Effects of local nonequilibrium in rapid eutectic solidification—Part 2: Analysis of effects and comparison to experiment

Semiconductor-metal composites, formed by the eutectic solidification of silicon and a metal silicide have been under investigation for some time for a number of electronic device applications. This composite system is comprised of a silicon matrix containing extended metal-silicide rod-shaped structures aligned in parallel throughout the material. The average diameter of such a rod in a typical system is about 1 μm. Thus, characterization of the rod morphology by electron microscope methods is necessitated.The types of morphometric information that may be obtained from such microscopic studies coupled with image processing are (i) the area fraction of rods in the matrix, (ii) the average rod diameter, (iii) an average circularity (roundness), and (iv) the number density (Nd;rods/cm2). To acquire electron images of these materials, a digital image processing system (Tracor Northern 5500/5600) attached to a JEOL JXA-840 analytical SEM has been used.

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Electron Back Scattering Diffraction Analysis of A357 Alloy Modified by Sr

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.160-162.831 ◽

2010 ◽

Vol 160-162 ◽

pp. 831-835

Author(s):

Zhong Wei Chen ◽

Hai Fang Zhang ◽

Jiang Chao Zhao

Keyword(s):

Cast Alloy ◽

Primary Aluminum ◽

Mapping Technique ◽

Eutectic Solidification ◽

Preparation Technique ◽

Ion Milling ◽

A357 Alloy ◽

Back Scattering ◽

Eutectic Si ◽

Eutectic Morphology

Microstructure of A357 alloy modified by Sr has been investigated by the Electron Back Scattering Diffraction (EBSD) mapping technique using a Field Emission Gun Scanning Electron Microscopy (FEG-SEM). An appropriate sample preparation technique by ion milling was applied to obtain a sufficiently smooth surface for EBSD mapping. Results show that the eutectic morphology in microstructure of A357 alloy modified by Sr was changed to fine fibrous, and the grain size was refined. By comparing the orientation of the aluminum in the eutectic to that of the primary aluminum dendrites, the nucleation and growth mechanism of the eutectic solidification in A357 cast alloy was determined. The eutectic Si phase of the modified sample nucleates on the heterogeneous nuclei located in the region between primary α-Al dendrites and grows up, while the eutectic Si phase of the sample without modification nucleates on the primary α-Al dendrites and grows up.

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PHASE-FIELD MODELING OF ELASTIC EFFECTS IN EUTECTIC GROWTH WITH MISFIT STRESSES

International Journal of Modeling Simulation and Scientific Computing ◽

10.1142/s1793962312500249 ◽

2012 ◽

Vol 04 (01) ◽

pp. 1250024

Author(s):

ZOHREH EBRAHIMI ◽

JOAO REZENDEH

Keyword(s):

Phase Field ◽

Elastic Energy ◽

Field Model ◽

Phase Field Model ◽

Solidification Process ◽

Eutectic Growth ◽

Point Of View ◽

Eutectic Solidification ◽

Elastic Model ◽

Sharp Interface Model

Elastic interactions, arising from a difference of lattice spacing between two coherent phases in eutectic alloys with misfit stresses, can have an influence on microstructural pattern formation of eutectic colonies during solidification process. From a thermodynamic point of view the elastic energy contributes to the free energy of the phases and modifies their mutual stability. Therefore, the elastic stresses will have an effect on stability of lamellae, lamellae spacing and growth modes. In this paper, a phase-field model is employed to investigate the influence of elastic misfits in eutectic growth. The model reduces to the traditional sharp-interface model in a thin-interface limit, where the microscopic interface width is small but finite. An elastic model is designed, based on linear microelasticity theory, to incorporate the elastic energy in the phase-field model. Theoretical and numerical approaches, required to model elastic effects, are formulated and the stress distributions in eutectic solidification structures are evaluated. The two-dimensional simulations are performed for directed eutectic growth and the simulation results for different values of the misfit stresses are illustrated.

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