In-Situ Characterization by High-Energy X-ray Diffraction of the Phase Transformations Leading to Transformation-Induced Plasticity-Aided Bainitic Steel

Zélie Tournoud,Frédéric De Geuser,Gilles Renou,Didier Huin,Patricia Donnadieu,Alexis Deschamps

doi:10.3390/qubs3040025

Abstract

The phase transformations occurring during the heat treatments leading to transformation-induced plasticity (TRIP)-aided bainitic steel have been investigated in-situ by high-energy X-ray diffraction (HEXRD) conducted with synchrotron light at 90 keV. Direct microstructure characterization has been performed by electron microscopy using electron backscatter diffraction and orientation and phase mapping in a transmission electron microscope. HEXRD data allow the quantification of the evolution of the austenite phase fraction with the heat treatments, as well as its carbon content and the fraction of carbides, from the lattice parameter evolution. It is shown that different combinations of austenite fraction and carbon content can be reached by adjusting the heat treatment temperature.

Highlights

In the last decade, a tremendous effort has been applied to developing advanced high-strength steels (AHSSs), offering a good combination of tensile strength and ductility [1]
The initial state studied here consists of a material subjected to hot rolling, coiling, and isothermal treatment at an intermediate temperature, which should leave the material close to an equilibrium microstructure
It is possible to conclude that the alloy consists of ferrite and cementite particles, whose sizes are typically of the order of a few QuteanntsumofBenamanSocim. 2e02t0e,r4s,.xTFhOiRsPiEnEitRiaRlEmVIiEcWrostructure is subsequently subjected to cold rolling befo4roef 1t7he aQuusantetunmitBizeaamtiSocni. h20e2a0t, 4t,rxeaFtOmRePnEtE.R REVIEW

Summary

Introduction

A tremendous effort has been applied to developing advanced high-strength steels (AHSSs), offering a good combination of tensile strength and ductility [1]. The critical parameters that enable this TRIP effect to take place are the fraction of austenite in the steel, which will be able to transform during deformation, and its stability [4], influenced by many factors such as its size [5], morphology, or composition, and, [6], its carbon content [7,8,9,10].

Results

Conclusion