Research Areas

Grain boundary (GB) diffusion governs microstructural evolution, thermal stability, and long-term performance of advanced alloys, and our work aims to uncover its underlying mechanisms in compositionally complex systems through a combination of tracer diffusion techniques and severe plastic deformation. In high-pressure torsion (HPT) processed CoFeNi alloy, tracer studies reveal a striking retardation in the relaxation of non-equilibrium grain boundaries, highlighting the persistence of defect-rich, metastable interfaces and their strong influence on atomic transport. Building on this, investigations in coarse grained and HPT CoCrNi alloy systematically probe GB diffusion across B-type and C-type kinetic regimes, enabling quantitative determination of grain boundary diffusivities, effective boundary widths, and the role of segregation and chemical complexity. Together, these studies provide a mechanistic framework for understanding diffusion in high-entropy alloys and challenge simplified notions such as universally sluggish diffusion. The tracer diffusion measurements are conducted at the Institute of Materials Physics, University of Muenster, Germany in the radiotracer lab headed by Prof. Dr. Sergiy Divinski.

Interdiffusion plays a decisive role in the performance and reliability of several technologically important material systems, and our research focuses on developing a mechanistic understanding of these processes under application-relevant conditions. A key area of interest is the thermo-kinetic analysis of interdiffusion during brazing of Ni-based superalloys, where phase evolution, reaction layer growth, and elemental redistribution critically influence joint integrity and service performance. Complementing this, we investigate coating–substrate interactions in high-temperature environments, aiming to understand how interdiffusion governs the stability, adhesion, and lifetime of protective coatings. These studies provide insights into the design of advanced coating systems with improved resistance to degradation at elevated temperatures. In parallel, our work on diffusion barriers for electronic applications addresses the challenge of controlling unwanted intermixing at interfaces, which can degrade device performance and reliability. Our most recent work involves assessing the alloying effects in model binary systems such as Fe-Cr through a combined approach of diffusion couple experiments and atomistic simulations. 

Interdiffusion and the resulting phase evolution are highly sensitive to the microstructural state of the interacting materials, and our research focuses on understanding how variations in grain structure influence both kinetics and phase selection. A sandwich assembly of coarse grained (CG) alloy, low melting metal and ultra-fine grained (UFG) alloy ensures reliable comparison under identical experimental conditions. By systematically tailoring the microstructure of end members, we examine how interdiffusion-driven phase growth responds to changes in grain size and boundary character. Model systems such as Ni/Sn, CoNi/Sn, and CoFeNi/Sn have been investigated using coarse-grained and fine-grained structures produced via spark plasma sintering, enabling controlled comparisons of diffusion pathways. These studies reveal that an enhanced grain boundary fraction in ultrafine-grained (UFG) alloys not only accelerates interdiffusion kinetics but also alters the sequence and nature of phase formation, underscoring the critical role of grain boundaries as active diffusion pathways and phase nucleation sites. The results provide new insights into how microstructural design can be leveraged to control interfacial reactions in technologically relevant systems. Building on this foundation, ongoing efforts explore the use of advanced processing routes such as high-pressure torsion, additive manufacturing, and thermomechanical processing to engineer microstructures with tailored diffusion characteristics in FCC and HCP systems. 

CALPHAD-based approaches provide a powerful framework for understanding and designing complex alloy systems, and our research leverages these methods to link thermodynamics with practical alloy development. A central focus is the CALPHAD-assisted design of multicomponent alloys, where computational thermodynamics guides the selection of compositions with tailored phase stability and targeted properties. In parallel, we investigate phase equilibria in rare-earth containing alloys, addressing the challenges associated with their complex interactions and limited experimental data. These efforts are complemented by detailed thermodynamic assessments of rare-earth-containing systems, involving the development and refinement of databases through integration of experimental results and modeling. Together, this work establishes a predictive foundation for exploring new alloy chemistries, enabling informed design strategies and deeper insight into phase stability across a wide range of technologically relevant materials systems. 

Understanding oxidation behaviour is critical for designing metallic alloys with reliable high-temperature performance, and our research integrates experiments with modeling to uncover the governing mechanisms. We investigate the oxidation response of dual-phase medium and high-entropy alloys, where phase distribution and compositional partitioning strongly influence oxide scale formation and stability. Complementary studies on non-equiatomic Cantor-type alloys with Nb and Al additions reveal how targeted alloying modifies oxidation resistance, scale adherence, and growth kinetics. These experimental efforts are supported by detailed thermo-kinetic analysis of oxide formation, enabling correlation between phase stability, diffusion processes, and oxidation pathways. At the atomic scale, density functional theory (DFT) calculations are employed to understand the preference for oxygen adsorption on different elemental sites and surfaces, providing fundamental insight into early-stage oxidation processes. By linking alloy chemistry, microstructure, and oxidation mechanisms across length scales, this work establishes a framework for designing oxidation-resistant alloys and offers a comprehensive platform for exploring degradation phenomena in complex metallic systems.

Complex concentrated alloys (CCAs), including high- and medium-entropy systems, offer a rich landscape for exploring the interplay between composition, processing, and functional performance. Our research aims to develop a unified understanding of these materials across multiple length scales and for a broad spectrum of applications. We investigate the effects of thermomechanical processing on microstructure and oxidation behaviour in dual-phase high-entropy alloys, alongside studies on Cu-added medium-entropy alloys to elucidate their diffusion and oxidation characteristics. The role of compositional complexity is further examined through interdiffusion-driven phase growth in multicomponent systems, as well as through systematic studies of self-diffusion and grain boundary diffusion, providing insights into atomic transport in chemically complex environments. In parallel, we explore high-entropy alloys for diffusion barrier applications, where controlled transport is critical for functional reliability. Our efforts also extend to the development of high-entropy shape memory alloys using machine learning-assisted approaches, enabling accelerated discovery of compositions with tailored properties. The antibacterial properties of high entropy alloys and development of light weight CCAs also form part of research interests. Additionally, the thermal stability of high-entropy alloys processed via mechanical alloying and spark plasma sintering is assessed to understand phase evolution and microstructural robustness.