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- Title
Ultrasounds Induced Microstructure Transition and Improved Mechanical Property of Directionally Solidified Ternary Cu–Al–Ni Alloy.
- Authors
Hu, Y. J.; Wang, J. Y.; Zhai, W.; Wei, B.
- Abstract
Two ultrasonic modes, i.e., continuous and pulsed ultrasounds, were introduced into the directional solidification process of Cu68.3Al27.6Ni4.1 alloy. A columnar-to-equiaxed structure transition occurred to primary β(Cu3Al) phase within continuous ultrasonic field, which was accompanied with a grain size reduction by 7.5 times. Under pulsed ultrasound, β phase maintained the fine columnar structures with a similar grain size. In the former case, numerous β phase nucleation sites formed ahead of solid/liquid (S/L) interface because of the large local undercoolings induced by transient cavitation. Meanwhile, intensive acoustic streaming suppressed the liquid temperature gradient from 120 to 85 K/cm, which interrupted the solute transportation along heat flow direction and resulted in equiaxed microstructures. Under the intermittent ultrasonic action in the latter case, fewer nucleation sites were generated near S/L interface but small columnar β grains were split from the original ones under stable cavitation. Since no steady convection was driven, the liquid temperature gradient of 110 K/cm remained almost constant, making those grains grow into refined columnar structures. Under the action of pulsed ultrasound, the yield strength was enhanced by a factor of 1.5 because of grain refinement strengthening, together with 94 pct shape recovery rate due to columnar grain structures.
- Subjects
ACOUSTIC streaming; COLUMNAR structure (Metallurgy); GRAIN refinement; TERNARY alloys; DIRECTIONAL solidification
- Publication
Metallurgical & Materials Transactions. Part B, 2024, Vol 55, Issue 5, p3736
- ISSN
1073-5615
- Publication type
Article
- DOI
10.1007/s11663-024-03213-z