Welding And Joining Of Magnesium Alloys Pdf
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Dissimilar joining of AZ31 Mg alloy to various steel sheets with different coatings galvanized GI , galva-annealed GA , cold rolled bare CR , and aluminized Aluminized steel sheets was performed by gas metal arc brazing.
- A Review of Dissimilar Welding Techniques for Magnesium Alloys to Aluminum Alloys
- Welding of Magnesium-base Alloys
- Welding and Joining of Magnesium Alloys
Part 1 General: Introduction to the welding and joining of magnesium; Welding metallurgy of magnesium alloys; Preparation for welding of magnesium alloys; Welding materials for magnesium alloys; Welding and joining of magnesium alloys to aluminium alloys; The joining of magnesium alloys to steel; Corrosion and protection of magnesium alloy welds. Part 2 Particular welding and joining techniques: Brazing and soldering of magnesium alloys; Mechanical joining of magnesium alloys; Adhesive bonding of magnesium alloys; Gas-tungsten arc welding GTAW of magnesium alloys; Metal inert gas welding MIG of magnesium alloys; Variable polarity plasma arc welding of magnesium alloys; Hybrid laser-arc welding of magnesium alloys; Activating flux tungsten inert gas A-TIG of magnesium alloys; Friction stir welding of magnesium alloys; Laser welding of magnesium alloys; Resistance spot welding of magnesium alloys; Electro-magnetic welding of Mg alloys. Due to the wide application of magnesium alloys in metals manufacturing, it is very important to employ a reliable method of joining these reactive metals together and to other alloys. Welding and joining of magnesium alloys provides a detailed review of both established and new techniques for magnesium alloy welding and their characteristics, limitations and applications. Part one covers general issues in magnesium welding and joining, such as welding materials, metallurgy and the joining of magnesium alloys to other metals such as aluminium and steel.
A Review of Dissimilar Welding Techniques for Magnesium Alloys to Aluminum Alloys
In this paper, weldability of magnesium alloys by friction stir welding FSW method which is difficult to join by the fusion welding have been investigated experimentally and numerically. To this end, the connection of magnesium alloys was performed using different welding parameters.
Temperature evolution in the weld zone during welding was measured by using embedded K-type thermocouples. The temperature measurements on both advancing and retreading sides were performed by ten thermocouples. Tensile and Vickers hardness tests were conducted to evaluate the mechanical properties and the hardness distribution on the weld, respectively. During FSW, heat is generated by the friction and plastic deformation.
Knowledge of the temperature distribution is requisite since mechanical properties and microstructure are substantially affected by the heat generation.
It was observed that the heat generated during the FSW process was increasing and the grain structure was refined as the translational speed was decreasing. Transient nonlinear finite element analyses were performed at two stages which the first step is thermal analysis which heat transfer from the pin and shoulder to the plates was modeled and the second is the structural analysis which the temperature data obtained from the thermal analysis in the first stage is used. Friction Stir Welding FSW , which has been developed over the past twenty years is used extensively nowadays.
In FSW process is a specifically projected as a rotating cylindrical tool, including a pin and a shoulder, is plunged into the workpiece. The tool is then traversed in the welding direction. The soften material caused by the rotating shoulder generate heat, the material under the processed zone exposes intense plastic deformation and dynamically recrystallized fine grain structure Darras et al.
Magnesium alloys are one of the lightest structural materials and have gained increased attention in recent years for applications in transport industries, such as automotive industry, where the weight saving hence fuel consumption is a major concern. They are mainly used for light-weight parts of transport systems which operate at high speeds, such as autos and high speed trains Cam, Weight reduction in the aircraft industry has increased researching field using magnesium alloys to substitute for aluminum alloys in some parts.
Also this alloys have outstanding to a high strength to weight ratio. Although formability of magnesium alloys at low temperature have limited because of their hexagonal close packed structure, they have good formability at high temperature. Magnesium alloys are also attractive due to their electromagnetic interference shielding properties and their recyclability Commin et al. Most Mg-alloys can be joined by arc welding processes. However, there are some difficulties in welding these alloys, especially the cast grades.
The major problems encountered in welding of Mg-alloys are the presence of porosity and the emission of large volumes of non-toxic fumes in arc welding. There are numerous experimental and numerical studies on the investigation of the welding performance of the plates joined by the friction stir welding method.
In the most of the experimental examinations, first, researchers tried to obtain optimum parameters for best welding performance. However, Gharacheh et al. Xunhong and Kuaishe, aimed to obtain the best parameters for FSWed AZ31 Mg alloy joint with excellent appearance and no distortion in their study.
Albakri et al. They showed the asymmetric nature of temperature distribution and material movements and their effects on flow during the FSW process so slightly higher temperatures in the range of K were developed on the advancing side of the sheet as compared to the retreating side under all processing conditions.
They also reported a combination of high translation and low rotational tool speeds were ideal to cause effective grain refinement. Darras, referred that more grain refinement can be achieved at lower rotational speeds. This is believed to be related to the thermal histories associated with the process because more heat is generated at higher rotational speeds and therefore, more grain growth takes place.
Wen et al. Cao and Jahazi, studied about effect of various welding speed of FSWed AZ31B-H24 magnesium alloys and they showed defect, microstructure, hardness and tensile strength. Yang et al. Also they researched grain refinement in welding zone, fracture features and ultimate tensile strength.
Chowdhury et al. They tried to characterize the microstructure, texture and tensile properties and they reported that rotational rate has stronger effect on the yield stress than ultimate tensile stress. Chang et al. Chai et al. They applied FSW in air and under water. They investigated thermal distribution on workpiece, microstructure and mechanical properties.
Suhuddin et al. Padmanaban et al. They compared to the results of each technique about microstructure, tensile properties and hardness. Fu et al. They reported that the joints which performed by higher rotational speed have better tensile properties.
