Fractal Dimension of Grain-boundary Fracture for Characterization of High-temperature Fracture in Heat-resistant Alloys
Fractal Dimension of Grain-boundary Fracture for Characterization of High-temperature Fracture in Heat-resistant Alloys
复制标题
用于表征耐热合金高温断裂的晶界断裂分形维数
DOI：
10.2355/isijinternational.49.1229
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发表时间：
2009
影响因子：
1.8
通讯作者：
R. Kato
中科院分区：
文献类型：
--
作者：
Manabu Tanaka;Junji Ono;M. Sakashita;R. Kato
提出了表征材料高温断裂特征的晶界断口分维df，(2<；df<；3)，它代表了三维空间中含有晶界微裂纹的断口形态。利用立体匹配法获得的耐热合金断口高度数据，在超过一个晶界长度的长度范围内，估算了Df值及其二维值Dfp(晶界断口轮廓的分维值1<；Dfp<；2)。HS-21合金在1089K断裂时，Df值随晶界表面轮廓(Dgb，1<；Dgb<；2)分维值的增大而增大，断裂寿命和蠕变塑性随Df值的增大而增加。对钴基、镍基和铁基耐热合金的二维分维分析也得到了类似的结果。通过对缺口试件表面的分维图进行分维分析，研究了包括主蠕变裂纹扩展在内的蠕变断裂过程。并将Inconel X-750合金的断口形貌分析结果与分形分析结果进行了比较。本文所用的分形分析比FRASTA更方便、更有优势，在材料高温断裂的研究中具有广泛的适用性。
The fractal dimension of the grain-boundary fracture, Df, (2<Df<3), which represents the fracture surface pattern with grain-boundary microcracks in three-dimensional space, is proposed for characterization of high-temperature fracture in materials. The value of Df as well as its two dimensional value, Dfp (the fractal dimension of the grain-boundary fracture surface profile, 1<Dfp<2), was estimated in the length scale range more than about one grain-boundary length using the height data of fracture surfaces of heat-resistant alloys obtained by the stereo matching method. The value of Df increased with increasing fractal dimension of the grain-boundary surface profile (DGB, 1<DGB<2) in the specimens of the HS-21 alloy ruptured at 1089 K. Both rupture life and creep ductility increased with increasing value of Df in these specimens. Similar results were obtained by the two-dimensional fractal analysis on other specimens of cobalt-base, nickel-base and iron-base heat-resistant alloys. Creep fracture process including the growth of the main creep crack was examined by the fractal analysis using the fractal dimension map (FDM, a color-coded map) on the surface notched specimens. The result of the fractal analysis was compared with that of the FRASTA (fracture surface topography analysis) in the Inconel X-750 alloy. The fractal analysis used in this study is more convenient and more advantageous than the FRASTA, and is widely applicable to the investigation of high-temperature fracture in materials.