Wojtacha Anna, Kozłowska Aleksandra, Skowronek Adam, Gulbay Oguz, Opara Jarosław, Gramlich Alexander, Matus Krzysztof
Faculty of Mechanical Engineering, Department of Engineering Materials and Biomaterials, Silesian University of Technology, Konarskiego 18a St, Gliwice, 44-100, Poland.
Faculty of Mechanical Engineering, Materials Research Laboratory, Silesian University of Technology, Konarskiego 18a St, Gliwice, 44-100, Poland.
Sci Rep. 2025 Jul 2;15(1):22843. doi: 10.1038/s41598-025-05854-9.
The isothermal heat treatment processing routes are designed for a novel 0.17 C-3.1Mn-1Si-0.55Al-0.22Mo-0.034Ti-0.073 V steel, aiming to obtain a homogeneous fine lath-type microstructure consisting of bainitic ferrite and retained austenite (RA). The phase transformation of the investigated steel is studied employing high-resolution dilatometry. Isothermal heat treatment cycles below and above the martensite start (M) temperature are performed to analyse the kinetics of bainitic transformation as well as the thermal stability of retained austenite. Microstructural characterization is carried out using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The quantitative analysis of individual microstructural constituents is performed based on the differences in diffraction pattern quality using the deep learning (DL) evaluation method and compared with the results of X-ray diffraction (XRD) measurements. The thickness of bainitic ferrite laths (BFL) is predicted using an approach integrating thermodynamic and kinetic parameters, achieving overall good agreement with the experimental observations. It is demonstrated that the isothermal holding temperature of 400 °C is the most beneficial material state in terms of the kinetics of bainitic transformation and stabilization of RA. The microstructure is consisted of fine BFLs with a mean thickness of 124 nm, the lath-type RA (10.3 vol%), and a small fraction of martensitic-austenitic islands.
针对一种新型的0.17C-3.1Mn-1Si-0.55Al-0.22Mo-0.034Ti-0.073V钢设计了等温热处理工艺路线，旨在获得由贝氏体铁素体和残余奥氏体（RA）组成的均匀细板条组织。采用高分辨率热膨胀仪研究了该钢的相变。在马氏体开始（M）温度上下进行等温热处理循环，以分析贝氏体转变动力学以及残余奥氏体的热稳定性。使用扫描电子显微镜（SEM）、电子背散射衍射（EBSD）和透射电子显微镜（TEM）进行微观结构表征。基于深度学习（DL）评估方法，利用衍射花样质量的差异对各个微观结构成分进行定量分析，并与X射线衍射（XRD）测量结果进行比较。采用一种整合热力学和动力学参数的方法预测了贝氏体铁素体板条（BFL）的厚度，与实验观察结果总体吻合良好。结果表明，就贝氏体转变动力学和残余奥氏体的稳定性而言，400℃的等温保温温度是最有利的材料状态。微观结构由平均厚度为124nm的细BFL、板条型残余奥氏体（10.3体积%）和一小部分马氏体-奥氏体岛组成。
