716 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Nucleus Action and Grain-growth.* — H. M. Howe discusses 

 Cohen's inoculation experiments, in which bright tin surfaces (usually 

 cold worked) were dulled when pressed against specimens of tin which 

 had previously been rendered dull. Most cases of this infection may 

 be explained on the assumption that the cold-worked metal is in a 

 metastable state, and that contact with normally crystalline metal 

 induces the change to the stable condition, a change which is accelerated 

 by raising the temperature. It is difficult, however, to apply this 

 explanation to the case of the dulling, by contact with dulled tin, of the 

 bright surface of a quietly frozen ingot of tin. The author indicates 

 the bearing on this question, of Charpy's discovery that overstrained 

 iron shows a much more rapid grain-growth between 650° and 800° C. 

 than iron which has not been overstrained. 



National Physical Laboratory.! — The existence of the compound 

 Al 9 Zn 3 has been fully established, but it is stable only within the tem- 

 perature range 254°-443° C. The microscopical effects of tensile 

 strain upon strips of various binary alloys of eutectic composition have 

 been investigated ; the differences observed in modes of deformation 

 appeared to indicate that the crystalline arrangement is fundamental Ly 

 different in different eutectics. A remarkably coarse crystallization was 

 observed in some electrolytic iron which had been prepared for experiments 

 on effects of strain at high temperatures. The iron had been annealed 

 after rolling into thin strips. It was possible to detach single crystals 

 from these strips ; the individual crystals were found to be perfectly 

 tough and ductile. 



\-' 



* Met. and Chem. Eng., ix. (1911) pp. 79-80. 

 f Nat. Phys. Lab. Ann. Eeport for 1910. 



