Scientific Events

Plasticity and fracture behavior of high-strength steels at low temperatures

High-strength steels with a body-centered cubic (bcc) crystal structure are generally expected to exhibit limited ductility at low temperatures due to the ductile-to-brittle transition. In this talk, we show that some high-strength bcc steels can nevertheless display unexpectedly large macroscopic plasticity during tensile deformation at cryogenic temperatures, even below their transition regime. A systematic tensile testing campaign across temperatures and stress states reveals strongly coupled effects on damage and fracture, which are captured using a mechanism-informed continuum damage model with implications for structural materials in extreme environments. [more]

“10th MSIT Winter School on Materials Chemistry”

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Nanoengineering of high strength steels

The diversities in crystalline structure and the hierarchical features of the structures in steels lead to their distinguished deformation behaviour, elastic properties, magnetic properties, mechanical properties, etc. In the research of steels, the linkage of structure-processing-property-performance-circularity is considered as the very important principle to understand the alloys. Following this basic principle, one can further design, select and assess suitable materials for a specific application. Over the last decades, based on multi-scale understanding - from metre to micrometre and further down to nanometre and atomic-scale, a number of extraordinary steels have been successfully developed and commonly applied globally. This research work will present the alloy design, multi-scale characterization and nano-engineering approaches that offer new opportunities to design and engineer the sustainable steels into hierarchical structures with tailored properties. New approach that aid controlling the process of phase transformation in tramp element tolerant steels will be discussed. [more]

Sintering Fundamentals of Nano-Metallic Particle Interconnects

Sintered copper (Cu) nanoparticles have emerged as a promising substitute for sintered silver (Ag) nanoparticles in power electronics packaging, offering comparable electrical and thermal conductivities, superior mechanical strength, and lower cost. However, the complex interactions between microstructure evolution, interfacial bonding, and mechanical performance during sintering remain insufficiently understood. This research investigates the mechanical behavior, fracture mechanisms, and reliability of sintered Cu nanoparticles through a combination of microscale experiments and multiscale modeling. The studies revealed the anisotropic fracture toughness of sintered Cu nanoparticles, developed an Anand viscoplastic model to describe high-temperature deformation, and quantified interfacial strength while elucidating the effects of oxidation on bonding quality. Furthermore, the influence of particle morphology on mechanical properties was examined using micro-cantilever bending tests and phase-field fracture simulations. Overall, this work advances the understanding of sintered Cu nanoparticles and supports the development of reliable and cost-effective interconnect materials for next-generation power electronics. [more]

Ancient craft, new perspective: Recovery and recrystallization of deformed metal nanoparticles

Metallic nanoparticles are utilized in a growing number of applications due to their unique and tunable properties. However, one of the primary tools used to tune bulk metals properties, recrystallization, is yet to be used in the case of nanoparticles. We studied pristine, single crystal platinum nanoparticles during a recrystallization annealing after deformation. We found that deformation causes a dramatic change in particles orientation, while annealing induced a plethora of different particle behaviors. Microstructurally, nucleation of new grains was observed, but in the smallest particles these new grains were quickly absorbed back into the deformed matrix. We describe a phenomenological kinetic model to explain the strong correlation between the particle properties and their annealing behavior. [more]

Challenges and Perspectives for the Development of High Temperature Materials

Colloquia Series on Sustainable Metallurgy
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"Intermetallics 2025"

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