Fracture initiation/propagation parameters for duplex TiAl grain boundaries based on twinning, slip, crystal orientation, and boundary misorientation

Crystallography of Fatigue Crack Initiation and Growth in Fully Lamellar Ti-6Al-4V

“…Whether or not these cracks continue to grow after initiation depends on details of the local microstructure. In passing, although not directly related to the present study due to the difference in crystal symmetries, it is worth mentioning that microcrack initiation in Ti-Al alloys has been observed at grain boundaries that are suited for slip transfer during monotonic loading [48][49][50][51] in Ti-Al alloys. In these studies, a statistically significant number of cracked and intact boundaries were analyzed using a combination of crystallographic and geometric criteria to identify those that were prone to microcrack nucleation.…”

“…This is indicative of a boundary that is crystallographically suited for slip transfer. Of course, there are morphological dependences as well, [47][48][49][50][51] such as the grain boundary inclination with respect to the loading axis, but m¢ does not account for them. A total of 18 slip systems were considered in each colony: 3 basal, 3 prism, and 12 first-order pyramidal slip systems.…”

Overview of constitutive laws, kinematics, homogenization and multiscale methods in crystal plasticity finite-element modeling: Theory, experiments, applications

“…A fip consists of several physical/geometrical factors that could enhance crack nucleation due to localized shear strain concentrated at the boundary. Variations of this idea are presented in equations as F i , where i is a label [380][381][382][383][384]. For example, the fip parameter F 1 is the product of three terms:…”

“…In addition to the comparison of corresponding simulations with experiments it would also make sense to derive adequate damage criteria, such as modified Griffith models, which can help to establish a quantitative link between mechanical quantities that the CPFE method provides and damage nucleation. Promising approaches along these lines were recently investigated by the group of Bieler [199,200,[380][381][382][383].…”

Study of 3-D stress development in parent and twin pairs of a hexagonal close-packed polycrystal: Part I – in-situ three-dimensional synchrotron X-ray diffraction measurement

“…Under tension along the c-axis of the crystal, the lack of easy slip systems results in reorientation of a discrete part of the grain by mechanical twinning. It is reported that formation of twins can affect crack nucleation [3,4] and the stress field around the crack tip [5][6][7][8][9]. Hence, understanding the mechanism of load sharing between grains and twins could effectively lead to a better insight into the analysis of crack initiation and propagation and a better estimation of the lifetime of in-service components.…”