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<p>Sequential ultrasonic welding (USW) is a process at the heart of ultrasonic consolidation (USC) technology. In the presented study, this method was used to consolidate four 0.7-mm-thick high-strength nickel plates with an initial ultrafine-grained (UFG) structure obtained by high-pressure torsion. It was established that intensive grain growth occurred during USW of ultrafine-grained nickel. Normal grain growth in the bulk regions of plates led to the formation of a gradient microstructure along the sample height and width, with the average grain size varying from 4.6 to 0.7&#xa0;μm. The origin of such a gradient microstructure was analyzed, basing on available data on the grain growth kinetics in UFG nickel. It was found that abnormal grain growth occurred in the vicinity of interfaces that resulted in an extremely heterogeneous microstructure. Abnormally large grains, with sizes of several tens of micrometers in the vibration direction and 5–15&#xa0;µm in the normal direction, as well as areas with fine grains of 0.5–2&#xa0;µm in size, were observed in the vicinity of interfaces. Thin gaps were visible along boundaries of abnormally large grains, and small voids were revealed between fine grains. The presence of discontinuities between the layers of the consolidated sample was associated with intense wear of the surfaces of high-strength plates during USW. In the defect-free regions, equiaxed grains with sizes of 3–7&#xa0;µm were formed as a result of the migration of grain boundaries across the faying surfaces of the joined plates.</p>

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Microstructure of multilayer sample produced by sequential ultrasonic welding of ultrafine-grained nickel

  • 期刊论文

  • 发表日期：

    2025年5月23日

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  • Mariya A. Murzinova,
  • Elvina R. Shayakhmetova,
  • Aygul A. Mukhametgalina,
  • Ayrat A. Nazarov

摘要

Sequential ultrasonic welding (USW) is a process at the heart of ultrasonic consolidation (USC) technology. In the presented study, this method was used to consolidate four 0.7-mm-thick high-strength nickel plates with an initial ultrafine-grained (UFG) structure obtained by high-pressure torsion. It was established that intensive grain growth occurred during USW of ultrafine-grained nickel. Normal grain growth in the bulk regions of plates led to the formation of a gradient microstructure along the sample height and width, with the average grain size varying from 4.6 to 0.7 μm. The origin of such a gradient microstructure was analyzed, basing on available data on the grain growth kinetics in UFG nickel. It was found that abnormal grain growth occurred in the vicinity of interfaces that resulted in an extremely heterogeneous microstructure. Abnormally large grains, with sizes of several tens of micrometers in the vibration direction and 5–15 µm in the normal direction, as well as areas with fine grains of 0.5–2 µm in size, were observed in the vicinity of interfaces. Thin gaps were visible along boundaries of abnormally large grains, and small voids were revealed between fine grains. The presence of discontinuities between the layers of the consolidated sample was associated with intense wear of the surfaces of high-strength plates during USW. In the defect-free regions, equiaxed grains with sizes of 3–7 µm were formed as a result of the migration of grain boundaries across the faying surfaces of the joined plates.