共查询到20条相似文献,搜索用时 14 毫秒
1.
《Intermetallics》2015
The paper presents new results concerning the influence of nickel addition (1 and 5 at.%) into tin on the development of the Cu/(Sn,Ni) interface area in diffusion couple experiment. The morphology and chemical composition of the intermetallic phases growing in the Cu/(Sn,Ni) diffusion couples were examined by means of the scanning (SEM) and transmission (TEM) electron microscopy after annealing at 215 °C in vacuum for different period time.It was shown that even 1 at.% of nickel addition into tin resulted in formation of intermetallics of complex microstructure. The presence of (Cu1−xNix)6Sn5 in two morphological and compositional variants was noted. The discontinuous layer consisting up to 7.2 at.% of Ni closer to copper end-member coexisted with needle-like and faceted precipitates with even 22.3 at.% of Ni, which intensively detached from the interface. At the Cu/(Cu1−xNix)6Sn5 interface the formation of Cu3Sn wavy layer compound was observed in all examined diffusion couples which became thicker with time. The porosity within the both formed intermetallic phases existed irrespective of the amount of added nickel. 相似文献
2.
Characterization of silicide phases formed during pack siliconizing coating on the Nb-1Zr-0.1C alloy
《Intermetallics》2015
The present paper describes the morphology, chemistry and crystallography of the phases observed in the silicide coatings produced by pack cementation technique on Nb based alloys. Cross-sectional microstructures examined by transmission electron microscopy and scanning electron microscopy techniques have shown that the coating has two silicide layers: NbSi2 and Nb5Si3. NbSi2 formed at the surface of the sample and Nb5Si3 formed in between the substrate (Nb alloy) and NbSi2 coating layer. Electron diffraction analyses revealed that NbSi2 has hexagonal crystal structure with lattice parameters as a = 0.48 nm and c = 0.66 nm and Nb5Si3 has tetragonal crystal structure with lattice parameters as a = 0.65 nm and c = 1.19 nm. Nb5Si3 showed fine equiaxed grains, whereas, NbSi2 exhibited duplex morphology having columnar grain morphology near to the Nb5Si3 layer and large equiaxed grains at the surface of the coating sample. The presence of duplex morphology was explained by estimating diffusion of various species and it was shown that columnar morphology of grains could be attributed to outward diffusion of Nb and equiaxed grains to inward diffusion of Si. In the case of Nb5Si3, growth takes place due to single element Si diffusion, leading to development of single equiaxed grain morphology of the Nb5Si3 phase. 相似文献
3.
An investigation of microstructural evolution with various current densities in a lead-free Cu/SnAgCu/Au/Cu solder system was conducted in this study. Current stressing induced migration of Cu toward the anode and resulted in the formation of Cu6Sn5 at the interface. The consumption rates of Cu were calculated to be 2.24 × 10−7 μm/s and 5.17 × 10−7 μm/s at 1.0 × 103 A/cm2 and 2.0 × 103 A/cm2, respectively, while the growth rates of Cu6Sn5 were 6.33 × 10−7 μm/s and 7.72 × 10−7 μm/s. The atomic fluxes of Cu were found to be 2.50 × 1012 atom/cm2 s and 5.88 × 1012 atom/cm2 s at the above-mentioned current densities. The diffusivities of Cu in Cu6Sn5 were 2.02 × 10−11 cm2/s and 2.38 × 10−11 cm2/s under 1.0 × 103 A/cm2 and 2.0 × 103 A/cm2 of current stressing. Current stressing effectively enhances the migration of Cu in Cu6Sn5 and results in a 1000-fold increase of magnitude in diffusivity compared to thermal aging. (Cu1−x,Aux)6Sn5 compound was formed near the anode after a long period of current stressing. 相似文献
4.
The crystallisation of the oxygen-stabilised amorphous phase in a Zr50Cu50 alloy has been investigated by means of neutron diffraction and electron microscopy. The crystallisation microstructure consists of ZrO2, Zr2Cu and Zr7Cu10. A two-stage crystallisation mechanism is suggested: (i) primary crystallisation of Zr2Cu and (ii) formation of nanocrystals ZrO2 and Zr7Cu10. In (i), it is proposed, Zr2Cu crystallises from the oxygen-stabilised amorphous phase, leaving an oxygen- and copper-enriched matrix ; Zr2Cu rapidly grows and eventually attains a grain size of about 100 nm. In (ii), it is suggested, the residual amorphous matrix crystallises into nanocrystals ZrO2 and Zr7Cu10 due to the sluggish growth of ZrO2 and to the already formed ZrO2 which acts as a growth barrier to Zr7Cu10. In this case there is no particular orientation relationship between Zr2Cu and Zr7Cu10. 相似文献
5.
