Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

The microstructural evolution and room/elevated-temperature tensile properties of Al-Mg-Si 6082 alloys subjected to thermomechanical processing (homogenization, hot rolling, T6 heat treatment, and thermal exposure) were investigated. Four experimental 6082 alloys were studied, including a Mn-free base alloy and three alloys containing Mn individually and in combination with Cr + V or Mo, in which a number of α-Al(MnFe)Si, α-Al(MnFeCrV)Si and α-Al(MnFeMo)Si dispersoids were formed, respectively. The results showed that both α-Al(MnFeCrV)Si and α-Al(MnFeMo)Si dispersoids had a higher coarsening resistance compared to α-Al(MnFe)Si dispersoids. The presence of α-dispersoids hindered the formation of Mg-Si clusters, which decreased the precipitation of β″-MgSi precipitates, resulting in reductions in room-temperature strengths. During thermal exposure at 300 °C, the α-dispersoids remained thermally stable and became the predominant strengthening phase, resulting in increases of 71 to 126% in the yield strength at 300 °C relative to the base alloy without dispersoids. Among the three dispersoid-containing alloys studied, the alloy containing Mn and Mo exhibited the highest yield strength of 70 MPa at 300 °C, providing the best combination of room- and elevated-temperature tensile properties.