Fine-grained nickel deformed by direct impact at different velocities: Microstructure and mechanical properties

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 527; no. 16; pp. 4128 - 4135
• Main Authors: Dirras, G., Couque, H., Gubicza, J., Ouarem, A., Chauveau, T., Jenei, P.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 25-06-2010; Elsevier
• Subjects: Boundaries; Cold working, work hardening; annealing, quenching, tempering, recovery, and recrystallization; textures; Compressive properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Deformation; Deformation and plasticity (including yield, ductility, and superplasticity); Dislocation density; Dynamic strain; Exact sciences and technology; Impact; Impact velocity; Materials science; Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Microstructure; Nanohardness; Nickel; Physics; Recrystallization; Treatment of materials and its effects on microstructure and properties; Impact; Nickel; Dynamic strain; Microstructure; Recrystallization; Nanohardness; Dynamical recovery; Plastic flow; Dynamical recrystallization; XRD; Test bar; Texture; EBSD; Dislocation density; Grain boundary misorientation; Hopkinson bar; Transition elements; Fine grain structure
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2010.03.045

High purity electrolytic nickel (99.99%) samples deformed dynamically in compression using a direct impact Hopkison pressure bar test at the velocities of 10.9, 28.2 and 70.6
m
s
−1 were investigated. The dislocation density increased with increasing the impact velocity up to 28.2
m
s
−1 resulting in an increase of nanohardness and quasi-static compressive flow stress. At the same time, a decrease of the fraction of Σ3 coincident site lattice boundaries was observed for the benefit of Σ1 low angle grain boundaries having misorientations lower than 15°. Increasing the velocity to 70.6
m
s
−1 led to a decrease of the dislocation density, in parallel with the regeneration of Σ3 boundaries. As a consequence, the nanohardness decreased to a similar value as in the initial state. These observations suggest possible dynamic recovery/recrystallization that might have occurred at the highest impact velocity.