Abstract

Hot deformation behavior of functionally graded steels (FGSs) has been investigated via conducting hot compression tests at different temperatures and strain rates by the researchers. FGSs are a group of functionally graded materials (FGMs) consisting of ferrite (α), austenite (γ), bainite (β) and martensite (M) phases placed over each other in different configurations and produced by electroslag remelting (ESR). In this article, the Zener-Hollomon model was used to describe the flow stress variations of FGSs withαβγMγ structure as a function of temperature and strain rates. The stress exponent (n) and activation energy (Q) were determined for the composite as 8.1138 and 365.67 kJ.mol^-1, respectively. The values determined for this model were in excellent agreement with the experimental results of other references. In addition, an analytical model was developed to determine the flow stress of αβγMγ steels under hot compression condition. This model just considers phase mixture law and boundary layers characteristics. The analytical results were also in good agreement with the experiments of other references.

Key words: Functionally graded steel, hot compression, different temperature and strain rates, Martensite and Bainite phases, novel analytical model.