Evaluation of Fatigue Properties under Four-point Bending and Fatigue Crack Propagation in Austenitic Stainless Steel with a Bimodal Harmonic Structure
Evaluation of Fatigue Properties under Four-point Bending and Fatigue Crack Propagation in Austenitic Stainless Steel with a Bimodal Harmonic Structure
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DOI：
10.3221/igf-esis.48.52
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发表时间：
2019-03
期刊：
影响因子：
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通讯作者：
S. Kikuchi;Y. Nakatsuka;Y. Nakai;M. Nakatani;M. Kawabata;K. Ameyama
中科院分区：
文献类型：
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作者：
S. Kikuchi;Y. Nakatsuka;Y. Nakai;M. Nakatani;M. Kawabata;K. Ameyama
采用粉末冶金技术制备了具有双峰谐波组织的奥氏体不锈钢(JIS-SUS304L)，该组织是一种由细晶网络包围的粗晶组织。为了研究SUS304L钢的疲劳裂纹扩展规律，在室温空气中进行了应力比R为0.1的四点弯曲疲劳试验和K下降试验。这种简谐组织材料的疲劳极限高于均匀粗晶组织材料。这是由于机械球磨形成了细小的颗粒，并抑制了气孔的形成。相反，简谐结构材料的门槛应力强度范围dKth比均匀粗晶材料的低，而裂纹扩展速率da/dN在相同的dK下较高。这些结果可以归因于简谐结构中细小颗粒的存在使有效阈值应力强度范围DKff，Th减小。
Austenitic stainless steel (JIS-SUS304L) with a bimodal harmonic structure, which is defined as a coarse-grained structure surrounded by a network of fine grains, was fabricated using powder metallurgy to improve both the strength and ductility. Four-point bending fatigue tests and K-decreasing tests were conducted in air at room temperature under a stress ratio R of 0.1 to investigate fatigue crack propagation in SUS304L. The fatigue limit of this harmonic-structured material was higher than that of the material with a homogeneous coarse-grained structure. This is attributable to the formation of fine grains by mechanical milling and to the suppression of pore formation. In contrast, the threshold stress intensity range, DKth, for the harmonic-structured material was lower than that for the homogeneous coarse-grained material, while the crack growth rates, da/dN, were higher at comparable DK. These results can be attributed to a reduction in the effective threshold stress intensity range, DKeff,th, due to the presence of fine grains in the harmonic structure.