A new method for microscale cyclic crack growth characterization from notched microcantilevers and application to single crystalline tungsten and a metallic glass

TL;DR

This paper introduces a novel nanoindenter-based method for measuring cyclic crack growth in microfabricated notched microcantilevers, enabling detailed analysis of fatigue behavior in materials like tungsten and metallic glass at the microscale.

Contribution

It presents a new, validated technique for microscale cyclic crack growth characterization using focused ion beam fabricated microcantilevers and nanoindenter testing.

Findings

Crack growth follows Paris' law in tested materials.

Method is reliable, reproducible, and comparable to macroscopic tests.

Applicable to microstructural features like grain boundaries.

Abstract

The lifetime of most metals is limited by cyclic loads, ending in fatigue failure. The progressive growth of cracks ends up in catastrophic failure. An advanced method is presented for the determination of cyclic crack growth on the microscale using a nanoindenter, which allows the characterization of > 10,000 loading cycles. It uses focused ion beam fabricated notched microcantilevers. The method has been validated by cyclic bending metallic glass and tungsten microcantilevers. The experiments reveal a stable crack growth during the lifetime of both samples. The metallic glass shows less plasticity due to the absence of dislocations, but shows shearing caused by the deformation. The crack growth rates determined in the tests follow Paris' power law relationship. The results are reliable, reproducible and comparable with macroscopic setups. Due to the flexibility of the method, it is suitable for the characterization of specific microstructural features, like single phases, grain boundaries or different grain orientations.