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This work utilizes electron energy loss spectroscopy (EELS) to identify oxidation state of alloying elements in Ni-based alloys after exposure to molten chloride salt systems. Pure Ni and Ni-20Cr model alloy were corroded in molten ZnCl₂ and KCl-MgCl₂ under argon atmosphere at various temperatures. Oxidation states of Cr (Cr³⁺) and Ni (Ni²⁺) in the molten salt after corrosion were determined by monitoring changes in the L_2,3 edges of corresponding EELS spectra. Oxidation state mapping technique using principal component analysis and multiple linear least squares fitting in HyperSpy Python package was developed.

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Deformation-induced twinning has been a notable example of overcoming the strength/ductility trade-off dilemma as a strengthening mechanism. By borrowing this concept from the area of TWIP steels, we designed a thermomechanical treatment for a CoCrFeMnNi high-entropy alloy to improve its mechanical characteristics. We used pre-straining at 77 K to introduce deformation-induced twins in the microstructure of the alloy, and then recovered it by annealing at 773 K, while avoiding recrystallization. The deformation-induced twins generated by pre-straining at 77 K were retained after this heat treatment, whilst partial recovery of dislocations occurred. As a result, the room-temperature mechanical properties of the alloy, including its strain hardening ability, were improved substantially.

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The surface oxide structures formed on two austenitic alloys after exposure in supercritical water were investigated via high-resolution characterization techniques. Results show that the corrosion processes of 19-Cr and 25-Cr alloys are internal oxidation and external oxidation, respectively. 19-Cr alloy shows a typical duplex thick oxide structure, while 25-Cr alloy has a much thinner protective oxide layer mainly composed of Cr₂O₃. The higher Cr content of 25-Cr alloy exceeds a critical value that enables the conversion from internal to external oxidation, thus facilitates the formation of a thin continuous Cr₂O₃ layer and protects the sub-surface from further oxidation.

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A new weldable Fe-Mn-Cr-Ni-Si seismic damping alloy with high fatigue resistance was developed by controlling phase transformation behaviour during both solidification and fatigue deformation. The solidification phase transformation was controlled by changing the Cr/Ni ratio to induce ferrite-austenite transformation and thus reduce the solidification cracking susceptibility. The Gibbs free energy difference between the austenite and ε-martensite was optimized to exhibit reversible transformation during fatigue deformation. The resultant alloy exhibited a prolonged fatigue life, and no solidification cracking was observed in a melt-run welding test. By using the newly developed alloy, a weld damper with excellent fatigue resistance can be fabricated.

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Excellent studies have been conducted to understand the mechanical behavior of thin films by buckling the films using heat-shrinkable substrates. A buckling-based method [Stafford et al., Nat. Mater. 3 (2004) 545] has been adopted to measure the mechanical properties of nanoporous gold (NPG) films. This method is highly suitable under low-strain conditions; however, we attempted to use this approach under high-strain conditions. The calculated (8.2 GPa) and measured (10 ± 1.3 GPa) values of Young's modulus are remarkably near the literature value (8.8 GPa). Owing to the high-strain conditions, the effects of pore size on the Young's modulus [J. Erlebacher, J. Mathur, Appl. Phys. Lett. 90 (2007) 061910] may not be considered, and the cracks and delamination of the NPG films from the shrunken substrate were considered to interpret the mechanical behavior of the films.

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Strain rate sensitivity and activation volume that dictate the kinetics of plastic deformation along with strain hardening response determine the plastic deformation behaviour of novel high entropy alloys. Although, the deformation behaviour of FCC single-phase Cantor alloy exhibits some similarity to that of conventional FCC solid solutions, the deformation behaviour over a wide range of temperature, strain rate, strain and grain size is unexplored. More importantly, theoretical understanding of solid solution strengthening, stacking fault energy and dislocation activation in 100 percent solute high entropy alloys (HEAs) and their flow kinetics is not yet established. This necessitates development of combined experimental and computational approaches to realise the mechanistic design of new single-phase and multi-phase transformative FCC HEAs to achieve optimum combination of strength and ductility in the novel complex concentrated alloys.