Effect of microstructure on fatigue crack growth of wire arc additive manufactured Ti-6Al-4V

In the present paper, the effect of microstructure on fatigue crack growth (FCG) behavior of wire arc additive manufactured (WAAMed) Ti-6Al-4V was investigated. The fatigue crack growth rate (FCGR) in WAAMed sample with heat-treated was lower than that in the forged sample. The 1050-AA (1050 degrees C/2h/air cooling (AA)+550 degrees C/ 4h/air cooling (AC)) sample showed the lowest FCGR because of its highest Delta KT (18.01 MPa m1/2), while the forged sample exhibited the highest FCGR because of its lowest Delta KT (13.3 MPa m1/2). The larger the plastic zone (rp) at the crack tip, the higher values of the stress intensity factor transition factor (Delta KT), the lower FCGR in the sample. In addition, the sample with continuous grain boundary alpha (alpha GB) or discontinuous alpha GB showed different FCG behavior and its mechanisms were discussed. For the sample with continuous grain boundary alpha (alpha GB), the crack in the horizontal sample (H-sample) passed through the continuous alpha GB and grew along with basket-weave microstructure and colony microstructure, while the crack in the vertical sample (V-sample) grew along with basket-weave microstructure. Therefore, the FCGR in these samples showed anisotropy. For the sample with discontinuous alpha GB, the crack in the H-sample and the V-sample passed through the discontinuous alpha GB and grew along with colony microstructure or basket-weave microstructure. The two samples showed the same FCG behavior, which indicated that there was no anisotropy.

Automated summary

This study investigates the effect of microstructure on fatigue crack growth (FCG) behavior in WAAM Ti-6Al-4V material. It was found that Delta KT plays a significant role in influencing the FCGR. Samples with different grain boundary alpha structures exhibit different FCG behaviors, with continuous alpha GB structures showing anisotropy.