Open Access System for Information Sharing

Login Library

 

Article
Cited 6 time in webofscience Cited 0 time in scopus
Metadata Downloads

Effects of untransformed ferrite on Charpy impact toughness in 1.8-GPa-grade hot-press-forming steel sheets

Title
Effects of untransformed ferrite on Charpy impact toughness in 1.8-GPa-grade hot-press-forming steel sheets
Authors
Jo, Min CheolPark, JaeyeongSohn, Seok SuKim, SeongwooOh, JinkeunLee, Sunghak
POSTECH Authors
Lee, Sunghak
Date Issued
Nov-2017
Publisher
ELSEVIER SCIENCE SA
Abstract
Hot press forming (HPF) steel sheets are austenitized, press-formed, and rapidly cooled to obtain a martensitic microstructure with an ultra-high strength. When they are insufficiently austenitized, their microstructures might contain a small amount of untransformed ferrite, which can deteriorate impact toughness as well as strength, but its causes and relevant fracture mechanisms have not been clearly verified yet. In this study, thus, 1.8-GPa-grade HPF sheets were austenitized at various temperature and time, and their tensile and Charpy impact test results were analyzed in relation with untransformed ferrite and its effect on fracture mechanisms. In the HPF sheets containing the untransformed ferrite, voids were formed mostly at ferrite/martensite interfaces, and were grown and propagated linearly to form a cleavage crack, whereas deformation bands were well developed without voids or cracks in the non-ferrite-containing sheets. The highly localized strains accommodated in the soft ferrite made ferrite/martensite interfaces or ferrite itself work as fracture initiation sites, which led to the brittle fracture and consequently to the deterioration of impact energy. This result can provide an important idea for optimization of austenitization conditions demanded for ultra-high strength and excellent impact toughness in HPF applications.
Keywords
DUAL-PHASE STEEL; DIGITAL IMAGE CORRELATION; MECHANICAL-PROPERTIES; DEFORMATION-BEHAVIOR; PLASTIC-DEFORMATION; MARTENSITE CONTENT; LIGHTWEIGHT STEEL; STAINLESS-STEEL; STRAIN; MICROSTRUCTURE
URI
http://oasis.postech.ac.kr/handle/2014.oak/50854
DOI
10.1016/j.msea.2017.09.027
ISSN
0921-5093
Article Type
Article
Citation
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, vol. 707, page. 65 - 72, 2017-11
Files in This Item:
There are no files associated with this item.

qr_code

  • mendeley

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

Related Researcher

Researcher

 LEE, SUNG HAK
Dept of Materials Science & Enginrg
Read more

Views & Downloads

Browse