Hardening and Thermal stability of nanocrystalline AlMg4.8 powder

Marco Hüller (1) , Johannes Vlcek (1) , Markus Dinkel (2) , Heinz Werner Höppel (2) , Mathias Goeken (2)

1 Metallic Technologies & Surface Engineering
2 WWI

Ball milled nanocrystalline AlMg4.8 powder was investigated in terms of hardening and thermal stability. The validity of the Hall-Petch relation was confirmed down to the minimum grain size of 44 nm. Prolonged milling in the range of the minimum grain size still increased the hardness. This development was discussed in terms of contamination effects and the influence of full and partial dislocations. Concerning thermal stability, recovery processes occur in the range of 100 – 230 °C while substantial grain growth starts at a temperature of about 250 °C. The enthalpy release for recovery was detected to be ~ 39 J/mol and ~ 208 J/mol for grain growth. Dynamic strain aging was indicated by an activation energy for recovery of Q ~ 120 kJ/mol. The activation energy of grain growth was calculated by means of the Kissinger theory (Q = 200 - 210 kJ/mol) and using the results of static grain growth (Q = 204 kJ/mol).

Mots clés: Physical Sciences

Marco Hüller, Johannes Vlcek, Markus Dinkel, Heinz Werner Höppel, Mathias Goeken. Hardening and Thermal stability of nanocrystalline AlMg4.8 powder. Philosophical Magazine, 2008, 88 (08), pp.1209-1226. ⟨10.1080/14786430802089854⟩. ⟨hal-00513891⟩