Effect of Ultrasonic Radiation Energy on Microstructure and Mechanical Properties of TC4 Titanium Alloy TIG Welded Joints
The coarse grain size and shallow weld penetration in welded joints have always been a challenge for titanium alloy TIG welding.To solve this problem,this work investigates the influence of ultrasonic coaxial assisted TIG(U-TIG)method on the formation,microstructure,and mechanical properties of TC4 titanium alloy weld seams by controlling ultrasonic radiation energy.The results show that the comprehensive properties of the welded joint are significantly improved after applying ultrasound.The maximum penetration depth of U-TIG weld seam reaches 1.34 mm,which is 112.7％higher than TIG.In addition,the microhardness and tensile strength of the weld joint reach up to 553 HV and 1244.72 MPa,which are 44.7％and 17％higher than TIG,respectively.In conventional TIG welding,the grain of the weld seam is mainly coarse columnar crystals.When the ultrasonic power reaches 1200 W,the grains of the weld seam change from columnar crystals to fine equiaxed crystals.The compression effect of ultrasound concentrates the energy of the arc,thereby improving the penetration depth of the weld.Ultrasonic cavitation and acoustic streaming effects play an important role in refining the grain size of the weld,thereby improving the strength of the weld.
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