SHORT FATIGUE-CRACK PATH DETERMINANTS IN POLYCRYSTALLINE NI-BASE SUPERALLOYS

被引:25
作者
BOYDLEE, A
KING, JE
机构
[1] Department of Materials Science and Metallurgy, University of Cambridge, Cambridge, Pembroke St
关键词
D O I
10.1111/j.1460-2695.1994.tb00768.x
中图分类号
TH [机械、仪表工业];
学科分类号
0802 ;
摘要
Fifty seven short fatigue cracks in the Ni-base superalloy APl have been examined, to ascertain how the paths taken by growing fatigue cracks are determined. The observations were made on the surface of a smooth specimen, and on the exposed fracture surfaces. Three dimensional reconstructions of the vulnerable microstructures in the vicinity of the cracks were produced. Initiation occurred in mode II, with the lines of intersection of the initiation sites with the specimen top surface orientated at approximately 45-degrees to the tensile axis. These initiation sites developed in slip bands which crossed a large grain and at least one other grain via a grain boundary with a low angle of misorientation. 'River markings' on one of the initiation facets, indicated that the crack first opened from the top centre of the initiation grain. Subsequent to initiation, the growth paths of these cracks are related to the misorientations of the grains and the progress of the crack front.
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页码:1 / 14
页数:14
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