Examination of Microstructure

The gouge sites had a bright metallic luster and various shapes (Figs. 11.22 and 11.23). Microstructural examinations of the gouged regions revealed that plastic deformation of the metal had not occurred. 

Pressure testing of the finned oil cooler in Fig. 15.29 revealed leaks. Examination of the interior of the cooler after sectioning in the vicinity of the leaks revealed a small cavity in the weld zone in the corner of some fins (Fig. 15.14) and porous areas inside the channel in the welded zone in other fins. Microstructural examinations of specimens cut through the sites revealed interconnected voids resulting from either shrinkage during solidification of the weld or lack of fusion of the base metal and weld metal. 

Microstructural examinations of the external surface revealed an interconnecting network of graphite flakes embedded in a matrix of iron oxide. 

Microstructural examination of billets A and B by SEM revealed the major difference between them was in the CVD layer deposited on the fibers before additional densification steps were performed. In billet A the layer appeared to be porous (see Figure 6), whereas billet B exhibited a uniformly dense CVD coating. The remaining portions of the matrix are derived from the liquid pitch impregnations, and these looked similar for A and B. It is possible that the lower shear strength of billet A can be attributed to the more porous and probably weaker CVD layer. 

Chen KN, Fan A, Rief R. Microstructure examination of copper wafer bonding. J Electr Mater 2001 30 (4) 331-335. 

In order to be able to optimize the mechanical stability of such systems, more tests must be performed along with in-depth microstructural examination of the interfaces. 

Microstructural examination of the powder processed materials indicated the pure Ni adial free-surface (Figures 5 and 6) the differences in the peak stresses within the AI2O3 between the Case 1 and Case 2 predictions were significantly greater than within the specimen interior (Figure 4). This result is due to the fact that the plastic strains are predicted to be considerably larger at this location, and differences in the assumed flow characteristics of the composite therefore become more obvious. 

Microstructural examination of their samples quenched from different stages of the process shows that two different diffusion paths (labeled A and B in fig. 43) are followed. Each path leads separately to particles of the phase Nd2Fe14B (). In order of increasing temperature the following events occur ... 

Microstructure examination of a finished surface is an important analysis to be carried out. It is very useful, since it can provide important information about the material properties and reliability. It can show the surface cracks or other machining damage improper machining causes transformation of the microstructure. So, microstructure examination is important in this investigation to show the effect of the DP and RB on the surface microstructure as well as the plastic deformation depth. 

Williamson SL, Armentrout RS, Porter RS, McCormick CL (1998) Microstructural examination of semi-interpenetrating networks of poly(N, N-dimethylacrylamide) with cellulose or chitin synthesized in lithium chloride N, N-dimethylacetamide. Macromolecules 31 8134-8141... 

Microstructural Examination of Silica Aerogels and Their Composites... 

In practice, nearly the entire array of characterization tools has been employed to determine the identities of unknown phases. The ensuing discussion begins by addressing the microstructural examination of phase distributions. Full identification of any particular phase in the microstructure requires knowledge of both crystal structure and chemical content each of these topics is discussed with respect to the types of analyses best suited to obtaining the necessary information. Both elementary techniques and advanced analytical approaches are mentioned one should... 

Cheng X, Chen L, Peng C, Chen Z, Zhang Y, Fan Q. Catalyst microstructure examination of PEMFC membrane electrode assemblies vs. time. J Electrochem Soc 2004 151 A48-52. 

Crevice corrosion on titanium typically generates irregularly shaped pits. Microstructural examination of hand-polished and etched sections of crevices often reveals a surrounding layer of predpi-tated titanium hydride in a alloys. These are a by-product of hydrogen reduction at cathodic sites surrotmding the crevice. 

Y. Chen, K. Sridharan, T. R. Allen, S. Ukai, Microstructural examination of oxide layers formed on an oxide dispersion strengthened ferritic steel exposed to supercritical wateT, Journal of Nuclear Materials 359 (2006) 50-58. 

