Abstract
The effect of Cu content on the microstructures and mechanical properties (yield strength, ultimate tensile strength, impact energy, fracture toughness) of austempering ductile iron (ADI) treated by two-step austempering process were investigated. High Cu content in nodular cast irons leads to a signifcant volume fraction of retained austenite in the iron after austempering treatment, but the carbon content of austenite decreases with the increasing of Cu content. Moreover, austenitic stability reaches its maximum when the Cu content is 1.4% and then drops rapidly with further increase of Cu. The ultimate tensile strength and yield strength of the ADI frstly increases and then decreases with increasing the Cu content. The elongation keeps constant at 6.5% as the Cu content increases from 0.2% to 1.4%, and then increases rapidly to 10.0% with further increase Cu content to 2.0%. Impact toughness is enhanced with Cu increasing at frst, and reaches a maximum 122.9 J at 1.4% Cu, then decreases with the further increase of Cu. The fracture toughness of ADI shows a constant increase with the increase of Cu content. The infuencing mechanism of Cu on austempered ductile iron (ADI) can be classifed into two aspects. On the one hand, Cu dissolves into the matrix and functions as solid solution strengthening. On the other hand, Cu reduces solubility of C in austenite and contributes more stable retained austenite.
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Male, born in 1963, Ph.D., Professor. His research interests mainly focus on nodular ductile cast irons and cast steels.
This work was fnancially supported by the National Natural Science Foundation of China (Grant Nos. 51374086 and 51674094).
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Yi, Py., Guo, Ej., Wang, Lp. et al. Effect of Cu content on microstructures and mechanical properties of ADI treated by two-step austempering process. China Foundry 16, 168–176 (2019). https://doi.org/10.1007/s41230-019-8145-3
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DOI: https://doi.org/10.1007/s41230-019-8145-3