TY - JOUR

T1 - Direct observation of crack arrest after bridge notch failure

T2 - A strategy to increase statistics and reduce FIB-artifacts in micro-cantilever testing

AU - Zhang, Yinxia

AU - Bartosik, Matthias

AU - Brinckmann, Steffen

AU - Lee, Subin

AU - Kirchlechner, Christoph

N1 - Publisher Copyright: © 2023 The Authors

PY - 2023/9

Y1 - 2023/9

N2 - Focused ion beam (FIB) milling has been widely used to prepare micron-sized specimens for micromechanical testing, however, at the same time, unavoidable artifacts originating from the Ga + ion beam might alter the obtained mechanical properties. Using a bridge notch geometry, which can promote the formation of a sharp natural crack after bridge-failure rather than creating a comparably blunt FIB notch was proposed as a strategy to reduce FIB-induced artifacts more than a decade ago. Even though bridge-failure is widely assumed and predicted by finite element method (FEM) simulations, it has never been observed and quantified experimentally. This study presents the first experimental observation of bridge notch failure and crack arrest before the entire through-thickness main notch (after crack arrest) propagates, which is possible by designing thin bridges and using a stiff experimental setup with superior load resolution. Consequently, we obtained up to three corresponding fracture toughness values from one bending cantilever and significantly less scattered data. Using previously reported geometry correction factors calculated by FEM, the fracture toughness estimated from the bridge-failure was compared with the one from the failure of the main through-thickness notch in CrN/AlN multi-layered and CrN hard coatings.

AB - Focused ion beam (FIB) milling has been widely used to prepare micron-sized specimens for micromechanical testing, however, at the same time, unavoidable artifacts originating from the Ga + ion beam might alter the obtained mechanical properties. Using a bridge notch geometry, which can promote the formation of a sharp natural crack after bridge-failure rather than creating a comparably blunt FIB notch was proposed as a strategy to reduce FIB-induced artifacts more than a decade ago. Even though bridge-failure is widely assumed and predicted by finite element method (FEM) simulations, it has never been observed and quantified experimentally. This study presents the first experimental observation of bridge notch failure and crack arrest before the entire through-thickness main notch (after crack arrest) propagates, which is possible by designing thin bridges and using a stiff experimental setup with superior load resolution. Consequently, we obtained up to three corresponding fracture toughness values from one bending cantilever and significantly less scattered data. Using previously reported geometry correction factors calculated by FEM, the fracture toughness estimated from the bridge-failure was compared with the one from the failure of the main through-thickness notch in CrN/AlN multi-layered and CrN hard coatings.

KW - Bridge notch

KW - Fracture toughness

KW - Geometry influence

KW - Micro-cantilevers

UR - http://www.scopus.com/inward/record.url?scp=85166181320&partnerID=8YFLogxK

U2 - 10.1016/j.matdes.2023.112188

DO - 10.1016/j.matdes.2023.112188

M3 - Article

VL - 233.2023

JO - Materials and Design

JF - Materials and Design

SN - 0264-1275

IS - September

M1 - 112188

ER -