Metallography And Microstructures Of Zinc And Its Alloys

Metallography and Microstructures of Zinc and Its Alloys

Page 1 of 1 Metallography and Microstructures of Zinc and Its Alloys, Metallography and Microstructures, Vol 9, ASM Handbook, ASM International, 2004, p. 933–941

Metallography and Microstructures of Zinc and Its Alloys

Microexamination Grain size is best determined under polarized light illumination, which displays each grain as a different shade, depending on orientation (Fig. 2, 6, 7, 32). Grain counts can be made with good accuracy. Grain boundaries are poorly defined under bright-field illumination.

Fig. 32 Alloy 5, UNS Z35531, die cast with rapid freezing, unetched. (a) Polarized light illumination shows grain size but not alloy phases. Grains are larger than primary crystallites in (b), indicating that the zinc grains extend into the eutectic. (b) Fine primary crystallites of solid solution in fine lamellar eutectic. The fine structure imparts toughness and high strength to the alloy. Compare with Fig. 14 and 15 As-polished. Etchant 2, Table 1. 250×

Dendrite arm spacing can be measured on micrographs of selected areas using the linear intercept procedure in ASTM E 112 (Ref 8). Soundness values (porosity levels) can also be obtained in cast alloys by the use of quantitative analysis on a volume percent basis. Specimens to be examined for corrosion should be in the as-polished condition.

Reference cited in this section 8.

“Test Methods for Determining the Average Grain Size,” E 112, Annual Book of ASTM Standards, Vol 03.01, ASTM

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