Magnesium Alloy Joints Research Articles

Corrosion behaviour of soldered joints of magnesium alloys and dissimilar materials

In the last decade magnesium based materials have been used in many industrial applications. Problems arise from joining technologies and the corrosion behaviour of joined parts. The present study shows results of a new flux free soldering technology and the study of the corrosion properties of these soldered samples. Joints have been obtained by soldering of magnesium alloy AZ31 samples among each other or to aluminum alloy AlMgSi1 as well as to unalloyed, low-carbon steel. Different corrosion protection layers have been applied by thermal spraying. The corrosive potential of different soldered samples has been examined using current density-potential measurements. The corrosion behaviour of coated samples has been studied by salt spray testing in comparison to uncoated samples.

Two Pass FSW Joint of Magnesium Alloy

Two Pass FSW Joint of Magnesium Alloy

Gas tungsten-arc filler welding of AZ31 magnesium alloy

Optical microscopy and scanning electron microscopy (SEM) were used to examine the microstructure and fracture of AZ31 magnesium alloy joint welded by automatic gas tungsten-arc filler (GTAF) welding process with AZ61 wire. More endeavors have been put on investigating the effect of filler wire on microstructure and performance of welded joint. The result showed that the grain size in heat-affected zone (HAZ) of GTAF welded joint holds significant variety compared with that of GTA welded joint (without filler wire). The modification of microstructure in HAZ has changed the fracture location as well as the ultimate tensile strength (UTS) of joint in tensile test.

Continuous Wave ND:YAG Laser Welding of Sand-Cast ZE41A-T5 Magnesium Alloys

ABSTRACT A continuous wave 4 kW Nd:YAG laser system was used to weld 2-mm butt joints of sand-cast ZE41A-T5 magnesium alloys at a power of 2.5 kW, welding speed of 6.0 m/min, and defocusing distance from − 2 to + 3 mm for the material in the machined surface conditions. It was found that the adjustment of defocusing distance greatly influences the establishment of conduction or keyhole mode welding. Conduction welding is obtained at a power density of 4.0 × 10 5 W/cm 2 . Keyhole welding is reached at a threshold irradiance of 1.5 × 10 6 W/cm 2 . The fusion zone consists of refined equiaxed grains formed through cellular growth in the Zr-containing magnesium alloys. The partially melted zone is rather narrow, only a few grains wide. No grain growth or coarsening but softening is observed in the heat affected zone (HAZ). The weld defects observed include three main types: imperfect shape, cavities, and weld cracks. The mechanisms of their formations are discussed. In addition, the original cast quality was found to have a significant influence on the formation of defects such as underfill, surface depression, porosity, and burn-through during laser welding.

Laser–tungsten inert gas hybrid welding of dissimilar AZ based magnesium alloys

The microstructure and mechanical properties of dissimilar AZ based magnesium alloys subjected to laser–tungsten inert gas (TIG) hybrid welding have been investigated. The results show that magnesium alloys can be readily welded as dissimilar joints using this process. The microstructure of the dissimilar magnesium alloy joints is composed of primary α phase (Mg) and β phase (Mg17Al12), based on electron probe microanalysis (EPMA) and X-ray diffraction (XRD) data. In addition, the tensile strength of AZ31B–AZ61 and –AZ91 joints is equal to that of AZ31B base metal. It has also been found that the presence of β phase has a severe influence on the tensile strength and mirohardness of dissimilar magnesium alloy joints.

