Standard test specimens of zinc bronze (Cu88, Sn10, Zn2)--Parts I and II . D, Specimen 437; looX Fig. 14.—Microstructure as affected by the rate of cooling[A and C were etched with ferric chloride; B and D with ammonium hydroxide containing hydrogen peroxide] Standard Zinc-Bronze Test Bars 53 the angles between the interlocking fingers next to the tin-richlayers of the dendrites. From 790° C to 500° C, as the alloy, nowsolid, cools, no appreciable structural change other than diffusionoccurs. At 500°, the ^ solution breaks up into an intimate mix-ture of the a and h solutions of copper and tin
Standard test specimens of zinc bronze (Cu88, Sn10, Zn2)--Parts I and II . D, Specimen 437; looX Fig. 14.—Microstructure as affected by the rate of cooling[A and C were etched with ferric chloride; B and D with ammonium hydroxide containing hydrogen peroxide] Standard Zinc-Bronze Test Bars 53 the angles between the interlocking fingers next to the tin-richlayers of the dendrites. From 790° C to 500° C, as the alloy, nowsolid, cools, no appreciable structural change other than diffusionoccurs. At 500°, the ^ solution breaks up into an intimate mix-ture of the a and h solutions of copper and tin. The 6 solutionis still richer in tin than is the jS. This break-up at 500° is anal-ogous to the formation of pearlite in steel. The solid solutionsOf, jS, 5, etc., are probably not simple solutions of tin in copper ofprogressively increasing tin content but their theoretical natureis not of importance here. The 88-10-2 alloy, then, at ordinary. Fig. 12.—Illustration of pine-tree^ or dendritic crystalline structure temperatures, directly after casting, consists of a mass of solidtreelike crystals the branches of which constitute the a solutionof tin and copper (plus the zinc) and show a variation in composi-tion from center outward. In the interstices between thebranches are inclusions of bronzite, a eutectoid consistingof a mechanical mixture of a and b solutions of copper and tinwhich resulted from the break up of a pre\dousIy existing con-stituent, the /3 solution of copper and tin. By increasing thetin content of the alloy the amount of bronzite increases at theexpense of the a solution until at about tin; there is no free a. 54 Technologic Papers of the Bureau of Standards Beyond this point free 5 solution appears and at approximately28 per cent Sn the bronzite has disappeared and the alloy is all6 solution. IV. RELATION BETWEEN METHOD OF CASTING ANDMICROSTRUCTURE From theoretical considerations, no essential chan
Size: 1511px × 1653px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpublisherwashingtongovtprin
