Research on Fatigue Crack Growth Rate of Electron Beam Welded Joint of TA1 Medium Plate

Electron beam welding（ EBW） tests have been conducted on TA1 commercially pure titanium medium plates with a thickness of 30 mm.The effect of EBW welding process on microstructures and properties of TA1 material has been investigated by observing the microstructures and conducting Vickers hardness tests on base metal,heat affected zone and weld seam of the welded joints.The effects of microstructure distributional difference on the macroscopic crack growth path and crack propagation rate of welded specimens are discussed by combining the fatigue crack growth characteristics with the microstructures in different parts of the joint.Test results show that compared with the base metal of TA1,the weld seam and heat affected zone（ HAZ） of the welded joint have higher fatigue crack growth resistance,which leads to the deflection of fatigue crack propagation path and the paths extend to base metal finally.Compared with the base metal with equiaxed α phase,the serrated α and α columnar crystals produced by EBW welding have a restrict impact on the fatigue crack growth,which makes the fatigue crack growth rate of the HAZ and weld seam lower than that of the base metal.Under test conditions with stress ratio of 0.1,the fatigue crack growth rate of weld seam is the lowest,the fatigue crack growth rate of HAZ is the second,and the base metal showes the highest fatigue crack growth rate.