Metallographic procedures

In an auto theft case, the vehicle information number tab (VIN) had been removed and a second one welded on to replace it. The VIN tab was examined in the SEM and the weld, the remaining fracture surfaces, the grinding marks and the swarf remnant from the grinding were easily identified and photographed. These features are shown in Figure 1. Metallographic procedures were also used after the SEM analysis to confirm the fact that a welding operation had been performed. 

Cautions. Precise determination of the cause of weld-root cracks can be difficult. Determining correct repair procedures and preventive measures may require metallographic examinations and analyses. 

Numerous compounds are observed in the Li-Ag phase diagram. The alloys are heated under Ar and cast in mild steel crucibles for metallographic examination, with homogeneity achieved by remelting under vacuum. Similar procedures were employed in an earlier study, except that H2 was used in place of Ar. An Ar cover gas was also employed to prepare the brasslike yj phase in the Li-Ag system for structural study. The silver and lithium were melted together in an iron crucible for 15-30 s before cooling without quenching to minimize the loss of lithium-. ... 

Sample Size. Since the aim of this study is to relate the data to the metallurgical structure, all analytical measurements were made on metallographical sections taken from the objects. This procedure limited the volume which could be sampled. 

Specimen preparation involves wet grinding to remove the surface layer, which may be decarburized or otherwise nonrepresentative of the bulk of the specimen, followed by standard metallographic polishing and etching. This procedure ensures a flat, reproducible surface for the x-ray examination, and allows a preliminary examination of the specimen to be made with the microscope. In grinding and polishing, care should be taken not to produce excessive heat or plastic deformation which would cause partial decomposition of both the martensite and austenite. 

Weld procedure qualification tests for submerged arc welding of the main vessel shell and cladding destructive tests metallographic techniques to check that Heat Affected Zone (HAZ) reheat cracks are absent. 

TbRe4Si2 with the ZrFe4Si 2-type structure was synthesized and characterized by Pecharskij (1979) by means of X-ray powder and metallographic techniques [P42/mnm, a = 7.325(5) and c = 4.106(2)]. Samples were prepared by arc melting powder compacts under argon, followed by an annealing procedure in evacuated silica tubes at 800°C for 400 + 600 h. Starting materials were 98.4% Tb, 99.99% Si and 99.99% Re. 

Tests for corrosion of alloys in deep melts should involve primarily immersion tests. The procedures to be followed in using immersion or crucible tests are similar to those used for thin deposits namely, exposure of specimens with weight change versus time measurements and metallographic examination of the exposed specimens. 

Metallographic examination offers valuable information once the sample is sectioned, mounted, hand-p>olished, and KroU etched per recommended procedures outlined in Ref 37. The remaining metal sample thickness and the alpha-case layer thickness along the sample surface can be determined from the cross-sectioned mount. This alpha-stabilized layer is not visually discemable in a alloys, but should be readily apparent when heavier than a few tenths of a mil in ot/p and P alloys (see Fig. 11). Subscale or... 

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