《Intermetallics》2013
Nb–Al intermetallic nanoparticles were directly synthesized via sodiothermic reduction process in molten salts using NbCl5 and AlCl3 as the raw materials. The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The NbCl5 and AlCl3 were dissolved in LiCl–KCl–CaCl2 or LiCl–KCl–NaCl–CaCl2 molten salts forming a homogeneous system. It was found that a series of intermetallic nanoparticles, such as Nb3Al, Nb2Al, NbAl3 and Nb2Al/NbAl3, were successfully synthesized at low temperature of 350–500 °C using the homogeneous molten salt systems. The phase transformations of Nb3Al, Nb2Al and NbAl3, were achieved via the controllable variation of molar ratio of Nb to Al. Furthermore, the influence of the reaction temperature on the particle size of the intermetallic nanoparticles was also investigated. 相似文献
6.
《Intermetallics》2014
A Ti–45Al–2Nb–2Mn + 0.8 vol.% TiB2 (at.%) alloy with fully lamellar microstructure consisting of hexagonal-close-packed (hcp) α2 and face-centred-tetragonal (fct) γ phases was irradiated by implanting helium ions to different fluences. Microstructural examination showed that helium cavities are formed in both the α2 and γ phases after He-ion irradiation. However, the helium cavities and their size change with fluence are much larger in the α2 phase than those in the γ phase, indicating that the γ phase exhibits better tolerance to the He-ion irradiation than the α2 phase. Since α2 and γ phases have different crystal structures, they possess differences in helium solubility and interstitial migration. These differences are responsible for the variation in radiation damage behaviour between the two phases. 相似文献
7.
《Intermetallics》2015
The deformation mechanisms associated with different fracture surface appearances of a fatigue tested lamellar TiAl-based alloy have been studied in detail by focussed ion beam and transmission electron microscopy. The results show that linear markings within translamellar plates correspond to twins and/or slip bands. The markings in interlamellar region are associated with the crack propagation from a lamellar boundary to another. The fan-like region with linear markings belongs to a γ grain and the markings are related to twins. Intralamellar crack propagation is associated with twin–twin interaction within a γ lamella. 相似文献
8.
《Intermetallics》2014
The microstructures of the as-cast and as-extruded Mg-9Li-xY alloys (x = 0, 0.3; wt%) were observed to investigate the effect of Y on the Mg-9Li alloy, and the crystallographic calculations between Mg24Y5 and the matrix were examined on the basis of the edge-to-edge matching model. The results indicated that with the addition of 0.3 wt% Y, the average grain size of α-Mg phases in the as-cast Mg-9Li alloy and β-Li phases in the as-extruded Mg-9Li alloy were reduced remarkably, which was caused by the formation of Mg24Y5 intermetallic compound. Furthermore, crystallographic calculations confirmed that Mg24Y5 particles were effective grain refiners for both α-Mg and β-Li phases in Mg-9Li alloy. 相似文献
9.
《Intermetallics》2015
Grain boundary diffusion of 44Ti and 63Ni in the B2 Ti−50.2 at.% Ni polycrystalline alloy was measured in Harrison's B regime (573−923 K) using the radiotracer technique. The triple product P = sδDgb (s is the segregation factor, δ the grain boundary width, and Dgb the corresponding grain diffusion coefficient) for Ti and Ni was determined. Although the absolute values of the triple products P are typical for the B2-ordered alloys, both Ti and Ni GB diffusion in NiTi reveals a unique behavior with significant deviations from a linear Arrhenius-type temperature dependence. Transmission electron microscopy analysis of GB structures at 673 K and 923 K substantiated the occurrence of different interface types which may provide the slower and faster grain boundary diffusion paths in agreement with the experimental data. The influence of different types of precipitates on grain boundary diffusion and possible diffusion mechanisms in the different regimes are discussed. 相似文献
10.
《Intermetallics》2013
Vacuum-arc melted Ni24.7Ti50.3Pd25.0 and Ni24.7Ti49.3Pd25.0Sc1.0 (at.%) alloys were investigated to study effect of Sc micro-addition on microstructure and transformation behaviour of NiTiPd alloy. Study showed that microstructure of homogenized NiTiPd alloy consisted of NiTiPd matrix interspersed with Ti2(Ni,Pd) precipitates. In contrast, NiTiPdSc alloy showed a single phase NiTiPdSc matrix with a few scandium oxide particles at isolated places. TEM and X-ray diffraction studies confirmed matrix phase of the alloys to be of orthorhombic B19 structure. TEM observations showed that NiTiPdSc alloy had relatively larger martensite plates with a smaller twin ratio compared to that of NiTiPd alloy. Also, APB (anti-phase boundary) like regions with twinless martensites was observed in both the alloys, area fraction of APB-like regions being more in NiTiPdSc alloy. Thermal analysis showed that transformation temperatures (TTs) of NiTiPd alloy decreased significantly with addition of Sc. The martensite finish temperature (Mf) of 181 °C for NiTiPd alloy lowered to 139 °C upon 1.0 at.% Sc addition. The transformation hysteresis of Ni24.7Ti49.3Pd25.0Sc1.0 (at.%) alloy was measured to be 7 °C, significantly lower than that of 15 °C for Ni24.5Ti50.0Pd25.0Sc0.5 alloy, reported in literature. Alloy purity, lower volume fraction of second phase and presence of twinless/small twin ratio martensite in microstructure is believed to be the reasons for such low transformation hysteresis. The transformation behaviour of the alloys upon stress-free thermal cycling was found stable, variation in TTs being within 1–2 °C. 相似文献
11.
