Metallurgy; an introduction to the study of physical metallurgy . lecules, andthus each retains its original electrical conductivity unaltered,and the alloy exhibits a behaviour which is the arithmeticmean of its two constituents. The curve of conductivities isthus—^if plotted in relation to composition by volume—asimple straight line joining the values for the two simple an actual case is probably never met with in practice,and, indeed, it can be shown that there must be a slight degreeof mutual solid solubility between any two metals—completeabsence of molecular interpenetration
Metallurgy; an introduction to the study of physical metallurgy . lecules, andthus each retains its original electrical conductivity unaltered,and the alloy exhibits a behaviour which is the arithmeticmean of its two constituents. The curve of conductivities isthus—^if plotted in relation to composition by volume—asimple straight line joining the values for the two simple an actual case is probably never met with in practice,and, indeed, it can be shown that there must be a slight degreeof mutual solid solubility between any two metals—completeabsence of molecular interpenetration cannot really exist. 112 STUDY OF PHYSICAL METALLURGY Consequently, although several binary systems of alloys^—such as those of cadmium and zinc, and of lead and antimony—closely approach the limiting case, in the majority of binary 60 ?Z40 P \ 1 jg 20 \ y ? ^--— ^.--^ 10 20 30 Au 10 BO 30 IOO%CaCu 40 50 60Composition. Fig. 38.—Curve of Speoiflo Electric Conductivity typical of anunbroken series of Solid Solutions. (Alloys of Gold and Copper.). 0Co IOO%CaCu Fig. 39. 40 SO 60Composition, -Curve of Specific Electric Conductivity typical of a Eutecti-ferous Series. (Alloys of Cobalt and Copper.) alloys of the eutectiferous type, the curve of conductivitydrops sharply at either end for a short distance and then becomeshorizontal. This form is, of course, typical of the intermediatetype of alloys in which there is a Mmited range in which thetwo metals form solid solutions, the remainder of the systems PHYSICAL PROPERTIES OF ALLOYS 113 being eutectiferous. Here we have a drop of the conductivitycurve at either end very marked, with a straight line formingthe intermediate part. Typical curves of this kind are givenin Figs. 38 and 39, representing data obtained from the alloysof gold and copper, which form an unbroken series of solidsolutions, and those of copper and cobalt, which are eutecti-ferous over the greater part of their range. Reference tothese figures serves to
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