PSI - Issue 80

Tomáš Vražina et al. / Procedia Structural Integrity 80 (2026) 244 – 255 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

253

10

5(e) with grain structure obtained by EBSD mapping (Fig. 2b). The highest proportion of intercrystalline crack occurred in the sample tested with the ε a = 0.35%. No striations or striation-like patterns were explicitly observed in FeAlOY. Nevertheless the slip steps indicative of plastic deformation were evident on intergranular facets (Fig. 5d f). Near the crack initiation site in FeAlOY, PSMs exhibited a wall-channel structure (Fig. 5d) similar to PSMs observed at the edge of the fracture surface of copper (Polák et al., 2025).

Fig. 8 (a) KAM map of Sanicro 25 with labeled plastic strain localization (b) EBSD map detailed the neighboring grains in Sanicro 25 (c) Detail of intercrystalline cracking on the extracted sample of Sanicro 25. (d) STEM micrograph of dislocations near the GB of FeAlOY. (e) Formation of PSB on the neighboring grains of FeAlOY. (f) Dense dislocation structure in fine grains of FeAlOY In FeAlOY specimens subjected to cyclic loading, PSMs were absent on the outer surfaces Fig.8(d). This absence can be attributed to the presence of yttria-oxide nanoparticles in FeAlOY that enhances its strength and so hand in hand brittleness at room temperature, leading to premature cracking that prevents the accumulation of sufficient plastic strain on the specimen ’s outer surface. However, near the crack tip, the cyclic plastic zone experiences elevated stress concentrations, facilitating the activation of multiple slip systems (Polák et al., 2025) and the accumulation of localized plastic strain for the production of PSMs as shown in Fig 6(e). FeAlOY scrutinized in this work exhibited a bimodal grain size distribution, with some grains reaching 1 mm in diameter and other only 1 µm Thompson (Thompson, 1972) and Liang (Liang and Laird, 1989b) investigated coarse grain structures and find that larger grains can facilitate PSB-GB interactions and subsequent intergranular cracking. This statement was proven on the FeAlOY specimen Fig. 8(e) and with Fig. 5. The internal dislocation structure of FeAlOY, shown in Fig. 7(a-c), revealed PSBs despite the weak contrast between yttria oxides and dislocations, complicating the detailed analysis of PSB-GB interactions. In fine grain areas a higher dislocation density was observed Fig. 8(f). Yet the larger grains exhibited more developed PSBs, aligning with the concept that cyclic plasticity may localize differently depending on grain size and morphology. While some studies suggest crack initiation is more likely in larger grains (Zhu et al., 2019) due to localized cyclic plasticity, recent work by Barbe (Barbe et al., 2020) emphasizes the role of bimodal grain size distributions, indicating that boundaries between large and small grains may act as critical initiation sites due to heterogeneous stress distribution and distinct grain morphologies.