1. Significantly enhanced fatigue resistance and mechanisms of hypoeutectic Al-Si composite calibrated using trace in-situ nanocrystals.
- Author
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Liu, Tian-Shu, Zhu, Lin, Yang, Hong-Yu, Cui, Hong-Yu, Meng, Jia, Qiu, Feng, Dong, Bai-Xin, Shu, Shi-Li, Jiang, Qi-Chuan, and Zhang, Lai-Chang
- Subjects
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FATIGUE limit , *METALLIC glasses , *FATIGUE life , *STRESS concentration , *HIGH cycle fatigue , *CRACK initiation (Fracture mechanics) , *ALUMINUM composites , *NICKEL-titanium alloys , *GRAIN size - Abstract
Fatigue resistance under extreme stress conditions is an important indicator to evaluate industrial application potential of Al-Si-Mg alloys, but their fatigue resistance is inherently weakened by large grain size, long-needle Si phases and coarse precipitates. This work reports significantly optimized microstructure configuration and fatigue resistance of hypoeutectic Al-Si composite optimized by the nanocrystallization products of a NiNbTi metallic glass. It was proved the in-situ NiTi (B2) nanocrystals can serve as the heterogeneous nucleation sites of α-Al and β-Mg 2 Si and the growth retarder of eutectic Si. Particularly, the optimized composite exhibited nearly 5 times and 6 times longer fatigue life than the unoptimized alloy at 120 MPa (60 Hz) and 240 MPa (20 Hz), respectively. The fatigue strength (N = 107) was increased by 21.7 % and 25.9 % at 60 Hz and 20 Hz, respectively. The α-Al refinement enhanced the resistance to fatigue crack initiation. The refinement and spheroidization of eutectic Si phases reduced stress concentration. Also, the austenite-martensite phase transformation of NiTi afforded more energy for precipitation. Refined β-Mg 2 Si and β'' phases were facilitated to interact with dislocations, improving the resistance to dislocation slip during cyclic strain through the dislocation shearing effect. This work provides a theoretical basis for the future development of Al-Si alloys and composites with excellent fatigue resistance for expanding their industrial application scope. [Display omitted] • The microstructure was fully manipulated by trace in-situ nanocrystals. • The σ b , ε l , a k , and U T were improved by 20.4 %, 29.1 %, 13.3 % and 58.7 %. • The mean fatigue strengths were 21.7 % (60 Hz) and 25.9 % (20 Hz) improved. • Refined α-Al, eutectic Si and precipitates enhanced fatigue life. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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