Research Training Group 2154 - Materials for Brain

Joined colloquium by the Faculty of Engineering & RTG 2154: Prof. Xian (Sherry) Chen: Enhanced fatigue properties of phase-transforming materials by satisfying the cofactor conditions

Hong Kong University of Science and Technology

May 14, 2018 from 05:15 PM to 06:00 PM

TF Aquarium


Materials undergoing reversible solid-solid phase transformations provide emerging applications such as biomedical implants and stents, microelectronic actuators and sensors. The essential functionality of these materials is the ability to recover large deformation (i.e. 5~8%) before and after the structural transformation driven by temperature/stress/electromagnetic fields. The change of the lattice parameters and the breaking of symmetries, in turn, will cause the formation of microstructures, which lead to the accumulation of intrinsic defects at the stressed transition layer between phases.  It has been theorized that the macroscopic behaviors strongly depend on the kinematic properties of the transition layer between phases. If the lattice parameters satisfy some special mathematical conditions (the cofactor conditions), we observe that the functional fatigue properties of the phase-transforming materials have been tremendously improved. In this talk, we will briefly review the mathematical framework of the cofactor conditions and introduce an algorithmic way to evaluate these conditions directly from the X-ray measurements. We will also show some experimental results how the functional fatigue properties are enhanced at various length scales. 

Prof. E. Quandt

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