Authors' reply
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Authors' Reply YASUYA OHMOR[ and IMAO TAMURA In our previous article on the aging process of highcarbon martensite, 11) we have claimed the following two points: one is the quite basic fact that the parallel striated contrasts observed in the aged high-carbon martensite do not arise from the planar structures similar to that formed in the case of spinodal decomposition, but arise from the line defects such as dislocations; and the other is an interpretation of the origin of the striations. Taylor e t al. t2j confirmed, using a much more precise technique compared with our visual inspection, that the striations are always almost normal to the streaks formed on the reflected spots in the selected area electron diffraction patterns and that the striations can also be observed even in the orientation such as the [111] zone where the tweedlike images cannot be expected by our rather complicated model. On this point, we appreciate very much the quite important information given by Taylor e t al. TM This suggests that we should change our interpretation, although further detailed observation will be necessary to raise a new model. The first point which is the most important and shows that the striations do not arise from planar structures, however, has not been affected by the results of Taylor e t al. TM Of course Taylor e t al. mentioned that there can be components of structural periodicity, implying that 2588--VOLUME 24A, NOVEMBER 1993
the periodic images due to the planar structures can be observed even in the case with a slight inclination to the incident beam. The periodic structures arising from the spinodal decomposition in the alloys examined so far, however, can be resolved only in the case where the modulated planes are exactly parallel to the incident beam and are very sensitive to the Bragg conditions. 13'4j Thus, it is difficult to imagine that the modulated planar structures inclining about 20 to 30 deg to the incident beam direction (this is not a slight inclination) can be clearly observed as in Figure 2 in the previous article, tll It can, therefore, be concluded that the striations do not arise from some planar structures due to spinodal decomposition. If the striations are due to some line structures, the most probable interpretation of such structures will be of dislocations and the disklike broadening of the reciprocal lattices normal to these line defects will produce the diffuse streaks observed. The other points which were raised by Taylor e t al. 12~ are the X-ray line broadening, tS1 the increase of resistivity trj by aging, and the disappearance of the tweedlike structure by aging at 120 ~ prior to the e-carbide pre9 121 The line broadening in this case, Isj however, cipitation. is thought to arise from the local decrease of tetragonality due to the carbon redistribution and does not seem to conflict with the present interpretation. TMAnother possibility to increase the line width is the initial stage of a coherent precipitation of e-carbide, because this process occurs almost simultaneously
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