Papers by Keyword: Coarsening

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Authors: Marek Gebura, Juraj Lapin
Abstract: Microsegregation induced inhomogeneity of the coarsening of cuboidal γ’(Ni3(Al,Ti)) precipitates was studied in a single crystal nickel-based superalloy CMSX-4 at temperatures ranging from 850 to 1000 °C and for an ageing time up to 5000 h. Experimental results showed a significant statistical difference in the size of the γ’ precipitates between the dendrites and interdendritic region. The achieved results are analyzed and discussed from the point of chemical heterogeneity, activation energy for coarsening, time exponent, effective diffusion coefficient and γ/γ’ interfacial energy which control coarsening kinetics of the cuboidal γ’ precipitates within the dendrites and interdendritic region.
Authors: Qing Liu, W.Q. Cao, Andrew Godfrey
Abstract: The transition from discontinuous recrystallization to a continuous recovery process during annealing of aluminium deformed to high plastic strains has been investigated by following several different microstructural parameters. Samples were examined following equal channel angular extrusion (ECAE), accumulated roll bonding (ARB) and high-strain conventional rolling (HSCR). Local variations in the uniformity of coarsening have been characterized by an analysis of grain size distributions, obtained from electron backscatter pattern investigations. Except for at the lowest strains the distributions were not obviously bimodal. Methods of separating the distributions into two parts based on the mean value have therefore also been examined. The results suggest that the presence of a high fraction of high angle boundaries (>15o) in the microstructure may be a necessary but not sufficient condition for continuous recovery during annealing. The annealing behaviour can be related in part to the heterogeneity of the deformed microstructures, which can be pronounced even after strains of ≈ 10 (ECAE). The presence of oxide particles in the ARB sample has a beneficial effect in limiting the grain growth.
Authors: Fei Wang, Ya Ping Wang
Abstract: Microstructure evolution of high energy milled Al-50wt%Si alloy during heat treatment at different temperature was studied. Scanning electron microscope (SEM) and X-ray diffraction (XRD) results show that the size of the alloy powders decreased with increasing milling time. The observable coarsening of Si particles was not seen below 730°C in the high energy milled alloy, whereas, for the alloy prepared by mixed Al and Si powders, the grain growth occurred at 660°C. The activation energy for the grain growth of Si particles in the high energy milled alloy was determined as about 244 kJ/mol by the differential scanning calorimetry (DSC) data analysis. The size of Si particles in the hot pressed Al-50wt%Si alloy prepared by high energy milled powders was 5-30 m at 700°C, which was significantly reduced compared to that of the original Si powders. Thermal diffusivity of the hot pressed Al-50wt%Si alloy was 55 mm2/s at room temperature which was obtained by laser method.
Authors: Mickael Serriere, Charles-André Gandin, Elisabeth Gautier, Pierre Archambault, M. Dehmas
Authors: G. Martin, Pascal Bellon, Frédéric Soisson
Authors: Tanja Pettersen, Steinar Benum, Arve Johansen, Arild Håkonsen
Authors: Suk Won Kang, Ki Bae Kim, Dock Young Lee, Jung-Hwa Mun, Eui Pak Yoon
Authors: Fabienne Berthier, Emile Maras, Isabelle Braems, Bernard Legrand
Abstract: We compare three models of 2D precipitation kinetics that give access to different time-space scales. Kinetic Monte Carlo simulations (KMC), cluster dynamics (CD) and nucleation-growth-coalescence model (NGCM), based on a same atomic model, lead to an excellent agreement as long as the interfacial free energy is evaluated accurately and the interaction between diffusion fields is taken into account in the CD. The NGCM model noticeably improves the previous approaches of the same kind by using a constrained-equilibrium hypothesis to describe the solid solution. Moreover, in the coalescence regime, we show that CD leads to cluster distributions that are wider and more symmetric than the LSW distribution due to the probabilistic feature of the growth law of a cluster, that makes it differ from the purely deterministic NGCM approach.
Authors: M.G.D. Geers, R.L.J.M. Ubachs, M. Erinc, M.A. Matin
Abstract: The past years have triggered considerable scientific efforts towards the predictive analysis of the reliability of solder connections in micro-electronics. Undoubtedly, the replacement of the classical Sn-Pb solder alloy by a lead-free alternative constitutes the main motivation for this. This paper concentrates on the theoretical, computational and experimental multi-scale analysis of the microstructure evolution and degradation of the conventional solder material Sn-Pb and its most promising lead-free alternative, a Sn-Ag-Cu (SAC) alloy. Special attention is given to the thermal anisotropy of bulk SAC and the interfacial fatigue failure of SAC interconnects.
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