(21) X-Ray Micro Computed Tomography Based Study of the Effects of Copper-Rich Segregation Structures on Microstructurally-Small Fatigue-Crack Propagation in Al-Cu Alloys
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Microstructural features significantly influence fatigue crack growth, particularly during the early stages of initiation and growth, which can account for the majority of life. In the present study, high-resolution X-Ray micro computed tomography (uCT) is used to study the influence that individual copper-rich segregation (CRS) structures have on microstructurally-small fatigue-crack (MSFC) propagation. Several single-crystal specimens of Al-Cu are fabricated and heat-treated to produce specific CRS structures, where their density and distribution are varied. By observing the crack propagation path and interaction with the CRS structures periodically using X-Ray uCT, the mechanisms governing how such features influence the early stages of crack growth are examined. With the capability to control the density and distribution of the copper segregation structures relative to loading direction, design of optimal copper segregation structures to decelerate MSFC growth rates by producing tortuous crack paths to maximize closure is proposed.
Jacob Hochhalter, PhD ‘10Materials Research Engineer, Durability and Damage Tolerance Branch, NASA Langley Research Center
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