702 Ti-6Al-4V合金の腐食疲労き裂進展特性に及ぼす材料異方性の影響(GS-4 機械材料・材料加工(1))

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Effects of anisotropy on fatigue crack growth behavior have been investigated using CT specimens of Ti-6Al-4V alloy in laboratory air, in dry air, in 3.5%NaCl solution and in 1/3mol/l-H_3BO_3+1/30mol/l-KCl solution. The effect of crack plane orientation was not observed in laboratory air and in dry air, while a considerable effect was observed in 3.5%NaCl solution and in 1/3mol/l-H_3BO_3+1/30mol/l-KCl solution. In T-L crack plane orientation, the fatigue crack growth rate in 3.5%NaCl solution and in 1/3mol/l-H_3BO_3+1/30mol/l-KCl solution was enhanced compared with that in dry air. However, in 3.5%NaCl solution and in 1/3mol/l-H_3BO_3+ 1/30mol/l-KCl solution, their crack paths in L-T crack plane orientation were changed toward the rolling direction and accordingly the fatigue crack growth rate became lower compared with that in T-L crack plane orientation. TDS (Thermal Desorption Spectroscopy) was carried out to investigate the relation between the hydrogen evoluteion rate and fatigue crack growth behavior. Fractographic observations were performed using a scanning electron microscope (SEM).
2001-03-16