and 1.6×l0-3 in 517.5 kA·m-1 applied field. Morphology changes with the increasing of the growth velocity from facet to nonfacet. Seed crystals can speed up competitive growth of crystals and promote 110 and 113 preferred orientations along axial direction. It has also been found that heat treatment can improve the magnetostriction in the TbDyFe alloy.TbDyFe magnetostrictive alloy, directional solidification, seed crystal
A tribological research advance in recent years for PEEK and its composites were described as following three aspects: Research about friction and wear properties; Research about the transferred film formed during sliding; Research about the wear debris. The tribological properties of bearing and gear of PEEK composites were discussed. The comparison of tribological tests for the plasma treatment specimen and the grain-reinforced specimen of PEEK and its composites was made. It is shown that the tribological properties are improved a lot. These research are useful for the industrial applications of PEEK and its composites.
The multicomponent Zr-Al-Ni-Cu-Ag amorphous alloy powders were obtained by me- chanical alloying from the elemental constituents. The crystallization of mechanical alloyed amorphous Zr-based alloy was studied by DSC, X-ray diffraction. After isothermally annealed at a temperature in the supercooled liquid region. the icosahedral quasicrystal and some unknown phases precipitated in the Zr65Al7.5Ni10Cu7.5Ag10 amorphous alloys. After annealing at 713K, Zr2Cu phase precipitated. After the samples were annealed at 758K, the Zr2Cu phase were found as a single precipitation phase. The transformation of the amorphous alloy upon heating can be represented as follows: amorphous phase→icosahedral phase+amorphase→+amorphous phase→Zr2Cu + Zr2Ni + Zr2Al3.
The Zr55Al10Ni5Cu30 metallic-glass matrix composite with 6.5 cm in length and 4.3 mm in diameter have been produced by using the melt infiltration casting method. The samples reinforced by continuous tungsten fibers were quenched after infiltration the reinforcement. The mi-crostructure of the composite was analyzed by x-ray diffraction and scanning electron microscopy at different conditions. The lower interface reaction and fully amorphous matrix can only be obtained by a suitable infiltration temperature and time. The conditions were more rigorous compared to those of making Zr-Ti-Ni-Cu-Be matrix composite due to the lower glass forming ability and higher melting temperature of Zr55Al1ONi5Cu30 alloy.
Monolayer film of n-Alkanoic acid expected to be an excellent lubricant for micro- machines was successfully prepared on PEI-coated glass substrate for the first time. The results of Contact-angle measurement and X-ray photoelectron spectroscopy (XPS) showed that n-Alkanoic acid chemically attached to the functional surface of PEI coatings. As a result, steady monolayer film of n-Alkanoic acid was prepared in the presence of a covalent amide bond between carboxylic group in n-Alkanoic acid and the primary or secondary amine groups in PEI. The lower surface energy generated lower friction forces and well-ordered and high packing densities of organic films corresponded to excellent properties of tribology.
The microstructure and strengthening mechanism of NiCrBSi system alloy powder (1.0%C, mass fraction) surfacing layer by light beam heating were investigated by means of X-ray diffraction, SEM, EDAX, microhardness, Rockwell hardness, etc.. The results showed that the light beam Ni-based alloy powder surfacing layer can metallurgically bond with the Fe-C alloy substrate. The surfacing layer has lower dilution and no cracks. The influence of heat input on dilution and burning loss of alloy elements determines the microstructure and the phase constitution of surfacing layer. When lower heat input is used, the microstructure of surfacing layer with lower dilution (n=3.5%) consists of high hardness phases (Cr23C6, (Cr, Fe)7C3) precipitated on hypoeutectic matrix composed of a little of primary y-Ni and a lot of trinary eutectic of γ-Ni+Ni3B+Ni3Si. When higher heat input is used, the dilution of surfacing layer is as high as 12% and the surfacing layer consists of a lot ofγ-(Fe, Ni) dendrite and a little ot γ-(be, Ni)+M7C3 binary eutectic. T here is no primary carbide in this kind of surfacing layer. The precipitation of carbide M23C6 and M7C3 and eutectic Ni3B and Ni3Si, and the oversaturatedγ phase by alloy elements result in the strengthening of surfacing layer. Compared with TIG surfacing, the wear resistance of light beam surfacing layer is 3 times higher than that of TIG surfacing layer with the analogical heat input.
The deformation behavior and energy absorption characteristics of cellular Al alloy (ZL111) with high strength have been investigated. The stress-strain curve of cellular Al alloy consists of three distinct regions, i.e., the linear elasticity region, the plastic collapse region or brittle crushing region, and the densification region. The cellular Al alloy has a higher collapse stress than that of the cellular Al. The rake of the plateau of the compressive curve of the cellular Al alloy is smaller than that of cellular Al. So the cellular Al alloy is more suitable for energy absorbing. The peak of the energy absorbing efficiency of the cellular Al alloy is 0.85 at the strain 0.15-0.6.
