Further Observations on Slip-Bands in Metallic Fractures. 557 



" Further Observations on Slip-Bands in Metallic fractures. 

 Preliminary Note." By WALTER ROSENHAIN, B.A., B.C.K. 

 Communicated by Professor EVVING, F.E.S. Received 

 February 9, Read February 16, 1905. 



[PLATR 14.] 



The main purpose of the present paper is to describe what the author 

 believes to be a novel method of investigating the micro-structure of 

 metals, and to give some account of preliminary results obtained by its 

 aid. The method was devised in order to throw further light on the 

 true nature of slip-bands, and the preliminary results relate mainly to 

 this question. The investigation described in this paper is thus a 

 further development of researches carried out in the first place by 

 Professor J. A. Ewing, F.R.S. and the author jointly (" The Crystal- 

 line Structure of Metals," Bakerian Lecture, 1899),* and subsequently 

 by the present author alone (" The Plastic Yielding of Iron and 

 Steel.")! In the course of correspondence on the latter paper, M. F. 

 Osmond drew the attention of the author to certain experimental facts 

 concerning the behaviour of slip-bands under oblique illumination, which 

 had formerly escaped attention. The difficulty met with in convincing 

 M. Osmond of what the author believes to be the true interpretation of 

 these phenomena has led him to seek another means of examining the 

 character of slip-bands, which should not be based upon the interpreta- 

 tion of effects of illumination. 



A direct means of examining the surface configuration of a piece of 

 metal upon which slip-bands have been produced would be presented 

 by a transverse section of such a specimen, provided that the section 

 could be produced with an absolutely sharp edge, and that the 

 sectional elevation of the features in question were large enough to be 

 visible under the microscope. The difficulties in the way of obtaining 

 a section even approximately satisfying the first of these conditions are, 

 however, considerable. No useful result can be obtained by cutting 

 the specimen through and simply polishing the exposed section. 

 It is -a well-known fact that the extreme edges of specimens prepared 

 by the usual methods of polishing are always more or less rounded off, 

 so that it becomes impossible to focus upon any definite edge with 

 high-power lenses; and even apart from this defect, there would be no 

 guarantee that the edge represented a true section of the pre-existing 

 surface, since the processes of cutting, grinding, and polishing would 

 probably fray out the edge and remove some of the weaker or more 

 delicate features. In some departments of optics a somewhat simil; 



* ' Phil. Trans,' A, 1899, vol. 193, pp. 353 to 375. 



f 'Journal of the Iron and Steel Institute,' 1904, pp. 33o to 390. 



