Abstract by Kaylee Johnson
Chemistry and Biochemistry
Nondestructive Testing of Aluminum
Second Harmonic Generation (SHG) occurs when two photons of equal energy combine at the surface of a material to generate a single photon with twice the energy. The amount of signal produced varies based on the make-up and structure of the material it hits. The SHG signal changes significantly in relation to deformation and chemical sensitization in materials allowing for detection of small chemical and morphological changes. An example of testing for chemical changes is using SHG to detect sensitization in naval grade Al. When this sensitization occurs, a new material, beta phase, is formed from the Mg in the alloy moving toward the grain boundaries. Beta phase is prone to both corrosion and material failure. There are no practical methods to detect whether beta phase has formed and needs to be repaired or replaced. Using SHG we have been able to detect differences in SHG response with changing degrees of sensitization. We have been working on finding a trend that would allow the Navy to detect signs of failure with a nondestructive material evaluation.