Properties Of AZ31 Magnesium Alloy Research Articles

Room temperature corrosion properties of AZ31 magnesium alloy processed by extrusion and equal channel angular pressing

The electrochemical properties of AZ31 magnesium alloy processed by extrusion and equal channel angular pressing (ECAP) were investigated. The electrochemical properties were evaluated using potentiodynamic tests and electrochemical impedance spectroscopy in corrosion solution of 0.1 M sodium chloride. The electrochemical changes of the sample surface were correlated with microstructure evolution. Material processed by extrusion and subsequently by 8 passes of ECAP shows similar or even inferior corrosion resistance to the extruded material after immersion time up to 96 h. However, corrosion resistance of material after extrusion and ECAP is significantly better than that of the extruded material for immersion time of 168 h. This sudden improvement is caused by different formation and fall off of protective corrosion products. Microstructure after extrusion is inhomogeneous and contains relatively large grains, whereas material after ECAP possesses homogeneous ultrafine-grained (UFG) microstructure. As a result, material after ECAP offers more corrosion nucleation sites, but UFG microstructure causes that only smaller clusters of corrosion products fall off the surface. The easier and faster corrosion protective layer restoration on the surface of UFG material after ECAP leads to enhanced corrosion resistance.

Microstructure and mechanical properties of AZ31 magnesium alloy processed by cyclic closed-die forging

AZ31 alloy was subjected to cyclic closed-die forging (CCDF) under various processing conditions. Then tensile tests were carried out to investigate the relationship between tensile properties and microstructural parameters that include grain size and the texture generated by CCDF. With increasing the number of CCDF passes, a finer grain size and more homogeneous microstructure but stronger basal texture are obtained along with significant improvement in both strength and ductility. An average grain size of ∼5.2μm is achieved after five passes at 350°C. AZ31 alloy exhibits a yield strength of 173MPa and elongation of 15.3% compared to initial 42MPa and 10.2%, respectively. On the other hand, in the samples processed at 350°C, yield strength is higher than those of samples processed at higher temperatures, but elongation is smaller. This can be ascribed to difficult basal slip caused by the textures in which the basal plane is oriented parallel to the tensile direction.

Effect of Antimony and Yttrium Addition on the High Temperature Properties of AZ91 Magnesium Alloy

Abstract The effect of individual and combined additions of Y and Sb on the microstructure and mechanical properties of AZ91 alloy has been studied. The results indicate that the additions introduce new Al2Y and Mg3Sb2 phase along with the Mg17Al12 -β phase besides, refining the grains significantly. It can be seen that the β phase in Y added AZ91 + Sb alloy becomes much finer and distributed more uniformly than that of any other alloys. Minimum grain size 140 μm is observed in AZ91alloy with 0.6 yttrium and 0.5 antimony additions. Moreover, improved room- and high-temperature mechanical properties are obtained in Sb added AZ91 + xY alloys. The maximum tensile properties are obtained with the alloy having the combined additions of 0.6 yttrium and 0.5 antimony.

Investigation on Lead and Yttrium Addition on the Microstructure and Mechanical Properties of AZ91 Magnesium Alloy

Investigation on Lead and Yttrium Addition on the Microstructure and Mechanical Properties of AZ91 Magnesium Alloy

Influence of number of ECAP passes on microstructure and mechanical properties of AZ31 magnesium alloy

The aim of this work was to investigate the influence of the number of equal channel angular pressing (ECAP) passes on the microstructure and mechanical properties of AZ31 magnesium alloy. The microstructure after two and four passes of ECAP at 423 and 523 K was investigated by means of optical and transmission electron microscopy. The mechanical properties were carried out using Vickers microhardness measurements and compression test. The grain refinement in AZ31 alloy was obtained using ECAP routes down to 1,5 μm at 423 K. Processes of dynamic recrystallization during ECAP were observed. It was found that a gradual decrease of grain size occurs with the increasing of number of ECAP passes. The grain refinement increases mechanical properties at ambient temperature, such as Vickers microhardness and compression strength proportionally to d-0.5.

Effect of High-Pressure Solution Temperature on Microstructure and Mechanical Properties of AZ61 Magnesium Alloy

As-cast AZ61 magnesium alloy was treated by solution under a high-pressure of 3 Gpa at different temperatures, atmospheric temperature, 200, 400, 600, 800 and 1000 °C. The microstructure of the products was observed by optical microscope. The mechanical properties of the products were investigated by brinell hardness tester and tensile testing. The results show that increasing solution temperature promotes the dissolution into α-Mg matrix of β-Mg17Al12 phase of AZ61 alloy, especially for over 400 °C. With increasing solution temperature, the tensile strength and elongation percentage of AZ61 increase gradually, but the hardness decreases.

