1072 THE BELL SYSTEM TECHNICAL JOURNAL, SEPTEMBER 1953 



was found that roughness is caused by cannibalistic grain growth of the 

 nickel after recrystallization; that is, some of the grains grow at the 

 expense of others, thus causing surface roughness. In this connection it 

 may be interesting to refer to the photomicrographs of Fig. 24. In each, 

 the top, light and almost structureless portion depicts the basic material 

 (steel). The adjacent layer characterizes the nickel plating, the columnar 

 structure being typical of the electro-plating process. The next layer 

 shows the chromium flash and the black portion, a block used to mount 

 the specimen. 



The top view of Fig. 24 is representative of the material as received 

 from the supplier. The center view illustrates satisfactory stress relief 

 annealing. The bottom view illustrates unsatisfactory annealing. It 

 will be noted that after satisfactory annealing some recrystallization 

 of the nickel has taken place and that grain growth has started but has 



MATERIAL AS FURNISHED 



MATERIAL SATISFACTORILY STRESS-RELIEF ANNEALED 



MATERIAL ANNEALED AT TOO HIGH A TEMPERATURE 



Fig. 24 — Photomicrographs of sections of cards (lOOOX) 



