Thermal stability of Al3(Scx,Zr1-x)-dispersoids in extruded aluminium alloys

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 475; no. 1-2; pp. 241 - 248
• Main Authors: FORBORD, B, HALLEM, H, ROYSET, J, MARTHINSEN, K
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 25.02.2008
• Subjects: Cold working, work hardening; annealing, quenching, tempering, recovery, and recrystallization; textures; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Precipitation; Treatment of materials and its effects on microstructure and properties; SC lattices; Annealing; Dispersoids; Thermal stability; Precipitation; Zirconium; Aluminium alloys; Recrystallization; Scandium; Recrystallisation; Extrusion; Chemical composition; Kinetics; Activation energy; Recovery (properties); Scandium alloys; Zirconium alloys
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2007.04.054

In aluminium alloys the highest resistance against recrystallisation is obtained through combined additions of Sc and Zr. Upon annealing these elements form a high number density of homogeneously distributed and coherent Al3(ScxZr1-x)-L12-dispersoids, and the coarsening of these phases subsequently control the softening processes of recovery and recrystallisation. In this work the kinetics of Al3(ScxZr1-x)-coarsening has been investigated during annealing of two precipitation annealed and extruded Al-(Mn)-Fe-Si-Sc-Zr-alloys at temperatures between 500 deg C and 600 deg C. A simple analysis based on widely used theories for volume diffusion controlled dispersoid coarsening (R3(t)-R03{proportional to}t) was used to identify the dominant mechanisms. It was found that coarsening in both alloys is controlled by volume diffusion of Zr, as activation energies, Q, of 285+/-31kJ/mol and 250+/-43kJ/mol were obtained, respectively.