Influence of melt purification on mechanical properties of AZ31 magnesium alloy

This experimental study was conducted to investigate the effect of melt cleanliness with respect to the presence of inclusions on the mechanical properties of AZ31 alloy. The type, morphology and size distribution of inclusions in the alloy were analysed. The tensile properties of the AZ31 alloy with and without melt purification were tested at room temperature. The fracture surface of the AZ31 alloy was observed by SEM to reveal the mechanism of fracture nucleation. By melt purification treatment, most of the inclusions are removed from the AZ31 alloy, and the average size of inclusions in the alloy is decreased from 16·5 to 2·0 μm. In addition, the tensile strength and especially the elongation of the alloy are increased. Tensile fracture analysis showed that the inclusions act as crack initiation sites during fracture. The MgO film, which is the main inclusion in the alloy, contributed to poorer mechanical properties.

Research on Damage and Bending Properties of AZ31 Magnesium Alloy

Through the four-point bending test of lath-shaped heat treated AZ31 magnesium alloy, the bending properties and damage characteristics were explored. The results show that the optimal bending strength of the magnesium alloy were 355.1MPa and 259.2MPa for extruded and cast samples, respectively, after corresponding heat treatment with 350°C, 90min and 400°C, 30min. The initial cracks both occurred at the loading point after applied load exceeded the yield limit of AZ31 magnesium alloy. Surface bump, cracks and other damage morphology accompanied by a large number of twinning organizations were found on the surface of the samples.

Microstructural and mechanical properties of AZ31 magnesium alloy with Cr addition and CO2 incorporation during processing

AZ31 Mg-alloy with ∼5wt.% Cr and incorporated with CO2 during processing were produced using the disintegrated melt deposition technique. The effect of Cr addition and CO2 incorporation on the microstructural and mechanical properties was investigated after extrusion.Microstructural investigation revealed that the addition of Cr (AZ31–5Cr) significantly refined the grain size, and the incorporation of CO2 (AZ31–5Cr–CO2) resulted in the in situ formation of chromium carbide (Cr23C6) phase. The evaluation of mechanical properties indicated that when compared to the AZ31 base alloy, both AZ31–5Cr and AZ31–5Cr–CO2 showed significant improvement in the strength properties. Based on the structure–mechanical properties correlation, it was identified that in AZ31–5Cr, Cr acted as a metallic reinforcement that improved the hardness, tensile and compressive yield strengths. In AZ31–5Cr–CO2, the in situ formed Cr23C6 phase acted as a strengthening phase and enhanced the mechanical properties, which were significantly higher than those of AZ31 base alloy and AZ31–5Cr.

Effect of Rapid Solidification on the Structure and Mechanical Properties of AZ91 Magnesium Alloy

The present paper reports an experimental investigation of rapid solidification (RS) influence on the structure and mechanical properties of commercial AZ91 magnesium alloy. In order to obtain RS material melt spinning process was applied in protective atmosphere, resulting in formation of 50 to 100 μm thickness RS ribbons. Application of plastic consolidation (PC) by hot extrusion to the highly fragmented magnesium strips allowed to obtain high bulk strength material. It was found that yield strength (YS) and ultimate tensile strength (UTS) of RS+PC material with comparison to the cast and extruded samples were increased from 220 MPa to 303 MPa and from 287 MPa to 385 MPa, respectively, while plasticity of the RS material was slightly decreased. It was noticed that the grain size of both materials was at the same level of 2 μm, thus higher mechanical properties of RS material was ascribed to dispersion strengthening caused by the high amount of fine (below 50 nm in diameter) Mg17Al12phases evenly distributed in the material structure.

