Fatigue behavior of ultrafine grained medium Carbon steel processed by severe plastic deformation
Fatigue behavior of ultrafine grained medium Carbon steel processed by severe plastic deformation
复制标题
剧烈塑性变形加工超细晶中碳钢的疲劳行为
DOI：
10.1088/1757-899x/63/1/012163
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
E. Kerscher
中科院分区：
文献类型：
--
作者：
C. Ruffing;Yu. Ivanisenko;E. Kerscher
在具有超细晶组织的材料[1，2]中，已经观察到材料的持久极限显著提高。然而，由于这一效应在钢中尚未被研究，我们对一种碳含量为0.45wt.-%的非合金中碳钢进行了高温高压扭转处理的疲劳试验[3-5]。对具有不同初始碳化物形态的圆盘进行了处理，HPT后的硬度比初始状态增加了1.75-3.2倍，因此增加的幅度取决于初始碳化物形态。获得的最大硬度为810HV。将圆盘切割成4 mm×1 mm×600克的棒状疲劳试件。在硬度达到500HV之前，耐久极限与硬度成线性关系。在硬度较高的情况下，这种情况不再是这样，在这种情况下，固有的和工艺引发的缺陷会导致较低的疲劳极限。在载荷比R=0.1时，四点微弯最大疲劳极限超过1050 Mpa。断口分析显示，由非金属夹杂物引起的HPT或鱼眼断裂导致了不同的裂纹起始点，如预裂纹和剪切带[6，7]。
The endurance limit of materials has been observed to be significantly increased in materials with an ultrafine grained microstructure [1, 2]. As this effect, however, has not yet been investigated in steels, fatigue experiments of an unalloyed medium carbon steel with a carbon content of 0.45 wt.-%, which was treated by high pressure torsion (HPT)[3-5] at elevated temperature were carried out. The treatments were applied to discs which had different initial carbide morphologies and showed an increase of hardness after HPT by a factor of 1.75–3.2 compared to the initial states, whereby the amount of increase depends on the initial carbide morphology. The maximum hardness achieved was 810 HV. The discs were cut into fatigue specimens in the form of bars of the size of 4 mm x 1 mm x 600 gm. Until a hardness of 500 HV the endurance limits correspond linearly with the hardness. This is no longer the case at higher hardness values, where inherent and process-initiated flaws lead to lower fatigue limits. The maximum endurance limit exceeded 1050 MPa in 4-point-micro-bending and at a load ratio of R= 0.1. Fractography revealed different crack initiation sites like pre cracks and shear bands [6, 7] resulting from HPT or fisheye fractures initiated from non-metallic inclusions.