Understanding imprint formation, plastic instabilities and hardness evolutions in FCC, BCC and HCP metal surfaces

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61388998%3A_____%2F21%3A00544732" target="_blank" >RIV/61388998:_____/21:00544732 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/49777513:23640/21:43962528

Výsledek na webu

<a href="https://www.sciencedirect.com/science/article/pii/S1359645421005024" target="_blank" >https://www.sciencedirect.com/science/article/pii/S1359645421005024</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.actamat.2021.117122" target="_blank" >10.1016/j.actamat.2021.117122</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Understanding imprint formation, plastic instabilities and hardness evolutions in FCC, BCC and HCP metal surfaces

Popis výsledku v původním jazyce

Nanoindentation experiments in metal surfaces are characterized by the onset of plastic instabilities along with the development of permanent nanoimprints and dense defect networks. This investigation concerns massive molecular dynamics simulations of nanoindentation experiments in FCC, BCC and HCP metals using blunted (spherical) tips of realistic size, and the detailed comparison of the results with experimental measurements. Our findings shed light on the defect processes which dictate the contact resistance to plastic deformation, the development of a transitional stage with abrupt plastic instabilities, and the evolution towards a self-similar steady-state characterized by the plateauing hardness at constant dislocation density . The onset of permanent nanoimprints is governed by stacking fault and nanotwin interlocking, the buildup of nanostructured regions and crystallites throughout the imprint, the cross-slip and cross-kinking of surfaced screw dislocations, and the occurrence of defect remobilization events within the plastic zone. As a result of these mechanisms, the ratio between the hardness and the Young's modulus becomes higher in BCC Ta and Fe, followed by FCC Al, HCP Mg and large stacking fault width FCC Ni and Cu. Finally, when nanoimprint formation is correlated with the uniaxial response of the indented minuscule material volume, the hardness to yield strength ratio, , varies from 7 to 10, which largely exceeds the continuum plasticity bound of 2.8. Our results have general implications to the understanding of indentation size-effects, where the onset of extreme nanoscale hardness values is associated with the occurrence of unique imprint-forming processes under large strain gradients.

Název v anglickém jazyce

Understanding imprint formation, plastic instabilities and hardness evolutions in FCC, BCC and HCP metal surfaces

Popis výsledku anglicky

Nanoindentation experiments in metal surfaces are characterized by the onset of plastic instabilities along with the development of permanent nanoimprints and dense defect networks. This investigation concerns massive molecular dynamics simulations of nanoindentation experiments in FCC, BCC and HCP metals using blunted (spherical) tips of realistic size, and the detailed comparison of the results with experimental measurements. Our findings shed light on the defect processes which dictate the contact resistance to plastic deformation, the development of a transitional stage with abrupt plastic instabilities, and the evolution towards a self-similar steady-state characterized by the plateauing hardness at constant dislocation density . The onset of permanent nanoimprints is governed by stacking fault and nanotwin interlocking, the buildup of nanostructured regions and crystallites throughout the imprint, the cross-slip and cross-kinking of surfaced screw dislocations, and the occurrence of defect remobilization events within the plastic zone. As a result of these mechanisms, the ratio between the hardness and the Young's modulus becomes higher in BCC Ta and Fe, followed by FCC Al, HCP Mg and large stacking fault width FCC Ni and Cu. Finally, when nanoimprint formation is correlated with the uniaxial response of the indented minuscule material volume, the hardness to yield strength ratio, , varies from 7 to 10, which largely exceeds the continuum plasticity bound of 2.8. Our results have general implications to the understanding of indentation size-effects, where the onset of extreme nanoscale hardness values is associated with the occurrence of unique imprint-forming processes under large strain gradients.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

20301 - Mechanical engineering

Projekt

Výsledek vznikl pri realizaci vícero projektů. Více informací v záložce Projekty.

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2021

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Acta Materialia

ISSN

1359-6454

e-ISSN

1873-2453

Svazek periodika

217

Číslo periodika v rámci svazku

September

Stát vydavatele periodika

GB - Spojené království Velké Británie a Severního Irska

Počet stran výsledku

14

Strana od-do

117122

Kód UT WoS článku

000691327100002

EID výsledku v databázi Scopus

2-s2.0-85111040252