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31.
Homogeneous amorphous and nanocrystalline phases formed in the nugget zone of a friction stir-processed Al–Cu–Mg alloy have been studied. X-ray diffraction analysis indicated a diffuse scattering peak with characteristics of an amorphous phase existed in the range 15°–29°. Further, TEM analysis proved the existence of an amorphous structure. Friction stir processing provides special physical conditions, such as high temperature, high hydrostatic pressure and large shear stress, which could induce the amorphization of the alloy. 相似文献
32.
Tomoyuki Homma Yusuke Matayoshi Roman Voskoboinikov 《Philosophical Magazine Letters》2015,95(12):564-573
Zr-containing Ti alloys have widely been developed owing to the infinite solid solubility of Zr in Ti and its avirulence, leading respectively to high strength and good biocompatibility. It is known that the Zr addition gives rise to grain refinement when rolled Ti–Zr alloys are annealed; nevertheless, the governing mechanism by which Zr addition in Ti can reduce grain size is not fully understood. In this study, the grain growth behaviour of rolled Zr-free and Zr-containing (Ti–10Zr, wt.%) alloys is analysed using analytical transmission electron microscopy and the classical and Bons–Azuma methods by evaluating the grain growth exponent. Irrespective of the evaluation technique and Zr content, the grain growth exponent is found to be close to ~0.3, indicating the occurrence of normal grain growth in the Zr-free alloy and solute drag mechanism in the Zr-containing alloy. It is found that the grain size and grain growth rate are significantly reduced by Zr segregation near grain boundaries, resulting from the solute drag mechanism. 相似文献
33.
Saeed Farahany Ali Ourdjini Alireza Hekmat-Ardakan 《Philosophical Magazine Letters》2015,95(12):587-593
Results of electron back-scattered diffraction and transmission electron microscopy studies reveal that the orientation of aluminium in the eutectic phase is different from the surrounding aluminium dendrites and that twin spacing of eutectic silicon increased significantly due to the interaction between strontium and antimony. In addition, the formation of ternary Mg2Sb2Sr intermetallic compound that precedes the eutectic reaction was proposed to be responsible for interaction. 相似文献
34.
Subrata Panda Dipankar Banerjee Ganesh S. Avadhani 《Philosophical Magazine Letters》2013,93(7):273-282
ABSTRACTThe variant selection criteria during β to α phase transformations in a metastable β-titanium alloy (Ti-5553) in the presence of deformation are examined. Two distinct metallurgical states in the β matrix, heavily deformed and fully recrystallized, were obtained from a 90% cold-rolled alloy. The deformed and recrystallized samples were subjected to aging heat treatment for a short time to allow the precipitation of an intragranular α phase. Electron backscattered diffraction was used to assess the α crystallographic variant occurrence in the deformed as well as in the recrystallized β grains. A discrete pole figure analysis revealed that a limited number of variants were evolved in the deformed β grains while there was no variant selection in the recrystallized β matrix. The results suggest that activation of {112}<111>β slip systems determines a strong variant selection in the plastically deformed β matrix. 相似文献
35.
Composition formulae for alloy phases are developed using first-neighbour coordination polyhedra plus their connections. The resultant cluster formulae [cluster](glue atom) x , similar to molecular formulae for chemicals, contain key structural and composition information on the alloy phases. As examples, Al–Ni–Zr alloy phases are analysed with the objective of revealing cluster formula properties such as the principal cluster, the cluster phase and the definition of complex alloy phases. 相似文献
36.
The Ti36Ni41Hf15Cu8 melt-spun ribbon undergoes a B2 ? B19′ transformation upon cooling and heating. When the Ti36Ni41Hf15Cu8 melt-spun ribbon is annealed at 873 K for 1 h, the spherical (Ti, Hf)2Ni particles with a diameter of 20–40 nm precipitate in the grain interior. The fine (Ti, Hf)2Ni precipitates improve the stability of phase transformation temperatures and cause martensite domains, with (001) compound twins in three orientations dominant instead of (011) type I twins. {111}-, {113}- and (001)//{111}-type boundaries are observed among these martensite domains. When the (Ti,Hf)2Ni precipitates coarsen, (011) type I twins become main martensite structures in the ribbon annealed at 973 K for 1 h. 相似文献
37.
ABSTRACTA direct chill (DC) cast Al-15% Si alloy was processed by hot rolling with a single pass at a temperature of 520°C with a thickness reduction of 80%. Scanning electron microscopy (SEM), electron backscattering diffraction (EBSD) and transmission electron microscopy (TEM) were used to investigate the evolution of the sample’s microstructure. After hot rolling, silicon particles homogeneously distributed in the Al matrix with fine equiaxed grains of average size ~ 0.95?μm. High-angle boundaries (HABs) (about ~75.8% in percentage) dominate in the Al matrix structure. There is evidence for Si-particle-stimulated continuous dynamic recrystallization (CDRX) during hot rolling. 相似文献
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39.
Off-axis electron holography has been used to map the electric potential derived from the spontaneous polarity in a ZnO film. A wedge-shaped ZnO film, in which the holograms and the object wave were reconstructed, was used. To interpret the phase image correctly, the reconstructed amplitude image was used to obtain information on the thickness, which was then applied to eliminate the thickness effect on the phase shift. The electric potential distribution was characterized and the polarity of the ZnO film determined. 相似文献
40.
Satoru Kobayashi Riko Kawagoe Hiroaki Murakami Kazuki Ohishi Yukihiko Kawamura Jun-ichi Suzuki 《Philosophical Magazine Letters》2013,93(6):217-225
Abstract The ability of amorphous metallic alloys to resist irradiation-induced structural changes will depend on the composition of the alloy and the particle fluences used. In this paper we show that a fast neutron fluence of 1020 cm?2 can induce local crystallization in a refractory NiTi glass. For specimens irradiated with lower fluences, the mode of crystallization of the amorphous matrix is changed from that of a primary process to a eutectic mechanism. 相似文献