In the laser treatment of a workpiece (9), e.g. for surface hardening, melting, alloying, cladding, welding or cutting, the adverse effect of reflectivity of the surface, when a pure, monochromatic laser (6) is used, is remedied by the simultaneous application of a relatively shorter wavelength beam (1). The two beams (1)(5) may be combined by a beam coupler (4) or may reach the workpiece (9) by separate optical paths (not shown). The shorter wavelength beam (1) improves the coupling efficiency of the higher- powered laser beam (5).

Laser Material Processing

Effect of Zn alloy interlayer on interface microstructure and strength of diffusion-bonded Mg–Al joints

Today, hybrid manufacturing technology has drawn significant interests from both academia and industry due to the capability to make products in a more efficient and productive way. Although there is no specific consensus on the definition of the term ‘hybrid processes’, researchers have explored a number of approaches to combine different manufacturing processes with the similar objectives of improving surface integrity, increasing material removal rate, reducing tool wear, reducing production time and extending application areas. Thus, hybrid processes open up new opportunities and applications for manufacturing various components which are not able to be produced economically by processes on their own. This review paper starts with the classification of current manufacturing processes based on processes being defined as additive, subtractive, transformative, joining and dividing. Definitions of hybrid processes from other researchers in the literature are then introduced. The major part of this paper reviews existing hybrid processes reported over the past two decades. Finally, this paper attempts to propose possible definitions of hybrid processes along with the authors’ classification, followed by discussion of their developments, limitations and future research needs.

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A review of hybrid manufacturing processes – state of the art and future perspectives

Welding of dissimilar magnesium alloys and aluminum alloys is an important issue because of their increasing applications in industries. In this document, the research and progress of a variety of welding techniques for joining dissimilar Mg alloys and Al alloys are reviewed from different perspectives. Welding of dissimilar Mg and Al is challenging due to the formation of brittle intermetallic compound (IMC) such as Mg17Al12 and Mg2Al3. In order to increase the joint strength, three main research approaches were used to eliminate or reduce the Mg-Al intermetallic reaction layer. First, solid state welding techniques which have a low welding temperature were used to reduce the IMCs. Second, IMC variety and distribution were controlled to avoid the degradation of the joining strength in fusion welding. Third, techniques which have relatively controllable reaction time and energy were used to eliminate the IMCs. Some important processing parameters and their effects on weld quality are discussed, and the microstructure and metallurgical reaction are described. Mechanical properties of welds such as hardness, tensile, shear and fatigue strength are discussed. The aim of the report is to review the recent progress in the welding of dissimilar Mg and Al to provide a basis for follow-up research.

A Review of Dissimilar Welding Techniques for Magnesium Alloys to Aluminum Alloys.

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

Microstructure of laser-TIG hybrid welds of dissimilar Mg alloy and Al alloy with Ce as interlayer

One of the major concerns during high speed welding of magnesium alloys is the presence of porosity in the weld metal that can deteriorate mechanical properties. This study seeks to analyze the presence method and quantity of pore during hybrid laser-tungsten inert gas arc (TIG) welding of magnesium alloy AZ31B by radiography, optical microscopy and electron probe microanalysis (EMPA). At the same time, it identifies both the mechanism of pore formation and a remedy for this problem. The experimental results indicate that lacking of shielding gas for laser beam is the dominant cause of macroporosity formation during the hybrid of laser-TIG welding of magnesium Alloys AZ31B plate, and hydrogen is not main cause to form large pores. A favorable weld without porosity can be obtained by appending lateral shielding gas for laser beam.

Pore formation during hybrid laser-tungsten inert gas arc welding of magnesium alloy AZ31B—mechanism and remedy

Surface quality and forming characteristics of thin-wall aluminium alloy parts manufactured by laser assisted MIG arc additive manufacturing

This paper presents the results of recent investigations on the overlap weldability of magnesium alloy AZ31B sheets by laser-arc hybrid welding process The effects of key welding parameters such as welding speed, defocusing distance, and laser-to-arc distance on overlap weldability of magnesium alloys sheets were analyzed, as well as the microstructure and properties of hybrid lap-welded joint The results showed that sound overlap-welded joints of magnesium alloy AZ31B sheets without defects can be obtained Among the welding parameters, defocusing distance and laser-to-arc distance were key factors to affect the penetration depth and bead shape It also found that the cross-section of hybrid overlap-welded joint appears a “thumb pin” shape due to the characteristics of laser-arc hybrid welding Hybrid overlap-welded joints can be divided into two parts: one was the zone of laser acting alone, while the other was the zone of laser and arc cooperation Besides, it was concluded that the tensile shear strength of AZ31B overlap-welded by laser-arc hybrid welding was 80% comparable to those of base metal, and the corrosion resistance of weld bead was equivalent to that of base metal in 5 mol% NaCl solution

Liming Liu

Papers

Microstructure of laser-TIG hybrid welds of dissimilar Mg alloy and Al alloy with Ce as interlayer

Pore formation during hybrid laser-tungsten inert gas arc welding of magnesium alloy AZ31B—mechanism and remedy

Surface quality and forming characteristics of thin-wall aluminium alloy parts manufactured by laser assisted MIG arc additive manufacturing

Overlap welding of magnesium AZ31B sheets using laser-arc hybrid process

Gas tungsten arc welding of magnesium alloy using activated flux-coated wire