Enhanced microstructure homogeneity and mechanical properties of AZ31 magnesium alloy by repetitive upsetting

An as-cast AZ31 Mg alloy in the form of thick plate (100 mm diameter and 20 mm height) with an initial grain size ∼200 μm was processed by a novel severe plastic deformation technique, repetitive upsetting (RU). Experiments were carried out for 1, 3, and 5 deformation passes at 250, 300, and 350 °C through route A and route B. Finite element analysis of the deformation process indicates homogeneous deformation during RU. With the number of RU passes, a finer grain size and more uniform microstructure are obtained along with significant improvement in both strength and ductility. A homogeneous grain structure with an averaged grain size of ∼2.6 μm through route A and ∼1.6 μm through route B are achieved after 5 passes at 350 °C. A tensile strength of 304 MPa and elongation of 28% are obtained in route B RU processing. AZ31 alloy exhibits a mean grain size of 1.3 μm and yield strength of 294 MPa and tensile strength of 354 MPa after 5 RU passes at 250 °C as compared to initial 43 MPa and 174 MPa, respectively.

Effects of solution and aging treatments on microstructures and mechanical properties of AZ61 magnesium alloy welded joints

The effects of solution and aging treatments on the microstructures and mechanical properties of tungsten inert gas arc welded AZ61 magnesium alloy joints were investigated by microstructural observations, microhardness tests and tensile tests. The results showed that the solution treatment led to the β-Mg17Al12 particles dissolved into the α-Mg grains. Hence, the microhardness of the fusion zone and the ultimate tensile strength of the welded joints were the lowest. With the increase of the aging temperature, the volume fraction of the β-Mg17Al12 particles in the fusion zone increased and this enhanced the microhardness of the fusion zone gradually. Also, the elongation of the welded joints was increased slightly with the increase of the volume fraction of the β-Mg17Al12 particles. However, the ultimate tensile strength of the welded joints increased at first and dropped at 190 °C due to cracks formed at the boundaries of the β-Mg17Al12 particles.

Effect of Ultrasonic Treatment on the Grain Refinement and Mechanical Properties of AZ91 Magnesium Alloy

The present study examines the microstructural evolution and mechanical properties of AZ91 magnesium alloy solidified under high intensity ultrasonic treatment (UST). High intensity ultrasonic vibrations were introduced isothermally below the liquidus temperature into the solidifying AZ91 alloy for the refinement of primary α-Mg grains and β-Mg17Al12intermetallic phase.Various microstructures were produced using different intensity of ultrasonic vibration at a constant temperature and fixed duration of UST. Without any ultrasonic treatment, the structure contains dendrites of primary α-Mg phase which are coarser and non-uniform in size. Nearly uniform, equiaxed grains with continuous and uniform network of intermetallic phase segregated along the grain boundaries were obtained in alloy subjected to high intensity ultrasonic vibration. The average grain size in this case decreased drastically from 300 μm for (without UST) to 17 μm (with UST at intensity of 4 kW/cm2). Vickers hardness also increased steadily with increase in ultrasonic intensity. The mechanisms for microstructural refinement are discussed and it is concluded that the fine uniform grain structure achieved under ultrasonic vibrations is attributed to the cavitation and the acoustic flow induced by ultrasonic vibrations.

多軸鍛造により作製したAZ31マグネシウム合金の機械的特性および疲労特性に及ぼすショットピーニングの影響

To improve the fatigue properties of AZ31 magnesium alloys, two technical approaches were used to reform the material structure. The first approach is grain refinement of the material structure by multi-axial alternative forging (MAF) to reduce anisotropy and to improve the strength. The second approach created an inclined recrystallized surface layer by shot peening to retard crack initiation on the surface layer and the propagation rate in the tissue layer of the fine-grained structure. The relationship between the microstructures and fatigue properties was examined. As a result, by combining MAF and heat treatment the endurance limit increased by 15%. Moreover, shot peening at medium temperatures formed a recrystallized submicrometer grain size microstructure in the surface layer and an inclined structure to a depth of over 100 μm below the surface, and the fatigue properties increased by about 30%. From measurement of the crack propagation rate, it was found that the improvement in fatigue properties led to the delay in crack initiation in the fine-grained surface layer and decreased the crack propagation rate in the residual strained layer.

A Study on Brazing Process and Mechanical Properties of AZ31 Magnesium Alloy

The brazing process of magnesium alloy AZ31 was studied, and the mechanical properties of the weld were examined, and the main factors were analyzed through brazing furnace tests in this work. Only with the protection of self-made brazing flux, a lap joint with the average shear strength of 30MPa could be obtained in an ordinary resistance furnace without inert gas protection, which is much better than that without flux in which the shear strength is lower than 10MPa.

