Speaker
Description
Improving the creep lifetime of high-temperature materials remains one of the grand challenges in modern materials science. Despite decades of research, many established concepts still rely on classical descriptions of dislocation-driven plasticity. But do these models truly capture what happens at the atomic scale during creep?
In this plenary lecture, I will demonstrate how advanced transmission electron microscopy (TEM), and in particular high-resolution analytical scanning transmission electron microscopy (HR-STEM), is transforming our understanding of creep mechanisms in single-crystalline Ni-base superalloys. Atomic-scale observations reveal that creep deformation is governed by a complex interplay of displacive and diffusive processes, challenging long-standing paradigms.
Using purpose-designed double-shear creep experiments, planar defects such as superlattice extrinsic stacking faults (SESFs), anti-phase boundaries (APBs), and microtwins are selectively activated. These defects, far from being purely structural features, emerge as chemically active entities: solute segregation, driven by temperature-dependent partitioning fluxes, leads to the formation of new, dynamic compositional steady states at the nanoscale. Their impact on planar fault energies is discussed in the context of thermodynamic predictions and directly linked to the observed deformation behavior.
Complementary in situ high-temperature micropillar experiments further reveal how these defect-mediated phases act as effective obstacles to dislocation motion, providing a direct and intuitive link between atomic-scale processes and macroscopic creep resistance.
This talk aims to bridge the gap between classical metallography and cutting-edge atomic-scale characterization. It highlights why modern TEM is not merely a tool for observation, but a key enabler for rethinking deformation mechanisms and guiding the design of next-generation high-temperature materials.
By combining advanced microscopy, innovative mechanical testing, and thermodynamic insight, this lecture offers new perspectives on how we can move beyond traditional models—and ultimately design materials with significantly improved creep performance.