Blunting effect in notched micro-cantilever bending on a ductile alloy highlighted by multi-scale testing

This is the authors' abstract. We don't add key points for this paper.

Notched bending tests were carried out to investigate the ductile fracture behavior at different scales of a Ni-20wt.%Cr alloy printed by Laser Power Bed Fusion. Three sizes of specimen were employed for evaluation of J-R curves covering a wide range of dimensions, from a few microns, through an intermediate size of several tens of microns, up to several millimeters. In microscopic specimens, there is evidence of severe ductile tearing and blunting, as a result of prominent plastic effects occurring at the notch tip. It is not possible to dissociate the influence of the local microstructure on fracture properties from the influence of blunting effects due to the change in measurement scales. Despite the documented approach, the validity of the results obtained for small specimens is not achieved. These results highlight that standard toughness testing methods are not suitable and directly applicable to micro-cantilever bending tests on ductile materials, mainly due to significant blunting. To overcome these limitations and extract local toughness values, it would be necessary to focus on developing different loading methods, alternative test geometries, or methods coupled with simulation. Finally, the wide range of dimensions tested allows to discuss the applicability of the test standard to micromechanical tests, as these standards have been initially developed for macroscopic testing. This work underscores the need for revised testing protocols tailored to microscale ductile fracture.