Production of Fe-P-C amorphous wires by in-rotating-water spinning method and mechanical properties of the wires

Continuous amorphous wires with high strength and good ductility have been produced in the Fe-P-C alloy system by the in-rotating-water spinning technique; however, no amorphous wires are formed, using the same technique, in the Fe-P-B, Fe-P-Si and Fe-B-C systems. The Fe-P-C amorphous wires have a circular cross-section, smooth peripheral surface, and diameters in the range of about 80 to 230m. Their tensile strength, _f, and Vickers hardness,H _v, increase with increasing phosphorus and/or carbon content and reach 3000 MPa and 895 DPN for Fe₇₅P₁₀C₁₅. Fracture elongation, _f, including elastic elongation is about 2.8%. Cold-drawing to an appropriate reduction in area causes an increase in _f and _f of about 3.7 and 79%, respectively. This increase is interpreted to result from an interaction between crossing deformation bands introduced by cold-drawing and the increase in the uniformity of shape for the drawn wires. Further, the undrawn and drawn amorphous wires are so ductile that no cracks are observed even after a sharp bending test. Thus, the Fe-P-C amorphous wires are attractive for fine-gauge high-strength materials both because of the uniform shape of the wires and because of their superior mechanical qualities.     

Mechanical properties and microstructure of high toughness Fe-base filaments produced by glass-coated melt spinning

High toughness Fe_57.5Co₅Cr₁₅Mn₁₀Cu₂B₁₀Ti_0.5 filaments having a high tensile strength of 1740 M Pa and high elongation of 11.0% were produced by the method of glass-coated melt spinning. A noticeable feature of the stress-strain curves of the filament was that rapid hardening to a high stress-level of more than 1500 M Pa was reached in the first few per cent of tensile elongation. The filament was 14.5m diameter and micropolycrystalline with a grain size of 27 nm. The crystal structure of the filament was a mixture of bcc and fcc phases and the two phases were distributed homogeneously in the filament. The high toughness of the filament related to its micropolycrystalline structure and the uniformly mixed structure of bcc and fcc phases. After heat treatment at 573 K for 600 sec, the filament developed a higher toughness with a tensile strength of 2150 M Pa and an elongation of 12.0%.     

Phase transformation of calcia-alumina-magnesia fibres produced by inviscid melt spinning

CaO-Al₂O₃-MgO (CAM) ceramic fibre produced via inviscid melt spinning (IMS) was investigated for phase transformation. Differential thermal analysis (DTA) on the as-spun CAM fibre gave two transformation peaks, one for exothermic peak at around 927°C and the other for endothermic one at around 1100°C. In order to identify each phase transformation x-ray diffraction (XRD) analysis was performed on the CAM fibres heat-treated to each phase transformation completion temperature. The exothermic peak was determined to represent crystallization of remaining amorphous phase in the as-spun CAM fibre. The endothermic peak was determined to correspond to transformation of non-equilibrium CaO · Al₂O₃ phase to equilibrium 3CaO· 5Al₂O₃ phase.     

Microstructure and mechanical properties of magnesium AZ31 sheets produced by extrusion

In the last decade magnesium has regained importance for lightweight and transportation industries since it is the lightest metal for structural applications. Therefore the increasing demand of sheet-like magnesium applications required manifold forming strategies. The extrusion is an alternative solution for the production of magnesium sheets and thin flat profiles, which are produced today mainly by rolling. This study presents the influence of the process temperature and extrusion ratio on the microstructure and mechanical properties of AZ31 extrusion sheets. The extruded sheets exhibit a coarse-grained microstructure and a pronounced mechanical anisotropy in the sheet plane caused by the extrusion texture. This texture leads to a strong dependence of deformation systems on the loading direction delivering the highest value for yielding in extrusion direction, but the lowest in transverse direction due to the easy activation of the {10-12}<10-11> extension twinning system in favorably oriented grains.     

Thermoelectric and mechanical properties of the Bi0.5Sb1.5Te3 solid solution prepared by melt spinning

This paper reports the preparation and characterization of pressed microcrystalline materials based on a p-type Bi_0.5Sb_1.5Te₃ solid solution produced from a melt-spun powder. We have examined the effect of melt spinning conditions (temperature, disk rotation rate, and purity of the inert gas in the heat treatment chamber) on the particle size and morphology of the powders and the microstructure and thermoelectric properties of hot-pressed samples and investigated the mechanical properties (compression and bend tests) of materials prepared by various methods. The thermoelectric properties of the materials (thermopower, electrical conductivity, and thermal conductivity) were studied at room temperature and in the range 100–700 K. The highest thermoelectric figure of merit ZT of the materials prepared by pressing the melt-spun powder was 1.3, whereas the ZT of the materials prepared by the other methods did not exceed 1.1. The higher ZT of the materials studied was due to their lower lattice thermal conductivity and slightly higher thermopower.     

