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Most current scanning electron microscopes (SEMs) have the ability to analyze samples in a low vacuum mode, whereby a partial pressure of water vapor is introduced into the SEM chamber, allowing the characterization of nonconductive samples without any special preparation. Although the presence of water vapor in the chamber degrades electron backscatter diffraction (EBSD) patterns, the potential of this setup for EBSD characterization of nonconductive samples is immense. In this chapter we discuss the requirements, advantages and limitations of low vacuum EBSD (LV-EBSD), and present how this technique can be applied to a two-phase ceramic composite as well as hydrated biominerals as specific examples of when LV-EBSD can be invaluable.

Electron backscatter diffraction (EBSD), when employed as an additional characterization technique to a scanning electron microscope (SEM), enables individual grain orientations, local texture, point-to-point orientation correlations, and phase identification and distributions to be determined routinely on the surfaces of bulk polycrystals. The application has experienced rapid acceptance in metallurgical, materials, and geophysical laboratories within the past decade (Schwartz et al. 2000) due to the wide availability of SEMs, the ease of sample preparation from the bulk, the high speed of data acquisition, and the access to complementary information about the microstructure on a submicron scale. From the same specimen area, surface structure and morphology of the microstructure are characterized in great detail by the relief and orientation contrast in secondary and backscatter electron images, element distributions are accessed by energy dispersive spectroscopy (EDS), wavelength dispersive spectroscopy (WDS), or cathodoluminescence analysis, and the orientations of single grains and phases can now be determined, as a complement, by EBSD.

Developing a quantitative understanding of ultrasonic beam propagation in engineering materials such as Ti-6A1-4V is important because flaw signals can be altered greatly by the macrostructure that the ultrasonic beam propagates through between the transducer and the flaw. Two consequences of the macrostructure are particularly important: 1) back scattered noise which competes with flaw signals and 2) forward scattered signals and the associated beam profile fluctuations which can modulate the strength of flaw signals [1,2,3], These effects are particularly important when ultrasonic beams are used to detect subtle defects such as unvoided, uncracked hard-alpha inclusions (regions with a high content of interstitial nitrogen or oxygen), because the flaw signal is inherently weak due to a small mismatch of acoustic impedance. Each of these effects is controlled by the inherently complex macrostructure which develops during routine processing. Current theories suggest that the most important physical feature which controls noise is the two-point correlation of elastic constants, which is in turn controlled by local variations in crystallographic orientation [4]. Therefore, in order to quantify the effects of the macrostructure on ultrasonic beam propagation, one must determine the elastic constants on a microscopic level with length scales less than the ultrasonic wavelength, approximately 600 μm at 10 MHz.