Size Effect in Intermetallics: Experiments and Numerics

Abstract

Intermetallics such as γ-Titanium Aluminide (TiAl) alloys materials are attractive replacements of currently used Nickel based super alloys in the low pressure and low temperature sections of a jet engine. TiAl alloys have better specific strength and excellent oxidation resistance compared to Nickel based super alloys. However, due to their complex microstructure sensitive macroscale mechanical response these advanced materials have not found wide acceptance in the aerospace industry until now. In this work, an investigation of the sensitivity of the fracture strength of TiAl alloys to the specimen size is performed. The observed size effect is not predicted by the classical weakest link Weibull model. The simulations of failure in TiAl are performed with the method of phase field fracture. The simulation results show that the critical fracture energy is dependent on the volume of the specimen and decreases as the volume increases. An empirical relation for this size dependent critical fracture energy is proposed in this work.