Observation of Morphology Changes of Fine Eutectic Si Phase in Al-10%Si Cast Alloy during Heat Treatment by Synchrotron Radiation Nanotomography.

Shougo Furuta,Kentaro Uesugi,Hiromi Miura,Akihisa Takeuchi,Tomoya Aoba,Masakazu Kobayashi

doi:10.3390/ma11081308

Abstract

A series of three-dimensional morphology changes of fine eutectic Si-particles during heat treatment have been investigated in Self-modified and Sr-modified Al-10%Si cast alloys by means of synchrotron radiation nanotomography utilizing a Fresnel zone plate and a Zernike phase plate in this study. The coral-like shape particles observed in Sr-modified cast alloy fragmented at branch and neck during heat treatment at 773 K. The fragmentation occurred up to 900 s. After that, the fragmented particles grew and spheroidized by Ostwald ripening. On the other hand, rod-like shaped eutectic Si-particles observed in self-modified cast alloy were larger in size compared with the particle size in Sr-modified cast alloy. Separation of eutectic Si-particles in Self-modified cast alloy occurred up to approximately 900 s, which was similar tendency to that in Sr-modified cast alloy. However, it was found that the morphology change behavior was very complex in rod-like shape Si-particles. The three-dimensional morphology changes of fine eutectic Si-particles in both cast alloys, specifically fragmentation and spheroidizing, can be connected to changes in mechanical properties.

Highlights

Since the building of large synchrotron radiation facilities throughout the world in the latter half of the twentieth century, the performance of synchrotron radiation tomography has gradually improved up to the present day [1,2,3]
Synchrotron radiation tomography can be used for various studies in various fields
The advantages of X-ray tomography are that three-dimensional morphologies are obtained, and that the observation is non-destructive

Summary

Introduction

Since the building of large synchrotron radiation facilities throughout the world in the latter half of the twentieth century, the performance of synchrotron radiation tomography has gradually improved up to the present day [1,2,3]. In the Japanese synchrotron radiation facilities, SPring-8, three-dimensional non-distractive observation with a spatial resolution of 50–160 nm is available constantly in the imaging beamline by using an X-ray focusing device of a Fresnel zone plate [4,5,6]. Improvement of the performance of X-ray 2D detector system has rapidly shortened scanning time. Synchrotron radiation tomography can be used for various studies in various fields. The advantages of X-ray tomography are that three-dimensional morphologies are obtained, and that the observation is non-destructive. In studies of structural materials, material behaviors changing over time can be visualized, for instance, damage and fracture mechanisms [7,8,9,10,11,12,13,14], fatigue

Methods

Results

Conclusion