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Influence of the specific surface area of secondary material on the solidification process and microstructure of aluminium alloy AA7075

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Abstract

Recycling activities are encouraged to conserve natural resources and reduce pollution. If waste is pre-treated and appropriately sorted, recycled aluminium can be used for almost all applications. The quality of the secondary material depends on several factors, including the purity of the material, coatings and size. Melting material with larger specific surface causes higher melt losses and greater number of inclusions. The control of impurities is important because they have a major influence on the mechanical properties of recycled alloys. The aim of the study was to determine basic thermal characteristics of the recycled aluminium alloy AA7075 using thermal analysis known as cooling curve analysis and differential scanning calorimetry. It was found that the smallest enthalpy of solidification was measured in sample with greater specific surface, which suggests that high-melting inclusions are present in the sample. Mass losses reached up to 11 mass%. Linear correlation between the specific surface of the input material and the melt losses was confirmed. Metallographic examinations of samples were performed using optical microscopy and scanning electron microscopy. Phases, inclusions and trace elements were determined by energy-dispersive spectroscopy.

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Acknowledgements

This work was supported by the Republic of Slovenia, Ministry of Education, Science and Sport and by the European Commission, European Regional Development. This work was made in a frame of the program Materials and Technologies for New Applications (MARTINA, Grant Number: C3330-16-529008).

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Authors and Affiliations

  1. Department of Materials and Metallurgy, Faculty of Natural Sciences and Engineering, University of Ljubljana, Aškerčeva 12, 1000, Ljubljana, Slovenia

    Lina Jerina, Jožef Medved & Maja Vončina

  2. Blok d.o.o, IOC Zapolje II 7, 1370, Logatec, Slovenia

    Lina Jerina

  3. Institut of Metals and Technology, Lepi Pot 11, 1000, Ljubljana, Slovenia

    Matjaž Godec

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  1. Lina Jerina
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  2. Jožef Medved
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Correspondence to Lina Jerina.

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Jerina, L., Medved, J., Godec, M. et al. Influence of the specific surface area of secondary material on the solidification process and microstructure of aluminium alloy AA7075. J Therm Anal Calorim 134, 455–462 (2018). https://doi.org/10.1007/s10973-018-7425-2

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  • DOI: https://doi.org/10.1007/s10973-018-7425-2

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