Jovanović Gvozden, Glišić Dragomir, Dikić Stefan, Međo Bojan, Marković Branislav, Vuković Nikola, Radović Nenad
Institute for Technology of Nuclear and Other Mineral Raw Materials, Metallurgical and Environmental Engineering, Bulevar Franše d'Eperea 86, 11000 Belgrade, Serbia.
Faculty of Technology and Metallurgy, University of Belgrade, Karnegijeva 4, 11120 Belgrade, Serbia.
Materials (Basel). 2023 Nov 16;16(22):7192. doi: 10.3390/ma16227192.
Two medium-carbon microalloyed steels with a predominant acicular ferrite microstructure were investigated in this study in order to determine the initial micro-crack formation mechanism and the role of acicular ferrite structure in cleavage fracture. In order to ensure cleavage fracture, samples were investigated at -196 °C for uniaxial tension and four point bending fracture. Previous investigations have shown that cleavage fracture for steels with a predominant acicular ferrite microstructure has not been initiated by the fracture of coarse TiN particles as in ferrite-pearlite, bainite, or martensitic microalloyed steels. The average maximal thickness of cementite plates measured in this work is 0.798 µm and 0.966 µm, for V and TiV steel, respectively. The corresponding stress values required for their fracture according to Griffith's equation are 1970 MPa and 1791 MPa, respectively. Estimated values of the effective surface energy for the V steel with an average cementite volume fraction of 3.8% range from 40 Jm to 86 Jm, and for the TiV steel with an average cementite volume fraction of 18.3% range from 55 Jm to 82 Jm. The fracture of coarse cementite plates was found to not to be responsible for the cleavage fracture initiation in case of both steels.
本研究对两种具有主要针状铁素体微观结构的中碳微合金钢进行了研究，以确定初始微裂纹形成机制以及针状铁素体结构在解理断裂中的作用。为确保解理断裂，对样品在-196°C下进行单轴拉伸和四点弯曲断裂试验。先前的研究表明，具有主要针状铁素体微观结构的钢的解理断裂并非像铁素体-珠光体、贝氏体或马氏体微合金钢那样由粗大TiN颗粒的断裂引发。在本工作中测得的渗碳体板的平均最大厚度，V钢和TiV钢分别为0.798 µm和0.966 µm。根据格里菲斯方程，它们断裂所需的相应应力值分别为1970 MPa和1791 MPa。平均渗碳体体积分数为3.8%的V钢的有效表面能估计值在40 J/m²至86 J/m²范围内，平均渗碳体体积分数为18.3%的TiV钢的有效表面能估计值在55 J/m²至82 J/m²范围内。结果发现，两种钢的粗渗碳体板的断裂均与解理断裂的起始无关。
