{"title":"Effect of Microstructure on Mechanical Properties of 1.0G TRIP Steels Produced by Quenching and Partitioning (Q&P) Process","authors":"Wontae Cho, Ho Hyeong Lee, Dong-Woo Suh","doi":"10.1007/s12540-024-01875-7","DOIUrl":null,"url":null,"abstract":"<div><p>The influence of microstructure on tensile properties and stretch-flangeability of TRIP steels with tensile strengths higher than 1.0 GPa has been investigated under various Quenching and Partitioning conditions. Lowering the quenching stop temperature (QT) from 300 °C to 190 °C after intercritical annealing increased the volume fraction of tempered martensite (TM), decreased that of bainite, and maintains that of ferrite and retained austenite constant in the final microstructure. 300 °C was Ms temperature, thus, QT 300 °C sample consisted of negligible TM and 36% bainite. So, as the QT was reduced to 190 °C, the TM phase was integrated into the bainite up to 13.8%. The yield strength (YS), tensile strength (TS), and hole expansion ratio (HER) of QT 300 °C steel were inferior compared to that of QT 190 °C steel; however, the total elongation was improved by 2.9% for QT 300 °C steel. The elevated YS and TS of the QT 190 °C steel were attributed to the increased micro hardness caused by the increased TM fraction. Furthermore, the high HER of the QT 190 °C steel was elucidated by the reduced micro void formation compared to the QT 300 °C steel under the same reduction ratio. That was because QT 300 °C steel, comprised mainly of bainite, has a higher fraction of blocky retained austenite that, when subjected to deformation, transforms into mechanically induced blocky martensite, acting as a significant source of micro voids. Finally, enhanced total elongation in QT 300 °C steel was attributed to more stable retained austenite during deformation compared to the QT 190 °C steel.</p><h3>Graphical Abstract</h3><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":703,"journal":{"name":"Metals and Materials International","volume":"31 8","pages":"2253 - 2265"},"PeriodicalIF":4.0000,"publicationDate":"2025-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Metals and Materials International","FirstCategoryId":"88","ListUrlMain":"https://link.springer.com/article/10.1007/s12540-024-01875-7","RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
The influence of microstructure on tensile properties and stretch-flangeability of TRIP steels with tensile strengths higher than 1.0 GPa has been investigated under various Quenching and Partitioning conditions. Lowering the quenching stop temperature (QT) from 300 °C to 190 °C after intercritical annealing increased the volume fraction of tempered martensite (TM), decreased that of bainite, and maintains that of ferrite and retained austenite constant in the final microstructure. 300 °C was Ms temperature, thus, QT 300 °C sample consisted of negligible TM and 36% bainite. So, as the QT was reduced to 190 °C, the TM phase was integrated into the bainite up to 13.8%. The yield strength (YS), tensile strength (TS), and hole expansion ratio (HER) of QT 300 °C steel were inferior compared to that of QT 190 °C steel; however, the total elongation was improved by 2.9% for QT 300 °C steel. The elevated YS and TS of the QT 190 °C steel were attributed to the increased micro hardness caused by the increased TM fraction. Furthermore, the high HER of the QT 190 °C steel was elucidated by the reduced micro void formation compared to the QT 300 °C steel under the same reduction ratio. That was because QT 300 °C steel, comprised mainly of bainite, has a higher fraction of blocky retained austenite that, when subjected to deformation, transforms into mechanically induced blocky martensite, acting as a significant source of micro voids. Finally, enhanced total elongation in QT 300 °C steel was attributed to more stable retained austenite during deformation compared to the QT 190 °C steel.
期刊介绍:
Metals and Materials International publishes original papers and occasional critical reviews on all aspects of research and technology in materials engineering: physical metallurgy, materials science, and processing of metals and other materials. Emphasis is placed on those aspects of the science of materials that are concerned with the relationships among the processing, structure and properties (mechanical, chemical, electrical, electrochemical, magnetic and optical) of materials. Aspects of processing include the melting, casting, and fabrication with the thermodynamics, kinetics and modeling.