XPS analysis was used to study the composition and structure of passive film of 304 stainless steel in Simulated Occluded Corrosion Cell(SOCC) containing MoO42- + Cl- and the retarding function and inhibiting effect of MoO42- to local corrosion. The effect of MoO42- to passive film is found, MoO42- was absorbed in the surface of metal when it migrated into Occluded Corrosion Cell (OCC) to replace or partly replace Cl- absorbing in the surface of steel, and to react with Fe2+ producing dissolved FeMo04 depositing in corrosive hole, contributing to repassive of corrosive hole, and retarding propagation of corrosion; The absorption of MoO42- resulted in transform of the hydrateferrous oxide deposition film from anions selection to cation selection and diffusion of H+ out from film, and it is difficult to diffuse for Cl- into film to rich, so MoO42- had inhibiting function.
The microstructures and mechanical characteristics of the semi-solid 60Si2Mn rolled for one pass were investigated. Results show that the microstructures of semi-solid slurry were obviously improved although only one pass rolling. The liquid and solid phases in rolling state were separated. The solid phase gets together at the center of the rolled piece, and the liquid phase flows to the edge of the rolled piece, these led in liquid segregation and the difference of microstructural and mechanical characteristics between center and edge region. Only when the solid fraction overpasses critical value, the solid phase can be deformed and solid particles are extended.
The solid state synthesis reactions between elemental α-Fe powder and m-phenylene diamine (C6H4(NH2)2) have been studied. The phase transformation in the milling process is α- Fe→α＇-Fe(N)→e-Fe2-3N. The single supersaturated e-Fe2-3N phase with nitrogen concentration up to 11.53%(mass fraction) was obtained after ball milling for 250h. Owing to the local inhomogeneity of N content the e-Fe2-3N phase can be formed by ball milling at room temperature, even though the sample has a low average N content. The saturation magnetization Ms and coercivity Hc of e-Fe2-3N are 81.4 emu/g and 16.3 kA/m respectively. Thermal analysis experiments show structural stability of the e-Fe2-3N phase up to 512.0℃. The results show that the solid-solid reaction is more efficient than the solid-gas reaction.
The phase transformation induced by 0.0049N and 0.049N Vickers indentation in GaAs single crystal has been investigated using high-resolution electron microscopy. The results showed that the transformations from crystal to micro-crystal line and amorphous phase were caused by the high and low load indentations, respectively. The micro-crystal consists of nano-crystals and amorphous structure. Nano-crystals with the size of tess than 10 nm have different orientations. Some clusters with the size of several atoms were found in the amorphous phase. Many defects, along which lattices distorted and amorphous phase islands formed, were observed in the interface between amorphous phase and crystal. High-pressure induced amorphization and shear-deformation induced amorphization are proposed to interpret the amorphization induced by indentation in GaAs.
The amorphous Ag11ln12Te26Sb51 thin films were crystallized by initializer. The crystallization behavior of amorphous Ag11In12Te26Sb51 thin films was investigated by using differential scanning calorimetry (DSC), XRD, and optical transmissivity measurements. For amorphous Ag11In12Te26Sb51 thin film, the crystallization temperature is about 210℃ and the melting temperature is 481.7℃. The activation energy for the crystallization, Ea, is 2.07 eV/atom. The crystallization dynamics for Ag11ln12Te26Sb51 thin film obeys the law of nucleation and growth reaction. A mixed crystalline, including AgSbTe2, AglnTe2, Sb and Ag2Te phase, was observed during the laser-induced Ag11ln12Te26Sb51 phase change process. The initialization power and velocity affect the Ag11ln12Te26Sb51 film's crystallization fraction.
The Nd2Co17_xMnx compounds have a rhomhedral Tr2Zn17-type structure. Their unit-cell volumes increase slowly with increasing x, then rapidly with the further increase of x. This implies there is a positive spontaneous volume magnetostriction in the magnetic state for Nd2Co17_xMnx compounds. The Curie temperature and the saturation magnetization at 4.2 K of these compounds rapid drop with increase of x. This implied there is a crossover between the low x range, where the Co sublattice is ferromagnetic and the Co-Co ferromagnetic interaction is dominant, and the high x range where the antiferromagnetic interactions play a substantial role. The spin reorientation is observed at about 234 K in the Nd2Co14Mn3 compound.
