Microstructure‐Dependent Local Fatigue Cracking Resistance of Bimodal Ti–6Al–4V Alloys

• Published in: Advanced engineering materials Vol. 20; no. 4
• Main Authors: Zeng, Ling‐Rong, Lei, Li‐Ming, Yang, Jia, Luo, Xue‐Mei, Zhang, Guang‐Ping
• Format: Journal Article
• Language: English
• Published: 01.04.2018
• Subjects: Crack growth rate; Fatigue; grain boundary; microstructure; Ti alloy
• ISSN: 1438-1656; 1527-2648
• DOI: 10.1002/adem.201700702

The fatigue crack growth behavior of the bimodal Ti–6Al–4V alloys with two different volume fractions of the primary α phase (αp) of 76 and 36% is investigated by the in situ testing technique. The experimental results show that the crack growth rate of the αp = 36% Ti–6Al–4V alloy is lower than that of the αp = 76% one. The local fatigue crack growth rate is evidently decreased by the various boundaries including αp grain boundaries, boundaries between the αp phase and basketweave microstructure, and α/β lamellar interfaces. A criterion associated with the boundary characteristics is obtained to evaluate the grain boundary resistance to the fatigue crack growth in the engineering alloys. Local crack growth rate and fatigue cracking resistance of the Ti–6Al–4V alloys with different volume fractions of primary α phases are investigated in situ in SEM. Local resistance to fatigue cracking related to the boundary characteristics is evaluated quantitatively by EBSD. A criterion for the grain boundary resistance to the crack growth is proposed.