《Intermetallics》2015
The stability of a Co-based alloy designed to possess a microstructure comprising of L12, γ′ Co3Ti-type precipitates embedded in an A1, γ Co solid solution matrix has been investigated. The alloy showed acute microstructural instabilities upon ageing at 700 °C, resulting in the degeneration of the γ-γ′ aggregate into i) a faulted Co-based martensite and Co3Ti and ii) a lamellar aggregate of A3-Co and Co3Ti. The faulted Co-based phase was formed by isothermal diffusionless transformation of the metastable A1-phase, whilst the lamellar aggregate was a discontinuous reaction product. 相似文献
12.
《Intermetallics》2014
The microstructural features of the 980 °C isothermally forged Ti–22Al–25Nb (at.%) orthorhombic alloy during heat treatment were quantitatively investigated. The volume fraction of the O phase precipitates, the width and length of the lath O phase, and the diameter of equiaxed grains at different heat treatment temperatures were measured using an image analysis software. Quantitative relationships among heat treatment temperature, microstructure parameters, and microhardness were established. The relationship between microstructure parameters and microhardness was analyzed with a multiple regression analysis technique. The results indicate that the microstructure of this alloy is mainly depended on the heat treatment schedule. Only equiaxed O/α2 grains and B2 matrix existed when the samples were solution-treated above 980 °C, while equiaxed α2 grains, rim O around α2, and equiaxed/lath O could be obtained after the samples were solution treated below 980 °C. The width of lath and acicular O phases, and volume fraction of total precipitates could be controlled in the range of 0.37–0.88 μm, 0.09–0.48 μm and 10.91–60.18%, respectively. Experimental and statistical analysis showed a linear relationship between the microstructure parameters and microhardness. 相似文献
13.
《Intermetallics》2015
Vacuum induction melting device combined with temperature control system was employed to investigate the effect of isothermal heat treatment (IHT) during solidification process on the microstructure evolution of a high Nb containing TiAl alloy. The microstructures of the alloy in as-cast condition and after IHT were studied. The results show that the as-cast microstructures exhibit a significant microstructural inhomogeneity with fine grains in dendrite core and coarse grains in interdendritic region. A new treatment approach by means of a short-term IHT within the β phase field during solidification process is proposed to obtain a uniform and refined microstructure. Compared with the as-cast alloy, IHT can reduce the tendency for crack. This phenomenon is attributed to the improvement of microstructural homogeneity by the elimination of peritectic α phase and the microstructure refinement by β → α transformation. 相似文献
14.
《Intermetallics》2013
The effects of alloy stoichiometry on the dry sliding wear behavior of B2-structured FeAl were investigated using four different FeAl alloys containing 40, 43, 48, and 50 at.% Al. Room temperature pin-on-disk tribotests were performed against an yttria-stabilized zirconia counterface in four different environments: air, oxygen, 4% hydrogen in nitrogen, and argon. It was found that the alloys had lower wear rates in both oxygen-free and water vapor-free environments, where the wear loss was roughly inversely related to the hardness. Interestingly, the wear rates were little affected by the presence of molecular hydrogen. In oxygen- or water vapor-containing environments, the effects of the environment predominated over any effects from the mechanical properties of the alloys. The tips of the worn pins were examined using both scanning electron microscopy and transmission electron microscopy, the latter using specimens produced by focused ion beam milling. Zirconia particles were found to be embedded in a tribolayer on the worn tips of the pins. The results indicate that both two-body and three-body abrasive wear, as well as plastic deformation and delamination were the main wear mechanisms. The abrasive particles largely consisted of the counterface material. 相似文献
15.
A key microstructural feature that controls the sintering behavior of Ni + Ti powders was determined to be the transformation of alpha-Ti to beta-Ti during heating. The use of very fine Ni powders causes this transformation to occur at the eutectoid temperature (i.e., 765 °C). The use of coarse Ni powders causes a gradual beta-Ti transformation from 765 to 882 °C. At 950 °C a large volume fraction of beta-Ti remains in coarse Ni/Ti mixtures whereas in fine Ni/Ti mixtures this phase is almost eliminated. Further heating above 950 °C causes the beta-Ti to melt, initiating a large exothermic reaction in the coarse Ni/Ti mixtures (i.e., 158 J/g) at 980 °C. The use of fine Ni significantly reduces this reaction (i.e., 3 J/g). Consequently, Ni powder size, and its influence over beta-Ti content can be used to control the reactive sintering behavior of Ni + Ti mixtures. 相似文献
16.
