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There have been remarkable improvements in the research field of magnesium over the last few decades, especially in the magnesium metal matrix composite in which micro and nanoparticles are used as reinforcement. The dispersion phase of nanoparticles shows a better microstructural morphology than pure magnesium. The magnesium metal matrix nanocomposite shows improved strength with a balance of plasticity as compared to the traditional magnesium metal matrix composite. In this research, Nb2O5 (0 wt.%, 3 wt.%, and 6 wt.%) nanoparticles were used to reinforce AZ31 with the stir casting method, followed by heat treatment, and finally, an investigation was conducted using microstructural analysis. Factors such as the degree of crystallinity, crystallite size, and dislocation density are affected by the concentration of Nb2O5 and heat treatment. With the compositional increase in Nb2O5 weight percentage, the grain size decreases up to 3% Nb2O5 and then increases gradually. The SEM image analysis showed a grain size reduction of up to 3% Nb2O5 and fracture morphology changed from basal slip to a mixture of basal slip and adiabatic shear band.

Magnesium (Mg)-based alloys are biodegradable metallic biomaterials that show promise in minimizing the risks of permanent metallic implants. However, their clinical applications are restricted due to their rapid in vivo degradation and low surface hemocompatibilities. Surface modifications are critically important for controlling the corrosion rates of Mg-based alloys and improving their hemocompatibilities. In the present study, two heparinization methods were developed to simultaneously increase the corrosion resistance and hemocompatibility of the AZ31 Mg alloy. In the first method, the surface of the AZ31 alloy was modified by alkali–heat treatment and then aminolyzed by 3-amino propyltriethoxy silane (APTES), a self-assembly molecule, and heparin was grafted onto the aminolyzed surface. In the second method, before heparinization, polyamidoamine dendrimers (PAMAM4-4) were grafted onto the aminolyzed surface with APTES to increase the number of surface functional groups, and heparinization was subsequently performed. The presence of a peak with a wavelength of about 1560 cm−1 in the FTIR spectrum for the sample modified with APTES and dendrimers indicated aminolysis of the surface. The results indicated that the corrosion resistance of the Mg alloy was significantly improved as a result of the formation of a passive layer following the alkali–heat treatment. The results obtained from a potentiodynamic polarization (PDP) test showed that the corrosion current in the uncoated sample decreased from 25 µA to 3.7 µA in the alkali–heat-treated sample. The corrosion current density was reduced by 14 and 50 times in samples treated with the self-assembly molecules, APTES and dendrimers, respectively. After heparinization, the clotting time for pristine Mg was greatly improved. Clotting time increased from 480 s for the pristine Mg sample to 630 s for the APTES- and heparin-modified samples and to 715 s for the PAMAM- and heparin-modified samples. Cell culture data showed a slight improvement in the cell-supporting behavior of the modified samples.

Postweld plastic deformation was reported to be able to largely enhance the mechanical properties of friction stir‐welded (FSW) Mg alloys by changing microstructures in the regions with a soft‐oriented texture. However, few studies have concentrated on the effects of postweld plastic deformations on the corrosion behavior of FSW Mg alloys, which has an impact on their application. In the present study, electrochemical measurements, hydrogen evolution, and mass loss tests were used to study the influences of postweld compression along the transverse direction and subsequent annealing on the corrosion rate of FSW AZ31 Mg alloys. It was found that owing to the grain refinement in the weld zones, an improvement in the corrosion resistance and hardness was observed in the FSW AZ31 sample compared to the base metal (BM) sample. Postweld compression was very harmful to the corrosion resistance of the FSW AZ31 alloys. On the basis of the mass loss results, the corrosion rate of the compressed FSW sample was ~17.62 mm/year, which was ~8.99 times that of the FSW sample (~1.96 mm/year). Subsequent annealing could slightly reduce the corrosion rate of the compressed FSW AZ31 plates, whereas the corrosion rate of the FSW‐C‐T sample (~13.63 mm/year) was much worse than that of the BM sample (~4.73 mm/year). [ABSTRACT FROM AUTHOR]

Laser shock peening (LSP) is a promising surface technique to improve mechanical properties. The effect of LSP on the microstructure, high-temperature mechanical properties and residual stress of the AZ31 alloy was investigated by 3D profilometer, transmission electron microscopy, x-ray diffraction, Vickers tester, respectively. The results reveal that both nano-grain layer and compressive residual stress layer were formed in the surface of AZ31 alloy after LSP treatment. The strength of AZ31 alloy is remarkably improved by LSP as the tensile temperature is below 200 °C. While LSP has no obvious effect on the mechanical properties as the tensile temperature is above 300 °C. Fractographs of as-rolled and LSPed AZ31 alloys indicate that quasi-cleavage fracture is the dominant fracture model as the tensile temperature is below 200 °C, while ductile fracture is dominant fracture model as the tensile temperature is above 300 °C. Additionally, the strengthening mechanism of the mechanical properties of the AZ31 alloy by LSP treatment was analyzed in detail. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study is to evaluate the effect of pH treatment on the formation of hydroxyapatite (HA) coating layer and the biodegradation rate of hydroxyapatite coated AZ31 alloy for applications in biodegradable implants. Methods: HA was grown on the surface of AZ31 substrate at three different pH solutions of 7.5, 9.0, and 10.5 respectively by chemical solution treatment method. The coated samples were evaluated their biodegradation behavior by immersion test in the simulated body fluid (SBF) for 14 days. The biodegradation rate of the samples during immersion test was observed by Mg2+ ion quantification method and measuring the increase of pH of the medium. Results: HA coatings were successfully grown on the AZ31 substrate at three different pH conditions. The sample coated at pH 7.5 showed its uniform and dense coating layer resulted in highest corrosion resistance. While the highest biodegradation rate was observed for the sample coated at pH 10.5 due to many micro-cracks formed in the HA layer. After 14 days of immersion, Mg(OH)2 and calcium phosphate were corrosion products on the surface of the specimens coated at pH 10.5 and pH 9.0 respectively. While HA almost remained on the surface of sample coated at pH 7.5. Conclusion: AZ31 alloy coated with HA at pH 7.5 has lowest biodegradation rate and become suitable for applications in biodegradable implants. [ABSTRACT FROM AUTHOR]

