PSI - Issue 7

C. Garb et al. / Procedia Structural Integrity 7 (2017) 497–504 C. Garb et Al. / Structural Integrity Procedia 00 (2017) 000–000

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testing temperature of 25 % for ch AlSi8 Sr T5 Pos. 1 and of 7 % for cc AlSi8 Sr T6 Pos. 1 compared to room temperature. These specifications show less microporosity incorporating comparably small micropore sizes (120 µm and 85 µm). However, a significant change in the failure mechanism from defect at room temperature to slip band induced crack origin at 150 °C is observed. • The cc AlSi8 Sr T6 Pos. 2 hardly shows any decrease in fatigue strength at 150 °C and reveals only defect induced failures at room temperature as well as at 150 °C. In addition, the micro porosity and micropore size is significantly higher (537 µm) and the fatigue strength level is generally lower. • The specifications showing slip band induced failures at 150 °C exhibit a significantly higher drop in fatigue strength compared to the specification with only defect induced failures. • It seems that a lower boundary for the failure mechanism change for the investigated materials and defect sizes at 150 °C exists. At a micropore size value of approximately 100 µm to 120 µm the failure mechanism change mostly occurs. • The specifications with less porosity and smaller defect sizes reveal a significant higher influence by the elevated temperature of 150 °C. Future work will deal with a characterization of further Al-Si alloys and the set-up of a defect size based material model incorporating the effect of elevated temperatures. Acknowledgements The authors would like to thank Nemak Linz and Nemak Dillingen for the appropriation of the casted components. Further on, execution of the CT scans at the Materials Center Leoben GmbH is highly appreciated. Finally, financial project support was gladly provided by MAGMA Gießereitechnologie GmbH and AVL List GmbH. Financial support by the Austrian Federal Government (in particular from Bundesministerium für Verkehr, Innovation und Technologie and Bundesministerium für Wissenschaft, Forschung und Wirtschaft) represented by Österreichische Forschungsförderungsgesellschaft mbH and the Styrian and the Tyrolean Provincial Government, represented by Steirische Wirtschaftsförderungsgesellschaft mbH and Standortagentur Tirol, within the framework of the COMET Funding Programme is gratefully acknowledged. References Ammar HR, Samuel AM, Samuel FH. Effect of casting imperfections on the fatigue life of 319-F and A356-T6 Al– Si casting alloys. Materials Science and Engineering: A 2008;473(1-2):65–75. ASTM. Standard Practice for Statistical Analysis of Linear or Linearized Stress-Life (S-N) and Strain-Life (e-N) Fatigue Data, 1998. Beck T, Löhe D, Luft J, Henne I. Damage mechanisms of cast Al–Si–Mg alloys under superimposed thermal– mechanical fatigue and high-cycle fatigue loading. Materials Science and Engineering: A 2007;468-470:184– 92. Buffière J-Y, Savelli S, Jouneau PH, Maire E, Fougères R. Experimental study of porosity and its relation to fatigue mechanisms of model Al–Si7–Mg0.3 cast Al alloys. Materials Science and Engineering: A 2001;316(1-2):115– 26. Canales AA, Carrera E, Silva JT, Valtierra S, Colás R. Mechanical properties in as-cast and heat treated Al-Si-Cu alloys. IJMMP 2012;7(4):281. Ceschini L, Morri A, Toschi S, Seifeddine S. Room and high temperature fatigue behaviour of the A354 and C355 (Al–Si–Cu–Mg) alloys: Role of microstructure and heat treatment. Materials Science and Engineering: A 2016;653:129–38. Chang-Yeol Jeong. High Temperature Mechanical Properties of Al–Si–Mg–(Cu) Alloys for Automotive Cylinder Heads. Dengel D. Die Arcsin-Wurzel-P Transformation - ein einfaches Verfahren zur graphischen und rechnerischen Auswertung geplanter Wöhlerversuche. Journal of Materials Technology 1975;6(8):253–88. Di Sabatino M, Arnberg L. Castability of aluminium alloys. Trans Indian Inst Met 2009;62(4-5):321–5. Gao YX, Yi JZ, Lee PD, Lindley TC. The effect of porosity on the fatigue life of cast aluminium-silicon alloys. Fat