First Year Assessment of Alejandro Rodríguez, entitle “Analysis of the nucleation and growth mechanisms of fatigue cracks in Ni-based superalloys” – In the Seminar Room at 4:30 pm


Ni-based superalloys play an extremely important role in the aerospace industry due to their outstanding strength and chemical stability at high temperature. Most demanded components employed in jet engines are manufactured with these novel materials. Several statistical studies confirm that about 50% of the mechanical failures in these components are triggered by fatigue. Therefore, a great deal of attention needs to be paid to the cyclic behaviour and damage mechanisms of Ni-based superalloys in order to increase the useful life and improve the performance of jet engines.

The main objective of this first year assessment is to stablish a strong foundation for the study of the role of microstructural attributes (grain size, twin density and  volume fraction) on the fatigue behaviour of Ni-based alloys with the aid of advanced techniques, such as EBSD or DIC. The microstructure of three materials having different composition and SFE (pure Ni, Inconel 600 and Hastelloy C-276) will be altered and characterized by performing tailored heat treatments. In parallel, an experimental DIC-based methodology for obtaining the cyclic stress-strain curves and examine the cyclic behaviour of dog-bone specimens will be developed.

The information attained from fatigue experiments will be eventually used to validate a homogenization-based crystal plasticity model capable of quantitatively estimating the effect of microstructure on the fatigue life of Ni-based alloys. This multi-scale model will allow to increase safety and reduce the costs arising from the validation, certification and maintenance of jet engines.