Effect of Carbon Content on Bainite Transformation Start Temperature on Fe–9Ni–C Alloys

Abstract

Upper bainite in steels has many common features with lath martensite in steels. But there are some studies that indicate that bainite transformation start temperature (Bs) is greater than T0 on steels containing high carbon content. We measured Bs on Fe–9 mass% Ni alloys containing 0.003–0.89 mass% C. In low carbon alloys, Bs is below T0, and the increasing of carbon content decreases Bs standing in a line that is parallel to T0. On the other hand, in high carbon alloys, carbon content does not affect Bs which stands around 753 K. The border between these two tendencies and Bs in high carbon alloys seem to correspond to the intersection point between the line of Bs on low carbon alloys and the calculated γ/(γ + θ) phase boundary.