Metallurgy; an introduction to the study of physical metallurgy . either side of the eutectic the quantities ofheat evolved duringcooling are plotted asordinates against thecomposition of thealloys as abscissae theresulting curve showsa peak or maximumwhich indicates theeutectic composition,in the manner shown in Fig. 37. In the same way, the endof a eutectic hne where it either abuts against a verticalhne indicating a compound or a pure metal, or where itmerges into the curved solidus of a series of soHd solu-tions, as at F and H in Fig. 48, may be inferred by con-tinuing such
Metallurgy; an introduction to the study of physical metallurgy . either side of the eutectic the quantities ofheat evolved duringcooling are plotted asordinates against thecomposition of thealloys as abscissae theresulting curve showsa peak or maximumwhich indicates theeutectic composition,in the manner shown in Fig. 37. In the same way, the endof a eutectic hne where it either abuts against a verticalhne indicating a compound or a pure metal, or where itmerges into the curved solidus of a series of soHd solu-tions, as at F and H in Fig. 48, may be inferred by con-tinuing such a curve as that of Fig. 37 to the point where itcrosses the axis of composition, but this extrapolation is alwaysrather uncertain. Similarly, where a compound is formed bya reaction between sohd and Hquid portions of an alloy, thecomposition of the compound may be determined by finding,much as in the case illustrated in Fig. 49, the compositioncorresponding to the maximum heat-evolution ; but here it isparticularly important to be certain that in every case the. Composition oF Alloy Fig. 37.—^Diagram of Thermal AnalysisCurves. THERMAL STUDY OP METALS AND ALLOYS 105 reaction has had time to complete itself, otherwise the quantityof heat evolved may depend more on the rate of cooling thanon the true composition of the compound. The constitutional diagram as discussed in the preceding pageswould almost appear to be httle more than a summary of thepurely thermal data obtained from heating and cooling while these are extremely useful and important in assistingan investigator to establish such a diagram, they are not inthemselves quite sufficient for that purpose, and their indica-tions must be checked and amphfied by microscopic many cases this is merely a question of observing whether anew constituent appears where the supposed hues of thediagram would lead one to anticipate its coming, and whetherthe typical eutectic structure occurs, as the diagram woulds
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectmetals, bookyear1922
