Leveraging high-energy X-Ray diffraction microscopy and crystal plasticity simulations to study grain scale stress redistribution within a Ti-7Al sample subjected to creep

A series of far-field high-energy X-Ray diffraction microscopy (ff-HEDM) measurements gathered at discrete temporal points from the illuminated gage section of a Ti-7Al coupon subjected to creep revealed significant stress relaxation in soft grains neighboring a hard grain. A crystal plasticity finite element (CPFE) framework was used to perform a creep simulation on the tessellated volume of the gage section of the coupon based on the grain centroid data obtained from ff-HEDM. For a contiguous hard and soft grain pair, a correlation was found between grain-average stress relaxation (measured from experiments) and total accumulated slip (estimated from CPFE simulations). However, the magnitude of stress relaxation from CPFE simulation was significantly underpredicted due to the inherent homogeneous nature of the crystal plasticity framework which cannot resolve the mechanisms underpinning events (e.g., intermittent motion of dislocations, slip band formation, precipitate shearing, etc.) leading to stress relaxation in grains.