Preparation of amorphous Fe-Zr alloys by mechanical alloying and melt spinning methods

Amorphous iron-zirconium alloys have been obtained by mechanical alloying (MA) starting from either pure elemental powders or from intermetallic compounds. X-ray diffraction was used in monitoring the amorphization process. Differences in the amorphization kinetics have been detected for the two different starting situations. The possibility of obtaining totally amorphous samples when starting from intermetallic compounds has been discussed. Amorphous iron-zirconium ribbons were also obtained by the classical melt-spinning (MS) method. A detailed structural comparison of the radial distribution functions led to the conclusion that the arrangement of the first neighbours is indistinguishable in the amorphous samples prepared by MA and MS methods.     

Enhancement of superconductivity in Pb-Bi-Sn and Pb-Bi-In alloy filaments produced by glass-coated melt spinning

The enhancement ofT _c in Pb-Bi-Sn and Pb-Bi-In system alloy filaments produced by glass-coated melt spinning was investigated as a means of producing a new type of superconducting filament with highT _c. Long filaments of Pb-Bi-Sn alloy withT _c higher than 10 K and Pb-Bi-In alloy withT _c higher than 9 K were obtained from the molten state at a temperature of 1500 K with a winding speed of 2.63 m sec^–1. For example, a Pb₄₅Bi₃₅Sn₂₀ filament withT _c of 10.1 K was 15 m in diameter and polycrystalline with a grain size of 100 nm. The structure of the filament was a mixture of , tin and bismuth phases and a metastable phase of mixed structure of bismuth and supersaturated solid solution of tin in -phase was detected. TheT _c of the filament decreased on heat treatment. A metastable phase of mixed structure of bismuth and -phase was also detected for a Pb₄₅Bi₄₅In₁₀ filament withT _c of 9.3 K. As the metastable phase for the Pb-Bi-In filament was more unstable than that for the Pb-Bi-Sn filament, theT _c of the filament was drastically decreased by heat treatment. The metastable phase was considered to play an important role in the enhancement ofT _c for Pb-Bi-Sn and Pb-Bi-In alloy filaments.     

Microstructure and mechanical properties of NiAl produced in the SHS process induced by low-temperature hydrostatic extrusion

A stoichiometric nickel aluminide intermetallic alloy produced by self-sustained high-temperature synthesis (SHS) induced to the green compacts of the mixture of elemental Ni and Al powders by mechanical heavy deformation during low-temperature hydrostatic extrusion has been investigated. The process was performed with the high strain rate (>10² s^?1) at the low temperature (～500°C). To reduce the porosity, grain size and non-homogeneity of the obtained material a further high-temperature (～950°C) hydrostatic extrusion was applied. Mechanical properties of the material were measured on the samples cut out from extruded rods in the longitudinal and transverse directions. Elastic anisotropy (elastic tensor) was determined using a resonant ultrasound spectroscopy (RUS) method applied to small cylindrical samples of the material. Its value described as the ratio of the coefficients of linear compressibility in transverse and longitudinal directions was at the level of 2 for extruded material even after annealing. Plastic anisotropy of the material was determined in uniaxial compression tests using an acoustic emission (AE) method for monitoring early stages of microcracking process in the samples under investigation. The phenomenon of the yielding point was observed for the samples compressed in the direction of extrusion.     

Poly-L-lactic acid braided fibres produced by melt spinning: characterization and in vitro degradation

Bioabsorbable fibres showing stress at break of 500 MPa and modulus of 10 GPa, have been obtained through a melt-spinning, hot-drawing process. Multifilament braids present the characteristic S-shaped stress-strain curve of human ligaments. Mechanical behaviour is affected by twisting and braiding such that stiffness can vary from 0.8 GPa to 6.2 GPa, covering the whole ligament physiologic range, reported to be 1.5 GPa, according to age and sport activity. A cyclic tension load applied for 2×10⁶ cycles lead to initial mechanical improvement and causes no creep. During degradation in vitro, yield stress increases continuously while the ultimate tensile strength (UTS) starts to decrease after 5 weeks. After 13 weeks degradation, strength loss amounts to 6% of the initial UTS. At this time the surface of the fibres shows isolated longitudinal cracks.This paper was accepted for publication after the 1995 Conference of the European Society of Biomaterials, Oporto, Portugal, 10–13 September     

