Ni-superalloy, fatigue crack propagation

This sample shows fatigue crack propagation in Udimet 720, a nickel-base superalloy. To improve its high temperature mechanical properties Udimet 720 utilises a strengthening mechanism, known as order hardening. There is a large volume fraction of coherent γ' precipitates in the γ matrix. As a fatigue crack propagates through the superalloy there is a plastic region in front of the crack tip