Grain refinement in low SFE and particle-containing nickel aluminium bronze during severe plastic deformation at elevated temperatures. (20th August 2021)

• Record Type: Journal Article
• Authors: Barr, C.J.; Xia, K.
• Is Part Of: Journal of materials science & technology. Volume 82(2021)
• Page Start: 57
• Page End: 68
• Publication Date: 2021-08-20
• Subjects: Equal channel angular pressing -- Copper alloys -- Grain refinement -- Stacking fault energy -- Severe plastic deformation; Metals -- Periodicals; Materials science -- Periodicals; Materials science; Metals; Periodicals; 620.1105
• DOI: 10.1016/j.jmst.2020.12.016
• Languages: English
• ISSNs: 1005-0302

Abstract

Graphical abstract: Highlights: Non-shearing particles alter the grain refinement sequences found in particle free metal during severe plastic deformation. Influence on grain refinement dependent on stacking fault energy, deformation temperature, particle size, and morphology. At elevated temperatures, coarse particles facilitate dynamic recrystallization in surrounding deformation zones. Fine particles delay grain refinement by hindering twin formation, which is a key mechanism for low stacking fault energy. Broken lamellae accelerate grain refinement by creating numerous high angle grain boundaries to initiate recrystallization. Abstract: The influence of particle size and morphology on grain refinement in low stacking fault energy (SFE) alloys was studied by comparing the grain structures in single- and multi-phase Al-bronze (AB) alloys following equal channel angular pressing (ECAP) between 350 and 500 °C. In particular, nickel aluminium bronze (NAB) was chosen as it contained both coarse and fine rounded particles, as well as a lamellar phase which evolved during ECAP. Grain refinement in the single-phase alloy was achieved through dynamic recrystallisation initiated at deformed twin boundaries. By contrast, different mechanisms were observed in the particle-containing NAB. Recrystallisation around the coarse κII particles (∼5 μm) was promoted through particle stimulated nucleation (PSN), whereas recrystallisation in the region of the fine κIV (∼0.4 μm) was delayed due to the activation of secondary slip. Grain refinement in areas of the lamellar κIII showed significant variation, depending on the lamellar orientation relative to the shear plane of ECAP. As the lamellae deformed, numerous high angle grain boundaries were generated between fragments and served as nucleation sites for recrystallisation, while PSN occurred around spheroidised lamellae. The spreading of the κIII particles by ECAP then enhanced the total area of recrystallised grains.