Engineering

Neutron Scattering Studies of Hard Metals

PhD: Ahmet Bahadir Yildiz, KTH Royal Institute of Technology (2021)

This project used neutron scattering techniques to study the nano- and microstructural evolution of hard metals during processing, providing insights critical for optimizing their mechanical performance and durability. By combining small-angle neutron scattering (SANS) and neutron diffraction (ND) with laboratory methods and computational modeling, the research captured structural transformations under realistic industrial conditions.

SANS experiments quantified microstructural features such as binder pocket size, WC grain dimensions, and interfacial (V,W)Cx layer characteristics, revealing how vanadium doping suppresses grain coarsening by reducing interface mobility and coarsening drive. In-situ SANS at temperatures up to 1500 °C provided direct evidence of how phase chemistry controls interfacial evolution. Complementary in-situ ND experiments tracked phase separation in (Ti,Zr)C-based systems, showing that minor additions of HfC or NbC significantly retard decomposition. A newly designed multi-principal element carbide, (Ti,Zr,Hf,W)C, exhibited exceptional hardness and thermal stability due to its sluggish decomposition behavior.

The results advanced the understanding of high-temperature processing mechanisms in hard metals and demonstrated the value of neutron scattering as an industrial characterization tool, offering guidance for future alloy design and manufacturing optimization.

Ahmet Bahadir Yildiz earned a BSc in Metallurgical and Materials Engineering from Istanbul Technical University and completed his MSc in Metallurgical Engineering at RWTH Aachen University in 2017. During his master’s studies, he focused on the mechanisms governing the behavior of high-manganese steels, using ex situ and in situ synchrotron X-ray diffraction to characterize microstructure and small-angle neutron scattering to study the evolution of Mn–C clusters.