The Effect of Testing Temperature on Fracture Toughness of Austempered Ductile Iron

Authors: Hsu, Cheng-Hsun; Lee, Shen-Chih; Feng, Hui-Ping; Shy, Yih-Hsun

Source: Metallurgical and Materials Transactions A, Volume 32, Number 2, 1 February 2001 , pp. 295-303(9)

Publisher: Springer

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Abstract:

The effect of testing temperature (-150 °C, 25 °C, and +150 °C) on the fracture toughness of austempered ductile iron (ADI) was studied. Specimens were first austenitized at 900 °C for 1.5 hours and then salt-bath quenched to 360 °C or 300 °C, for 1, 2, or 3 hours of isothermal holding before cooling to room temperature. The resulting matrices of the iron were of upper-ausferrite and lower-ausferrite. It was found that raising the testing temperature to 150 °C from ambient improved the fracture toughness by 18, 30, and 7 pct for the as-cast/lower-ausferrite ADI/upper-ausferrite ADI, respectively. Lowering the testing temperature to-150 °C produced a decrease of-15, -35, and -48 pct. Optical microscopy, X-ray diffraction analysis, and scanning electron microscopy (SEM) fractography were applied to correlate the toughness variation with testing temperatures.

Document Type: Research article

Publication date: 2001-02-01