Microstructural examinations of both composites showed that, reinforcing SiC particles were uniformly distributed in the matrixes. Although the pure A1 matrix and the Al-8 wt.% Mg alloy matrix composites had similar amounts of SiC particles (60 vol. %), the resulting porosity contents were quiet different (Table 1). Addition of 8 wt.% Mg to the matrix decreased the amount of porosity significantly as compared to pure A1 matrix composite, which can be attributed to improved... 

Y. Chen, K. Sridharan, et al., Microstructural Examination of Oxide Layers Formed on an Oxide Dispersion Strengthened Ferritic Steel Exposed to Supercritical Water, Journal of... 

The surface from which the cracks originate may not be apparent without a microstructural examination. Stress-corrosion cracks invariably produce brittle (thick-walled) fractures regardless of the ductility of the metal. 

Microstructural examinations revealed that the tube was annealed brass. All cracks originated on the internal surface at pit sites. Cracks were fine, branched, and ran through the metal grains (transgranular). Crack density over the specimens examined averaged 40 cracks per linear inch (16 cracks/cm) of surface. 

Microstructural examinations revealed that the cracks originated on the external surface (Fig. 9.15). The cracks were highly branched and transgranular. The branched, transgranular character of these cracks is typical of stress-corrosion cracking of austenitic stainless steels. The thick-walled fracture faces are also typical of cracking by this mode. 

Microstructural examinations disclosed highly branched, predominantly transgranular cracks originating on the internal surface. Cracks of this form are typical of SCC in austenitic stainless steels. 

Microstructural examinations revealed branched, transgranular cracks originating on the external surface (treated cooling water). Analysis of material covering the crack surfaces revealed the presence of chlorine. 

Microstructural examinations revealed that branched cracks originated at shallow pit sites on the external surface. The pits, which may have formed during idle periods from differential oxygen concentration cells formed beneath deposits, acted as stress concentrators. The transverse (circumferential) crack orientation and the localization of cracks along just one side of the tube revealed that bending of the tube was responsible for the stresses involved. 

Visually, the sites resemble mechanically induced gouges or indentions in the tube wall. However, examinations of the microstructure at these sites revealed no distortion of the metal, which would certainly occur had the indentions been mechanically induced. The erosive character of the highly localized turbulent flow was the predominant aspect responsible for the metal loss, there being little or perhaps no contribution from corrosion of the metal. 

Examination of the microstructure of the cavitated surface will commonly disclose evidence of deformation such as twins (Neumann hands) in carbon steel and general cold working in other metals (Case History 12.6). Damage from cavitation can be differentiated from attack by a strong mineral acid, which can produce a similar surface appearance, by observing the highly specific areas of attack characteristic of cavitation. Acid attack is typically general in its extent (Case History 12.6). 

Microstructural examinations revealed graphitic corrosion (see Chap. 17) of the metal surfaces. The evidence of graphitic corrosion indicates one of the following ... 

Microstructural examinations revealed V-shaped openings along the tube seam, some extending into as much as 50% of the tube wall thickness. The incompletely closed seam provided a crevice in which differential concentration cells developed (see Chap. 2, Crevice Corrosion ). The resulting localized corrosion caused the observed pits. 

Most of the surface is covered with a black corrosion product that is thicker in relatively low-flow areas near the hub. This layer of soft corrosion product can be shaved from corroded surfaces. Microstructural examinations revealed flakes of graphite embedded in iron oxide near the surfaces. 

The specimen in Fig. 17.15 is part of a cast iron pump impeller. The spongelike surface contours are apparent, as is the black coating that covers surfaces exposed to the cooling water. Microstructural examinations revealed preferential deterioration of the iron matrix surrounding the graphite flakes. 

Other instruments which have been devised for microstructure examination include the X-ray microscope, with greater resolving power than the EM (Ref 41), and the electron microprobe, capable of indicating subtle changes in composition over small specimen areas (Refs 57 62)... 

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