Papers by Keyword: Mg-Al-Zn Alloy

Abstract: Thixoforming process is one method to improve the mechanical properties, especially in the manufacture of magnesium alloy components. This method is an alternative to lightweight structures and simultaneously efficient use of raw materials, fuel efficiency and environmental friendliness. The aim of this study is investigates the effect of ZnO nanoparticles addition on grain refinement of Mg-Al-Zn alloy by thixoforming. In these experiments, ZnO nanoparticles added from 0.1, 0.2, 0.3, 0.4 and 0.5 wt. % to Mg-Al-Zn alloy and thixoforming temperature set-up at 530°C. The results showed that the increasing of weight % ZnO nanoparticles cause decreasing grain size average of Mg-Al-Zn alloy both as-cast and thixoforming. On 0.5 wt. % ZnO addition was obtained grain refinement 39.87 μm (decreased 29.29%) and hardness 73.80 HB (increased 53.94%) compared to as-cast.

Abstract: The Mg-Al-Zn alloy is used in the coolant systems of automobile engines. Corrosion of Mg-Al-Zn engine components by coolants, which consist of 30% aqueous ethylene glycol as a coolant composition, is an important issue in automobile industries. With this preview, in the present study it is intended to study the effect of environmental contaminant sulphate ions on the corrosion behavior of Mg-Al-Zn alloy in 30% (v/v) aqueous ethylene glycol solution. Electrochemical investigations were carried out by potentiodynamic polarization and electrochemical impedance spectroscopy techniques. Scanning electron microscopy (SEM) and energy dispersion X-ray analysis (EDX) were used to study the surface morphology and composition of the alloy. Activation parameters for the corrosion process were calculated by conducting the corrosion studies at different temperatures. It was observed that corrosion rate of the alloy in 30% (v/v) aqueous ethylene glycol increases with the increase in the concentration of sulphate ions and also with the increase in temperature.

Abstract: In recent years, Mg-Al-Zn system alloy has been used for the parts in the automobile for weight reductions. The age-hardening behavior of Mg-6mass%Al (-1mass%Zn)-0.3mass%Mn alloys sand mold castings were investigated by Vickers hardness measurement and optical microscopic observation. Both alloys were solution-treated and then isothermal-aged at 473, 498 and 523K. For each aging temperature, both alloys were indicated age-hardening obviously, and decreased the value of maximum hardness and shorten time to maximum hardness with heighten aging temperature. Age-hardening curves for both alloys approximately showed the same change of hardness. However, these optical micrographs after aging treatment are observed different microstructure. In case of AM60 magnesium alloy, discontinuous precipitation preferentially occurred in aged sample. The volume fraction of discontinuous precipitation was larger than that of continuous precipitation. On the other hand, in case of AZ61 magnesium alloy, the volume fraction of continuous precipitation was larger than that of discontinuous precipitation. Furthermore, over-aged sample of both alloys were consisted of discontinuous precipitation, continuous precipitation and pre-precipitation area.

Abstract: According to von-Mises criterion, five kinds of independent slip systems are required for uniform deformation, so it is necessary to activate non-basal slip systems to show good ductility. However, it has not become clear the effect of Zn or Al for non-basal slip systems yet. To investigate deformation behavior of magnesium crystal by non-basal slip and alloying effect for the non-basal slip, pure magnesium and Mg-Al-Zn single crystals were stretched in the [110] direction. While {112}<23> second order pyramidal slip was activated at room temperature in pure magnesium, {101}<23> first order pyramidal slip became active slip at higher temperature. In Mg-Al-Zn alloy single crystal, {101} twin also activated by adding aluminum. These results indicate that active non-basal slip systems and twin in magnesium strongly depend on deformation temperature and alloying elements.

Abstract: _{Subscript text} Nd can obviously improve the mechanical properties of spray deposited 1%Nd, 2%Nd extruded and heat treatment alloy. Nd solid solution in α-Mg matrix lead to the hardness of 2%Nd spray deposited magnesium alloy extruded is higher than that of after heat treatment. A large number of Al₂Nd particles precipitation is the key factor to the highest hardness value(139.4Hv) in 2%Nd magnesium alloy after 370°C/3h+205°C/24h heat treatment. Moreover, the precipitation of Al₂Nd accompany with Al₂Ca and Al-Mn phase increased.

