Optimizing the Properties of Thin Wall Austempered Ductile Iron

TLDR: In this paper, a short-term austempered ductile iron (TWADI) treatment process was used to obtain thin wall ADI castings with different thicknesses of 2, 4, 6 and 8 mm.

Abstract: Production of thin wall austempered ductile iron (TWADI) components can have strength-to-density and elastic-to-density ratios that approach those of cast aluminum, making it theoretically possible to apply ADI in high strength light weight parts. Therefore, development of thin wall ADI technology is essential to permit designers for energy consuming equipment to choose the most appropriate material based on material properties, and not solely on weight or density. In the present work, ductile iron castings with different thicknesses of 2, 4, 6 and 8 mm were cast with an appreciate casting design to assure good mold filling. Short term austempering treatment process was used to obtain thin wall ADI castings. The samples of 2 and 4 mm thickness were austenitized at 900 °C for 30 minutes followed by holding at 350 °C and 400 °C for 10 minutes for each temperature. While, the samples of 6 and 8 mm wall thickness were austenitized at 900 °C for 30 minutes and followed by holding at 350 °C and 400 °C for 30 minutes. The microstructure of TWADI austempered at 350 °C showed finer structure than that austempered at 400 °C. Tensile strength and hardness increased with decreasing casting wall thickness austempered at 350 °C due to the structure refinement effect and decreasing the volume fraction of retained structure in matrix.