Austenite formation and mechanical behavior of a novel TRIP- assisted steel with ferrite/martensite initial structure
Austenite formation and mechanical behavior of a novel TRIP- assisted steel with ferrite/martensite initial structure
复制标题
DOI：
10.1016/j.msea.2020.140468
复制
发表时间：
2020-11
期刊：
影响因子：
6.4
通讯作者：
Xingli Gu;Yunbo Xu;Xu Wang;Ren-dong Liu;F. Peng;Hongliang Liu;R. Misra;Jiayu Li;X. Hou
中科院分区：
文献类型：
--
作者：
Xingli Gu;Yunbo Xu;Xu Wang;Ren-dong Liu;F. Peng;Hongliang Liu;R. Misra;Jiayu Li;X. Hou
新开发的具有铁素体/马氏体初始结构的 TRIP 辅助钢旨在研究整个退火周期期间的微观结构演变。结果与传统冷轧TRIP钢进行了比较。通过实验和建模相结合，阐明了不同初始显微组织形成奥氏体的特征。结果表明，相间退火获得的新奥氏体晶粒细小、分布均匀。它由在预先存在的马氏体（Mpre）基体中形成的针状结构和出现在相界面或旧奥氏体晶界处的块状结构组成。含有 Mpre 的试样中奥氏体形成的动力学在早期加热阶段相似，然后在温度高于 770 °C 时随着 Mpre 含量的降低而降低。实验和DICTRA结果均表明，Mprefraction为90%和100%的试样的奥氏体分数在加热结束时几乎达到最大值，并在临界退火过程中随着等温保温时间的延长而降低。此外，铁素体和预存相界面处的残余奥氏体与邻近的回火马氏体遵循Kurdjumov-Sachs（K-S）关系，而只有部分残余奥氏体与邻近的铁素体具有相同的关系。此外，残余奥氏体的量随着Mpre含量的增加而增加，尽管它们在拉伸试验期间抵抗马氏体转变的稳定性与冷轧试样相似并且更高。结果，屈服强度从 590 MPa 增加到 753 MPa，抗拉强度从 995 MPa 略有增加到 1046 MPa，M 预折率从 50% 增加到 100%，总伸长率约为 30%，与第三代先进高强度钢类似。
A newly developed TRIP-assisted steel with ferrite/martensite initial structure was designed to investigate the microstructural evolution during overall annealing cycle. The results were compared with the traditional cold-rolled TRIP steel. The characteristic of austenite formation from different initial microstructure was clarified based on combining the experiments and modeling. Results indicated that the new austenite obtained during intercritical annealing was fine-grained and uniformly-distributed. It comprised of acicular structure formed in pre-existing martensite (Mpre) matrix and blocky structure occurred at phase interfaces or prior austenite grain boundaries. The kinetics of austenite formation in specimens involving Mpreare similar in the early heating stage, and then decreased with decreasing Mprecontent at temperatures greater than 770 °C. Both experimental and DICTRA results indicated that the austenite fractions of specimens with 90% and 100% Mprefraction attained almost the maximum at the end of heating, and decreased with isothermal holding time during the intercritical annealing. Moreover, the retained austenite at interfaces of ferrite and pre-existing phase followed the Kurdjumov-Sachs (K–S) relationship with adjacent tempered martensite, while only part of the retained austenite had identical relationship with neighboring ferrite. In addition, the amount of retained austenite increased with Mprecontent, although their stability against martensite transformation during tensile testing was similar and greater than that of cold-rolled specimen. As a consequence, the yield strength was increased from 590 MPa to 753 MPa and the tensile strength increased slightly from 995 MPa to 1046 MPa with Mprefraction increasing from 50% to 100%, and the total elongation was ~30%, similar to the third generation advanced high strength steels.