Structure and properties of EB- and TIG-welded joints of high-strength two-phase titanium alloys

Abstract

Modern two-phase high-alloyed alloys based on titanium are characterized by a high specific strength. The thermal cycle of welding results in change of structures of weld and HAZ metal and also in deterioration of mechanical characteristics of the joint. In the work the properties of welded joints of titanium alloys VT23, T110 and high-alloyed alloy Ti-6.5Al-3Mo-2.5V-4Nb-1Cr-1Fe-2.5Zr, produced using electron beam and argon arc welding, were evaluated. In weld and HAZ metal of the TIG-welded joints of alloy Ti-6.5Al-3Mo-2.5V-4Nb-1Cr-1Fe-2.5Zr, the structure is formed with a predominance of metastable β-phase and low values of strength and impact toughness, the joints require postweld high-temperature annealing at temperature of not less than 900 °C. The joints of VT23 alloy have high values of strength and impact toughness. High-strength titanium alloy T110 is characterized by good weldability in EBW and TIG welding, has high values of impact toughness of weld metal and HAZ after annealing, the strength of welded joints is at the level of 0.9 of base metal strength. 7 Ref., 2 Tables, 4 Figures. K e y w o r d s : titanium alloys, tungsten-electrode argon-arc welding, electron beam welding, propertiesModern two-phase high-alloyed alloys based on titanium are characterized by a high specific strength, nowadays the growing attention is paid to widening the use of welded structures and assemblies of high-strength titanium alloys (σ t > > 1100 MPa) [1,2]. The weldability of twophase high-alloyed titanium alloys, the use of which may provide the greatest reduction in mass of the structure, is significantly worse than that of low-alloyed alloys, and according to this indicator they are inferior even to some highstrength steels, therefore, when developing new titanium alloys, a significant attention is paid to the possibility of producing welded joints with strength of not less than 0.90-0.95 of base material strength.The aim of the work is to evaluate the properties of welded joints of both industrial and also new two-phase high-titanium alloys having σ t > > 1000 MPa (Table 1), developed at the E.O.Paton Electric Welding Institute, as well as to study the influence of thermal cycle of welding and postweld heat treatment on structural and phase transformations in weld metal and HAZ.In the course of investigations the properties of welded joints, produced by electron beam welding (EBW) and argon arc welding with tungsten electrode (TIG) without using filler metal were compared.The joints of high-strength titanium alloy VT23 [3] were made of 10 mm thick plates, joints of titanium alloy of grade T110 were made of 7 mm thick plates. The high-grade alloy of T110 system Ti-5.5Al-1.2Mo-1.2V-4Nb-2Fe-0.5Zr was developed at the PWI together with the O.K. Antonov ASTC [4]. It contains the following alloying elements, wt.%: 5-6 Al, 3.5-4.8 Nb, 0.8-1.8 Mo, 0.8-2 V, 1.5-2.5 Fe, 0.3-0.8 Zr. Alloy T110, as compared to VT23, has a higher resistance to the formation of fatigue cracks and according to the number of service characteristics...

Effect of TIG-Welding on the Structure and Mechanical Properties of the Pseudo-β Titanium Alloy VT19 Welded Joints

“…The influence of the welding on properties and structure of the pseudo-β titanium alloy VT19 welded joints made by TIG-welding with through penetration [15] and TIG-welding using flux layer (ATIG) were studied [16].…”

Influence of filler metal on structure and properties of welded joints of high-strength two-phase titanium alloys produced using argon arc welding

“…8-component alloy Ti-6.5A1-3Mo-2.5V-4Nb-1Cr-1Fe-2.5Zr in the initial state had fine-dispersed structure in the ranges of primary β-grains [3]. The morphology of a-phase in the base metal after annealing at 900 °C during 1 h and furnace cooling is laminar, and the plate width amounts to 1-1.5 mm (Figure 4, a).…”

“…The aim of the work is the evaluation of effect of thermal welding cycle, type of filler metal and PWHT on the structure and properties of welded joints of two-phase high-alloyed titanium alloys having σ t > > 1000 MPa. The properties of high-strength titanium alloys VT23, T110 and experimental alloy Ti-6.5A1-3Mo-2.5V-4Nb-1Cr-1Fe-2.5Zr welded joints [3], produced using argon arc welding applying tungsten electrode (TIG) with application of filler metal to the groove and without the edge preparation, were compared.…”

“…After welding, all the welded joints were subjected to annealing. The temperature of annealing for experimental alloy Ti-6.5A1-3Mo-2.5V-4Nb-1Cr-1Fe-2.5Zr was selected in order to provide the highest impact toughness of weld metal and, according to the results of work [3], it amounted to 900 o C (1 h) in combination with the subsequent furnace cooling. The examples of produced welded joints are given in Figure 2.…”

“…In the weld metal the plates have a greater length and thickness of 1.5-2 µm, and in the gaps between the plates the (a + β) structure is dispersed. As compared to annealing at 750 °C, when the metal structure of all the zones of welded joints remained INDUSTRIAL fine-dispersed [3], the coagulation of a-phase after annealing at 900 °C can provide some increase in the ductile properties.…”