Microstructure and mechanical properties of Cu and Cu-Zn alloys produced by equal channel angular pressing

Ultrafine-grained (UFG) Cu and Cu-Zn alloy were prepared using equal-channel angular pressing (ECAP) to investigate the effects of stacking fault energy (SFE) on microstructure evolution and mechanical properties. Combining with the previous researches, the grain refinement process of ECAP is divided into three stages based on the variation of tensile strength and plasticity. According to the influences of defects on strength and ductility during plastic deformation, the three stages are discussed in detail by considering the dislocation density, grain and twin boundaries. Besides, the impact of SFE on the strength and ductility of the UFG Cu-Zn alloys are evaluated, indicating that these two mechanical properties can be improved simultaneously in the whole ECAP process either through slightly or widely adjusting the SFE. This significant effect of SFE reflects in two aspects, one is in the microstructure evolution during ECAP processing and the other is in the subsequent tensile plastic deformation, both of which can be achieved through regulating the dislocation motion via changing the SFE.     

Microstructure and mechanical properties of 780 MPa high strength steels produced by direct-quenching and tempering process

Microstructure and mechanical properties of 780 MPa grade steel plate manufactured by conventional reheat-quenching and tempering (RQ-T) and direct-quenching and tempering (DQ-T) processes were investigated. The DQ process was found to enhance the hardenability of steel effectively so that tensile strengths of a range from 780 to 860 MPa have been achieved using DQ-T process, while tensile strength of about 770 MPa has been obtained from the RQ-T sample. In contrast, low temperature toughness of DQ-T samples was generally inferior to that of RQ-T sample, unless hot rolling and cooling processes were optimized in a controlled manner. For example, fracture appearance transition temperature (FATT) of DQ-T samples was varied in a range from –50°C to –120°C, while RQ-T specimens exhibited nearly constant FATT of about –80°C. The finish-rolling temperature (FRT) was one of potential process parameters to determine strength/toughness balance of the steel manufactured by DQ process, while the effect of FRT was closely associated with the cooling rate applied in the process. It has been demonstrated that, for the specimens quenched with a cooling rate higher than 20°C/sec, it may seem to be appropriate to adjust the FRT as low as possible in the non-recrystallization region. In contrast, for the specimens quenched with a low cooling rate of less than 10°C/sec, it may seem to be proper to apply higher FRT to obtain excellent strength/toughness balance of the steel.     

熔融纺丝方法制备纳米碳管/聚丙烯复合纤维及其拉伸性能

采用传统的熔融纺丝技术大量制备了定向性良好的纳米碳管／聚丙烯复合纤维。扫描电镜观察证实了纳米碳管在纤维里的定向性以及分散性都得到了较大的改善。通过拉伸实验测试了纳米碳管／聚丙烯复合纤维的力学性能，采用weibull统计分析发现纳米碳管的添加显著提高了复合纤维的拉伸强度，当添加纳米碳管的质量分数达到3％时，纤维强度最高，达到61MPa，超过聚丙烯纤维强度120％。复合纤维拉伸断口的形貌特征也证实了纳米碳管添加对复合纤维拉伸性能影响存在临界现象。     

Young's modulus of Fe-, Co-, Pd- and Pt-based amorphous wires produced by the in-rotating-water spinning method

This paper presents the Young's modulus of Fe_100?x?y Si _x B _y , Fe_100?x?y P _x C _y , Co_100?x?y Si _x B _y , Pd_77.5Cu₆Si_16.5, Pd₄₈Ni₃₂P₂₀ and Pt₆₀Ni₁₅P₂₅ amorphous wires determined from the Young's modulus sound velocity measurement. With increasing metalloid content, the Young's modulus increases from 1.58×10¹¹ to 1.87×10¹¹ N m^?2 for Fe-Si-B, from 1.40×10¹¹ to 1.52×10¹¹ N m^?2 for Fe-P-C and from 1.73×10¹¹ to 1.75×10¹¹ N m^?2 for Co-Si-B systems. The increase in Young's modulus with the amount of metalloid elements is the largest for B, followed by Si, C and then P. The Young's modulus of Fe- and Co-Si-B amorphous wires increases significantly with the replacement of iron or cobalt by IV–VII group transition metals. It was recognized that there existed a strong correlation between Young's modulus (E) and tensile fracture strength (σ _f); the ratio of σ _f to E is approximated to be 0.02 for all the amorphous wires investigated. These results imply that the Young's modulus is dominated mainly by the structural and compositional short-range orderings due to the strong interaction between metal and metalloid atoms which hinders the internal displacements. The existence of a constant ratio for σ _f/E was interpreted to originate from a common mechanism for plastic flow of the amorphous wires. Further, it was noted that the Young's modulus of the Fe- and Co-based amorphous wires with diameters of ? 100 to 120 Μm was slightly lower than that of the amorphous ribbons with thicknesses of ? 20 to 25 Μm. This difference was attributed to the difference in structural ordering due to the differences in the solidification processes.     