《Intermetallics》2017
The precipitation of γ phase and heterogeneous nucleation of ωo phase within βo phase areas are common phenomena in TiAl alloys. However, detailed explanation on the corresponding phase transformation mechanisms is still lacking. In this study, the precipitation behaviors of γ and ωo phases in a quenched Ti-45Al-8.5Nb-0.2W-0.2B-0.02Y alloy are investigated. The results show that large γ grains form after quenching whereas small γ particles can directly nucleate within the remaining βo phase during annealing. Semi-coherent interfaces are observed between γ and βo phases and the average distance between dislocations is evaluated. The heterogeneous nucleation of ωo phase at the lamellar colony boundary is imaged by HRTEM. Edge-to-edge method is used to calculate the orientation relationship between γ and ωo phases. The γ phase grows up faster than ωo phase within the βo phase areas during annealing at 800 °C. 相似文献
17.
《Intermetallics》2014
Driven by the necessity to improve the reliability of lead free electronic products and by the trend towards miniaturization, researchers are putting intense efforts to improve the properties of Sn based solders. The present work investigates the effects of Zn nanoparticle addition to Sn-3.5Ag (SA) alloy through paste mixing on the interfacial structure between solder and copper substrate during reflow. Results show that the addition of Zn nanoparticles does not alter the morphology of the interfacial intermetallic compounds although they substantially suppress their growth. Zn nanoparticles are seen to be most efficient compared with Co and Ni nanoparticles in suppressing the growth of Cu3Sn layers. It is suggested that Zn nanoparticles exert their influence through an in-situ dissolution and alloying effect. 相似文献
18.
Equiatomic FePd thin films have been deposited at room temperature by pulsed laser deposition (PLD) on amorphous, Si3N4 and SiO2, and crystalline, (100)-NaCl, substrates. The resulting FePd film microstructures have been characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). We observed a complex orientation relationship between grains in nanocrystalline thin films of FCC FePd and the single crystal NaCl substrates. FePd films obtained under identical deposition conditions using the amorphous substrates also exhibited nanocrystalline morphology but with a fiber texture and consisted of a phase mixture of FCC FePd and the tetragonal ordered L10-FePd phase. 相似文献
19.
《Intermetallics》2014
A fully lamellar γ-TiAl alloy Ti–45Al–2Mn–2Nb + 0.8 vol.% TiB2 was exposed at 700 °C for 10,000 h in air. No perpendicular decomposition of α2 into α2 + β/α2 + γ sections and no recrystallisation of β equiaxed grains on decomposed α2 + γ lamellae were observed all through the prolonged exposure. The dominant change in microstructure was that the α2 lamellae thinned gradually and became increasingly discontinuous with increasing exposure time. The average thickness of α2 lamellae reduced to a half and the volume fraction reduced by 1/4 after 10,000 h exposure. Correspondingly, the tensile properties were hardly changed, while fatigue strengthening was increased by 30%. The reasons for the relatively high degree of stable microstructure and mechanical properties are discussed based on production processing and alloy composition. The “exposure-induced fatigue strengthening” observed after 10,000 h exposure is assumed to be caused by structure relaxation and stress dissipation throughout the specimen. 相似文献
20.
《Intermetallics》2017
In order to investigate the influence of the temperature increase due to frictional heating on the wear behavior of the nanostructured alloy Fe30Ni20Mn25Al25, which consists of alternating b.c.c. and B2 phases with interfaces aligned along 〈100〉, dry sliding pin-on-disk tests were conducted in air at several sliding velocities (0.1 m s−1, 0.25 m s−1, 0.5 m s−1, 0.75 m s−1 and 1 m s−1) for 1 km. Disks of yttria-stabilized zirconia were used as the counterface. A combination of state-of-the-art techniques was used to characterize the pins, disks and debris after wear tests. It was found that the pins had much higher wear rates at a lower sliding velocity compared to a higher sliding velocity, although the wear rate of the zirconia counterface was higher at the higher sliding velocities. It was concluded, based on X-ray diffraction and transmission electron microscopy, that the increase in zirconia wear at higher sliding velocities was due to localized phase transformation of the zirconia caused by high frictional contact temperatures. The zirconia debris removed from the disk because of the phase transformation also contributed to the lower mass loss of the pins in wear tests at sliding velocities of 0.5 m s−1 or higher because zirconia embedded in the surface of the pins provided added protection against pin wear. 相似文献