Abstract
Development of high power laser beams with increasing beam quality and decreasing purchase cost lead to a strong development of laser welding techniques. Narrow weld beads, high welding speed, and low heat input are the main advantages of this reliable and repeatable joining process. The aim of this study is to investigate properties of weld seam obtained by Gaussian and annular power distribution, on butt joints of 0.9 mm annealed Ti6Al4V sheet by mean of an experimental design varying power level, spot size and shape, welding speed, and face gaseous protection flow. Examined characteristics of the weld seams are geometrical (Fusion Zone FZ and Heat Affected Zone HAZ shapes and dimensions, defects like porosities, undercut and underfill, distorsions of welded plates), microstructural (FZ and HAZ nature and morphology) and mechanical (tensile test, hardness filiations). Major features concerning the use an annular power distribution concern the flawless weld seam geometry and fair mechanical properties, with relatively low levels of distortions due to residual stresses.
Highlights
Laser welding is a well-known technique to perform reliable assemblies in many industrials areas
The welding domain is presented at figure 1, on an Interaction time vs Power density plot
The possibility offered by the controlled modulation of focused spot size and shape allowed to explore weldability domain and to highlight distinctive effects of process parameters on the welding of thin Ti-6Al-4V sheets
Summary
Laser welding is a well-known technique to perform reliable assemblies in many industrials areas. Continuous improvements in beam quality, versatility of equipment and in particular the emergence of Yb: YAG disk technology allows developments of new approaches in welding techniques [1,2]. In this particular case, the effects of size and shape of the focused spot on welding performances were scarcely investigated. Varying focused spot size allows independent modulation of power density (welding mode) and interaction time, without defocusing the beam. This feature could be a way to overcome thin sheets welding specific issues, namely a narrow process window. This work deals with butt joint welding of thin sheets of Ti-6Al-4V titanium alloy, and interprets effects of these new process parameters on microstructures and mechanical properties of obtained seams
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