Ultrafine gradient microstructure induced by severe plastic deformation under sliding contact conditions in copper
- Centro Tecnológico Aragón, Facultad de Estudios Superiores Aragón, Universidad Nacional Autónoma de México, Av. Rancho Seco s/n, Col. Impulsora, Cd. Nezahualcóyotl 57130, Estado de México (Mexico)
- Departamento de Materiales y Manufactura, Facultad de Ingeniería Edificio O, Universidad Nacional Autónoma de México, Avenida Universidad 3000, Coyoacán 04510, México D.F. (Mexico)
- Metal Science and Technology Group, EEMMeCS Department, Ghent University, Technologiepark 903, 9052 Zwijnaarde (Ghent) (Belgium)
Highlights: • Sliding contact produces a gradient microstructure by severe plastic deformation. • Nanohardness is increased strongly by grain size and dislocation hardening. • The texture components in the deformed layer correspond to pure shear. • Grain size distribution, boundary misorientation and KAM were analysed. • Strain induced effects compete with crystallisation to determine the microstructure. - Abstract: Sliding contact induces severe plastic deformation (SPD) at the surface of ductile materials and induces a microstructural gradient associated to a significant increase of hardness toward the surface. This gradient allows observing all stages of grain refinement in SPD, as illustrated here by the analysis of polycrystalline electrolytic copper tested in a coaxial tribometer. Materials tested in the cold-rolled state and after annealing were characterised by high-resolution electron backscattering diffraction and nano-indentation. The incremental plastic strain produces an ultrafine microstructure in the top layers, which gradually changes to the original size in unaffected material. In cold-rolled material, an intermediate recrystallised layer is observed. The separation of the Misorientation Angle Distribution (MAD) in a low-angle portion and a high angle portion allows characterising the accumulation of strain induced misorientation, while the Kernel Average Misorientation (KAM) provides information on the evolution of substructure at the finest levels. The results point toward a process where strain-induced effects compete continuously with recrystallisation, except for the surface layer in the cold-rolled material, where dynamic recrystallisation is dominant. Combining the information from KAM and subgrain size distribution, the measured hardness can be explained as a combination of grain size and dislocation hardening.
- OSTI ID:
- 22804953
- Journal Information:
- Materials Characterization, Journal Name: Materials Characterization Vol. 138; ISSN 1044-5803; ISSN MACHEX
- Country of Publication:
- United States
- Language:
- English
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