Experimental Study on Fatigue Crack Growth in a Titanium Alloy

Abstract:

A series of test for the fatigue crack growth rate da/dN and the threshold ΔKth values were performed with CT specimens on a ship-condenser material titanium alloy plate and rolled ring. Base metal, welded joint and HAZ (heat affected zone) materials were used to make different test specimens. Specimens made from the titanium plate were cut along L-T direction, those made from rolled ring were obtained along C-R and L-R direction respectively. Results show that the fatigue crack growth rate value of welded joint is much higher than those of base metal and HAZ material. The da/dN values of C-R direction specimens are much higher than those of L-R direction specimens, whereas the ΔKth values are lower. It means that welding process may lead to a great reduction in the fatigue property for titanium alloy and the effect of crack orientation on fatigue property is not negligible for titanium alloy. To select a proper orientation of titanium material is therefore very important in engineering practice. Results also indicate that a simplified method can be used to calculate the ΔKth values for titanium material, that is, ΔKth values may be calculated directly from the da/dN expression in a zone near the threshold and the laborious measurements of ΔKth may therefore be saved.

• Periodical: Key Engineering Materials (Volumes 297-300)
• Pages: 2489-2494
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.297-300.2489
• Online since: November 2005
• Authors: Qing Fen Li, Peng Wang, Dong Liu, Jun Wang, Hong Juan Liu, Yan Bo Wang
• Keywords: Fatigue Crack Growth (FCG), Heat Affected Zone (HAZ), TiAl, Weld Joint

References

[1] GB6398-86: Standard Method of Test for Fatigue Crack Growth Rate of Metallic Material (Chinese Standard Institution, Beijing 1986).

[2] GB9447-88: Standard Method of Test for Fatigue Crack Growth Rate of Metallic Material (Chinese Standard Institution, Beijing 1988).

[3] K.T. Wang and G.Y. Qin: Development and Application of Material Vol. 10 (1996), p.8.