Enhancement of Superplastic Properties in Ultrahigh Carbon Steel through Silicon Addition

Abstract

The superplastic behaviour of ultrahigh carbon steels (UHCS) has been greatly improved by silicon additions and thermomechanical processing. A UHC steel containing 3 wt% Si shows superplastic behaviour in a wide temperature range from 650 to 900°C. This behaviour is observed even at high strain rates, i.e. 10-2 s-1, in the temperature range between 800 and 825°C. Furthermore, the flow stress required for superplastic deformation is reduced drastically, i.e. σ=12 MPa at a strain rate of 10-4 s-l. Finally, it is found that the flow stress at a given strain rate is relatively constant over a wide range of temperatures (750-900°C) due to a unique transformation behaviour in the UHCS-3Si alloy.