Ultrafine-grained Al–0.2Sc–0.1Zr alloy: The mechanistic contribution of nano-sized precipitates on grain refinement during the novel process of accumulative continuous extrusion

• Published in: Acta materialia 2015-11, Vol.100, p.247-255
• Main Authors: Shen, Y.F., Guan, R.G., Zhao, Z.Y., Misra, R.D.K.
• Format: Article
• Language: English
• Subjects: Accumulative extrusion process; Aluminum base alloys; Aluminum–scandium alloy; Dislocation density; Dislocation pinning; Grain refinement; Intermetallic compounds; Nanostructure; Precipitates; Precipitation; Zirconium
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2015.08.043

Graphical abstract Mechanistic contribution of precipitates on the formation of low-angle and sub-boundaries and the impact on CDRX site. [Display omitted] We elucidate the potential significance of nanosized, Al3(Sc, Zr), precipitates in obtaining ultrafine-grained structure in an Al–0.2Sc–0.1Zr alloy during the novel process, referred as accumulative continuous extrusion forming (ACEF). The grain size of the alloy was dramatically refined from 100μm to 800nm through continuous dynamic recrystallization (CDRX). The effectiveness of nanosized precipitates on CDRX was pronounced with increase in the ratio of the volume fraction (Fv) to the diameter (d) of the Al3(Sc, Zr) precipitates. Nanosized Al3(Sc, Zr), precipitates promoted grain refinement through three mechanisms: (i) the precipitates facilitated retention of high dislocation density in the alloy by promoting the generation of dislocation and pinning dislocation slip, which increased the driving force for CDRX, (ii) promoted the formation of deformation bands, providing sites for activation of CDRX, and (iii) activated CDRX near the grain boundary.