FIB-DIC Residual Stress Evaluation in Shot Peened VT6 Alloy Validated by X-ray Diffraction and Laser Speckle Interferometry

Abstract

Ga-ion micro-ring-core FIB-DIC evaluation of residual stresses in shot peened VT6 (Ti6Al-4V) alloy was carried out and cross-validated against other non-destructive and semidestructive residual stresses evaluation techniques, namely, the conventional sin2 ψ X-ray diffraction and mechanical hole drilling. The Korsunsky FIB-DIC method of Ga-ion beam microring-core milling within FIB-SEM with Digital Image Correlation (DIC) deformation analysis delivered spatial resolution down to a few micrometers, while the mechanical drilling of circular holes of ~2 mm diameter with laser speckle interferometry monitoring of strains gave a rough spatial resolution of a few millimeters. Good agreement was also found with the X-ray diffraction estimates of residual stress variation profiles as a function of depth. These results demonstrate that FIB-DIC provides rich information down to the micron scale, it also allows reliable estimation of macro-scale residual stresses.