102 BELL SYSTEM TECHNICAL JOURNAL 



systems, in which a solid phase, composed principally of one con- 

 stituent, is dispersed in a liquid phase, whose composition and abun- 

 dance is a function of the temperature and the gross composition of 

 the alloy. These facts suggest that the character of a solder may be 

 related in the wiping range to the following properties: solid-liquid 

 ratio, solid particle size, viscosity of the liquid phase, tendency to 

 segregation, and the interfacial tension between solid and liquid 

 phases. 



Objects of Investigation 



The objects of the investigation may be summarized under the 

 following headings: 



1. Character of Flow: It was hoped that by means of plasticity deter- 

 minations, data would be obtained permitting the flow of the various 

 alloys to be formulated in simple terms, and that appropriate flow 

 constants could be evaluated which would suffice to describe the nature 

 and extent of deformation under specified conditions of stress. This 

 object was largely realized through the discovery that the flow is 

 similar in character to that of many colloidal dispersions, corresponding 

 approximately to what would be expected if a power relation exists 

 between stress and velocity gradient, 



2. Relation of Plasticity to Workability: The primary purpose of the 

 plasticity studies was to determine if the information thus obtained 

 could be related to the working characteristics of the solders. If a 

 clear-cut relation could be found, the plastometer could be employed 

 in testing new alloys for use as solders, and in making control tests on 

 solders as supplied to the splicers. As a matter of fact, a simple 

 relation between the plasticity data and workability was found to 

 exist, on which can be based a method of employing the plastometer in 

 research studies of solders. In addition the plasticity appears to be 

 very sensitive to composition changes, and its measurement with the 

 plastometer should in consequence be useful as a control test. 

 Whether this latter possibility can be realized in engineering practice 

 has not, as yet, been ascertained. 



3. Plasticity and Solid-Liquid Ratio: Early in the investigation it 

 was suggested that the plasticity might be related to the solid-liquid 

 ratio. If this were so, the plasticity and its temperature gradient 

 could be predicted from the equilibrium diagram for any particular 

 alloy, and calculation of solid-liquid ratios could be used to supplant 

 or to corroborate plasticity determinations. While for any one 

 solder, of course, the plasticity increases with the ratio of liquid to 

 solid, no relation common to any group of solders was found to hold 

 between plasticity and the solid-liquid ratio. 



