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URN etd-0830106-155811 Statistics This thesis had been viewed 2437 times. Download 388 times. Author Chi-Fan Han Author's Email Address No Public. Department Materials Engineering Year 2005 Semester 2 Degree Master Type of Document Master's Thesis Language zh-TW.Big5 Chinese Page Count 115 Title Effects of Nickel and Cobalt Elements and Variable Austempering on Microstructure and Mechanical Properties of Ductile Iron Keyword ductile iron austempeting austempeting ductile iron Abstract Austempered ductile iron (ADI) is produced via the austempering treatment of ductile iron. The focus the past researches is to study the effects of isothermal austempering heat treatment and two-step austempering heat treatment, but seldom probe into the effects of variable austempering heat treatment. The phase of this research is to study the effects of variable austempering heat treatment on properties of ADIs.
In this study, 4 wt% nickel (Ni) and 4 wt% cobalt (Co) was added to ductile iron as experimental material, and then performed a series of austempering treatment consisting of different temperatures (300, 360, 300→360, 360→300℃) for 2hrs. Microstructures of ADI were observed and both mechanical properties and retained austenite of ADI were also measured, respectively.
The experimental results showed that Microstructures of ADI produced via variable austempering treatment are in relation to quenching temperature and they are similar to the microstructure of ADI treated isothermally in the same quenching temperature. Furthermore, Mechanical properties of ADI produced via variable austempering treatment are generally better then ADI produced via isothermal austempering treatment. The optimum fracture toughness appeared in the non-alloyed ADI produced via decreased austempering treatment
Advisor Committee C.H Hsu - advisor
L.W Tsay - co-chair
Y.S. Shin - co-chair
Files Date of Defense 2006-07-28 Date of Submission 2006-08-30