PSI - Issue 71

Gnaneshwar Sampathirao et al. / Procedia Structural Integrity 71 (2025) 484–491

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Fig. 6. Representation of Dislocations at maximum loading on Al bi-crystal with (100), (110) orientation when T=~0K

As shown in Table 2, increasing grain size leads to increase in hardness values, above, observations highlight the grain size, boundary role in dictating dislocation behaviour and mechanical response. 3.4. Effect of 10 Å thickness α -Al 2 O 3 Here, it has been tried to understand the effect of α -Al 2 O 3 layer on the substrate’s mechanical properties, Fig. 7 shows hardness variations at different indentation velocities and temperatures. Like the crystalline substrate, the hardness does not exhibit a simple trend. However, the deformation mechanism in the amorphous layer differs fundamentally from that in the crystal. Without a long- range ordered structure, the α -Al 2 O 3 layer undergoes plastic deformation via shear transformation zones (STZs) rather than dislocations.

Fig. 7. Evolution of hardness values for α -Al 2 O 3 + Al single crystal indentation on (100) surface

To better understand the atomic-scale processes in amorphous region, it has been analysed atomic strains and calculated radial distribution functions (RDFs). Upon indentation, the α -Al 2 O 3 layer undergoes structural rearrangements indicating of a phase-like transformation, as observed using OVITO Stukowski, A. (2010) visualization. However, directly identifying and visualizing the shear transformation zones (STZs) was challenging due to computational constraints and the amorphous nature of the material. Fig. 8 presents a representative RDF for