The tensile and compressive behaviors of 316L stainless steel at room temperature were compared. The differences between the stress–strain responses during tension and compression were explained by the different evolutions of the texture, defect structure, and phase composition. It was found that up to true strain of ~ 25 pct the flow stress during tension was only slightly higher (by ~ 40 MPa) than that during compression, which can be explained by the different textures of the two types of specimens. On the other hand, between the strains of 25 and 50 pct, the strain hardening for tension was much higher, which resulted in a ~ 200 MPa larger flow stress in the tensile-tested specimen at 50 pct strain. It was revealed that the higher flow stress in tension was caused by the harder texture, the higher dislocation density, and the larger fraction of martensite phase.
Cu nanoporous foams are promising candidates for use as an anode material for advanced lithium ion batteries. In this study, Cu nanofoam was processed from pack-cemented bulk material via dealloying. In the as-processed Cu nanofoam, the average ligament size was ~105 nm. The hardness in this initial state was ~2 MPa, and numerous cracks were observed in the indentation pattern obtained after hardness testing, thus indicating the low mechanical strength of the material. Annealing for 6 h under an Ar atmosphere at 400 °C was shown to result in crystalline coarsening and a reduction in the probability of twin faulting in the ligaments. Simultaneously, the junctions of the ligaments became stronger and hence more difficult to crack. This study demonstrates that moderate heat treatment under Ar can improve the resistance against crack propagation in Cu nanofoam without a large change in the ligament size and the surface oxide content, which can thus influence the electrochemical performance of the material in battery applications.
Cu nanofoams are promising materials for a variety of applications, including anodes in high-performance lithium-ion batteries. The high specific surface area of these materials supports a high capacity and porous structure that helps accommodate volume expansion which occurs as batteries are charged. One of the most efficient methods to produce Cu nanofoams is the dealloying of Cu alloy precursors. This process often yields nanofoams that have low strength, thus requiring additional heat treatment to improve the mechanical properties of Cu foams. This paper provides the effects of heat treatment on the microstructures, mechanical properties, and electrochemical performance of Cu nanofoams. Annealing was conducted under both inert and oxidizing atmospheres. These studies ultimately reveal the underlying mechanisms of ligament coarsening during heat treatment.
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