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Stretch-flangeability correlated with hardness distribution and strain-hardenability of constituent phases in dual- and complex-phase steels

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Abstract
Stretch-flangeability as a parameter of formability is measured on dual-phase (DP) and complex-phase (CP) steels by the hole-expansion ratio (HER), and nanoindentation is introduced to assess the hardness of constituent phases before and after HER testing. Hole-expansion ratios of two dual-phase (DP1, DP2) and one complex-phase (CP1) steels are measured as 51%, 126% and 136%, respectively. The primary site of void formation is found to be the interfacial boundary for DP1, the ferrite phase close to the martensite phase where numerous geometrically necessary dislocations (GNDs) are formed for DP2, and the martensite phase for CP1. The hardness ratio of the hard to soft phase is a key indicator of formability, and this introduces the stress concentration from strain disparity at the interfacial boundaries between the hard and soft phases. Here, it is founded that strain hardenability of constituent phases depends on the hardness of the GND layer, and the strain disparity under deformation is determined by the GND layer hardness as well as the hardness ratio of the hard to soft phase. This study suggests the GND layer as a stress-dispersion layer and the hardness of GND layers in soft phases as a critical role in formability.
Author(s)
송은지이건희전한솔박봉준이정구김주영
Issued Date
2021
Type
Article
Keyword
NanoindentationDual-phase steelsComplex-phase steelsFormabilityStrain-hardenability
DOI
10.1016/j.msea.2021.141353
URI
https://oak.ulsan.ac.kr/handle/2021.oak/8969
https://ulsan-primo.hosted.exlibrisgroup.com/primo-explore/fulldisplay?docid=TN_cdi_gale_infotracacademiconefile_A663551262&context=PC&vid=ULSAN&lang=ko_KR&search_scope=default_scope&adaptor=primo_central_multiple_fe&tab=default_tab&query=any,contains,Stretch-flangeability%20correlated%20with%20hardness%20distribution%20and%20strain-hardenability%20of%20constituent%20phases%20in%20dual-%20and%20complex-phase%20steels&offset=0&pcAvailability=true
Publisher
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
Location
스위스
Language
영어
ISSN
0921-5093
Citation Volume
817
Citation Number
1
Citation Start Page
141353
Citation End Page
141353
Appears in Collections:
Engineering > Material Engineering
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