Author : Mélanie Ollat
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (16 download)
Book Synopsis Characterization and Modeling of Microstructural Evolutions During the Thermal Treatment of Cold-rolled Dual-Phase Steels by : Mélanie Ollat
Download or read book Characterization and Modeling of Microstructural Evolutions During the Thermal Treatment of Cold-rolled Dual-Phase Steels written by Mélanie Ollat and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dual-Phase steels (DP) are one of the most used Advanced High Strength Steels (AHSS) for automotive applications because they present good strength/ductility compromise and they adapt to number of industrial constraints (low price, shaping, welding, coating etc.). Nowadays, the development of DP steels seems to be promising and sustainable for the body-in-white structure. The typical ferrite-martensite microstructure, characteristic of DP steels, are obtained by a thermal treatment composed of different stages during which metallurgical evolutions occur. Major difficulties of their processing are due to the fact that (i) microstructural evolution kinetics are influenced by cycle parameters (heating rate, annealing temperature etc.), (ii) different stages are interconnected and (iii) some microstructural evolutions may overlap and, therefore, interact. This PhD-work aimed at getting a better understanding of microstructural evolutions during the thermal cycle of DP steel and, namely, the influence of cycle parameters. Different microstructural evolutions occurring during the thermal cycle were first characterized coupling different experimental techniques (dilatometry, hardness, TPE etc.) and with a particular protocol in order to decorrelate overlapping and interconnected phenomena. As example, two major evolutions occurring during the intercritical annealing were first studied individually ((1) recrystallization was investigated below austenite formation temperature and (2) austenite formation was investigated on prior recrystallized steels) before investigated cold-rolled steel case where recrystallization and austenite formation overlap. The study was then attached to develop some predictive tools to describe microstructural evolutions based on phenomenological approaches (JMAK law) towards more physical based models (mixed-mode, diffusive models). A particular care was attached to discuss on model reliability, versatility, strengths and limitations.