266 JOHNSTON: ELASTIC behavior of metals 



conductivity for heat or electricity, etc. According to Faust and 

 Tammann, 7 on the other hand, the change of properties on defor- 

 mation is parallel to the formation of smaller crystallites. 



Whichever be the correct interpretation — if indeed these views 

 are mutually exclusive — the fact remains that changes in the 

 properties of a metal ensue upon deformation, the most important 

 one from a practical standpoint being an increase in its rigidity. 

 The considerations presented in this paper are not inconsistent 

 with either of the above views, and in addition, account easily 

 for the increased rigidity of metal which has been strained. 

 For, exactly as in the case of the consolidation of loose snow to 

 a block of ice, as soon as the stress reaches an appropriate value 

 (the lower elastic limit), melting and flow into the interstitial 

 spaces take place, with immediately subsequent recrystalliza- 

 tion; this process continues until flow is no longer possible (the 

 upper elastic limit), whereupon increased stress produces a rup- 

 ture of the material. Now, the actual process of flow diminishes 

 the volume of the spaces into which flow is possible, and to this 

 extent diminishes the inequality of pressure acting on liquid and 

 solid; hence it requires progressively higher pressures absolutely 

 (though at the same temperature the same excess of pressure on 

 the solid) to produce flow; in other words, the rigidity of the 

 material is increased. 



Moreover, it is a well-known fact that the strength of eutec- 

 tics (which are always fine-grained) is always greater than that of 

 their components; further, that the varieties of steel possessing 

 the greatest tensile strength (e.g., vanadium steels) are very 

 fine-grained. From the standpoint of this paper, such metals 

 are strong because they are fine-grained, and hence, if we wish to 

 make a steel of high tensile strength, we should endeavor to obtain 

 a very fine-grained structure, producing this by whatever means 

 (addition of foreign material, heat-treatment, or mechanical 

 treatment) may be found suitable for this purpose. 



Summary. The object of this preliminary note is to establish 

 the* existence of a parallelism between the elastic properties of 



7 Z. physik. Chem., 75: 108-26. 1911. 



