Yi Xiong

Bio: Yi Xiong is an academic researcher from Henan University of Science and Technology. The author has contributed to research in topics: Microstructure & Indentation hardness. The author has an hindex of 13, co-authored 42 publications receiving 337 citations. Previous affiliations of Yi Xiong include Yanshan University.

Cryorolling impacts on microstructure and mechanical properties of AISI 316 LN austenitic stainless steel

Abstract: Microstructure evolution and mechanical properties of AISI 316 LN austenitic stainless steel (SS) after cryorolling with different strains were investigated by means of optical, scanning and transmission electron microscopy, X-ray diffractometer, microhardness tester, and tensile testing system. The deformation-induced martensite transition and the deformation microstructure occurred during cryorolling process were always composed of high-density dislocations, deformation twins, and deformation-induced martensites. Following the strain, the dislocation density in deformation microstructure approached saturation state and the volume fraction of deformation twins combined with deformation-induced martensites increased significantly. At the 70% strain, original austenite was transformed into martensite completely. Further increasing the strain to 90% would refine the martensitic lamellae to nanoscale. The deformation degree also led to remarkable increase of the strength and hardness of the cryorolled SS, and drastic reductions of the elongation. Due to the cryorolling, the tensile fracture morphology changed from typical ductile rupture to a mixture of quasi-cleavage and ductile fracture.

Microstructure evolution of Al–12Si–CuNiMg alloy under high temperature low cycle fatigue

Abstract: Microstructure evolution of the Al–12Si–CuNiMg alloy under high temperature low cycle fatigue was investigated with scanning and transmission electron microscopy. The alloy exhibits cyclic softening at diverse total strain amplitudes and loading temperatures. The material fatigue life obviously decreases with the increase of the strain amplitude at the same temperature. However, fatigue life increases and microstructure improves with temperature increase at the same strain amplitude. At certain loading temperatures and strain amplitudes, the microstructure can be refined. The fracture morphology changes gradually from brittle quasi-cleavage fracture, with numerous small cracks, to quasi-cleavage fracture with numerous small dimple gliding fractures.

Mechanical properties and fracture characteristics of high carbon steel after equal channel angular pressing

Abstract: The ultra-microduplex structure was fabricated in a fully pearlitic Fe–0.8 wt% C steel after equal channel angular pressing (ECAP) at 923 K via the Bc route. The microstructures and mechanical properties, before and after deformation, were investigated using scanning electron microscopy and mini-tensile tests. The cementite lamellae are gradually spheroidized by increasing the number of ECAP passes. After four passes, the cementite lamellae are fully spheroidized. Microhardness and the ultimate tensile strength of pearlite increase with the strain, up to a peak value (after two passes) and then decrease significantly. The yield strength, elongation and percentage of reduction in area increase with the number of ECAP passes. The tensile fracture morphology changes gradually from brittle cleavage to typical ductile fracture after four passes.

Recent advances and challenges in divalent and multivalent metal electrodes for metal–air batteries

Abstract: Metal–air batteries (MABs), which possess exceptionally high energy density and exhibit other ideal features such as low cost, environmental benignity and safety, are regarded as promising candidates for the next generation of power sources. The performance of MABs and the challenges involved in these systems are primarily related to metal electrodes. In the present work, different types of MABs are overviewed from the perspective of the metal electrodes. Most metal electrodes that have been studied in recent years are reviewed, among which Zn, Al, Mg and Fe are highlighted. The advantages and disadvantages of each system are presented, and recent advances that address challenges such as corrosion, passivation and dendrite growth are introduced. In addition, investigations focused on revealing interactions between the metal electrodes and electrolytes or exploring electrolytes to improve the performance of metal electrodes are also discussed. Finally, a general perspective on the current situation of this field and on future research directions is provided.

Advanced Technologies for High-Energy Aluminum–Air Batteries

Abstract: Aluminum-air batteries are considered as next-generation batteries owing to their high energy density with the abundant reserves, low cost, and lightweight of aluminum. However, there are several hurdles to be overcome, such as the sluggish rate of the oxygen reduction reaction (ORR) at the air electrode, precipitation of aluminum hydroxides and oxides at the anode, and severe hydrogen evolution problems at the interface of the anode and the electrolyte. Here, recent advances in silver metal and metal-nitrogen-carbon-based ORR electrocatalysts, aluminum anodes, electrolytes, and the requirements of future research directions are mainly summarized.

Tailoring the microstructure and mechanical properties of AISI 316L austenitic stainless steel via cold rolling and reversion annealing

Abstract: Tensile properties of cold rolled AISI 316L stainless steel after full reversion of martensite to austenite, recrystallization of retained austenite, and grain growth were studied at 850, 950, and 1050 °C. At higher temperatures, it was found that the kinetics of the reversion and recrystallization processes enhance but coarser grain sizes will be obtained at the end of recrystallization. At 1050 °C, appreciable grain growth was observed after the completion of the recrystallization process, which was not the case for a low temperature of 850 °C. At the stage of full recrystallization, by decreasing the annealing temperature, the yield stress (YS) and the ultimate tensile strength (UTS) values increased and total elongation decreased, which was related to the grain size strengthening by the Hall-Petch law. However, the Hall-Petch slope for the UTS was found to be much smaller than that of YS, which reveals that YS has greater grain size dependency. The latter was ascribed to the improved work-hardening behavior and enhanced transformation-induced plasticity (TRIP) effect by coarsening of grain size. To obtain high-strength and ductile steel with tensile toughness higher than 300 MJ/m3 and yield ratio of ∼0.5, the average grain size of ∼3 μm was found to be desirable.