Abstract: The novel coupling recrystallization model is proposed in this study. First, the deformation
microstructure was simulated by the finite element method based on the strain gradient crystal
plasticity theory. The calculated dislocation density and crystal orientation were transferred to the
recrystallization phase-field simulation. The initial subgrain structures used in phase-field simulation
were determined by a relationship between dislocation density and subgrain size with the dislocation
density distribution calculated by crystal plasticity simulation. The so-called KWC phase-field model,
which can introduce both subgrain rotation and grain boundary migration, was employed, and
spontaneous nucleation and grain growth were simulated simultaneously.
Abstract: The present work concerns the simulation of metallurgical evolutions in 3D multi-pass
forming processes. In this context, the analyzed problem is twofold. One point refers to the
management of the microstructure evolution during each pass or each inter-pass period and the
other point concerns the management of the multi-pass aspects (different grain categories, data
structure). In this framework, a model is developed and deals with both aspects. The model
considers the microstructure as a composite made of a given (discretized) number of phases which
have their own specific properties. The grain size distribution and the recrystallized volume fraction
distribution of the different phases evolve continuously during a pass or inter-pass period. With this
approach it is possible to deal with the heterogeneity of the microstructure and its evolution in
multi-pass conditions. Both dynamic and static recrystallization phenomena are taken into account,
with typical Avrami-type equations. The present model is implemented in the Finite Element code
FORGE2005®. 3D numerical simulation results for a multi-pass process are presented.
Abstract: Plastic deformation induces the dislocation and residual stress fields, which rest in a
material after releasing of applied external forces. One can distinguish the stored energy connected
with dislocation density and that with residual stresses. The stored energy distributions can be
determined experimentally by diffraction experiments and also can be predicted by deformation
models. The so obtained distributions of the stored energy versus crystal orientation were correlated
with deformation and recrystallization textures of low carbon steel.
Abstract: The kinetics and microstructure evolution during static recrystallization (SRX) of
hot-deformed austenite in a low carbon steel are simulated by coupling a cellular automaton (CA)
model with a crystal plasticity finite element model (CPFEM). The initial deformed characteristics,
which include the stored energy of deformation and the crystallographic orientation induced by a
plane strain hot compression are simulated using a crystal plasticity finite element model. These
data are mapped onto the CA regular lattices as the initial parameters for SRX simulation. The
coupled simulation results reveal that the heterogeneous distribution of the stored energy of
deformation results in non-uniform nucleation and a slower kinetics. The influence of non-uniform
distribution in stored energy on the SRX kinetics and microstructure evolution is discussed based on
a microstructural path (MP) analysis.
Abstract: An improved Monte Carlo (MC) Potts model algorithm has been implemented allowing
an extensive simulation of three-dimensional (3D) normal grain growth. It is shown that the
simulated microstructure reaches a quasi-stationary state, where the growth of grains can be
described by an average self-similar volumetric rate of change, which depends only on the relative
grain size. Based on a quadratic approximation of the volumetric rate of change a generalized
analytic mean-field theory yields a scaled grain size distribution function that is in excellent
agreement with the simulation results.
Abstract: The grain growth kinetics of silica and calcia doped alumina at 1400oC and their grain
boundary complexion is characterized. These data are compared to predictions of both diffusion
controlled and nucleation limited interface controlled grain growth theory. It is deduced from the
indicators that the mechanism for normal and abnormal grain growth in these aluminas is diffusion
Abstract: The effect of carbon addition on the grain growth and ordering kinetics of FePt film has
been experimentally studied by sputter-depositing a monolithic FePt-20at.%C film of 24 nm. Carbon
addition of 20at.% to FePt thin film in a form of FePt (20 nm)/Cn (4 nm) (n = 1, 4) significantly
reduced both the grain growth and ordering kinetics. Reducing the thickness of carbon layer, i.e. from
n = 1 to n = 4, led to a much finer grain size distribution as well as to a finer grain size. The Monte
Carlo simulation study indicated that the decrease of grain growth and ordering kinetics is primarily
due to a continuous decrease of the mobility of order – disorder inter-phase with the progress of
ordering reaction. This can eventually lead to a stable 2-phase grain structure inter-locked by low
mobility inter-phases and is responsible for the formation of a fine grain size distribution in the
FePt/Cn film with n = 4.
Abstract: Use of silver (Ag) nanoparticle suspension for various applications such as ink-jet
printing of electronic circuits has been of prime interest. We observed the microstructure evolution
of the inkjet-printed Ag thin films on Si substrates under various annealing conditions using the
field-emission scanning electron microscopy (FE-SEM). Abnormal grain growth characteristics
were identified when annealed at about 240 oC under ambient air. Growth characteristics of pores
were found to be in accordance with that of grains. Competition between grain and pore growth is
attributed to small grain sizes, low packing density and high porosity, which are characteristic of
inkjet-printed Ag films as dried.
Abstract: Multi-component ceramic composites consisting of two, three and four phases, based on
duplex microstructures of zirconia and alumina, were fabricated by a polymer complexation route
employing polyethylene glycol (PEG) as a polymeric carrier. The polymer complexation route
provided porous and soft powders and they were sintered after a simple ball milling process. In this
study, the microstructures and flexural strengths of the multi-component (Al2O3-ZrO2-Y2O3-SrO)
ceramic composites were examined on the processing variations of mole ratio and sintering
temperature. The composites showed various grain morphologies according to the sintering
temperature, and flexural strength of 410 MPa was obtained in the Al2O3·ZrO2·0.5Y2O3·0.4SrO
composite sintered at 1600 °C for 1 h. In particular, needle-shape grains were observed in the
four-component composites sintered at 1500 °C.
Abstract: Mineral wool products can be used for thermal and acoustic insulation as well as for fire
protection. The high temperature properties and the crystallization behaviour (devitrification) of the
amorphous fibres during heating have been examined.
Commercial stone wool and commercial hybrid wool (stone wool produced by a glass wool
process) have been compared, as well as specially produced stone wool fibres. The fibres differed in
chemical compositions and degree of oxidation given by Fe3+/Fetotal ratios.
The materials were studied by thermal stability tests, X-ray diffraction, Mössbauer spectroscopy,
secondary neutral mass spectroscopy, differential scanning calorimetry and thermal gravimetric
When stone wool fibres were heated at 800 °C in air, oxidation of Fe2+ to Fe3+ occurred
simultaneously with migration of divalent cations (especially Mg2+) to the surface. Decreasing
Fe3+/Fetotal ratios resulted in increasing migration and improved thermal stability. The cations
formed a surface layer mainly consisting of MgO.
When heated to above 800 °C, bulk crystallization of the fibres took place with diopside and
nepheline as the main crystalline phases.
Commercial stone wool and the specially made fibres were considerably more temperature stable
than the commercial hybrid wool. Commercial hybrid wool has a high Fe3+/Fetotal ratio of 65%
resulting in less migration of cations during heat treatment.