Ultrasonic Fractional Purification of Recycled Al Alloys
Lead Research Organisation:
Brunel University London
Department Name: Inst of Materials & Manufacturing: BCAST
Abstract
Abstract
This PhD project will develop fundamental and applied basis for fractional solidification technology of recycled aluminium alloys. The novelty of the project is in combination of thermochemistry of recycled alloys, ultrasonic processing of melt and fractional solidification for achieving higher purity of aluminium extracted from recycled stock.
Keywords
Solidification, aluminium, partitioning, ultrasound, recycling
Project Scope and Research Objectives Defined
Recycled Al alloys are typically contaminated with harmful impurities of Fe, Mn and other elements that form eutectic systems with Al. Currently the re-use of such alloys involves their dilution with primary alloys or aluminium (expensive and with larger carbon footprint) or by additions that modify the shape of the intermetallics (maybe expensive and harmful for other properties, e.g. corrosion).
There are some earlier works where interrupted (fractional) solidification was suggested as a technologically viable way of purification of the melt from soluble impurities. In eutectic systems, e.g. Al-Fe, Al-Mn, Al-Cu, Al-Mg, Al-Si, hypoeutectic alloys show large partitioning of solute elements between liquid and solid phases, with these (impurity) elements accumulating in the liquid phase while the solid phase (Al) remaining almost pure especially in the early stages of solidification.
In the fractional solidification method, a water- or air-cooled substrate is put into a contaminated melt and solidification of relatively pure Al starts on it, while the rejected solute is accumulated in the rest of the melt. At a certain moment the substrate with the purified Al is extracted from the residual melt. The remaining melt can be recycled as master alloys or subjected to repeated fractional solidification.
Ultrasonic processing of melts is known to induce special conditions such as heating, cavitation and streaming that may have potential benefits for fractional solidification, accelerating the diffusion and transport of the melt from the solidification (reaction) zone.
There are three main challenges in the proposed project
a better understanding and the related ability to establish control of fractional solidification using dedicated experiments, thermodynamic modelling and heat/mass transfer simulations.
understanding the mechanisms of ultrasonic treatment in the fractional solidification through smaller scale experiments.
design and test a prototype system and demonstrate the feasibility of the approach in application to the scrap of different origin and composition.
The results obtained will be of considerable scientific and applied value and publishable in leading scientific journals and conferences (following the agreed approval procedure).
The research objectives are:
1. Study the fundamentals of fractional solidification based on thermodynamic modelling (Thermocalc) and experimental work. - knowledge transfer.
2. Establish the relation between the process parameters (melt and substrate temperatures, solidification and cooling rates, ultrasonic parameters, composition of the initial and target alloys) and the degree of purification. - knowledge transfer.
3. Design and built a lab-scale prototype to test the feasibility of the developed approach as applicable to the recycled alloys of different origin (automotive, construction, aircraft scrap). - knowledge transfer.
4. Educate a young scientist. Milestone - PhD.
Expected key project outcomes defined, i.e. New technology or PhD or Creation of new Standards or creation of new processes, etc.
This project will create new knowledge for JLR in the form a PhD thesis in the subject of aluminium recycling which will help shape the sustainable future for JLR products.
This project will provide a working lab-scale prototype for further technological development along with a number of reports and scientific papers.
This PhD project will develop fundamental and applied basis for fractional solidification technology of recycled aluminium alloys. The novelty of the project is in combination of thermochemistry of recycled alloys, ultrasonic processing of melt and fractional solidification for achieving higher purity of aluminium extracted from recycled stock.
Keywords
Solidification, aluminium, partitioning, ultrasound, recycling
Project Scope and Research Objectives Defined
Recycled Al alloys are typically contaminated with harmful impurities of Fe, Mn and other elements that form eutectic systems with Al. Currently the re-use of such alloys involves their dilution with primary alloys or aluminium (expensive and with larger carbon footprint) or by additions that modify the shape of the intermetallics (maybe expensive and harmful for other properties, e.g. corrosion).
There are some earlier works where interrupted (fractional) solidification was suggested as a technologically viable way of purification of the melt from soluble impurities. In eutectic systems, e.g. Al-Fe, Al-Mn, Al-Cu, Al-Mg, Al-Si, hypoeutectic alloys show large partitioning of solute elements between liquid and solid phases, with these (impurity) elements accumulating in the liquid phase while the solid phase (Al) remaining almost pure especially in the early stages of solidification.
In the fractional solidification method, a water- or air-cooled substrate is put into a contaminated melt and solidification of relatively pure Al starts on it, while the rejected solute is accumulated in the rest of the melt. At a certain moment the substrate with the purified Al is extracted from the residual melt. The remaining melt can be recycled as master alloys or subjected to repeated fractional solidification.
