Nanomechanical characterization of the fracture toughness of Al/SiC nanolaminates

TL;DR

This study measures the fracture toughness of Al/SiC nanolaminates with varying layer thicknesses, revealing how crack propagation modes and interface interactions influence toughness, with implications for nanostructured material design.

Contribution

It provides new insights into how layer thickness and crack orientation affect fracture toughness in Al/SiC nanolaminates, using micropillar splitting and bending tests.

Findings

Toughness increases with layer thickness when crack propagates parallel to layers.

Toughness increases with decreasing layer thickness when crack propagates perpendicular to layers.

10 nm layer thickness nanolaminates show reduced toughness due to grain boundary cracking.

Abstract

The fracture toughness of Al/SiC nanolaminates with different layer thicknesses (in the range 10 to 100 nm) was measured by means of micropillar splitting and bending of a notched beam. The crack plane was perpendicular to the layers in the former while notched beams with the notch parallel and perpendicular to the layers were milled in the latter. It was found that crack propagation parallel to the layers took place along the metal-ceramic interfaces and the toughness increased with the layer thickness due to the contribution of the plastic deformation of the Al layers. Crack propagation perpendicular to the layers showed evidence of crack deflection/arrest at the interface. The toughness in this orientation increased as the layer thickness decreased due to the higher density of interfaces except for the nanolaminates with 10 nm layer thickness. In the latter case, crack propagation took place along the weak columnar grain boundaries, leading to a marked reduction in toughness.