Effect of twins and non-basal planes activated by equal channel angular rolling process on properties of AZ31 magnesium alloy

Ultrafine-grained (UFG) metallic materials because of their superior properties have received considerable research interest. Recently, severe plastic deformation (SPD) processes are widely used for refining the grain size in magnesium alloys. Equal channel angular rolling (ECAR) is a SPD process based on equal channel angular pressing (ECAP) which is carried out on large, thin sheets. After doing this process, no significant change is occurred in cross-sectional area of specimen. In this research, an AZ31 magnesium alloy was subjected to ECAR. After completing eight passes of process, significant grain refinement was occurred, and the average grain size of about 3.9 μm was achieved. The distribution of grain size becomes more limited by increasing number of passes. Rotation of basal plane and activation of non-basal and twin planes were clearly observed in X-ray diffraction (XRD) pattern results. Mechanical properties were studied via tensile and hardness tests at room temperature. Tension tests indicated that better ductility due to the rotation of basal plane was achieved. Elongation-to-failure was increased from 8% of as-received material to 19% after two passes of process. Hardness values showed an increase of about 53% at eighth pass.

Study on the Effects of Deformation Temperature on Microstructure and Mechanical Properties of AZ80 Magnesium Alloy

The effects of deformation temperature on microstructure and mechanical properties of AZ80 magnesium alloy were investigated. The mechanical properties and microstructure were carried out in Gleeble-1500 thermal simulation experiment and optical microscope. The extrusion deformation, dynamic recrystallization had taken place in all the deformation samples, grains were thinner than before deformation.The reasonable deformation process can make the dynamic recrystallization organization of grain smaller and obtain higher strength. The best deformation temperature was about 360°C to 390 °C.

Effects of La on the Microstructures and Mechanical Properties of AZ91 Magnesium Alloy and its Mechanism

Microstructure changes brought by the addition of La element to AZ91 magnesium alloy are studied, also, the precipitating phases were identified and their influence on the mechanical properties of alloys was investigated. Results show La makes refinement of microstructure of the AZ91 alloy, and decrease the size of Mg17Al12 phase. La element takes a priority to react with Al element over Mg, forming binary phase Al11La3 with high melting point. Certain amount of La increases tensile strength, yield strength and elongation. With more addition, La would combine more Al in matrix and decrease strengthening effect, because Al11La3 phase would become coarsening. The mechanical poroerties tests indicate that AZ91+0.16%La alloy has the best properties. Maximum tensile strength, maximum yield strength and elongation are 245MPa, 178MPa and 14.5% respective, increased by 21%, 19% and 48% respectively. The mechanism of La strenthing mechanical properties is proposed that Al11La3 phase enriched on solid-liquid interface, increased the degree of supercooling, refined the grain size and changed the crystal style.

Effects of grain size, texture and twinning on mechanical properties and work-hardening behavior of AZ31 magnesium alloys

Abstract Rolled sheets with various microstructures and (0 0 0 2) pole intensities have been obtained successfully using conventional flat rolling (CFR), differential speed rolling (DSR) and heat treatment methods. The mechanical properties of AZ31 magnesium alloys with different grain sizes, basal texture intensities and twinning conditions were investigated at room temperature. It was found that the rolled sheets show good ductility when grain size is around 15 μm. Finer grains and random (0 0 0 2) basal intensity are hardly achieved simultaneously using both DSR-RS and CFR-AR processing methods in current study. In the determination of the rolling processing, it is important to consider preferred grain refinement or lowered basal texture intensity. Moreover, the influences of grain size, basal texture intensity and twinning conditions on work-hardening rate were examined as well. As grain size decreases, extrapolated work-hardening rate decreases; while basal texture intensity has little effect on it. On the other hand, twinning plays a vital role in decreasing work-hardening in plastic flow stage; while twin boundaries increase the work-hardening rate in easy glide stage and linear hardening stage. However, they drop faster than un-twinned samples in stage III when the true strain is higher than 0.06.

Effects of Gd on Microstructure and Mechanical Properties of AZ61 Magnesium Alloy

The effects of different amounts of rare earth Gd added into AZ61 on the microstructure and mechanical properties of magnesium alloys were studied in this paper. And it adopts T6 heat treatment. When 2% Gd has been added, the microstructure of the alloy becomes uniform. The grains are refining. Gd is prior to reacting with Al for forming Al2Gd phase with high melting point. It is in the form of dot-like and globosity along the grain boundary. And β-Mg17A112 phase is reduced and its shape is thinner. The Al2Gd phase hinders dislocation movement. It markedly improves the mechanical properties of the alloy at room temperature and high temperature.