|About this Abstract
||MS&T21: Materials Science & Technology
||Probing Defect Properties and Behavior under Mechanical Deformation and Extreme Conditions
||Irradiation Defects and Strain-induced Martensitic Transformations
||Janelle P. Wharry, Chao Yang, Yangyang Zhao, Keyou S. Mao, Yash Pachaury, Anter El-Azab
|On-Site Speaker (Planned)
||Janelle P. Wharry
The objective of this talk is to understand how irradiation-induced defects modulate deformation-induced martensitic transformations. Martensitic phase transformations are low-temperature deformation mechanisms in which γ-fcc austenite transforms into α'-bcc martensite, either directly or indirectly through metastable ε-hcp martensite. Irradiation enhances the propensity for transformations to occur, although the reasons are not clearly understood. This experimental and theoretical work focuses on irradiation-induced cavities (e.g. voids, bubbles). Experiments are conducted on neutron irradiated 304L stainless steel and ion implanted Fe-xMn (x=30-50 wt%) containing systematically varied cavity populations. Micro-mechanical testing with site-specific transmission electron microscopy (TEM) reveal deformation mechanisms and their interaction with the microstructure. Cavity size generally governs whether the transformation occurs, while cavity number density controls whether the transformation pathway is direct (γ→α') or indirect (γ→ε→α'). Molecular dynamics (MD) simulations show that stress concentrations on cavity surfaces lead to bcc martensite nucleation through a strain-induced mechanism.