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1.
The results of a study of the phase composition and microstructure of foils of Sn–8.0 Zn–3.0 Bi–X In (X = 1.5, 2.5, 4.5, 9.0) (wt %) alloys formed by rapidly quenching from the melt at a cooling rate of up to 5 × 105 K/s have been presented. The dependence of the phase composition of the rapidly quenched foils on the concentration of In has been determined. It has been shown that, in rapidly quenched foils, crystallization occurs with the formation of supersaturated solid solutions based on β-Sn and γ phase (Sn4In). The mechanisms and rates of decomposition of the supersaturated solid solutions at room temperature have been established. The specific features of the formation of the microstructure of the foils have been discussed. The grain structure has been studied by the electron back-scatter diffraction (EBSD) method; the formation of an elongated shape of grains and the high specific surface area of small-angle boundaries has been explained. 相似文献
2.
《International Journal of Cast Metals Research》2013,26(1-4):264-267
AbstractAn Fe–Mo–Cr–Mn–Si–C alloy was prepared in an induction furnace and was cast into cylindrical rod in a copper mould in castmatic equipment (low pressure casting). A single phase non-equilibrium featureless (no visible microstructures after deep etching) phase was observed over a certain range of thickness of the rod. In this present work, the extent of the featureless phase was studied with different concentrations of Mo (5–25 wt-%) for 5·5 mm diameter of cylindrical rod at a cooling rate of 1100 K s–1. Light optical microscopy, scanning electron Microscopy and Vickers hardness tests were used to analyse the samples. The amount of the featureless area varies as the Mo content changes and the maximum featureless area was obtained for 7 wt-% of Mo. This single phase featureless structure exhibits very high hardness (>1350 HV) which can be used in many interesting applications with or without suitable heat treatments. 相似文献
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《Intermetallics》2000,8(3):279-286
A powder metallurgy route has been used for producing binary and ternary alloys of the Ni–Al–Mo system. Elemental powder mixtures were compacted and, then, sintered in a dilatometer. In this way the dimensional changes involved with thermally induced transformations could be followed during continuous heating runs up to the sintering temperatures. Sintering was assisted by the formation of a liquid phase, promoted by the heat output coming from the intermetallic phase formation reactions. The amount of liquid phase and the efficiency of sintering was highly dependent on the heating rate. A threshold value for optimal densification was identified for some compositions. The effect of other processing parameters, such as pre-sintering compaction pressure and sintering atmosphere has been considered too. The characterisation of the final products was mainly based on X-ray diffraction analyses. The microstructural parameters and the phase composition of the sintered materials were evaluated. On the basis of these results it is possible to draw some conclusions concerning the main phenomena occurring during the sintering process. 相似文献
5.
《Scripta materialia》2004,50(11):1389-1393
The effects of increasing chromium content on the phase transformations in Fe–Al–Mn–Cr alloys have been investigated by means of transmission electron microscopy and energy-dispersive X-ray spectrometry. The experimental results revealed that increasing the chromium addition would expand both the A12α-Mn and DO3 phase-field regions. 相似文献
6.
A comparative investigation on the wettability and tensile strength of a Sn–2Ag, a Sn–40Bi and the traditional eutectic Sn–Pb solder alloys was carried out. The wettability is represented by thickness of covered layer (TCL) and spread area (SA) while the mechanical behaviour by the ultimate tensile strength (UTS). It is shown that the TCL of studied alloys decreased with the increase in the dipping temperature. It is also shown that TCL and SA have opposite behaviour with respect to the cooling rate. The Sn–Bi solder alloy has lower SA when compared with those of the Sn–Ag solder when similar cooling rates are considered. The Sn–Bi solder exhibits the best UTS/SA combination for dendritic spacings between 25 and 27?µm, associated with cooling rates ~2°C?s?1, 2× lower than those of the Sn–Ag alloy. Besides, the Sn–Bi alloy has shown SA >70~80% associated with higher UTS (~80?MPa) as compared with the other alloys examined. 相似文献
7.
Studies using advanced analytical techniques indicated that the reactiveelements (RE) segregate along the oxide grain boundaries and at theoxide–alloy interface during oxidation of -Al2O3forming alloys. The segregation results in inward oxygen diffusion along theoxide grain boundaries as the predominant transport process in the oxidegrowth. The present work establishes a mathematical model based on themechanisms of inward oxygen diffusion along the grain boundaries and oxidegrain coarsening. This model has been used to describe the oxidationkinetics of Y-doped Fe–Cr–Al alloys. The results showed a muchbetter agreement with the experimental data than the parabolic rate law. Byusing this model, the exponential number for the grain coarsening of aluminascales during oxidation was calculated to be 3. The activation energyfor oxygen diffusing along the grain boundaries was 450 kJ/mol. They arealso in good agreement with values reported in the literatures. 相似文献
8.
I. J. Beyerlein N. A. Mara J. Wang J. S. Carpenter S. J. Zheng W. Z. Han R. F. Zhang K. Kang T. Nizolek T. M. Pollock 《JOM Journal of the Minerals, Metals and Materials Society》2012,64(10):1192-1207
Interfaces, such as grain boundaries, phase boundaries, and surfaces, are important in materials of any microstructural size scale, whether the microstructure is coarse-grained, ultrafine-grained, or nano-grained. In nanostructured materials, however, they dominate material response and as we have seen many times over, can lead to extraordinary and unusual properties that far exceed those of their coarse-grained counterparts. In this article, we focus on bimetal interfaces. To best elucidate interface structure?Cproperty?Cfunctionality relationships, we focus our studies on simple layered composites composed of an alternating stack of two metals with bimetal interfaces spaced less than 100?nm. We fabricate these nanocomposites by either a bottom?Cup method (physical vapor deposition) or a top?Cdown method (accumulative roll bonding) to produce two distinct interface types. Atomic-scale differences in interface structure are shown to result in profound effects on bulk-scale properties. 相似文献
9.
《Scripta materialia》2004,50(5):583-588
Zr52.5Ti5Cu17.9Ni14.6Al10 metallic glass machining chips were characterized using SEM, X-ray diffraction and nano-indentation. Above a threshold cutting speed, oxidation of the Zr produces high flash temperatures and causes crystallization. The chip morphology was unique and showed the presence of shear bands, void formation and viscous flow. 相似文献
10.
This work reports the procedure for selection of alloying elements to refine the microstructure of hardfacing Ni–Cr–B–Si–C alloys by providing in situ formed nucleation agents. It is concluded that the refining element should be able to spontaneously produce precipitates at high temperatures with little solubility in their Cr-rich counterparts. After exploring the theoretical backgrounds on how to select the refining element, Nb and Zr were selected and the phase formation reactions of Zr- or Nb-modified Ni–Cr–B–Si–C alloys were calculated using Thermo-Calc® simulations. Detailed microstructural analyses of the rapidly solidified samples deposited from the modified alloys showed that addition of Nb in specific quantities induces a significant microstructural refinement in the original Ni–Cr–B–Si–C alloy without deteriorating its high hardness. The Nb-modified alloy could be used to further investigate the viability of microstructural refinement as an effective toughening mechanism for Ni–Cr–B–Si–C and similar alloy systems. 相似文献
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《Acta Materialia》2001,49(1):65-75
In the present investigation a special control volume formulation of the classical precipitation model for coupled nucleation, growth and coarsening has been adopted to describe the evolution of the particle size distribution with time during thermal processing of Al–Mg–Si alloys. The analysis includes both isothermal and non-isothermal transformation behaviour. Well established dislocation theory is then used to evaluate the resulting change in hardness or yield strength at room temperature, based on a consideration of the intrinsic resistance to dislocation motion due to solute atoms and particles, respectively following heat treatment. The model is validated by comparison with experimental microstructure data obtained from transmission electron microscope examinations and hardness measurements, covering a broad range in the experimental conditions. It is concluded that the model is sufficiently relevant and comprehensive to be used as a tool for predicting the response of Al–Mg–Si alloys to thermal processing, and some examples are given towards the end. 相似文献
13.
