Fabrication of the ultrafine-grained ferrite with good resistance to grain growth and evaluation of its tensile properties
Fabrication of the ultrafine-grained ferrite with good resistance to grain growth and evaluation of its tensile properties
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DOI：
10.1016/j.msea.2013.09.026
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发表时间：
2014-01
期刊：
影响因子：
6.4
通讯作者：
M. Hamzeh;A. Kermanpur;A. Najafizadeh
中科院分区：
文献类型：
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作者：
M. Hamzeh;A. Kermanpur;A. Najafizadeh
对低合金钢AISI 8620进行形变热处理，包括冷轧和退火，以形成以贝氏体为起始显微组织的超细晶粒组织。试样首先在425 °C下等温淬火以形成贝氏体显微组织，然后冷轧90%的厚度压下量。退火在550-700 °C下进行不同的时间。在不同的处理阶段的试样的显微组织和拉伸性能进行了表征。冷轧贝氏体在退火过程中表现出显著的热稳定性。在600 ° C和低于600 °C时不发生显著的重结晶。结果表明，使用贝氏体显微组织细化晶粒的显着潜力。在700 °C和650 °C下退火10 min和120 min后，形成平均晶粒尺寸约为0.7 µm的铁素体显微组织。90%冷轧贝氏体组织的硬度为380 HV，屈服强度为1110 MPa，延伸率小于2%。在断裂表面观察到的分层被认为是一个有效的因素低的延展性。超细等轴晶组织的硬度为250 HV，屈服强度为886 MPa（约为粗晶钢的2倍），总延伸率约为8%，断口有少量分层。
Thermomechanical treatment including cold rolling followed by annealing was conducted on a low alloy steel AISI 8620 to develop an ultrafine grain structure using bainite as the starting microstructure. The specimens were first austempered at 425 °C to form the bainitic microstructure and then cold rolled by 90% reduction in thickness. Annealing was conducted at 550–700 °C for different times. Microstructures and tensile properties of specimens were characterized during different stages of the treatment. Cold rolled bainite showed notable thermal stability during annealing. Significant recrystallization did not take place at and below 600 °C. The results show a notable potential for grain refinement using a bainitic microstructure. A ferritic microstructure with the average grain size of about 0.7 µm was developed after annealing at 700 °C and 650 °C for 10 min and 120 min. The 90% cold rolled bainite possessed the hardness of 380 HV and yield strength of 1110 MPa with the elongation of below 2%. The delamination observed in the fracture surface was considered as an effective factor for the low ductility. The ultrafine equiaxed grain structure possessed the hardness of 250 HV, yield strength of 886 MPa (about twice of the coarse-grained steel) and the total elongation of about 8% with some small delamination in the fracture surface.