ACTA

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

M. Vlach^a, I. Stulíková^a, B. Smola^a, H. Císařová^a, J. Piešová^a, S. Daniš^a, R. Gemma^b, D. Tanprayoon^c and V. Neubert^c
^aFaculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague, Czech Republic
^bInstitute of Material Physics, University of Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany
^cInstitut für Materialprüfung und Werkstofftechnik, Freiberger Str. 1, D-38678 Clausthal-Zellerfeld, Germany

Full Text PDF

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 Al₃Sc and/or Al₃(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 Al₆Mn and/or Al₆(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 Al₃Sc and Al₆Mn particles in the Al-Mn-Sc-Zr alloy was determined as (106 ± 10) kJ mol^-1 and (152 ± 33) kJ mol^-1, respectively.

DOI: 10.12693/APhysPolA.122.439
PACS numbers: 81.20.Ev, 81.30.Mh