Issue 77

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

approximately 74% of the AA 6061-T6 base material strength and 49% of the AA 2024-T351 base material strength. The tensile strength increased with higher rotational speed can be linked to multiple causes. Higher rotational speeds generate higher frictional heat, resulting in increased temperatures and increased plastic flow of the material. This enhances better intermixing of the dissimilar alloys and reduces the tendency for defects, namely tunnel voids or insufficient bonding. Additionally, the dynamic recrystallization process is more active at higher temperatures, leading to finer grain structures in the SZ, which strengthens the joint according to the Hall-Petch relationship[15][16].In the parameter range experimented, the increased feed rate maintains beneficial thermal cycles that prevent abrupt grain growth and precipitate coarsening while ensuring sufficient material consolidation. The shorter heat cycle exposure at higher feed rates helps retain strengthening precipitates in the heat-treatable alloys [17][18].

Sample No.

TRS (rpm)

WS (mm/min)

UTS (MPa)

S/N Ratio (dB)

1 2 3 4 5 6

600 600 600 700 700 700

25 30 35 25 30 35

145 158 167 163 178 185

43.2274 43.9731 44.4543 44.2438 45.0084 45.3434

7

800

25

190

45.5751

8

800

30

205

46.2351

9

800

35

230

47.2346

Table 6: S/N ratios for UTS.

Figure 4: Stir zone hardness values.

125