MSA  Vol.8 No.13 , December 2017
Impact Properties of Austempered Spheroidal Graphite Cast Irons
Abstract: This study aims to clarify the influence of external notch on impact characteristics of high toughness ductile cast irons prepared by austempering heat treatment. We produced ductile cast irons samples with various matrix microstructure tested by Charpy impact within five kinds of external notches whose stress concentration factors (α), with values taken from 1.0 (Un-notched) to 4.8. In addition, to clarify the initiation process of impact characteristics, we observed the evolution of microstructure surface during bending tests with a slow loading speed for the un-notched and the notched impact samples. The results showed that the impact fracture energy decreases strongly in the range of α from 1 to 2.3 but decreases slightly for α larger than 3. Moreover, the impact value of samples with austempered microstructure is sensitive to the external notch shape. The impact transition temperature increases with increasing the stress concentration factor. The fracture energy is decreasing with the external notch from the impact test since the crack initiation energy is directly affected by this later. This work contributes to get a better understanding in the basic theories of external notch effect on impact characteristics of austempered spheroidal graphite cast irons (ADI).
Cite this paper: Nobuki, T. , Hatate, M. and Shiota, T. (2017) Impact Properties of Austempered Spheroidal Graphite Cast Irons. Materials Sciences and Applications, 8, 948-958. doi: 10.4236/msa.2017.813069.

[1]   Keoung, J.R. and Hayrynen, K.L. (2000) Automotive Applications of Austempered Ductile Iron (ADI): A Critical Review. 2000 SAE World Congress, Technical Paper 2000-01-0764, 1-12.

[2]   Keoung, J.R., Hayrynen, K.L. and Pioszak, G.L. (2010) Designing with Austempered Ductile iron (ADI). AFS proceedings 2010, Schaumburg, paper 10-129, 1-15.

[3]   Wojciechowski, S. (2000) New Trends in the Development of Mechanical Engineering Materials. Journal of Materials Processing Technology, 106, 230-235.

[4]   Vasko, A. (2016) Evaluation of Shape of Graphite Particles in Cast Irons by a Shape Factor. Materials Today: Proceedings, 3, 1199-1204.

[5]   Shiota, T. and Komatsu, S. (1978) Influences of Notch Effect and Effective Sectional Area on Fatigue Strength of Cast Irons with Various Graphite Shapes. Journal of the Society of Materials Science, JAPAN, 27, 291-297. (In Japanese)

[6]   Nobuki, T., Shiota, T., Hatate, M. and Komatsu, S. (2003) Notch Effects on Impact characteristics of spheroidal and compacted vermicular graphite cast irons with various matrix. Proceedings of the 8th Asian Foundry Congress, Bangkok, Paper 48, 97-102.

[7]   Zambrano, H.R. and Harkegard, G. (2013) Self-Arresting Cracks at Notches in Ductile Cast Iron. Engineering Fracture Mechanics, 102, 146-155.

[8]   Schoenborn, S., Kaufmann, H., Sonsino, C.M. and Heim, R. (2015) Cumulative Damage of High-Strength Cast Iron Alloys for Automotive Applications. Procedia Engineering, 101, 440-449.

[9]   D’Agostino, L., Di Cocco, V. and Iacoviello, F. (2016) Overload Effects on Fatigue Cracks in Ferritic-Pearlitic Ductile Cast Irons. Procedia Structual Integrity, 2, 3369-3376.

[10]   Iacoviello, F., Lacoviello, D., Di Cocco, V., De Santis, A. and D’Agostino, L. (2017) Classification of Ductile Cast Iron Specimens Based on Image Analysis and Support Vector Machine. Procedia Structual Integrity, 3, 283-290.

[11]   Nishida, M. (1967) Ouryoku Syuutyuu. Morikita Press, Japan, 572-574. (In Japanese)

[12]   Coceru, A., Capelle, J. and Pluvinage, G. (2014) On the Use of Charpy Transition Temperature as Reference Temperature for the Choice of a Pipe Steel. Engineering Failure Analysis, 37, 110-119.

[13]   Kurishita, H., Kayano, H., Narui, M., Yamazaki, M., Kano, Y. and Shibahara, I. (1993) Effects of V-Notch Dimensions on Charpy Impact Test Results for Differently Sized Miniature Specimens of Ferritic Steel. Materials Transactions, 34, 1042-1052.

[14]   Nobuki, T., Shiota, T. and Hatate, M. (2003) Impact Bending Characteristics of Shperoidal Graphite Cast Iron with External Notch. Proceedings of the 1st Korea-Japan Conference for YFE, Korea, 9-12.

[15]   Nobuki, T., Shiota, T. and Hatate, M. (2003) Notch Effects on Impact and Bending Characteristics of Ferritic Spheroidal Graphite and Compacted Vermicular Graphite Cast Irons. Journal of Japan Foundry Engineering Society, 75, 749-755. (In Japanese)

[16]   Nobuki, T., Shiota, T. and Hatate, M. (2004) Notch Effects on Impact and Bending Characteristics of Pearlitic Spheroidal Graphite Cast Irons. Journal of Japan Foundry Engineering Society, 76, 555-561. (In Japanese)

[17]   Kobayashi, T. (2002) Progress in the Instrumented Charpy Impact Test. Journal of the Society of Materials Science, Japan, 51, 771-779. (In Japanese)