Effect of Heat Treatment on the Thermal Expansion Coefficient of Austempered Ductile Iron

Abstract:

Austempered ductile iron provide a unique combination of strength and toughness coupled with excellent design flexibility for automotive application as compared to forged or cast steels. Some material properties such as thermal expansion coefficient and its influence in final machining tolerance is a matter of discussion in the automotive industry. In this study the effect of heat treatment cycle on the microstructure & thermal expansion of ADI was investigated. Samples were austempered at 275 º C and 375 º C for one hour and then dilatometric test carried out in the temperature range of 50 °C to 350 °C, then the result was compared with the thermal expansion coefficient of forged steel. Microstructure and mechanical investigations were used to the assurance of these results. The results indicate that replacing of forged steel with ADI due to lower cost production and reduction in weight is possible if the correct tolerance were selected.

• Periodical: Materials Science Forum (Volumes 475-479)
• Pages: 203-212
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.475-479.203
• Online since: January 2005
• Authors: M.Tadayon Saidi, N. Baghersaie, N. Varahram
• Keywords: Austempered Ductile Iron, Dilatometry Expansion, Liner Thermal Expansion

References

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[11] B. Stokes and P.A.S. Reed, Fatigue Analysis of Austempered Ductile Iron Suitable for Automotive Camshaft Application, Materials Research Group, University of Southampton, Highfield, Southampton. SO171 BJ. Table 1. Chemical Composition of Specimens. Sample % C % Si %Mn %P %S %Cr %Ni %Mo %Cu %Fe Ductile iron 3. 65 2. 23 0. 55 0. 009 0. 007 0. 022 0. 855 0. 17 0. 72 Base Steel forge 0. 48 0. 29 0. 67 0. 012 0. 019 0. 16 0. 04 0. 02 0. 02 Base Table 2. Mechanical Properties of Specimens. Alloy Yield stress (Mpa) Ultimate tensile stress (Mpa) Thermal expansion Um/m ºc Elongation (%) A1 639 945 29 (50 ºc) 22 (100 ºc).

[19] 2 (150 ºc).

[17] 6 (200 ºc).

[17] 24 (250 ºc).

[17] 35 (300 ºc).

[16] 37 (350 ºc) 9 A2 1278 1526 23 (50 ºc) 18 (100 ºc).

[17] 14 (150 ºc).

[17] 84 (200 ºc).

[19] 100 (250 ºc).

[19] 06 (300 ºc).

[18] 44 (350 ºc).

[4] 5 B5 4 5 8 2 1.

[19] 08 (50 ºc).

[16] 09 (100 ºc).

[14] 659 (150 ºc).

[13] 944 (200 ºc).

[12] 872 (250 ºc).

[13] 578 (300 ºc).

[13] 944 (350 ºc) 16.