Effects of Microstructure and Environment on Fatigue Properties of Investment Cast Ti-6Al-4V Alloy Welds

Abstract:

Effects of microstructural and environmental factors on fatigue crack propagation behavior of welded regions of cast Ti-6Al-4V alloy were investigated. Fatigue crack propagation tests were conducted for the welded regions, which were processed by two different welding methods: gas tungsten arc (GTA) welding and electron beam (EB) welding, under various load ratios (R=0.1, 0.9) and atmosphere (air, seawater). EB weld consisting of very thin α platelets had the faster crack propagation rate than the base metal and GTA weld, regardless of load ratio and atmosphere. Fatigue crack propagation rates at high load ratio (R=0.9) were faster than those obtained at low load ratio (R=0.1) and there was no crack closure at high load ratio (R=0.9), indicating that fatigue crack propagation at high load ratio was mainly controlled by intrinsic factors such as microstructure. Fatigue crack growth resistances in seawater atmosphere were slightly lower than those in air, but showed the similar trend with variation of specimen conditions. The degrees of crack closure were almost same regardless of specimen conditions in seawater atmosphere, suggesting that the fatigue crack propagation in seawater was mainly controlled by intrinsic factors such as microstructure.

• Periodical: Materials Science Forum (Volumes 475-479)
• Pages: 595-598
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.475-479.595
• Online since: January 2005
• Authors: Hak Cheol Lee, Jin Won Choi, Jin Keun Oh, Nack Kim
• Keywords: EB Weld, Fatigue Crack Growth (FCG), GTA Welding, Investment Casting, Ti₆Al₄V Alloy

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