TY - JOUR

T1 - Interface mediated deformation and fracture of an elastic–plastic bimaterial system resolved by in situ transmission scanning electron microscopy

AU - Alfreider, Markus

AU - Balbus, Glenn

AU - Wang, Fulin

AU - Zechner, Johannes

AU - Gianola, Daniel S.

AU - Kiener, Daniel

N1 - Publisher Copyright: © 2022 The Authors

PY - 2022/9/14

Y1 - 2022/9/14

N2 - A wide variety of today’s engineering material systems consist of multiple layered constituents to satisfy varying demands, e.g. thermal barrier- or hard coatings, thermal- or electrical conduction or insulation layers, or diffusion barriers. However, these layers are commonly only of the order of a few hundred nanometers to microns thick, which renders conventional mechanical investigation of interfacial failure quite challenging, especially if plastically deforming constituents are involved. Herein, we present an in situ study of the mechanical deformation of a WTi-Cu model interface, commonly encountered in the microelectronics industry, utilizing transmission scanning electron microscopy. This approach elucidated the interplay between plastic deformation and fracture processes when loading either perpendicular (mode I) or parallel to the interface (mode II). Under mode I purely ductile failure in the Cu phase, exhibiting dislocation slip facilitated void nucleation and coalescence, was observed with an initiation value for dislocation propagation of Jdislocation≈15 J/m2. Mode II loading exhibited nucleation and propagation of an interface crack, with the initiation value for crack extension as Jcrack≈8.8 J/m2. The results are discussed with respect to the frameworks of classical fracture mechanics and dislocation plasticity, providing fundamental insight into the failure behaviour of elastic–plastic interfaces with respect to loading orientation.

AB - A wide variety of today’s engineering material systems consist of multiple layered constituents to satisfy varying demands, e.g. thermal barrier- or hard coatings, thermal- or electrical conduction or insulation layers, or diffusion barriers. However, these layers are commonly only of the order of a few hundred nanometers to microns thick, which renders conventional mechanical investigation of interfacial failure quite challenging, especially if plastically deforming constituents are involved. Herein, we present an in situ study of the mechanical deformation of a WTi-Cu model interface, commonly encountered in the microelectronics industry, utilizing transmission scanning electron microscopy. This approach elucidated the interplay between plastic deformation and fracture processes when loading either perpendicular (mode I) or parallel to the interface (mode II). Under mode I purely ductile failure in the Cu phase, exhibiting dislocation slip facilitated void nucleation and coalescence, was observed with an initiation value for dislocation propagation of Jdislocation≈15 J/m2. Mode II loading exhibited nucleation and propagation of an interface crack, with the initiation value for crack extension as Jcrack≈8.8 J/m2. The results are discussed with respect to the frameworks of classical fracture mechanics and dislocation plasticity, providing fundamental insight into the failure behaviour of elastic–plastic interfaces with respect to loading orientation.

KW - Crack extension

KW - Interface toughness

KW - Mode mixity

KW - Thin films

KW - TSEM

UR - http://www.scopus.com/inward/record.url?scp=85138455992&partnerID=8YFLogxK

U2 - 10.1016/j.matdes.2022.111136

DO - 10.1016/j.matdes.2022.111136

M3 - Article

AN - SCOPUS:85138455992

VL - 223.2022

JO - Materials and Design

JF - Materials and Design

SN - 0264-1275

IS - November

M1 - 111136

ER -