Properties of magnesium alloy joints welded by a CO2 laser beam

Because of their specific gravity, magnesium alloys find increasing applications in the automotive industry.1 Safety and travelling comfort requirements, satisfied by the use of steel or aluminium parts, are responsible for the increase in the car weight and, therefore, in increased fuel consumption and consequent environmental pollution.2 Replacement of these materials by magnesium alloys satisfies the two requirements while not changing the car mass. The factor which is responsible for the delay in the acceptance of magnesium alloys in the automotive industry is the lack of investigative work into the development of the methods of the manufacture of alloys which would possess the required microstructure, i.e. free of pores and homogeneous structure. The newly developed manufacturing methods indicated, however, that a significant increase in the use of magnesium alloys by the industry can be expected.3 Consequently, a rather limited usage of these alloys in the 1970s for the manufacture of parts, had been extended in the 1990s to whole systems of, mainly, pressure die-cast components (covers, oil sumps, etc) being produced for a number of car makers.4

Pulsed YAG laser weldability of magnesium alloys

Magnesium alloys are the most lightweight of practical metals, have high specific strength and specific rigidity and have attracted a great deal of attention as structural materials. They have been extensively applied, in particular, in automotive components and as cases for laptop computers/AV (audio-visual) appliances. The development of joining techniques is essential for the employment of magnesium alloys as structural materials. The author and others1–5 have previously reported on the microstructure, and mechanical properties, crack susceptibility of magnesium alloy joints made by TIG, electron beam and friction welding.

Transient liquid phase bonding of magnesium alloy (Mg–3Al–1Zn) using aluminium interlayer

Abstract The microstructure and mechanical properties of transient liquid phase (TLP) bonded magnesium alloy (Mg–3Al–1Zn) joint using aluminium interlayer have been investigated. The composition profiles and microstructures of the joint depend on the bonding time at bonding temperature of 480 °C. Increasing bonding time from 1 to 60 min, the concentration of aluminium and the amount of Al12Mg17 compound in the joint decrease. For longer bonding time (120 min), the most pronounced features of the joint are composition homogenization and grain coarsening. The brittle compound (Al12Mg17) and grain coarsening of the joint are main reason for impairing the joint shear strength. The joint shear strength of 76.1 MPa which is 92.4% of base metal strength (82.4 MPa) can be achieved after bonding at 480 °C for 60 min.

Transient liquid phase bonding of magnesium alloy (Mg – 3Al – 1Zn) using copper interlayer

The mechanism, microstructure and mechanical properties of transient liquid phase (TLP) bonded magnesium alloy (Mg – 3Al – 1Zn) joints using copper interlayers in an argon atmosphere have been investigated. The formation process of the TLP joint comprises a number of stages: plastic deformation and solid state diffusion, dissolution of the interlayer and base metal, isothermal solidification and homogenisation. The composition profiles and microstructures of the joint depend on the bonding time at a temperature of 530°C. With an increase in bonding time from 10 to 60 min, the concentration of copper and the amount of CuMg2 compound in the joint decrease. For longer bonding times, the most pronounced features of the joint are composition homogenisation, grain coarsening and elimination of the bond line within the joint centre. The presence of brittle CuMg2 and grain coarsening of the joint are the main reasons for impairing the joint shear strength. A joint shear strength of 70.2 MPa, which is 85.2% of the base metal strength (82.4 MPa), can be achieved by bonding at 530°C for 30 min.

Fatigue of Welded Magnesium Alloy Joints

Magnesium alloys have attracted special attention of researchers working in transportation industries because they are the best lightweight structural materials with a relatively high-strength to weight ratio and excellent technological properties. Enhancement of structural application of such a structural material depends on the ability of construction by welding. The welding of magnesium alloys has been investigated widely. Results indicate that FSW (friction stir welding) and TIG (tungsten inert gas arc welding) are successful welding methods for magnesium alloys and aluminum alloys. 1–4) Reliability is their salient attribute, especially for use in the transportation industry. Therefore, the clarification of fatigue properties must precede application of joining by welding. 5) This study investigated the factors which affect the fatigue strength of the welded commercial magnesium alloy joints as welded surface. Investigated alloys were extruded or rolled AZ31 and AZ61. The welding processes used in this investigation were TIG and FSW. Joint efficiencies (%)

A study on automatic seam tracking in pulsed laser edge welding by using a vision sensor without an auxiliary light source : S.K. Lee, S.J. Na, v21, n4, 2002, pp302–315

