Papers by Keyword: Ordering

Abstract: Recent progress in the growth of ordered Ge/Si quantum dots (QDs) is reviewed. We focus on the detailed progresses of the Ge/Si multiple layers QDs and the preparation of Ge/Si QDs by ion beam irradiation. In addition, the growth of Ge/Si QDs on patterned substrate by using different preparation methods are also well discussed, such as nanosphere lithography technology, extreme ultra-violet interference lithography technology, nanoimprint lithography technology, etc.

Abstract: The structure of the metastable austenite Fe–32%Ni alloy quenched for martensite and subjected to the α→γ transformation at slow heating (to 593–773 K) with the formation of a nanocrystalline austenite of different orientation was investigated. Electron diffraction analysis has revealed that nickel-enriched nanocrystalline γ-phase obtain ordered L10 superstructure. Together with the γ-phase, there was detected the disperse ε-martensite with a hexagonal close-packed (hcp) lattice. Along with the realization of ordinary orientation relationships (ORs) of Kurdjumov-Sachs, between a matrix α-phase and an ordered γ-phase in the sample of Fe-32%Ni alloy after slow heating to 773 K there have been established Headley-Brooks Ors. Cyclic transformation promotes the improvement of many functional properties of steels (strength, coercive force, controlling of the thermal expansion coefficient and others).

Abstract: With the increase of product data, it is one of the key problems if the existing resources can be ordered and reused rapidly. Focusing on the technical objects, the framework of ordering system is proposed for the technical objects based on meta object facility. The framework of ordering system includes four layers such as the layer of technical objects, models, meta-models and meta-meta-models. The description of each layer is analyzed in detail which set forth the ordering structure, the elemental composition and the relations of elements. The application indicates that the ordering system of technical objects realizes the reusing of existing objects, improves the efficiency of enterprise personnel. It is the guide of implementation for information in future.

Abstract: The effects of long-range atomic order and pinning of interfaces on anelastic properties of Cu-based martensite have been distinguished by means of studying strain amplitude dependences of internal friction and Young’s modulus defect, assuming that low-and high-amplitude stages of the strain amplitude dependence correspond to the oscillations within and beyond pinning atmospheres.

Abstract: The microstructure of high-entropy Alloys AlFeCuCoNiCrTix (x=0, 05, 1.0) with different titanium contents had been studied. The results showed that: (1) The microstructure of AlFeCuCoNiCrTix exhibited the trend from dendritic structure to eutectic-cell structure as the titanium contents increasing and spinodal decomposition, nanoprecipitation and amorphous phase can be also observed; (2) Composition segregation appeared (especially Cu) and Ti promoted the segregation of Cu; (3) Alloys was consisted of FCC and BCC, and phases gradually converted from FCC+BCC1 to FCC+BCC1+BCC2 with addition of titanium and BCC2 became the leading phase; (4) Both ordering and spinodal decomposition coincided due to the difference of atomic size and high entropy effect.

Abstract: Hypostoichiometric Fe-Pd binary alloys (35-45 at% Pd) were severely deformed (>90%) and subsequently aged to induce concomitant recrystallization, precipitation, and ordering. This thermomechanical processing strategy was articulated by Hornbogen [1] over thirty years ago. The resulting exchange-coupled ferromagnets contain ferrite precipitates and a complex metastable two-phase lamellar transformation product comprised of ordered L1₀ and a metastable FCC phase. The later duplex microconstituent is suggested to form in conjunction with a so-called pseudospinodal reaction [2] involving emerging cubic and tetragonal phases, whereby phase separation and ordering result from continuous changes in composition and a reduction in symmetry, cubic to tetragonal. The deformation texture of the parent austenite is substantially retained in the transformation product, resulting in anisotropy of the magnetic properties as determined by magnetometry (VSM). This paper presents electron microscopy results elucidating the crystallography and morphology of the phase mixtures including HREM. Magnetic field annealing is also included as a branch of our thermomechanical processing strategy, and we discuss the influence of the external fields on recrystallization, precipitation, and ordering.

Abstract: In this paper the concept of pseudospinodal decomposition introduced by Ni and Khachaturyan [1] as a symmetry-lifting continuous phase separation, which can produce coherent nanoscale morphologies ranging from nanowires to nanolaminates, is reviewed. The term spinodal arises from the continuous change in the compositions of emerging cubic and tetragonal phases resulting in quasi-periodic microstructures stemming from the attendant transformation strain and surface energy anisotropies. It is argued here that important features of the pseudospinodal mechanism can be understood in terms of conventional classical and non-classical nucleation and that the behaviour is more general than the cubic → tetragonal transformation context articulated by its authors. Also, the possible relevance of the pseudospinodal mechanism to studies of decomposition of hypostoichiometric Fe-Pd alloys will be presented.

Abstract: Molecular dynamics and molecular statics have been used to explore the transition between the partially Zener ordered state of carbon in octahedral sites. In this communication we have specifically used isothermal molecular dynamics with a recent Fe-C EAM potential to examine the observed high temperature transition from the Zener ordered state where carbon resides on only 1/3 of all octahedral sites to a state where all octahedral sites are available for occupation. It is shown that the Zener ordered state begins to disorder at temperatures well below the transition temperature and that this disordering occurs without any spatial correlation.

Abstract: A Fe₅₀Pd₅₀ alloy was severely deformed by High Pressure Torsion (HPT). For a processing temperature ranging from 20°C to 300°C, the Severe Plastic Deformation (SPD) induces a significant grain size reduction (in a range of 50 to 150 nm) but also a strong disordering of the long range ordered L1₀ phase. However, Transmission Electron Microscopy (TEM) data clearly show that few ordered nanocrystals remain in the deformed state. The deformed material was annealed to achieve a nanoscaled long range ordered structure. The transformation proceeds via the nucleation and growth of ordered domains along grain boundaries. Aging at lower temperature (400°C) gives rise to a smallest domain size and thus the highest coercivity.

Abstract: High silicon electrical steel prepared by EB-PVD was subjected to high temperature rapid thermal annealing and subsequent pack rolling. The phase composition and Fe configurations were characterized by X-ray diffraction and Mössbauer spectroscopy. The results show that the as-deposited, as-annealed and as-rolled samples mainly consist of DO₃ ordering phase and the as-deposited electrical steel is composed of six kinds of Fe sites corresponding to 333.8KOe, 319KOe, 302 KOe, 284 KOe, 249 KOe, 196 KOe, respectively, while the Fe site corresponding to 196 KOe hasn’t been found in the other two samples. Moreover, the other two samples show a larger Fe site occupancy corresponding to 284 KOe.