Micromechanisms of fatigue crack growth in cast aluminium piston alloys |
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| Affiliation: | 1. PSA Peugeot Citroën, Centre Technique de Vélizy, route de Gisy, 78943 Vélizy Villacoublay, France;2. Université de Toulouse, Mines Albi, INSA, UPS, ISAE, ICA (Institut Clément Ader), Campus Jarlard, F-81013 Albi, France;1. School of Materials Science and Engineering, Shenyang University of Technology, 111 Shenliaoxi Road, Shenyang 110870, PR China;2. Materials Fatigue and Fracture Laboratory, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, PR China;1. Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016, PR China;2. School of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, PR China;1. Key Laboratory of Aero-Engine Thermal Environment and Structure, Ministry of Industry and Information Technology, College of Energy and Power Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, PR China;2. Jiangsu Province Key Laboratory of Aerospace Power System, College of Energy and Power Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, PR China;3. Key Laboratory of Functional Materials and Applications of Fujian Province, Xiamen University of Technology, Xiamen 361024, PR China;4. State Key Laboratory of Mechanics and Control Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, PR China |
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| Abstract: | The fatigue crack growth behaviour in as-cast and hot isostatically pressed (HIP) model cast aluminium piston alloys with hypoeutectic Si compositions of 6.9 wt% and 0.67 wt% has been investigated. The HIP alloys showed slightly improved fatigue crack growth resistance. Analysis of the crack path profiles and fracture surfaces showed that the crack tends to avoid Si and intermetallic particles at low ΔK levels up to a mid-ΔK of ～7 MPa√m. However, some particles do fail ahead of the crack tip to facilitate crack advance due to the interconnected microstructure of these alloys. At higher levels of ΔK, the crack increasingly seeks out Si and intermetallic particles up to a ΔK of ～9 MPa√m after which the crack preferentially propagates through intermetallic particles in the 0.67 wt%Si alloy or Si and intermetallics in the 6.9 wt%Si alloys. It was also observed that crack interaction with intermetallics caused crack deflections that led to roughness-induced crack closure and possibly oxide-induced crack closure at low to mid-ΔK. However, crack closure appears unimportant at high ΔK due to the large crack openings and evidenced by the fast crack growth rates observed. |
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