O. V. Velichko S. Yu. Ivanov V. A. Karkhin V. A. Lopota I. D. Makhin 《Welding International》2016,30(8):630-634
A technology is developed for single-pass friction stir welding (FSW) of 11- and 35-mm-thick plates of Al–Mg–Sc alloys. The microstructural and mechanical heterogeneity of the welded joints is investigated. The welded joints obtained under the optimum welding conditions are free from macrodefects. The strength of the welded joint equals 98% of the strength of the parent metal, which is higher than the strength of fusion-welded joints. It is concluded that the FSW of thick plates of Al–Mg–Sc alloy can be used efficiently in practice. 相似文献
14.
《Intermetallics》2005,13(3-4):429-435
The high-cycle fatigue (HCF) behavior of the Zr41.2Ti13.8Cu12.5Ni10Be22.5 (in at.%) bulk-metallic glass (BMG) was studied. Two batches of samples that are from different lots (Batches 59 and 94) are employed in present experiments. The HCF experiments were conducted, using an electrohydraulic machine at a frequency of 10 Hz with a R ratio of 0.1 in air at room temperature and under tension-tension loading, where R=σmin./σmax.. (σmin. and σmax. are the applied minimum and maximum stresses, respectively). A high-speed and high-sensitivity thermographic-infrared (IR) imaging system was employed for the nondestructive evaluation of temperature evolutions during fatigue testing. No distinct sparking phenomenon was observed at the final fracture moment for this alloy. The fatigue lifetime of Batch 59 is longer than that of Batch 94 at high stress levels (maximum stresses >864 MPa). Moreover, the fatigue-endurance limit of Batch 59 (703 MPa) is somewhat greater than that of Batch 94 (615 MPa). The vein pattern and liquid droplets were observed in the apparent-melting region along the edge of the fractured surfaces. The fracture morphology suggests that fatigue cracks initiated from casting defects, such as porosities and inclusions, which have an important effect on the fatigue behavior of BMGs. 相似文献
15.
The microstructure evolution during annealing of Ti–5Al–2Sn–2Zr–4Mo–4Cr alloy was investigated. The results show that for the alloy compressed at 810 °C and 1.0 s?1 deformation amount (height reduction) 20% and 50% and annealed at 810 °C, thermal grooving by penetration of β phase is sufficient during the first 20 min annealing, resulting in a sharp increase in globularization fraction. The globularization fraction continuously increases with the increase of annealing time, and a height reduction of 50% leads to a near globular microstructure after annealing for 4 h. For the alloy with deformation amount of 50% by compressing at 810 °C, 0.01 s?1 and then annealed at 810 °C, thermal grooving is limited during the first 20 min of annealing and large quantities of high-angle grain boundaries (HABs) remain. With long time annealing, the chain-like α grains are developed due to the HABs, termination migration and Ostwald ripening. The present results suggest that a higher strain rate and a larger height reduction are necessary before annealing to achieve a globular microstructure of Ti–5Al–2Sn–2Zr–4Mo–4Cr. 相似文献
16.
A. Fabrizi R. Cecchini Ph. V. Kiryukhantsev-Korneev A. N. Sheveyko S. Spigarelli M. Cabibbo 《Protection of Metals and Physical Chemistry of Surfaces》2017,53(3):452-459
Nanostructured Ti–B–N and Ti–Si–B–N coatings were deposited on silicon substrate by ion implantation assisted magnetron sputtering technique. To evaluate the oxidation resistance and thermal stability the coatings were annealed on air and in vacuum at 700–900°C. As-deposited and thermal-treated coatings were investigated by transmission electron microscope, selected area electron and x-ray diffraction, atomic force microscopy, Raman and glow discharge optical emission spectroscopy. Nanoindentaion tests were also performed. Obtained results show that Si alloying significantly improves the thermal stability of Ti–B–N coatings and increases their oxidation resistance up to 900°C. It was shown that formation of protective amorphous SiO2 top-layer on the coating surface plays important role in the increasing of the oxidation resistance. 相似文献
17.
