Papers by Keyword: Magnesium Alloy AZ31

Abstract: In this study, magnesium alloy AZ31 was successfully welded with aluminum alloy 6061 by diffusion bonding method. In addition, annealing process was applied to refine micro-structure and improve mechanical property. Microstructure and elemental distribution of interface were investigated with Scanning Electron Microscope (SEM) and Electron Probe Micro Analyzer (EPMA). Furthermore, experiments on diffusion bonded specimens with the usage of Transmission Electron Microscope (TEM) were carried out. At last, tensile strength was measured. It can be obtained that the width of diffusion layers increase with the increasing annealing temperatures. Elemental distribution of specimens with annealing were more uniform than that without annealing. The intermetallic compounds in diffusion layers are Al₃Mg₂ and Al₁₂Mg_17, their crystal structure are respectively face-centered cubic (fcc) and body-centered cubic (bcc). What’s more, tensile strength turns to be strongest after annealing at 250°C.

Abstract: In the reverse hot strip rolling, the coiling and uncoiling of the strip leads to unstable conditions during the forming process. Both the temperature of the strip and the dwell time in the coil vary and influence the microstructure evolution passing in the coil during reverse rolling. It makes the design of this process difficult. Therefore, development of the temperature model for the reverse hot rolling including coiling and uncoiling was the main objective of the paper. The identification of the unknown parameters of the boundary conditions is proposed. Methods for their determination are discussed. The analysis is performed on example of the reverse hot rolling of the magnesium alloy AZ31. The resulting temperature model reveals good agreement with thermocouple and pyrometer measurements.

Abstract: Usefulness of the magnesium alloys for construction of structural components is determined, apart from their low density, by a number of favourable mechanical properties and in the case of their use for components of transport means additionally by good fatigue strength. In this study, 12 mm diameter extruded rods of AZ31 and AZ61 magnesium alloys were used as test material. After extrusion the rods were annealed at a temperature of 400°C, with a 60 min soaking period and subsequent cooling in air. Cylindrical specimens with a diameter of d₀ = 8 mm were made for the fatigue test under high-cycle rotary bending conditions with the cycle asymmetry coefficient R = -1. The tests were carried out for a limited fatigue strength range. Examination of microstructure of tested alloys and fatigue fractography were also performed. During the high-cycle fatigue tests it was found that the AZ61 alloy has a longer fatigue life. Based on the obtained results, fatigue life characteristics of the tested materials were drawn up.

Abstract: The aim of this work is to study the Amplitude Dependent Internal Friction (ADIF) of magnesium alloy AZ31 at room temperature at the frequency 20kHz. The internal friction of AZ31 at room temperature is mostly influenced by mechanical cycling at strain amplitudes in the microplastic deformation region. An excited state of the AZ31 alloy, which can be associated with a higher internal friction and lower dynamic modulus than usual state, was found immediately after mechanical cycling. When the strain amplitude drops, the diffusion of solute atoms restores the Zener atmosphere and the internal friction relaxes exponentially with the second root of time. The measurement methodology and obtained results are presented.

Abstract: Mg Alloys Are the Lightest Structural Alloys with Excellent Castability and Machinability as Well as Highest Specific Strength and Stiffness. According to their Hexagonal close Packed Crystal Lattice there Is an Urgent Requirement of Mechanical Property Evaluation Method for Industrial Application, Particularly to Wrought Mg Alloys. Cyclic Loading Is a Very Popular Mode for Most Structural Application Situations. Recent Development of Fatigue Examination of Extruded Profile Has Shown that Mg Alloys Show Not so Ideal Fatigue Property. so that the Further Detailed Study on Cyclic Loading for Plastic Deformed Mg Alloys Is Needed. Tension-Tension Fatigue Tests Were Conducted on Pre-Strained AZ31 Mg Alloys that Produced by Rolling and Extruding Procedures. the Results Show that the Compressive Plastic Deformation Leads to Reduction of Fatigue Life/limit Significantly. SEM Analysis on Fatigue Fracture Surfaces Indicates that the Fatigue Cracks Initiate in the Surface or Sub-Surface of Dramatically Deformed Zones. the Microstructure Analysis Reveals that the Pre-Strain Brings More Abundant Twinning Bands with the Increase in Pre-Strain. the Decrease in Fatigue Life Demonstrates Also some Critical Feature with the Pre-Strain Level.

Abstract: In this study, aluminum alloy A5052 and magnesium alloy AZ31 were joined by conventional parallel setup of explosive welding and underwater explosive welding. Microstructural characterization of conventional welded joints revealed a characteristic wave formation with vortices and contact surface melting layer containing intermetallics. In order to reduce the vortices and melting layer, underwater explosive welding was used. The welding parameters are regulated to reduce the kinetic energy loss during collision. The low kinetic energy loss in underwater explosive welding resulted in the formation of small waves with less vortices and no melting layer.

Abstract: The effect of different factors on the corrosion performance of the anodic film formed on AZ31 was studied by using electrochemical impedance spectroscopy (EIS) and Tafel polarization curves techniques. The result of EIS showed that the oxide film formed at 20 mA·cm^-2 had the highest corrosion resistance and the optimum temperature was 40°C. The similar conclusion was drawn by the Tafel polarization curves. Moreover, the equivalent electrical circuit R(C(R (QR))) (CR) was used to analyze the EIS data.

Abstract: Stress relaxation tests have been used in order to determine parameters of a possible thermally activated process in AZ31 magnesium alloy. The samples were deformed at a constant initial strain rate of 6.7x10-5 s-1 at various temperatures between room temperature and 300 °C. Stress relaxation, i.e. a decrease in the stress with time, was measured at various stress levels and at various temperatures. An analysis of the stress relaxation curves enabled to estimate the internal stress as a function of the strain and the test temperature. It has been shown that the activation volume is a function of the effective stress independently of the deformation temperature.

Abstract: This study aims to produce magnesium alloy strip with boss and rib directly from molten metal. Magnesium alloy is the lightest structural material, so it is expected to widely use for small electronic device and etc. We studied about melt drag process. Melt drag process is one of single roll strip casting process. We use model melt drag experimental device to produce rapid solidified magnesium strip with boss and rib. Substrate is used on model experimental device instead of roll to easily research shape of substrate. Diameter of boss is 5 mm, 7.5 mm and 10 mm. Height of boss is 6 mm. We revealed on this study that the experimental conditions to get good shape boss and rib, improvement substrate shape for good boss and rib, microstructure and etc.

Abstract: Experimental and numerical investigations have been performed in order to study the effect of welding parameters on properties of FSW-ed AZ31 magnesium alloy sheets. The results, presented in terms of tensile strength and numerical field variables distributions, allow to understand the behaviour of such material when FSW-ed using different rotational and welding speeds for a given tool geometry.