Metallurgy; an introduction to the study of physical metallurgy . eadily subjected to plastic extension while its surface is keptunder constant observation (^).- What is observed in these cir-cumstances is as foUows : so long as the metal remains in theelastic stage, or rather until the yield-point is reached, there isno visible change in the appearance of the surface ; elasticextension produces no visible effects under the soon, however, as the yield-point is reached and plasticor permanent deformation occurs, definite changes are seento take place on the surface observed under
Metallurgy; an introduction to the study of physical metallurgy . eadily subjected to plastic extension while its surface is keptunder constant observation (^).- What is observed in these cir-cumstances is as foUows : so long as the metal remains in theelastic stage, or rather until the yield-point is reached, there isno visible change in the appearance of the surface ; elasticextension produces no visible effects under the soon, however, as the yield-point is reached and plasticor permanent deformation occurs, definite changes are seento take place on the surface observed under the the previously plain white faces of the crystals fineblack Unes appear, at first in isolated groups, but in steadilyincreasing numbers until the surfaces of the crystals are cross-hatched with fine black fines. In iron or very mild steel theselines appear to be curved, irregular and branched, but in suchmetals as lead, tin, silver, gold, etc., the lines are very straightand regular. The appearance of these fines is illustrated in PLATE Fig. 97.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectmetals, bookyear1922
