Panin Sergey, Vlasov Ilya, Maksimov Pavel, Moiseenko Dmitry, Maruschak Pavlo, Yakovlev Alexander, Schmauder Siegfried, Berto Filippo
Institute of Strength Physics and Materials Sciences SB RAS, 634055 Tomsk, Russia.
School of Advanced Manufacturing Technologies, Tomsk Polytechnic University, 634055 Tomsk, Russia.
Materials (Basel). 2020 Oct 13;13(20):4531. doi: 10.3390/ma13204531.
The structure and mechanical properties of the 09Mn2Si high-strength low-alloyed steel after the five-stage helical rolling (HR) were studied. It was revealed that the fine-grained structure had been formed in the surface layer ≈ 1 mm deep as a result of severe plastic strains. In the lower layers, the "lamellar" structure had been formed, which consisted of thin elongated ferrite grains oriented in the HR direction. It was shown that the five-stage HR resulted in the increase in the steel fatigue life by more than 3.5 times under cyclic tension. The highest values of the number of cycles before failure were obtained for the samples cut from the bar core. It was demonstrated that the degree of the elastic energy dissipation in the steel samples under loading directly depended on the area of the grain boundaries as well as on the grain shapes. The fine-grained structure possessed the maximum value of the average torsional energy among all the studied samples, which caused the local material structure transformation and the decrease in the elastic energy level. This improved the crack resistance under the cyclic mechanical loading. The effect of the accumulation of the rotational strain modes at the grain boundaries was discovered, which caused the local structure transformation at the boundary zones. In the fine-grained structure, the formation of grain conglomerates was observed, which increased the values of the specific modulus of the moment of force. This could be mutually compensated due to the small sizes of grains. At the same time, the coarse-grained structures were characterized by the presence of the small number of grains with a high level of the moments of forces at their boundaries. They could result in trans-crystalline cracking.
研究了09Mn2Si高强度低合金钢在五阶段螺旋轧制（HR）后的组织和力学性能。结果表明，由于严重的塑性变形，在约1mm深的表层形成了细晶组织。在较下层，形成了“片状”组织，它由沿HR方向取向的细长铁素体细晶粒组成。结果表明，五阶段HR使钢在循环拉伸下的疲劳寿命提高了3.5倍以上。从棒材芯部切取的试样获得了最高的失效前循环次数值。结果表明，加载时钢试样中的弹性能耗散程度直接取决于晶界面积和晶粒形状。细晶组织在所有研究试样中具有最大的平均扭转能值，这导致了局部材料组织转变和弹性能级的降低。这提高了循环机械加载下的抗裂性。发现了晶界处旋转应变模式的积累效应，这导致了边界区域的局部组织转变。在细晶组织中，观察到晶粒团聚体的形成，这增加了比力矩模量的值。由于晶粒尺寸小，这可以相互补偿。同时，粗晶组织的特征是在其边界处存在少量具有高力矩水平的晶粒。它们可能导致穿晶开裂。
