Steven Van Petegem is a senior scientist in the Structure and Mechanics of Advanced Materials (SMAM) group at the Paul Scherrer Institute (PSI) and associated scientist in the Laboratory for X-ray Characterisation of Materials (CAM-X) at the École Polytechnique Fédéral de Lausanne (EPFL). He obtained his degree in Physics from Ghent University, Belgium, where his PhD research focused on the microstructure of nanocrystalline metals studied with positron annihilation spectroscopy combined with modeling.

He joined PSI in 2003, initially working at the Small Angle Neutron Scattering instrument in the Center for Neutron and Muon Sciences. In 2005, he moved to the Materials Science and Simulations group, where he investigated deformation mechanisms in metals using in situ diffraction techniques. From 2008 to 2015, he was responsible for the POLDI neutron diffractometer, leading experiments on time-resolved mechanical behavior of engineering materials.

In 2015, Van Petegem became part of the Photons for Engineering and Manufacturing group in the Center for Photon Science, with a focus on process–microstructure–property relationships in metallic systems. Since 2021, he has been a member of the SMAM group, where his research combines in situ and operando X-ray and neutron methods to study materials under thermo-mechanical processing and additive manufacturing conditions. Since 2022 he is lecturer at the EPFL.

Van Petegem’s research focuses on the use of in situ and operando X-ray and neutron diffraction and imaging to uncover how the internal structure of metals evolves during thermo-mechanical processing or additive manufacturing. By observing materials directly under relevant conditions, his work provides unique insights into the microscopic mechanisms that govern mechanical properties and performance.

Earlier in his career, Van Petegem made significant contributions to the understanding of size effects in plasticity. He studied plastic deformation in nanocrystalline metals, thin films, and single-crystal micropillars, providing fundamental insights into how deformation mechanisms change when dimensions are reduced to the micro- and nanoscale. Building on this foundation, he has explored the response of metals under more complex loading states. Using advanced diffraction techniques, he investigated the evolution of lattice strains, dislocation activity, and grain-scale interactions during uniaxial, biaxial, and shear deformation. These experiments provide essential benchmarks for validating advanced simulation approaches such as molecular dynamics and crystal plasticity modeling.

In more recent years, he has extended these efforts to the field of laser-based additive manufacturing. Operando diffraction and imaging have made it possible to follow solidification dynamics, defect formation, and residual stress development directly during printing. Such studies shed light on the fundamental origins of cracking and porosity, helping to guide the design of alloys and processing routes for more reliable 3D-printed metals.

By combining state-of-the-art experiments with modeling, his research bridges fundamental materials science and technological applications. The overarching goal is to establish knowledge-based strategies for tailoring microstructures and properties through processing.