This paper reports on a study aiming at comparing properties of the Ti6Al4V titanium alloy joints between pulsed Nd:YAG laser welding and traditional fusion welding. To achieve the research purpose, Ti6Al4V titanium alloy plates with a thickness of 0.8 mm were welded using pulsed Nd:YAG laser beam welding (LBW) and gas tungsten arc welding (TIG), respectively. Residual distortions, weld geometry, microstructure and mechanical properties of the joints produced with LBW and TIG welding were compared. During the tensile test, with the aid of a high speed infrared camera, evolution of the plastic strain within tensile specimens corresponding to LBW and TIG welding were recorded and analyzed. Compared with the TIG, the welded joint by LBW has the characters of small overall residual distortion, fine microstructure, narrow heat-affected zone (HAZ), high Vickers hardness. LBW welding method can produce joints with higher strength and ductility. It can be concluded that Pulsed Nd:YAG laser welding is much more suitable for welding the thin Ti6Al4V titanium alloy plate than TIG welding.

A comparative study of pulsed Nd:YAG laser welding and TIG welding of thin Ti6Al4V titanium alloy plate

Hybrid welding, using the combination of a laser and an electrical arc, is designed to overcome problems commonly encountered during either laser or arc welding such as cracking, brittle phase formation and porosity. When placed in close contact with each other, the two heat sources interact in such a way as to produce a single high intensity energy source. This synergistic interaction of the two heat sources has been shown to alleviate problems commonly encountered in each individual welding process. Hybrid welding allows increased gap tolerances, as compared to laser welding, while retaining the high weld speed and penetration necessary for the efficient welding of thicker workpieces. A number of simultaneously occurring physical processes have been identified as contributing to these unique properties obtained during hybrid welding. However, the physical understanding of these interactions is still evolving. This review critically analyses the recent advances in the fundamental understa...

Problems and issues in laser-arc hybrid welding

Titanium alloys used in aerospace structures require joints of high integrity to meet the design requirements. Gas tungsten arc welding (GTAW), laser beam welding (LBW) and electron beam welding (EBW) are all processes capable of creating fusion welded joints. Gas tungsten arc welding offers the potential to achieve welds of equal quality to EBW or LBW at much lower capital costs; however, the application of GTAW involves gaining an understanding of the complex process characteristics. This paper reviews the process characteristics for GTAW titanium alloys and compares these characteristics with EBW and LBW titanium alloys. The characteristics of active flux tungsten inert gas welding and keyhole mode GTAW, two recent developments to GTAW, are considered, as is keyhole mode plasma arc welding. These variants are capable of greater penetration and, in some cases, faster processing speeds than conventional GTAW. Finally, the current knowledge of weld microstructural development in cast and wrought α...

Gas tungsten arc welding of α + β titanium alloys: a review

In recent years, there is an increased in used of titanium alloys for some parts of mass-produced automobiles and aerospace. However, titanium alloys are characterized by difficult machinability, high melting temperature, high strength, low thermal conductivity, and high reactivity to oxygen, which overshadowed conventional manufacturing processes. To this end, there is a pressing need for more efficient technologies for the manufacture of low-cost titanium structures. Over the years, several joining techniques have been considered for fabrication of titanium alloys. Nevertheless, laser beam welding presents a viable option for welding of titanium due its versatility, high specific heat input, and flexibility. To date, under optimum processing conditions, the strength of the laser-welded titanium alloys can be close to the original material; however, there are still some processing problems such as lower elongation and corrosion resistance coupled with inferior fatigue properties. In this document, the laser beam welding of similar and dissimilar titanium alloys is reviewed, focusing on the influence of the processing parameters, microstructure-property relationship, metallurgical defects, and possible remedies.

A review on laser beam welding of titanium alloys

https://hal.archives-ouvertes.fr/hal-01289332/document

Microstructure and residual stresses in Ti-6Al-4V alloy pulsed and unpulsed TIG welds

The residual welding stresses in laser beam (LB) and tungsten inert gas (TIG) weldments of a titanium alloy in thin plate form were investigated experimentally in the present work. A hole drilling technique was used to measure the residual stresses in the weldments. The effects of the welding method and post-weld heat treatment (PWHT) on the residual stresses were analysed. The results show that (i) the residual stress distribution in the LB welded joints is similar to that obtained for traditional fusion welding processes, although the distribution zone is much narrower in LB welding, (ii) the residual stress in the heat affected zone for LB welding is about 100 MPa lower than that for TIG welding, and (iii) PWHT in vacuum greatly relieves the welding residual stress.

S. L. Gong

Papers

Residual welding stresses in laser beam and tungsten inert gas weldments of titanium alloy