Abstract: In order to develop favorable textures for deep drawing of Al-Mg-Si and Mg-Al-Zn alloys that are promising as automotive body panels, we have adopted the symmetric/asymmetric combination rolling (SACR) process consisting of conventional symmetric rolling and subsequent asymmetric rolling at relatively low reduction. The combination of symmetric cold rolling and asymmetric warm rolling for AA6022 sheets leads to the formation of “TD-rotated β-fiber texture”, resulting in the evolution of {111} recrystallization texture after solution treatment at a high temperature. The SACR processed and solution-treated sheets show a high average r-value with small in-plane anisotropy, and consequently the limiting drawing ratio increases significantly, compared to that of the cold-rolled and solution-treated sheets. In the case of AZ31 magnesium alloy, the SACR process by hot rolling causes the formation of a unique texture, which shows two (0001) poles with tilt angles of 0 and −40 degrees from the normal direction (ND) toward the rolling direction (RD). In addition, subsequent annealing weakens intensity of the double-peak texture, so that the drawability is greatly improved in comparison with that of the conventional warm-rolled sheets with a strong basal texture. At the same time, yield strength decreases to some extent, but the SACR processed and annealed sheets exhibit a good balance of strength and formability due to a mixed texture with basal and tilt components.

Abstract: Magnesium alloys containing Al have been used for industrial materials due to their lightweight and recyclability. The Mg-Al alloys are usually used for the industrial production. The Mg-Al alloys are divided into AZ-series alloys with the addition of Zn, and AM-series alloys with the addition of Mn, respectively. The addition of Zn to the Mg-Al alloy system reduces the solid solubility of Al in Mg, increases the amount of precipitate phases after ageing and thus causes a moderate increase in strength. The Mg₁₇Al₁₂ phase (γ) is reported as the precipitate formed in the Mg-Al alloys during aging after the solution heat treatment, which is the discontinuous precipitate in the grain boundary and continuous precipitate in the matrix. However, there is few report about the effect of Zn contents on age-hardening behavior and microstructure of AZ-series alloys. The propose of this study is to investigate the difference of the age-hardening behavior and microstructures of AZ-series alloys using hardness test and scanning electron microscopy (SEM) observation.

Abstract: The Mg-6wt%Al-1wt%Zn alloy powders mixture produced by gas atomization were spark plasma sintered (SPSed). The SPSed sample was coated by plasma electrolytic oxidation (PEO) method, and the microstructure, mechanical and corrosion properties were investigated and compared to the normally sintered sample. The SPSed sample exhibited a microstructure of well-bonded grains with approximately 48 ,m in grain size, which was bigger than that of the normally sintered sample. The coatings on the SPSed sample were characterized by dense and porous layers, while, in the case of the normally sintered sample, the coatings had grown through the grain boundary of substrate with increasing the coating time. The surface roughness, thickness and micro-hardness of coatings on the SPSed sample increased gradually with increasing the coating time. The corrosion property of coatings on the SPSed sample had a tendency to improve with increasing the coating time in 3.5%NaCl solution. However, it was worse than that of coatings on the normally sintered sample.

Abstract: Ductility of Mg – alloys is linked to a shortage of independent slip systems. Basaltextured samples of Mg-Al-Zn alloy are examined for presence of dislocations of different types after hot compression tests of cast samples and cold compression tests of hot-rolled samples. The JEM-1000, electron transmission microscope with an accelerating voltage of 750 kV using a dark field–weak beam method of observation and the g·b=0 invisibility criterion as a basic method of the analysis of Burgers vectors, is used to analyse the samples. Dislocations with Burgers vectors , [c] and are found. The results are used to evaluate the dislocation density and determine the possible dislocation reactions.

Abstract: Mg-Al-Zn alloys containing 0.5% Ca were strip cast into sheets with a thickness of about 1.0mm by twin roll caster. It is found that the addition of Ca to Mg95Al5-XZnX (wt%)alloys prevents the oxidation and burning of molten, and makes the melting and casting easy. The as-cast Mg96Al4Zn0.5Ca0.5 alloy sheet has few cracks at the edge. With increasing Zn content, the generation of cracks occurs more markedly. The as-cast alloys have equiaxed grains with an average grain size of 10 μm. A fine microstructure is obtained. All the samples consist of single hcp-Mg phase. The yield and ultimate tensile strength of the as-cast sheets are in the range of 180 to 200 MPa and 265 to 275 MPa, respectively. The alloy Mg95Al2Zn2.5Ca0.5 shows an elongation of 21% as well as a high strength of 275 MPa. The annealing at 400 °C causes an improvement of elongation to 24% and 30% for Mg96Al4Zn0.5Ca0.5 and Mg95Al2Zn2.5Ca0.5,respectively. A further enhancement of mechanical properties is expected by an appropriate thermomechanical treatment. The as-cast Mg96Al4Zn0.5Ca0.5 sheet was deep drawn at 250°C and a drawing ratio of 2.0 without cracking . In summery, the Ca added Mg alloys are suitable for the production of Mg alloy sheets by strip casting and the cast alloy sheet have high strength with ductility and good formability