Issue 77

C. N. Vikas et alii, Fracture and Structural Integrity, 77 (2026) 120-137; DOI: 10.3221/IGF-ESIS.77.09

Figure 11: Microstructure of TMAZ showing (a) Advancing side (AA 2024) - elongated and deformed grains with partial recrystallization, (b) Retreating side (AA 6061) - distorted grain structure with flow lines, (c) Interface between TMAZ and stir zone showing transition in grain morphology.

Figure 12: Heat-affected zone microstructure showing (a) HAZ in AA 6061-T6 with coarsened Mg ₂ Si precipitates, (b) HAZ in AA 2024-T351 with over-aged Al ₂ Cu precipitates. Heat-Affected Zone (HAZ) The HAZ is adjacent to TMAZ which experienced heat cycles without much undergoing plastic deformation, exhibited over-aged microstructures with coarsened precipitates. Fig 12 presents the HAZ microstructure for both base materials. The HAZ exhibited the lowest hardness across the entire weld cross-section, typically 15-25% lower than the base

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