The dissimilar joints of AZ61 and ZK60 magnesium alloys were obtained by tungsten inert gas arc (TIG) welding and activating tungsten inert gas arc (A-TIG) welding processes. Microstructure characterization shows that, the fine α-Mg equiaxed dendrite crystals contained Mg17Al12 and MgZn2 particles in the fusion zone. The average size of the α-Mg grains in the fusion zone was refined to 19 μm at welding current of 80 A, which resulted in the largest tensile strength of 207 MPa. The tensile strength and the width of the beam of the A-TIG welded AZ61/ZK60 joints showed strong dependence on the amount of TiO2. However, the inhomogeneity of the heat-affected zone near different base metals presented no significant effect on the mechanical properties of the welded joint.

204 AZ31マグネシウム合金TIG溶接継手の機械的性質に及ぼす溶接条件の影響(OS 溶接・接合)

204 AZ31マグネシウム合金TIG溶接継手の機械的性質に及ぼす溶接条件の影響(OS 溶接・接合)

202 AZ61マグネシウム合金電子ビーム溶接継手の組織と機械的性質(OS 溶接・接合)

202 AZ61マグネシウム合金電子ビーム溶接継手の組織と機械的性質(OS 溶接・接合)

Some characteristics of TIG welded joints of AZ31 magnesium alloy : Asahina, T. and Tokisue, H. J. Jpn. Inst. Light Met. (1995) 45 (2), 70–75 (in Japanese)

Degradation due to molten salt attack is one of the failure mechanisms of thermal barrier coatings. Thermochemical attack of the salt mixture Na2SO4–30 mol% NaVO3 on ZrO2–8 mol% YO1.5 (8YSZ) at 1100 °C for different times was investigated. In the present study, 8YSZ powder was synthesized using co-precipitation route. The graded morphologies and phase compositions were examined using SEM, XRD and Raman before and after hot corrosion test. The results obtained from XRD have shown that m-ZrO2 and YVO4 were the main corrosion products after hot corrosion test at 1100 °C. The results obtained from SEM and EDS observations have shown that large polyhedron crystals of m-ZrO2 and rod-like crystals of YVO4 formed as hot corrosion products after hot corrosion test for 6 h and 24 h. The phase transformation and chemical interaction are the primary corrosion mechanisms for degradation of 8YSZ ceramic.

ＡＺ３１マグネシウム合金と１０５０アルミニウムの摩擦圧接継手の機械的性質

The mechanical properties of friction welded joints of AZ31 magnesium alloy to 1050 aluminum, which were made by a brake type friction welding machine, were examined by mechanical tests and optical micrograph. The burr on the welds occurres from 1050 aluminum, and its enveloped in AZ31 alloy at the weld zone regardless of the welding conditions. It is recognized that the original fibrous structures disappeared at near the weld interface. Both compound layer and mechanical mixing layer were observed on the weld zone. Hardness of the weld interface has a higher value than those of the base metal. The tensile strength of welded joints are improved with increasing the friction time. In case of the friction pressure 70MPa, the tensile strength of welded joints are slightly higher than that of the 1050 aluminum, but friction welded joints under the friction pressure of 50MPa and 60MPa are inferior to the 1050 aluminum. The elongation of all the welded joints are inferior to that of the AZ31 alloy. All the tensile specimens are fractured at the weld interface. The impact specimens in which notch is put into the weld interface show impact strength lower than that of the AZ31 alloy.

摩擦圧接した１０５０アルミニウムとＡＺ３１マグネシウム合金の接合界面

Bonding interfaces of friction-welded 1050 aluminum/AZ31 magnesium alloy joints, before and after annealing at 673K for 1h, were examined by tensile test for bonding strength, by optical micrography, EPMA and X-ray analysis for phases in the interfacial reaction. Bonding strength of the friction-welded joints in the as-welded state was dependent on the thickness of interfacial reaction layer. The thinner layer had resulted in the higher bonding strength (about 45MPa). The interfacial reaction layer consisted of two sublayers of compounds (Al3Mg2 and Al12Mg17). The former compound predominantly grew by the annealing. That fact resulted in the brittlement of the interface.

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