Papers by Keyword: Variants

Abstract: Particle Swarm Optimization (PSO) is a novel artificial intelligent technique proposed by Eberhart and Kennedy which is a type of Swarm Intelligence. PSO is simulated as population-based stochastic optimization influenced by the social behavior of bird flocks. In past decades, more and more researcher has been targeting to improve the original PSO for solving various problems and it has great potential to be done further. This paper reviews the progress of PSO research so far, and the recent achievements for application to large-scale optimization problems.

Abstract: In this contribution, we investigate a method able to determine the local representative orientation relation occurring in phase transformation of steels. It is based on the analysis of sets of variant orientations and does not require the knowledge the parent austenite orientation. The method which is an optimization scheme employing quaternions allowed us to determine and investigate ORs of different low carbon steel products.

Abstract: We have investigated the martensitic transformation behavior in a single crystal of Ni2MnGa under various magnetic field. The single crystal used in the present study exhibits an intermediate phase (I-phase) transformation at TI = 250 K and a martensitic transformation at TM = 202 K. Since the martensite phase (M-phase) of Ni2MnGa has a large magnetocrystalline anisotropy, the effect of magnetic field depends significantly on the direction of magnetic field. We have measured the reverse (i.e., M-phase to I-phase) transformation start temperature As from a single variant state to examine the effect of magnetic field because the forward (I-phase to M-phase) transformation usually forms a multivariant state of the M-phase. When the magnetic field is applied parallel to the easy axis, As increases linearly with increasing magnetic field. On the other hand, when the magnetic field direction is not parallel to the easy axis, As decreases in a low field region and then increases on further increasing the magnetic field. Such behavior of magnetic field dependencies of As are quantitatively explained by the Clausius-Clapeyron equation, where we have assumed that the magnetic field dependence of As agrees with the magnetic field dependence of the equilibrium temperature.

Abstract: Phase separations of A1 (γ) supersaturated solid solution into γ, cubic-L12 (γ') and tetragonal-D022 (γ") phases were investigated in Ni-V-Ge alloys by means of transmission electron microscopy (TEM). When Ni-15.8at%V-9.0at%Ge alloy is aged at 1073 K, at the early stage of ageing γ" phases are observed in the γ matrix as triangle- or diamond-shaped precipitates. With further ageing, colonies of lamellar structure consisting of two variants of γ" phase are dispersedly formed in the γ matrix and then γ" plates grow along the <110> direction. When Ni-14.5at%V-8.8.at%Ge alloy is isothermally annealed at 1023 K, first spherical γ' particles precipitate homogeneously in the γ matrix, followed by the formation of lamellar structure of γ" phases. In the course of further ageing, the lamellar structure develops, and only γ' particles around the lamellar structure grow and others gradually fade out.

Abstract: This study aims to analyze the potential of grain boundary corners (GBCs) as nucleation sites of bcc precipitates in an fcc matrix. By combined serial sectioning and electron backscatter diffraction analysis, the crystallography of GBCs and GBC precipitates was analyzed in a Co-Fe alloy.

Abstract: We have studied effect of magnetic field on the martensite (10M) to intermediate phase transformation temperature (As) of Ni2MnGa in order to understand the influence of magnetocrystalline anisotropy on the transformation temperature under a magnetic field. In case of the transformation from multi-variant 10M phase to the intermediate phase, As decreases with increasing magnetic field H for H < 0.8 MA/m, and then it increases on further increasing H. On the other hand, in case of the transformation from the single-variant 10M to the intermediate phase, As increases monotonically with increasing H, where the easy axis of the single variant is parallel to the field direction. The difference between the multi-variant and single variant state can be explained by considering the high magnetocrystalline anisotropy of the martensite phase.

Abstract: The orientations of the inherited tetragonal (resp. cubic) variants are calculated from the parent hcp orientation in the case of a strict orientation relation. The numbering of the variants is proposed, as well as the misorientations between them. Conversely, a method for calculating the parent hcp orientation from a sufficient number of inherited variants is proposed. It is based on orientation correlating and orientation averaging, and it is particularly useful when the inherited variants are not exactly related to the parent orientation by a strict orientation relation or when the orientations of the inherited volumes slightly vary at different locations of the variant. The method is illustrated by considering the a to g phase transformation taking place in TiAl-based alloys