"Atomic-Scale Investigation on Mechanical Deformation in Refractory Metals" 

Changxin Han, MSE PhD Candidate 

Advisor: Professor Scott. X. Mao

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ABSTRACT

Refractory metals are leading options for fusion, advanced fission, aerospace propulsion, and high-temperature energy-conversion technologies because they combine extremely high melting temperatures, exceptional thermal stability, and the capacity to retain strength well above 1000 °C. Clarifying their deformation behavior requires real-time measurements at the atomic scale. In-situ transmission electron microscopy (TEM) provides direct movies of deformation, revealing dislocation nucleation, glide, and interactions, together with twinning and phase transformation processes. Activation of multiple defect pathways generates intricate planar and line defects that modify local structural stability and reshape operative deformation modes. These atomic-scale mechanisms exhibit strong size dependence and depart substantially from bulk responses. This review consolidates current understanding obtained via in-situ TEM on refractory metals and discusses its implications for plasticity in body-centered-cubic (BCC) refractory systems.