Materials Transactions, Vol.44 No.6 (2003) pp.1209-1218
© 2003 The Japan Institute of Metals
EXPRESS REGULAR ARTICLE
Effect of Microstructural Refinement on Ductility Deterioration of High Silicon Ferritic Spheroidal Graphite Cast Iron Caused by Cyclic Heating
Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan, R.O. China
This investigation applies cyclic heating and cooling to elucidate the effect of microstructural refinement on the tensile elongation deterioration of ferritic spheroidal graphite cast iron. In order to eliminate the oxidation factor, the cyclic heating/cooling test was performed in a 1.33∼ 0.133 Pa ambient vacuum atmosphere with cyclic heating at a maximum temperature of 1023 K. Severe embrittlement accompanied by intergranular fracture occurred after the ferritic spheroidal graphite cast iron was subjected to a certain number of heating and cooling cycles. A fair amount of inevitable inclusion particles were found to agglomerate in the eutectic cell boundary region, and so the cyclic heating induced embrittlement can be recognized to be strongly dependent on the solidification cooling rate of the materials. Based on experimental evidence, the cracking evolution can be divided into three steps: (1) crack initiation from the vicinity of the eutectic cell boundary at the surface, (2) crack linking and major crack formation, and (3) major crack inward extension. Cyclic heating cracks are mainly initiated at the eutectic cell boundary where a fair amount of MgO inclusions dispersed, and consequently propagated along the annealed eutectic cell boundary. While investigating the plastic deformation behaviors around the above mentioned MgO inclusions pertaining to the crack initiation and crack propagation, typical etch pit evidence was observed in the vicinity of the cell boundary area.
(Received March 4, 2003; Accepted May 8, 2003)
cyclic heating, solidification cooling rate, ferritic spheroidal graphite cast iron, etch pit, tensile elongation deterioration
Table of Contents
- Y. J. Park, R. B. Gundlach and J. F. Janowak: AFS Trans. 95 (1987) 267-272.
- C. P. Cheng, S. M. Chen, T. S. Lui and L. H. Chen: Metall. Trans. A. 28A (1997) 325-333.
- C. P. Cheng, T. S. Lui and L. H. Chen: Metall. Trans. A. 30A (1999) 1549-1558.
- K. Röhrig: AFS Trans. 87 (1979) 75-88.
- J. F. Janowak, J. D. Crawford and K. Röhrig: Casting Eng./Foundry World. 14 (1982) 32-41.
- W. Fairhurst and K. Röhrig: Foundry Trade J. 146 (1979) 657-681.
- S. C. Lee and L. C. Weng: Metall. Trans. A. 22A (1991) 1821-1831.
- F. T. Shiao, T. S. Lui and L. H. Chen: Int. J. Cast Metals Res. 10 (1997) 301-311.
- F. T. Shiao, T. S. Lui and L. H. Chen: Metall. Trans. A. 30A (1999) 1775-1784.
- F. T. Shiao, T. S. Lui and L. H. Chen: Int. J. Cast Metals Res. 14 (2001) 137-145.
- Y. Iwabuchi, I. Kobayashi, H. Narita and T. Takenouch: J. Japan Found. Eng. Soc. 68 (1996) 209-215.
- M. Takanezawa, Y. Kobayashi and Y. Tomota: J. Japan Found. Eng. Soc. 69 (1997) 41-48.
- S. F. Chen, T. S. Lui and L. H. Chen: Cast Metals. 6 (1994) 199-203.
- S. F. Chen, T. S. Lui and L. H. Chen: Metall. Trans. A. 25A (1994) 2305-2309.
- G. T. Hahn, P. N. Mincer and A. R. Rosenfield: Exp. Mech. 11 (1971) 248-253.
- G. T. Hahn, P. N. Mincer and A. R. Rosenfield: Metall. Trans. 3 (1972) 1189-1202.
- K. Tanaka, M. Hojo and Y. Nakai: Mater. Sci. Eng. 55 (1982) 85-96.
- Y. Waku, T. Masumoto and T. Ogura: Trans., JIM 24 (1983) 849-857.
- Y. Birol: Metallography 21 (1988) 77-90.
- Y. Birol: J. Mater. Sci. 23 (1988) 2079-2086.
- M. Sofue, S. Okada and T. Sasaki: AFS Trans. 87 (1979) 173-182.
- M. Sofue: Imono. 47 (1975) 681-687.
© 2002 The Japan Institute of Metals
Comments to us :