Soundararajan et al. The objective of this study is to investigate the effect of the rotation a land translational speeds on the mechanical properties both experimentally and numerically. In the experimental study, tensile tests, metallography and Vickers micro hardness measurements of FSWed AZ31 Mg-alloy plates were carried out.
AZ31 Mg-alloy plates with a thickness of 6. Figure 1 shows the view of the FSW process. The welding trials were used clamping and steel-backing plate. The tool used in the study was manufactured from H13 tool steel. Friction stir welding tools must have some special features such as ambient and elevated temperature strength, elevated temperature stability, wear resistance, fracture toughness. H13 is a chromium-molybdenum hot-worked air-hardening steel and is well known with its good high-temperature strength, thermal fatigue resistance and wear resistance Mishra and Mahoney, H13 chromium hot-work steel is widely used in hot and cold work tooling applications.
The shoulder diameter was 20 mm. The pin was threaded with a diameter of 8 mm M8. For the metals and alloys having high melting point, the heat generated by friction and stirring may be inadequate to soften and plasticize the material around the pin and shoulder. Therefore, preheating or additional external heating sources can help the material flow and welding process.
Preheating of theworkpiecebeforeweldingshould be beneficialforimprovingweldingspeedandminimizingtoolwear Jabbari, In this study, pre-heat was provided by holding of the tool to be rotated but not to be translated at the beginning of the welding process for 40 s. Pin used in the experimental study can be seen in Figure 2. Figure 3 shows the measurement setup used to determine the temperature histories on the plate during the welding operation.
Positions of the thermocouples are shown in Figure 4. Thermocouples were placed near the shoulder of the pin. Temperature values obtained by the measurements were compared with those predicted by the numerical analyses. In the experiments, K-type thermocouples with a diameter of 0.
Holes with a diameter of 3 mm were drilled on both sides of the workpiece to accommodate the thermocouples. The thermocouples were embedded in the holes. The distance between sequent thermocouples is 45 mm. Thermocouples N1 to N5 were located on the advancing side of the workpiece whereas N6 to N10 were on the retreating side of the workpiece.
In the numerical analyses, the thermomechanical analyses were carried out using ANSYS commercial software. These analyses were carried out in two stages.
Transient thermal analysis is the first stage followed by nonlinear transient structural analysis in the second stage. Since the problem involves nonlinear analysis, full Newton-Raphson option is used to solve the nonlinear equations. The thermomechanical coupled three-dimensional model was used in the numerical analyses.
Detailed explanations about the numerical models and stages of the numerical study were given in previous study Serindag et al.
Torque required to rotate the tool, heat generated by the shoulder and pin were determined in order to use them as the boundary conditions in the finite element analyses Serindag et al. Transient finite element analyses were performed considering moving heat source. Heat source during welding were considered as the friction between the rotating tool and the welded workpieces.
In modeling the thermal analyses, the moving heat sources of the shoulder and the pin were represented as moving the heat generation. Figure 6 shows the boundary conditions used in the thermal and structural finite element analyses.
Mechanical and physical properties of the AZ31 Mg alloy change with the temperature; so in the nonlinear finite element analyses, material properties were defined depending on the temperature.
Tables 2 and 3 show the thermal conductivity, k and heat capacity, C p values of AZ31 Mg-alloy depending on temperature used in the thermal analyses Gok and Aydin, , Yang et al. Figure 7 shows the stress-strain curves of AZ31 used in the nonlinear structural analyses under different ambient conditions.
Stress-strain curves are used in the structural analyses Gok and Aydin, In the present study, the modeling of friction stir welding was carried out using ANSYS commercial software. Transient thermal finite element analyses were performed in order to obtain the temperature histories in the welded AZ31 Mg alloy plates during the welding operation.
A moving heat source with a heat distribution simulating the heat generated from the friction between the tool shoulder and the work piece was used in the heat transfer analysis. To compare the results obtained by the numerical analyses, experiments were performed. First, the temperature histories were obtained by using the K -type thermocouple. Figures 8 - 10 show the temperature histories of the thermocouples with respect to welding time in various locations with respect to time during the FSW process.
As seen from the figures, temperature values increase with increasing the rotational speed of the pin. In order to ensure a better evaluation of the measurement results, the temperature values for the node defined as N4 are selected and Figure 11 is drawn for the same time scale.
Figure 12 presents the variation of temperature in location N4 obtained by the transient finite element analyses. As seen from the figure, temperature increases as the rotational speed increases as observing from the measurements. The maximum temperature values are Similar tendency as in the experiments is observed.
Welding of Magnesium-base Alloys
Microstructure and fractographic studies were carried out using scanning electron microscopy SEM. Vickers micro hardness test was performed to evaluate the hardness profile in the region of the weld area. Transverse tensile tests were conducted using universal testing machine UTM to examine the joint strength of the weldments at different parameters. Metallographic studies revealed that each zone shown different lineaments depending on the mechanical and thermal conditions. Significant improvement in the hardness was observed between the base material and weldments. Transverse tensile test results of weldments had shown almost similar strength that of base material regardless of welding speed.
Welding and Joining of Magnesium Alloys
In this paper, weldability of magnesium alloys by friction stir welding FSW method which is difficult to join by the fusion welding have been investigated experimentally and numerically. To this end, the connection of magnesium alloys was performed using different welding parameters. Temperature evolution in the weld zone during welding was measured by using embedded K-type thermocouples.
Meanwhile, joining interface, characterized by the IMCs, was attributed to inter diffusion caused by severe plastic deformation from ultrasonic and friction stirring. This is a preview of subscription content, access via your institution. Please try refreshing the page. If that doesn't work, please contact support so we can address the problem. Int J Adv Manuf Technol —
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