Papers by Keyword: AZ31B Magnesium Alloy

Abstract: Friction stir welding is an area of interest within ISIM Timisoara, several research projects that have addressed this issue being carried out. At ISIM the research started with the approach of FSW welding of some aluminum alloys (as similar and dissimilar materials) and later extended to other types of non-ferrous metallic materials (magnesium, titanium, copper alloys) and different types of steels respectively. New methods / possibilities of application of the FSW welding process were also researched. The paper presents results obtained by ISIM Timisoara within an ongoing national research project regarding the friction stir welding in inert gas environment (FSW-IG) of the AZ31B magnesium alloy. The experimental research aimed to perform a comparative analysis between the FSW-IG welding and the classic FSW welding for AZ31B magnesium alloy, in the same working conditions in terms of welding equipment, welding tools and technological process parameters. The obtained results show that the application of FSW-IG welding compared to the classic FSW welding brings benefits in terms of weld surface appearance, mechanical strength, elongation at break and behavior to the static bending tests.

Abstract: 10mm thickness AZ31B magnesium alloy was used as the friction stir welding object in this study. Different welding joints were obtained by setting different friction stir welding parameters. Metallographic analysis and impact loading test were carried out on the joint area. The experiment results show that (i) when the rotational speed of the stirring head is 600rpm and the welding speed is 120mm/min, the microstructure of the joint has the characteristics of compactness, thinning, and large-area twinning, which is beneficial to improve the plasticity of the joint area; (ii) the impact load of the joint is the highest, but lower than that of the base material, which is 95.5% of the base material; (iii) the fracture of impact specimen presents ductile fracture.

Abstract: Surface mechanical attrition treatment (SMAT) has so far been used as a technique for improving mechanical and tribological properties of magnesium and its alloys. However, the effects of the SMAT on corrosion and degradability of these materials are still rarely reported in open literature. In this research, the degradation behavior of AZ31B magnesium alloy after receiving the SMAT was characterized. The degradation behavior of the Mg alloy was determined from the weight losses after an immersion test for 24 h in 3.5 wt.% NaCl solution. During the test, the pH of the solution was also monitored. The results obviously showed higher corrosion rates of the Mg alloy that had been treated by using the SMAT. Interestingly, the degradation rate of the Mg alloy decreased once a longer duration of SMAT was applied. Meanwhile, the pH of NaCl solution increased up to 12 and 13.9 once the non-treated and the SMAT specimens were immersed into the solution, respectively. In addition, the energy dispersive X-ray spectroscopy (EDS) analysis confirmed the presence of corrosion products in all the Mg samples that were similar to those revealed in the literature.

Abstract: Numerical simulation of superplastic forming limit of AZ31B magnesium alloy sheet was investigated. The damage evolution equation based on the law of the micro-damage evolution and statistical mechanics was derived, and damage characteristic parameters as well as the critical value of damage variable were identified to provide a theoretical ground on which the plastic forming technology of magnesium alloy sheet can be optimized. The theoretical prediction was made with the numerical simulation program, and the results were verified by experiments. The forming limit curve of the theoretical prediction drawn by numerical simulation was established by the basic adaptation of the forming limit curve based on the experimental data.

Abstract: The Nd:YAG laser welding process of AZ31B alloys was performed by using the six-axis robot in this work. The microstructure characterization of AZ31B auto-welded joints was studied by using scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The laser welding process resulted in the formation of equiaxed grains in the center of the fusion zone (FZ) and columnar grains near the FZ boundary, meanwhile some eutectic β-Mg17Al12 particles were observed in the microstructure. No clear heat affected zone (HAZ) was observed in the welded AZ31B joint. Furthermore, some pores were observed in the base material (BM) and FZ.

Abstract: This Magnesium (Mg) alloys have been increasingly used in the automotive industry due to their superior mechanical properties compared with other metals. While there are some obstacles in the application of Mg alloy, one of that is its complex dynamic response characteristic. Many papers have studied the tensile and compression properties of AZ31B Mg alloys sheet, but lack of shear test. This paper presents experimental study, including the test method and test data analysis, on the AZ31B Mg alloy sheet. Uniaxial tension tests were carried out over a wide range of strain rates from to , which are of interest in vehicle crash CAE. At the same time uniaxial compression and shear tests at strain rates from to were also carried out. The different mechanical behavior of AZ31B Mg alloys sheet between tensile, compression and shear stress states can also be studied in this paper.

Abstract: The extruded AZ31B magnesium alloy plates of 4 mm thickness were butt welded using gas tungsten arc welding (GTA) process. The microstructure and corrosion behavior of the hot compressed welds were evaluated by conducting immersion test in NaCl solution at different immersion time and chloride ion concentrations. The specimens were exposed to immersion in order to characterize their corrosion rates. The corrosion morphology and pit morphology observation was carried out by scanning electron microscopy (SEM). The results showed that the corrosion rate of hot compressed magnesium alloy welds decreased with the increase in immersion time and the corrosion rate increased with the increase in chloride ion concentration, and the corrosion morphology was predominantly influenced by the distribution of β-phase.

Abstract: Recent research works indicate that magnesium alloy can be used for constructing light weight armor because of its density, which is 35% lower than aluminium and 77% lower than steel and also it exhibits superior vibration damping and better failure mechanisms than the contemporary ballistic materials. In this study, numerical simulations were carried out in a monolithic magnesium AZ31B plate using AUTODYN software to understand the effect of Impact velocity and plate thickness on the deformation of target plates. The projectiles are normally impacted on target plates of varying thickness plates at different velocities. Lagrangian solver was used for meshing, in which the grid developed by the solver distorts with the material helps in eliminating the inaccuracies caused by the cell growth due to the shear force of the bullet impact. The simulation results are verified with the experimental data available in the literature.

Abstract: The anodic oxidation/TiO₂ composite film was prepared on the surface of AZ31B Mg alloy by DC magnetron sputtering. The corrosion resistance and blood compatibility of the film were systematically studied by electrochemical, dynamic clotting time and platelet adhesion test. The results shows that the corrosion current of AZ31B Mg alloy was 6.409×10-8A/cm2 after anodic oxidation treatment, which has decreased 4 orders of magnitude compared to the untreated samples and the corrosion resistance is improved greatly. The clotting time of anodic oxidation/TiO₂ film is about 53 min, which has increased 1.3 times compared to anodic oxidation film (40min). Platelets adhesion to anodic oxidation/TiO₂ film are less than the one adhesion to anodic oxidation film, and there are no pseudopodia and aggregation, which indicate that the blood compatibility of anodic oxidation/TiO₂ film is better than anodic oxidation film.

Abstract: Superplastic instability and damage evolution of AZ31B magnesium alloy sheet were investigated in this paper. Maximum elongation of 216% and strain rate sensitivity of 0.36 were obtained at 723k and a strain rate of 1×10^-3s^-1, whose fracture was due to the growth and interlinkage of cavities that nucleated at grain boundary. After superplastic tensile tests and quantitative analysis of cavity volume fraction, A cavity growth model were established, and the damage evolution equation based on the law of the micro-damage evolution and statistical mechanics was derived out, and damage characteristic parameters as well as the critical value of damage variable were identified so as to provide a theoretical ground on which the plastic forming technology of magnesium alloy sheet can be optimized.