The effects of minor contents of Zr and Sc on the microstructures and mechanical properties of Al–Mg–Si–Cu–Cr–V alloy were studied. The results show that the effects of minor Zr and Sc on the as-cast grain refinement in the ingots, the improvement in the strength of the as-extruded alloys and the restriction of high angle grain boundaries in the aged alloys can be sorted as Al3Sc>Al3(Zr,Sc)>Al3Zr. None of them could stop the nucleation of recrystallization, but Al3(Zr,Sc) phase is a more effective inhibitor of dislocation movement compared to Al3Sc in the aged alloys. Compared with the mechanical properties of the aged alloy added only 0.15% Sc, the joint addition of Zr and Sc to the alloy leads to a very slight decrease in strength with even no cost of ductility. Taking both the production cost and the little bad influence on mechanical properties into consideration, an optimal content of Zr and Sc in the Al–Mg–Si–Cu–Cr–V alloy to substitute 0.15% Sc is 0.13% Zr+0.03% Sc. 相似文献
18.
《Intermetallics》2017
Ti-based bulk metallic glass composite alloys Ti56Zr6Cu19.8Pd8.4Sn1.8Nb8, Ti64Zr4Cu13.2Pd5.6Sn1.2Nb12 and Ti68Cu13.2Pd5.6Sn1.2Nb12 were designed to obtain the microstructure composing of β-Ti dendrites and glassy matrix. The compressive and three-point bending properties were investigated. It was found that the actual microstructure of the Nb-added alloys consisted of primarily precipitated β-Ti dendrites, network-like glassy matrix, and extra island-like Ti2Cu intermetallic phase with different volume fractions. Under compressive loading, all the Nb-added alloys presented higher yield strength combined with remarkably increased plasticity. Under bending condition, however, the alloys Ti56Zr6Cu19.8Pd8.4Sn1.8Nb8 and Ti64Zr4Cu13.2Pd5.6Sn1.2Nb12 with higher Ti2Cu volume fractions became completely brittle. The alloy Ti68Cu13.2Pd5.6Sn1.2Nb12 could keep its plastic deformability due to the decreased Ti2Cu volume fraction. Compressive deforming behavior of the Nb-added alloys was determined by the ductile β-Ti phase and glassy matrix, nevertheless, bending deforming behavior of the alloys was determined by the volume fraction and distribution of the brittle intermetallics. 相似文献
19.
C. P. Wu D. Q. Yi C. H. Xu J. Li B. Wang X. D. Lu H. Zhang 《Oxidation of Metals》2008,70(3-4):121-136
The gas atomized Ag-9.26wt%Sn-0.44wt%La alloy powders were oxidized in air between 400 and 900 °C. The oxidation thermodynamics, kinetics and microstructure of the alloy were investigated. We suggested that the addition of La may accelerate oxidation of Sn and prevent the formation of the dense SnO2 film. The suitable oxidation temperature of the alloy powders is 800 °C in air. After internal oxidation, many cracks were observed on the surface of the alloy powders. In addition, the whole oxidation process of the alloy powders is controlled by the oxygen diffusion. The diffusion coefficient of oxygen in the alloy powders at 800 °C is about 1.5 times larger than that at 700 °C on the initial stage of internal oxidation, while that is 4.5 times on the subsequent stage. 相似文献
20.
The plastic deformation behavior of Ti–22.4Nb–0.73Ta–2Zr–1.34O alloy was investigated by compression testing at room temperature. The multi-peak stress oscillations of the true stress–strain curve, characterized by a stress plateau, initial strain-hardening, followed by strain-softening and a second strain-hardening stages, is observed in a titanium alloy for the first time. The experimental results show that the above four-stage plastic deformation behavior is caused by a change in the dominant deformation mechanisms. At the stress plateau stage, the alloy deforms via multiple plastic deformation mechanisms. The initial strain hardening is caused mainly by tangling of dislocations. Subsequent strain softening is due to the formation of kink bands. The second strain hardening corresponds to the formation of shear bands. The above results suggest that the dominant deformation mechanisms of Ti–Nb–Ta–Zr–O alloys are related not only to the stability of the β phase, but also to the extent of plastic deformation. 相似文献