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Microstructure, Thermal and Mechanical Properties of Non-Isothermally Annealed Al-Sc-Zr and Al-Mn-Sc-Zr Alloys Prepared by Powder Metallurgy

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Vlach M., Stulíková I., Smola B., Císařová H., Piešová J., Daniš S., Gemma R., Tanprayoon D., Neubert V.

Acta Physica Polonica A

2012

vol. 122

issue 3

439-443

This paper reports results of a study aimed at understanding the precipitation processes occurring during the annealing of two Al-Sc-Zr-based alloys with and without Mn prepared by powder metallurgy with subsequent hot extrusion at 350°C. Samples were isochronally annealed up to ≈ 570°C. Precipitation behaviour was studied by electrical resistometry and differential scanning calorimetry. Mechanical properties were monitored by microhardness HV1 measurements. Transmission electron microscopy examinations and X-ray diffraction of specimens quenched from temperatures of significant resistivity changes helped to identify the microstructural processes responsible for these changes. Fine (sub)grain structure develops and fine coherent Al_3Sc and/or Al_3(Sc,Zr) particles precipitate during extrusion in both alloys. The distinct changes in resistivity (at temperatures above ≈ 330°C) of the Al-Mn-Sc-Zr alloy are mainly caused by precipitation of Mn-containing particles. The easier diffusion of Mn atoms along the (sub)grain boundaries is responsible for the precipitation of the Al_6Mn and/or Al_6(Mn,Fe) particles at relatively lower temperatures compared to the temperature range of precipitation of these particles in the classical mould-cast Al-Mn-Sc-Zr alloys The apparent activation energy for precipitation of the Al_3Sc and Al_6Mn particles in the Al-Mn-Sc-Zr alloy was determined as (106 ± 10) kJ mol^{-1} and (152 ± 33) kJ mol^{-1}, respectively.

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1 Acta Physica Polonica A

1 2012

1 Císařová H.

1 Daniš S.

1 Gemma R.

1 Neubert V.

1 Piešová J.

1 Smola B.

1 Stulíková I.

1 Tanprayoon D.

1 Vlach M.

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Microstructure, Thermal and Mechanical Properties of Non-Isothermally Annealed Al-Sc-Zr and Al-Mn-Sc-Zr Alloys Prepared by Powder Metallurgy