Microstructural and mechanical properties of Cu-Ni-Mn-Mo austempered ductile iron obtained from two-step hot air austempering
Leonardo Pereira, Regis Fabiano do Amaral, Mário Wolfart, Vinicius Karlinski de Barcellos
Abstract
In the present work, mechanical and microstructural properties of Austempered Ductile Iron (ADI) alloyed with Cu-Ni-Mn-Mo submitted to different hot air austempering cycles in a two-step mechanism were evaluated. In the first step, cooling and austempering were performed in an experimental hot air blower device. In the second step, the austempering was performed in a muffle furnace. Bars with Ø16.5 mm and 90 mm of length were austenitized in an electric resistive furnace for 90 min at 860°C. Austempering first step was performed for 10 min at 290°C, 320°C and 350°C corresponding to cycles I, II and III, respectively. Austempering second step was performed for 60 min at 380°C for all cycles. The measurements of Brinell hardness, elongation, yield strength, and ultimate tensile strength for cycle I were 288 HB, 5.0%, 840 MPa, and 988 MPa. For cycle II, the measurements were: 264 HB, 5.9%, 717 MPa, and 876 MPa. And for cycle III: 257 HB, 6.6%, 711 MPa, and 888 MPa. Microstructural analysis indicated the presence of pearlite-free ausferrite.