Ultrasonic processing of melts is known to induce special conditions such as heating, cavitation and streaming that may have potential benefits for fractional solidification, accelerating the diffusion and transport of the melt from the solidification (reaction) zone.
There are three main challenges in the proposed project
a better understanding and the related ability to establish control of fractional solidification using dedicated experiments, thermodynamic modelling and heat/mass transfer simulations.
understanding the mechanisms of ultrasonic treatment in the fractional solidification through smaller scale experiments.
design and test a prototype system and demonstrate the feasibility of the approach in application to the scrap of different origin and composition.
The results obtained will be of considerable scientific and applied value and publishable in leading scientific journals and conferences (following the agreed approval procedure).
The research objectives are:
1. Study the fundamentals of fractional solidification based on thermodynamic modelling (Thermocalc) and experimental work. - knowledge transfer.
2. Establish the relation between the process parameters (melt and substrate temperatures, solidification and cooling rates, ultrasonic parameters, composition of the initial and target alloys) and the degree of purification. - knowledge transfer.
3. Design and built a lab-scale prototype to test the feasibility of the developed approach as applicable to the recycled alloys of different origin (automotive, construction, aircraft scrap). - knowledge transfer.
4. Educate a young scientist. Milestone - PhD.
Expected key project outcomes defined, i.e. New technology or PhD or Creation of new Standards or creation of new processes, etc.
This project will create new knowledge for JLR in the form a PhD thesis in the subject of aluminium recycling which will help shape the sustainable future for JLR products.
This project will provide a working lab-scale prototype for further technological development along with a number of reports and scientific papers.
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/P510439/1 | 01/10/2016 | 30/09/2021 | |||
| 1815386 | Studentship | EP/P510439/1 | 01/11/2016 | 31/07/2020 | Susanna Venditti |
| Description | The research project focused on the application of the fractional solidification principle on selected semisolid aluminium alloys in order to recycle the aluminium. Initially a small set-up was built as proof of concept performing the fractional solidification as an isothermal squeezing of the semisolid allow towards a filter. Successively, this set up was upscaled in order to process up to 3 kg of material. Additional to the upscaling process, the set-up was optimised in order to define which parameters affect and enhance the purification process. Temperature and the squeezing procedure are key parameters from a technology aspect. On a more fundamental point of view, the role of ultrasound and grain refinement was studied and investigated along with the effect of deformation on the semisolid material. The purpose, in fact, is to process the alloy in the semi solid state in order to squeeze the liquid out of the mush as much as possible to achieve a high purification level. The key to do it is to understand how the liquid migrates through the mush. We studied the liquid migration with the help of Computed Tomography, SEM and EDX measurements and optical microscopy images. Moreover, through the use of a modelling calculation, we are able to confirm that no solid diffusion happens during the isothermal squeezing so that the purification is not affected. In conclusion, the set-up developed during this PhD course was able to purify aluminium from model binary alloys, and from real scrap, up to 50%. |
| Exploitation Route | The outcomes both fundamental and technological may be taken by JLR and partners to the practical implementation stage, e.g. technology development or prototype building. |
| Sectors | Aerospace, Defence and Marine,Energy,Environment,Manufacturing, including Industrial Biotechology,Transport,Other |
| URL | https://www.researchgate.net/publication/338845893_Fractional_Solidification_for_Purification_of_Recycled_Aluminium_Alloys |
| Description | The finding of this research work have been summarised in a PhD thesis that has been successfully defended during the viva voce examination. The thesis will be available online and potentially be used by other research groups to expand the investigation of the topic. Also, a copy of the thesis has been sent to JLR for their use. |
| Sector | Environment,Manufacturing, including Industrial Biotechology |
| Description | AMPC launch |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Other audiences |
| Results and Impact | i presented a poster about my research at the event organised for the launch of the AMPC facility in Bcast where I am enrolled as PhD student. It was a good occasion to share with my colleagues, and some external members of the Academia and the industrial environment, my research. I received interesting advice and I could also practice my skills in presentationa and public speaking. |
| Year(s) Of Engagement Activity | 2018 |
| Description | International Conference on Aluminium Alloys |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Industry/Business |
| Results and Impact | Presenting a poster on the project during a poster session at the International Conference on Aluminium Alloys in Montreal, Canada |
| Year(s) Of Engagement Activity | 2018 |
| Description | TMS2020 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | Oral presentation on the outcomes of this project at an Annual Meeting of TMS (The Minerals, Metals and Materials Society of America): symposium on recycling |
| Year(s) Of Engagement Activity | 2020 |