PSI - Issue 82

Juraj Belan et al. / Procedia Structural Integrity 82 (2026) 119–124

122 4

Juraj Belan et al. / Structural Integrity Procedia 00 (2026) 000–000

structures. Cracks on the surface became more dominant, more numerous, and significantly longer, locally reaching a length of almost 80 µ m.

a)

b)

Fig. 1. Microstructure of Ti6Al4V alloy; a) starting stage, b) after oxidation annealing 1050°C/1.5 h, etch. 1.5 ml HF + 2 ml HNO3 + 10 ml H2O, OM.

a)

b)

Fig. 2. Formation of an α-case layer on the surface of Ti6Al4V alloy after isothermal holding at a) 1050°C/0.5 h, b) 1050°C/1.5 h; at longer times, significant cracks in the α-case layer, etch. 1.5 ml HF + 2 ml HNO3 + 10 ml H2O, OM. The results of fatigue tests using a three-point bend are shown in Fig. 3.

Fig. 3. The S-N curves of Ti6Al4V after three-point fatigue test, starting stage vs. oxidation annealed specimens with a -case layer.