Deformation Behavior of Austenite Base Lightweight Fe-Mn-Al-C Steel Containing κ-Carbide Precipitates

Abstract

It is well known that the performance of transportation systems such as automobiles can significantly be improved by using lightweight materials, with concurrent reduction in fuel consumption and the emission of exhaust gases. One of the most effective ways of reducing the weight of transportation systems is using the materials with low density. Therefore automotive companies are trying to expand the usage of low density alloys such as Al alloys and Mg alloys. This imposes a serious threat to steel industries whose major products are for automotive applications. Recently, new type of high strength steels, so-called lightweight steels, has been developed. These lightweight steels have high specific strength and stiffness, and excellent ductility and formability. One of lightweight steels developed is the austenite base steel containing nano-sized κ-carbide particles as strengthening precipitates. Deformation behavior of the steels can be very complex, including transformation-induced plasticity (TRIP), Twinning-Induced Plasticity (TWIP), shear band induced plasticity and microband induced plasticity. However, the exact mechanism of deformation is not clear. In the present study, deformation behavior of austenite base Fe-28Mn-9Al-0.8C and Fe-28Mn-10Al-0.8C steel has been investigated, with particular emphasis on the effect of nano-sized κ-carbide precipitates. Aging conditions were varied to have variations in the size and volume fraction of κ-carbide precipitates based on the hardness test results. Detailed deformation behavior of the steel with various morphologies of κ-carbide precipitates has been investigated by TEM and correlated with tensile properties. Observation of microstructure of same area after each step also analyzed using EBSD to understand the mechanism of deformation behavior.