Fluorinated activated carbon fibers (FACF) were prepared from activated carbon fiber (ACF) reacting directly with fluorine. Compared XPS of FACF with that of reference materials, carbon atom is sp3 hybridization, and is combined with fluorine by covalent bond. The result of αs plots for nitrogen adsorption showed that the specific surface area and micropore volume of FACF were remarkably lower than those of ACF, but the micropore width was not changed. Type V isotherm is observed from the adsorption of water on ACF, however, the amount of water adsorbed on FACF is small. Fluorinated micropore possesses a perfect hydrophobicity and a high stability. The adsorption isotherms of ethanol and methanol on ACF are type I and those on FACF are close to type I, but amount of adsorption was markedly decreased by fluorination.
The effect of heating on the microstructure and mechanical properties of new-type high Co-Ni alloy is investigated. The optimal strength and toughness is attained when tempered at 482 ℃ for 5 h, σb ≥1960 MPa, σ0.2 ≥1740 MPa, and K1c ≥112 MPa·m1/2. Microstructure examinations show that the steel is the typical tempering martensitic steel, the superior performance is achieved by precipitating fine carbides during isothermal tempered and the needle-shaped carbides precipitated in the coherent way with ferrite matrix, and the reverted austenite had a thin-film morphology presenting in plate boundary. When tempered at much higher temperature, needle-shaped carbides of M2C would coarsen and loss the coherent relationship with matrix, and changed into other kinds stable carbides, such as M23C6 and M7C3; meanwhile, the volume fraction of revered austenite increased rapidly in-lath and inter-lath, which cause the properties descended dramatically.
The effect of the heat treatment on the content and morphology of δ-Ferrite in the as-cast duplex stainless steel 0Cr17Mn14Mo2N were studied. The results show that when the heat treatment temperature is between 1050 and 1150℃. the microstructure is the austenite matrix embodied by spheroid and strip δ-Ferrite, δ-Ferrite content and spheroidized rate increase with the temperature and the hold time. When the temperature is higher than 1250℃. the microstructure consist of only isometric δ-Ferrite. The tensile property of this duplex stainless steel at the room temperature was studied also.
The phase selection in Al65Cu20Cr15 quasicrystalline coating produced by laser cladding was studied as a function of the laser power and scanning speed. A parameter δ, defined as the ratio of the laser power, P, to the scanning speed, v, has been used to understand the effect of the laser parameters on the phase selection of layer claddings. Experimental results indicated that the icosahedral (i) phase could be formed for low value of δ, and that especially the volume fraction of (i) phase was essentially dependent on the scanning speed. On the contrary, high value of δ enabled the formation of the decagonal (d) as a consequence of Fe diffusion from the substrate. The surface microhardness of the cladding coatings is different from each other for specimens prepared with different parameters,owing to the difference of the phase composition.
The high temperature oxidation characteristics of a single crystal Ni-base alloy was investigated by means of observation of microstructure and measurement of kinetic curves of the isothermal and cyclic oxidation. Results show that the internal oxidation has obviously occurred in sub-layer of the alloy during high temperature oxidation in air. The poor Al areas appeared in near internal oxides, which resulted in the disappearance of γ' strengthening phase. The relationship between depth of internal oxidation layer and oxidation time obeyed a parabolic law, and the process aggravates when the external tensile stress was applied during high temperature oxidation. In the initial stage of cyclic-oxidation, the kinetic curves displayed a rapid mass loss as a result of peeling from the Al scale. In the period of 20-80 h of cyclic oxidation, there were gentle changes of mass gain or loss at 1040℃ and 1070℃. respectively.
The morphology, structure, fracture behavior and mechanical properties of TLCP/GF/PP in-situ hybrid composites were investigated. The addition of TLCP minimized the breakage of glass fibers during melt processing. Statistical results of solvent extracted samples indicated that the average length of GF in TLCP/GF/PP in-situ hybrid composite is 2.36 times of that in GF/PP composite, resulting in more significant main load-bearing role. The fracture process observed by SEM with a dynamic tensile stage showed that the dispersed phase of TLCP could delay and block the propagation of microcracks. The tensile strength and elongation at breakage of TLCP/GF/PP5/15/85 were 22.6% and 321%, respectively , higher than that of GF/PP15/85. The tensile strength of in-situ hybrid composite was improved further when using PP-g-MAH as the coupling agent and compatibilizer.
The phase field method is proposed based on the general Ginzburg-Landau theory of phase transitions. This method reflects these basic ideas in terms of differential equations, where diffusion, ordering potential and thermodynamic diving force are represented by operations of appropriate symmetry. The dendritic morphology of pure melt (Ni) undercooled has been computed during solidification in this paper. The anisotropy of crystal was taken into account . The phase field model equations have been solved using the explicit finite difference method on an uniform mesh. The simulated results show the dendritic crystal growth process, including primary and secondary arms, the competition between the dendritic arms as well as the necking during the dendrite growth process.
