Přejít k obsahu


Unraveling deformation mechanisms around FCC and BCC nanocontacts through slip trace and pileup topography analyses

Citace:
VARILLAS DELGADO, J., OČENÁŠEK, J., TORNER, J., ALCALÁ, J. Unraveling deformation mechanisms around FCC and BCC nanocontacts through slip trace and pileup topography analyses. ACTA MATERIALIA, 2017, roč. 125, č. 15 February 2017, s. 431-441. ISSN: 1359-6454
Druh: ČLÁNEK
Jazyk publikace: eng
Anglický název: Unraveling deformation mechanisms around FCC and BCC nanocontacts through slip trace and pileup topography analyses
Rok vydání: 2017
Autoři: magistr Javier Varillas Delgado , Ing. Jan Očenášek Ph.D. , Jordi Torner , Jorge Alcalá
Abstrakt CZ: Nanokontaktní zatížení skrývá potenciál pro výzkum plasticity krystalů ze skluzových čar, které jsou emitovány na povrch vzorku, a dalších deformací povrchu, kde individuální atomové terásky organizovány do větších výstupků a symetrických rozet. Naše MD simulace podrobně analyzují mechanismy interakce dislokací, dvojčatění i anihilaci poruch a ukazují charakteristické znaky deformačního procesu pro FCC a BCC krystaly.
Abstrakt EN: Nanocontact loadings offer the potential to investigate crystal plasticity from surface slip trace emissions and distinct pileup patterns where individual atomic terraces arrange into hillocks and symmetric rosettes. Our MD simulations in FCC Cu and Al nanocontacts show development of specific dislocation interception, cross-slip and twin annihilation mechanisms producing traces along characteristic <011> and <112> directions. Although planar slip is stabilized through subsurface dislocation interactions, highly serrated slip traces always predominate in Al due to the advent of cross-slip of the surfaced population of screw dislocations, leading to intricate hillock morphologies. We show that the distinct wavy hillocks and terraces in BCC Ta and Fe nanocontacts are due to dislocation kinking and outward spreading of surfaced screw segments, which originate from dislocation loops induced by twin annihilation and twin-mediated nucleation processes in the subsurface. While increasing temperature favors terrace formation in BCCs, surface decorations are enhanced in FCCs limiting hillock definition. It is found that material bulging against the indenter-tip is a distinctive feature in nanocontact plasticity associated with intermittent defect bursts. Bulging is enhanced by recurrent slip traces introduced throughout the contact surface, as in the case of the strongly linear defect networks in FCC Al, and by specific twin arrangements at the vicinity of BCC nanocontacts. Defect patterning also produces surface depressions in the form of vertexes around FCC nanoimprints. While the rosette morphologies are consistent with those assessed experimentally in greater FCC and BCC imprints, topographical pileup due to extensive bulging becomes prominent at the nanoscale.
Klíčová slova

Zpět

Patička