It is genuinely intriguing how materials that remain perfectly safe under static loading can fail catastrophically when the same stress or strain levels are applied cyclically. Fatigue has been a two-century-old puzzle for materials scientists. We have numerous empirical and numerical models that can describe fatigue limits and lifetimes, but the true origin of fatigue failure is far more subtle and complex.

 Why do materials actually fail under cyclic loading? The answer lies buried deep in the microstructural, and ultimately atomistic, realms. Yet uncovering it is far from simple. The governing mechanisms vary with loading mode, frequency, temperature, environment, and even the smallest changes in composition or processing. Tiny variations in primary or secondary manufacturing routes or even the smallest design flaws or overlooked details can determine the entire fate of a component under fatigue loading.

 History has shown us the consequences: the Comet aircraft, Liberty ships, the Alexander Kielland platform, failures that reshaped engineering understanding. I explore these intricate aspects of fatigue, probing how microscopic defects evolve, how slip localization intensifies, how microstructural barriers break down, and why some materials resist while others do not, why certain temperatures are lethal while certain are safe, and so on. The broader question that drives me is profound: Can we truly conquer fatigue, or only learn to delay it? 

For more insights, visit the below publications:

https://doi.org/10.1016/j.ijplas.2021.103140

https://link.springer.com/article/10.1007/s11661-020-05914-x

https://link.springer.com/article/10.1007/s11837-022-05547-y

https://www.sciencedirect.com/science/article/abs/pii/S0142112323002256

https://www.sciencedirect.com/science/article/abs/pii/S135964542030210X

Now, this is another phenomenon, far more recent than classical fatigue, that has emerged only over the past five decades. It is not ubiquitous, nor does it affect all materials equally. Yet it has become a villain capable of tarnishing the reputation of one of the most widely used advanced metallic alloy systems: titanium alloys.

At the heart of this challenge lies an unusual and often underappreciated characteristic of titanium: its high strain-rate sensitivity, nearly an order of magnitude higher than that of many conventional alloys. This makes titanium unexpectedly susceptible to time-dependent deformation, even at room temperature. Calling it “creep” in the classical sense may feel uncomfortable, but from an engineering application standpoint, the material does accumulate significant inelastic strain under sustained loads.

The root cause traces back to the mismatched rate sensitivities of different slip families in α/β titanium. Under high-stress, low-strain-rate conditions, titanium enters a complex multi-mechanism deformation regime where dislocation glide, thermally activated obstacle passage, and grain-boundary-mediated processes (such as grain boundary sliding) can coexist. This intricate interplay forms the foundation of the now-infamous dwell fatigue problem in titanium alloys.

Can we mitigate this? The good news is: yes. Understanding and controlling these mechanisms, through processing routes, texture optimization, microstructural engineering, etc., forms a core part of our ongoing research efforts.

For more insights, visit the below publications:

https://www.sciencedirect.com/science/article/pii/S1359645425007402?via%3Dihub

The plastic deformation of metallic materials is so intriguing, and at times so perplexing-that looking at them through just one lens never reveals the full picture. You need different spectacles to truly “see” what is happening. These spectacles are the various probes and characterization tools that allow us to examine materials across multiple length scales. Used in a correlative manner, each technique complements the other and helps uncover mechanisms that would otherwise remain hidden.

Take, for example, grain boundary sliding at ambient temperatures. A mechanism we usually reserve for high-temperature deformation suddenly appears in titanium alloys even at room temperature. The mechanism itself differs from classical high-temperature GBS, but the real surprise is its activation at such low temperatures, another reminder of the curious and often unpredictable nature of titanium.

Because of the strong elastic anisotropy of titanium’s hexagonal crystal structure and the wide disparity in slip-system strengths, each grain deforms differently, creating a highly heterogeneous deformation field. To maintain compatibility between neighbouring grains, additional mechanisms activate near grain boundaries. With twinning limited and pyramidal slip systems difficult to trigger, some components of strain must find alternate pathways, one of them being grain boundary sliding.

However, GBS is a double-edged sword. While it helps grains “fit” together during deformation, it also promotes void formation and eventually intergranular cracking. But this behaviour is not universal. Only certain grain boundary types are vulnerable to such deformation, and once we understand why, we can design microstructures that minimize these events, even if we cannot eliminate them completely.

For more insights, visit the below publications:

https://doi.org/10.1080/14786435.2021.1916116

For more insights, visit the below publications:

Coming soon. 

Our most ambitious technological goals, from establishing a permanent human presence on the Moon and Mars to realizing net-zero emission power generation, transportation, etc. are fundamentally limited by the materials available to us. Achieving maximum efficiency in propulsion and energy systems demands engines and reactors that operate at the highest possible temperatures (guided by Carnot efficiency), while cryogenic engines and space infrastructure require materials that retain ductility and toughness at extremely low temperatures. Furthermore, the transition to hydrogen-based energy necessitates reliable storage and transport systems. The challenge lies not in design, but in engineering materials that maintain structural integrity and chemical stability under simultaneous exposure to extreme thermal gradients, high stresses, and corrosive chemical environments, which are currently the primary barriers to these next-generation technologies.

 The core of this research is dedicated to addressing the complex mechanisms of environmental degradation. We focus intensively on phenomena like Hydrogen Embrittlement (HE), where the smallest atom infiltrates metal lattices, dramatically reducing the structural toughness of critical materials like high-strength steels and titanium alloys used in H2 infrastructure. By employing advanced characterization techniques, our work aims to design and synthesize novel material microstructures, including advanced superalloys, titanium alloys, and high-entropy alloys, that can withstand these unforgiving conditions, ultimately making zero-carbon aviation, fusion energy, and deep space exploration a reality. 

For more insights, visit the publications below:

Coming soon. 

For more insights, visit the below publications:

https://www.sciencedirect.com/science/article/pii/S1359645425007402

https://link.springer.com/article/10.1007/s11665-025-12207-0

https://www.sciencedirect.com/science/article/abs/pii/S1044580322004302