Investigating the Mechanical Properties Of 0.5 Copper and 0.5 Nickel Austempered Ductile Iron with Different Austempering Parameters

摘要

The purpose of this research is to investigate the mechanical and corrosion characteristics of Ni-Cu alloyed Austempered Ductile Iron before and after austempering process. Specimens of ductile iron and 0.5% Cu-Ni ductile iron were produced through conventional CO2 sand casting method. The specimens were then austenitized at 900°C before austempered at 350°C at three different holding times which were 1 hour, 2 hours and 3 hours subsequently. The corrosion characteristics of newly developed material were obtained by means of polarization test and the mechanical testing involved tensile test (TS 138 EN 1002-1), Rockwell hardness test and Charpy Impact test (ASTM E23). Density test as well as microstructure and SEM observations were also done to ductile iron and Cu-Ni alloyed ductile iron samples. All the testing was done to both as cast and austempered specimens. Addition of copper and Nickel was found to slightly increased the mechanical properties due to solid strengthening effect of Copper and Nickel. The results also indicated that austempering process at 1 hour gives the optimum mechanical properties in term of tensile strength and impact properties compared to other specimens. Increasing the austempering holding times to 2 hours and 3 hours, in contrast had resulted in decrement of the mechanical properties. There are however only slight improvement in hardness properties and no significant effect on density properties of the specimens.