<p> Digital Holography (DH) is an emerging tool for use in the structural investigation of temperature dependent material processes. DH is able to reveal deformations and topological details at ultrahigh sensitivity (a few tens of nanometers) for particular details such as point-like objects and interfacial structures, allowing for the investigation of a range of processes. However, while DH is able to provide high precision data, the height measurement range is limited by the probe wavelength. Therefore a 'synthetic' wavelength created from the superposition of two or more individual wavelengths is often required in order to increase the measurement range to a suitable value dependent upon the object dimensions. </p><p> The use of multiple wavelengths attached to one system thus allows for surface height measurements over a relatively long range. In addition as the complex wave-front of each wavelength can be captured simultaneously in one digital image, real-time performance is achievable. In this thesis a number of materials processes were investigated at differing temperatures. The structural changes associated with the martensite to austenite phase transformation were measured using dual-wavelength digital holography during thermal cycling of nickel-aluminum-platinum (NiAlPt) and single-crystal Fe-15Cr-15Ni alloys. Real-time in-situ measurements reveal the formation of striations within the NiPtAl alloy at ∼70°C, and the FeCrNi alloy at ∼520°C. The results demonstrate that digital holography is an effective technique for acquiring non-contact, high precision information of the 3D surface evolution of alloys at high temperatures.</p>
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:1537812 |
| Date | 19 June 2013 |
| Creators | Thiesing, Benjamin P. |
| Publisher | Northern Arizona University |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
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