Densities and viscosities of some liquid alloys of zinc and cadmium.pdfVIP

Densities and Viscosities of Some Liquid Alloys of Zinc and Cadmium A. F. CRAWLEY The dens i t i e s and v i s cos i t i e s of the al loy sy s t e ms Zn-Sn, Cd-Sn, and Cd-Pb and of z inc - and c a d m i u m - r i c h Z n - P b and Cd-T1 al loys have been de t e rmined accura t e ly by absolute tech- niques of p roven re l i ab i l i ty . I so the rma l m o l a r vo lumes for all five s y s t e m s show posi t ive devia t ions f rom ideal mixing in a g r e e m e n t with other publ ished data. I so the rma l v i s c os i t i e s demons t r a t e l a rge negat ive devia t ions f rom ideal mixing. In each sys tem, solute addi t ions give r i s e to sharp d e c r e a s e s in v i scos i ty at the z inc- and c a d m i u m - r i c h ends of the sys tem, a phenomenon not ref lec ted in the densi ty data. To explain the v i scos i ty r e su l t s , it is p r o - posed that a l loying addi t ions to zinc and cadmium a l t e r the i n t e r a tomic bonding a s soc ia t ed with the sur face s t r u c t u r e of these m e t a l s causing d i spropor t iona te v i scos i ty changes . Re- cent su r face t ens ion s tudies have aptly demons t r a t ed that the su r f ace s of zinc and cadmium are a tomica l ly m o r e o rdered than the bulk meta l . A S pointed out in rev iews by Brush ~ and Wi t tenberg and Ofte, 2 theore t ica l s tudies of v iscos i ty have had v e r y l i t t le succes s even for s imple l iquids l ike argon, and even l e s s for l iquid me ta l s . Indeed, it might safely be said that knowledge of the re levan t fac tors in v i s - cous flow has hardly advanced despi te grea t efforts by t heo re t i c i ans . Of course , in e a r l i e r yea r s e x p e r i m e n - tal and ma themat i ca l t echniques were l e s s re f ined than in the p re sen t day. This lack of good techniques led to rationalizations of, and deductions from, w