Microstructures and metastable phases produced in cold sintered blocks by mechanical alloying of NiAl-TiB2

The microstructure of cold sintered blocks formed on the mechanical alloying (MA) of NiAl-TiB₂ have been investigated by means of transmission electron microscopy (TEM). The results reveal that the blocks consisted of -NiAl with a B2 ordered structure and TiB₂, Al₂O₃ particles in addition to other metastable phases. The distribution of the phases and good bonding between them suggest that a sintering process occurred in-situ at low temperature in the later stage of the MA. The observed high density of dislocations and strong reaction between these dislocations and ceramic particles can explain the good toughness and high microhardness of the block. Minor crystalline and amorphous metastable phases have been found. A cold-sintering mechanism to form the block based on the metastable phase distribution has been proposed.     

Microstructure and magnetic properties of rare earth Nd-Fe system alloys produced by containerless processing

Nd_xFe_100?1.5xB_0.5x alloys (x=10, 11.8, and 14) were solidified from the undercooled melts by drop tube processing. The samples contained a large amount of the metastable phase with the composition near to their bulk composition in each alloy. The volume fraction of the metastable phase increased as the sample diameter decreased. The metastable phase was partially decomposed into very fine lamellar grains of the Nd₂Fe₁₄B and α-Fe or Nd₂Fe₁₄B and some Nd-rich phase by solid-state reaction in the samples with a diameter of 1200μm. The solidification behavior of the metastable phase was explained in terms of a hypothetic scheme of the pseudobinary Nd-Fe-B phase diagram     

熔融挤出HDPE/EVOH共混物的微观结构及性能

采用高密度聚乙烯(HDPE)接枝马来酸酐(MAH)或甲基丙烯酸缩水甘油酯(GMA)作为增容剂,熔融挤出制备HDPE/乙烯-乙烯醇共聚物(EVOH)共混物.通过扫描电镜观察、气体渗透试验以及力学性能试验,分析增容剂对共混物相容性的影响,并研究共混物的力学性能和阻隔性.结果表明:增容剂能显著提高共混物的相容性.与HDPE相...     

Fractographic analysis of vitreous calcia-alumina eutectic fibres produced by inviscid melt spinning (IMS)

The mechanical properties of inviscid melt spun (IMS) CaO-Al₂O₃ (46.5 wt % CaO-53.5 wt % Al₂O₃) eutectic fibres were examined by fractographic analysis as well as four-point bending and micro-indentation. The averaged fracture strength and elastic modulus values of the IMS Calcia-Alumina (CA) fibre were determined to be 460 MPa and 99.8 GPa, respectively by using four-point bending tests. The inner mirror constant (M) was determined to be 2.39 MPa·m^1/2 by using the plot of the fracture strength (_f) obtained from the bending tests as a function of r ^–1/2, where r is the inner mirror radius measured from scanning electron microscopy (SEM) on the fractured CA fibres. The flaw-to-mirror ratio (c/r) for the CA fibre was calculated to be 111.24. Also, the critical flaw size (c) of the CA fibre was estimated to be 2.35 m. The averaged elastic modulus value from Knoop micro-indentation was determined to be 102.5 GPa which is in good agreement with that from the four-point bending tests.     

Microstructure and mechanical performance of metal-composite hybrid joints produced by FricRiveting

The mechanical performance and microstructure of friction riveted metallic-insert joints made of polyether ether ketone composite reinforced with 30% short carbon fibers and titanium grade 3 was studied. The metallic-insert joints reached a maximal pull-out tensile force of 10.6 kN, which corresponds to 100% of the titanium base material strength. It was shown the pull-out force increased as the rivet tip widened. Frictional heat during the process was mainly generated by the friction between the tip of the rivet and the composite substrate in the friction zone. Microstructural analyses of the metallic part of the joint revealed the presence of different microstructural zones: a friction zone, and two thermomechanically affected zones 1 and 2. Based on the composite morphology, the composite part of the joint was categorized into three different zones: the stir zone, a thermomechanically affected zone and a heat-affected zone. A study of the material flow showed that the flow of the composite was strongly affected by the rotation and axial movement of the rivet.