Comparative study on microstructure and mechanical properties of a C-Mn-Si steel treated by quenching and partitioning (Q&P) processes after a full and intercritical austenitization

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• 作者：Shu Yan^a ; ^{yanshu_neu@sina.com} ; Xianghua Liu^a ; ^b ; Wayne J. Liu^b ; Taosha Liang^c ; Bin Zhang^a ; Lizhong Liu^d ; Yang Zhao^d
• 关键词：Q&P process ; Retained austenite ; Product of strength and elongation ; Mechanical stability ; TRIP effect
• 刊名：Materials Science and Engineering: A
• 出版年：2017
• 出版时间：27 January 2017
• 年：2017
• 卷：684
• 期：Complete
• 页码：261-269
• 全文大小：3178 K
• 卷排序：684

文摘

A C-Mn-Si steel with lean microalloy elements was treated by a series of quenching and partitioning (Q&P) processes after a full or intercritical austenitization (hereinafter referred as F-QP and I-QP process, respectively). The discrepancy in microstructure and mechanical properties of the samples under these two heat treatment processes was investigated. The results indicate that the austenite grains are mainly film-like in the F-QP samples, while blocky austenite grains account for the majority in the I-QP samples. And the later contains a larger amount of retained austenite than the former. In addition, the reason why the austenite fraction decreases with the increasing of partitioning time after the peak value can be related to the bainite transformation due to the dynamic change of phase region in the continue cooling transformation (CCT) diagram of untransformed austenite with carbon enrichment. The I-QP samples show higher product of strength and elongation (PSE) but relatively lower strength, while the F-QP samples are just the reverse. Notably, the one-step I-QP samples show an excellent strength–ductility balance, of which the tensile strength and total elongation are 1140–1280 MPa and 17–22%, respectively. The exponential function and Olson-Cohen (O-C) model were utilized to fit the variation of retained austenite fraction with strain. By comparison, retained austenite in the I-QP sample is more sensitive to the increasing strain, i.e., lower mechanical stability.