Within the grain boundary engineering (GBE) of alloys, a mixed grain boundary network with random grain boundaries interrupted by twin boundaries, contributes to enhancing the overall grain boundary-related properties. The higher density of twin boundaries is pursued herein. Furthermore, a two-stage deformation method, i.e., prior cold deformation followed by thermal deformation, was proposed for improving the mixed grain boundary network in the thermal deformation of Ni80A superalloy. The influence of prior cold deformation on the mixed grain boundary network was investigated through a series of two-stage deformation experiments. The analysis of the stress-strain curves shows that the critical strain for dynamic recrystallization (DRX) and peak strains decrease significantly under the effect of prior cold deformation. In comparison to the necklace-like microstructures that occur after a single thermal deformation, the microstructures apparent after a two-stage deformation are characterized by finer DRX grains with abundant Σ3 twin boundaries, with a significantly improved density of the Σ3 twin boundaries (BLD) by a factor of around nine. With increasing prior cold strain, the grain size, after a two-stage deformation, decreases continuously, while the BLD increases firstly and then decreases. The mechanisms for improving the mixed grain boundary network via two-stage deformation were uncovered. The sub-grain boundaries formed in prior cold deformation stimulate the nucleation of DRX grains and twins; meanwhile, the driving force for grain boundary migration is enhanced due to prior stored energy. Then, DRX is activated in advance and occurs more completely, thereby promoting the formation of Σ3 twin boundaries.
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http://dx.doi.org/10.3390/ma15186426 | DOI Listing |
Nanotechnology
January 2025
School of Instrumentation Science and Opto-electronics Engineering, Beijing Information Science and Technology University, 12 Qinghe Xiaoying East Road, Xisanqi Street, Haidian District, Beijing, Beijing, 100192, CHINA.
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January 2025
Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany.
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View Article and Find Full Text PDFNano Lett
January 2025
School of Chemical Sciences, University of Auckland, Auckland 1010, New Zealand.
Understanding metastable structural transitions under beam irradiation is essential for the phase engineering of nanomaterials. However, in situ studies of beam-induced structural transitions remain challenging. This work uses an electron beam in aberration-corrected high-angle annular dark-field scanning transmission electron microscopy to irradiate Au nanocrystals at room temperature.
View Article and Find Full Text PDFScience
January 2025
Center for Advancing Materials Performance from the Nanoscale (CAMP-Nano), Hysitron Applied Research Center in China (HARCC) and Center for Alloy Innovation and Design (CAID), State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an, China.
Higher strength and higher ductility are desirable for structural materials. However, ultrastrong alloys inevitably show decreased strain-hardening capacity, limiting their uniform elongation. We present a supranano (<10 nanometers) and short-range ordering design for grain interiors and grain boundary regions, respectively, in fine-grained alloys based on vanadium, cobalt, and nickel, with additions of tungsten, copper, aluminum, and boron.
View Article and Find Full Text PDFSmall
January 2025
Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016, China.
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