Operando study of the dynamic evolution of complex intermetallic phases in a multi-component Al alloy by simultaneous synchrotron X-ray diffraction and tomography

Authors

Mr Kang Xiang (1), Mr Shi Huang (1), Dr Yuliang Zhao (1), Prof. Dr. Jiawei Mi (1)

Affiliations

1. University of Hull

Keywords

Synchrotron X-ray; Diffraction; Tomography; Intermetallic phase: Aluminum alloy; Solidification

Abstract text

In most Al alloys, especially the million tons of recycled Al alloys currently circulating in society and industry, Fe is the most unavoidable and detrimental elements for mechanical properties. With other elements, Fe can form numerous brittle intermetallic phases with either complex Chinese script morphology or long and thin plates of sharp edges. They may act as stress concentration sites to initiate crack and then propagate at much lower stress level. Currently, extensive research has been carried out to develop processing strategies of either removing the Fe-rich phases or alter them into beneficial morphologies. Although the growth dynamics of plate-type Fe phases have been thoroughly studied, that of the complex Chinese script-type Fe phases and its interaction with Al dendrite are much less understood. Most of the Fe-based intermetallic phases have similar X-ray absorption contrast. Hence, it is very difficult to identify these phases accurately relying only on X-ray imaging.

In this work, we used synchrotron X-ray dual diffraction and tomography techniques to study in operando conditions the dynamic evolution of complex multiphases in a multi-component recycled Al alloy during the solidification process. The nucleation of the intermetallic phases, their growth dynamics and spatial interconnection are fully characterized and quantitatively determined. By analysing the very rich datasets, new strategy to control and modify the size and morphology of Fe intermetallic phases are discussed and proposed.