Tracking the dynamic evolutions of complex intermetallic phases of recycled Al alloys during solidification by the extremely brilliant source

Zoom webinar | Replay on Youtube (soon)

Jiawei Mi

University of Hull, UK

Globally, the annual demand for primary aluminium (Al) is ∼70 million tons and the uses of secondary Al or recycled Al consume only ∼7% of the energy compared to the primary Al. Therefore, it is vital to maximise the reuses and recycling rate of secondary Al to reduce the greenhouse gas emissions in Al industry.

In almost all commercial Al alloys, Fe is the most common detrimental element, which is often accumulated in the sorting and remelting processes and form different type of brittle Fe-rich intermetallic phases, damaging greatly castability and mechanical properties of the alloys. It is vital to develop efficient and effective methodologies to restrict the detrimental Fe phases or to modify/change the damaging phase morphology into beneficial ones in order to improve the mechanical properties.

Here, I present our recent operando research work of using the ultrafast synchrotron X-ray diffraction and tomography techniques at ID11 and ID19 of the ESRF plus machine-learning assisted phase segmentation methods to study the 3D nucleation dynamics of the Fe phases in a typical multiple-component recycled Al alloy. We revealed, in operando conditions, how the co-growth of multiple Fe phases lead to the formation of complex and convoluted 3D Chinese-script phases.

Furthermore, we have demonstrated that, by applying intensive ultrasound into the solidifying melt for just a few seconds, the primary Al dendrites and Fe phase growth dynamics can be effectively altered, resulting in much refined dendritic structures and intermetallic phases with less detrimental 3D morphology. The research has shown that ultrasound melt processing is a promising green technique for processing recycled Al alloys.