粒界反応型析出による常温疲労強度の改善

概要

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Effects of grain-boundary reaction (GBR) precipitates on the improvement of fatigue-crack initiation and propagation resistances were investigated in an austenitic 21Cr-4Ni-9Mn (21-4N)steel at room temperature. Grain boundaries were considerably serrated by the GBR precipitates. Fatigue cracks were initiated along slip lines and then propagated within the grains. The short cracks, whose length was one or two grain diameters, were deflected at the GBR nodules and propagated around the GBR nodules. Long cracks, which were longer than about 1.0mm, propagated initially within grains and then along grain boundaries. When the cracks propagated along grain boundaries, the crack propagation rates were lower along the serrated grain boundaries than along the straight ones. The geometrical effects such as the crack deflection and the crack closure, which were induced at the deflected portions of the crack paths, were important in improving the short and long crack propagation resistances.
社団法人日本機械学会の論文
1991-04-25