A synchrotron X-radiography study of the fragmentation and refinement of primary intermetallic particles in an Al-35 Cu alloy induced by ultrasonic melt processing

Feng Wang,Dmitry Eskin,Jiawei Mi,Chuangnan Wang,Billy Koe,Andrew King,Christina Reinhard,Thomas Connolley

doi:10.1016/j.actamat.2017.09.010

Abstract

The authors acknowledge financial support from the UK Engineering and Physical Science Research Council (EPSRC) for the Ultra-Cast project (grants EP/L019884/1; EP/L019825/1; EP/L019965/1). Mi also would like to acknowledge the financial support by the Royal Society Industry Fellowship awarded in 2012-2016. The experiments were performed on the Psiche beamline at Synchrotron SOLEIL, France (Proposal No. 2016076). Beamline I12 at Diamond Light Source, UK, is also thanked for loan of the high speed camera.

Highlights

Application of high-intensity ultrasonic vibrations to processing of liquid or semi-solid metals and their alloys during solidification has attracted considerable interest from the research community and casting industry
The dynamic fragmentation processes of well-grown Al2Cu intermetallic dendrites induced by Ultrasonic melt processing (USMP) and the subsequent solidification of the alloy which was contained in a thin channel of ~300 mm thickness were recorded at high frame rates (1000 fps) for the first time
In-situ observations clearly demonstrated that USMP induced fragmentation of primary intermetallic dendrites via acoustic cavitation and acoustic streaming flow, through various mechanisms

Summary

Introduction

Application of high-intensity ultrasonic vibrations to processing of liquid or semi-solid metals and their alloys during solidification has attracted considerable interest from the research community and casting industry. The other cavitation-enhanced nucleation mechanism [3,5] suggests that the formation, growth and implosive collapse of cavitation bubbles produces a high-energy shockwave or liquid jet flow near impurity particles. Both would improve wetting of the impurity particles by the melt and activate them to become effective nucleation sites for solid phase formation. A vast amount of results obtained from numerous dedicated solidification experiments followed by advanced characterisation [9,11e13] have made progress in understanding the mechanisms underlying the beneficial effects of USMP, almost all of these results are based on post-solidified microstructure analyses and are essentially indirect evidence.

Results

Discussion

Conclusion