Anti-corrosion and wear resistance of AZ31 alloy were enhanced through a three-stage surface treatment, which comprised surface micro-arc oxidation (MAO), sputtering and post supercritical CO 2 -assisted electroless plating (PSC–CO 2 -EP). In the MAO treatment, attempts were made to vary the F ion content in the electrolyte to investigate its impact on the morphology and composition of the oxide film. Subsequently, the MAO-treated AZ31 alloy underwent Ag sputtering, followed by the preparation of the Ni coating using the PSC-CO 2 -EP method (PSC–CO 2 –Ni). The SEM micrographs indicate that the addition of F ions to the electrolyte effectively improved the uniformity, thickness and compactness of the MAO-generated oxide film. Further modification with the sputtered Ag layer could enhance the adhesion between the Ni coating and the as-prepared oxide film. Additionally, the application of SC-CO 2 , with high diffusivity and low surface tension, significantly improved the anti-corrosion and wear resistance of the AZ31 alloy surface even after pressure release. The results demonstrate that the multilayer design proposed in this study addresses the vulnerability of the AZ31 alloy surface to corrosion. Furthermore, compared to the SC–CO 2 –assisted plating method, the PSC-CO 2 -EP technique offers greater process flexibility and exhibits high potential for practical applications. [Display omitted] • F ions included solution enhanced thickness of MAO-generated oxide film. • Sputtered Ag layer improved adhesion between Ni coating and MgO film. • MgO and PSC-CO 2 -Ni layers exhibited higher surface hydrophobicity than AZ31 alloy. • PSC-CO 2 -Ni/Ag/MAO/Mg alloy structure exhibited excellent corrosion resistance. [ABSTRACT FROM AUTHOR]

Effects of various friction stir processing (FSP) variables on the microstructural evolution and microhardness of the AZ31 magnesium alloy were investigated. The processing variables include rotational and travelling speed of the tool, kind of second phase (i.e., diamond, Al2O3, and ZrO2) and groove depth (i.e., volume fraction of second phase). Grain size, distribution of second phase particle, grain texture, and microhardness were analyzed as a function of the FSP process variables. The FSPed AZ31 composites fabricated with a high heat input condition showed the better dispersion of particle without macro defect. For all composite specimens, the grain size decreased and the microhardness increased regardless of the grooved depth compared with that of the FSPed AZ31 without strengthening particle, respectively. For the AZ31/diamond composite having a grain size of about 1 μm, microhardness (i.e., about 108 Hv) was about two times higher than that of the matrix alloy (i.e., about 52 Hv). The effect of second phase particle on retardation of grain growth and resulting hardness increase was discussed.

In the present research, the AZ31 alloy is machined by wire-cut electric discharge machining (WEDM). The experiments were designed according to the Box-Behnken design (BBD) of response surface methodology (RSM). The input process variables, namely servo feed (SF), pulse on-time (Ton), servo voltage (SV), and pulse off-time (Toff), were planned by BBD, and experiments were performed to investigate the cutting rate (CR) and recast layer thickness (RCL). The analysis of variance (ANOVA) was performed to determine the influence of machining variables on response characteristics. The empirical models developed for CR and RCL were solved using Multi-Objective Particle Swarm Optimization (MOPSO). Pareto optimal front is used for the collective optimization of CR and RCL. The optimal solution suggested by the hybrid approach of RSM-MOPSO is further verified using a confirmation test on the random setting indicated by the hybrid algorithm. It is found that the minimum RCL (6.34 µm) is obtained at SF: 1700; SV: 51 V; Toff: 10.5 µs; and Ton: 0.5 µs. However, maximum CR (3.18 m/min) is predicted at SF: 1900; SV: 40 V; Toff: 7 µs; and Ton: 0.9 µs. The error percentage of ±5.3% between the experimental results and predicted solutions confirms the suitability of the proposed hybrid approach for WEDM of AZ31.

The effects of Sr and Y on microstructure, tensile property and free bulge formability of AZ31 alloy sheet produced by twin-roll casting and sequential hot rolling were investigated to improve the mechanical properties and formability of the AZ31 alloy. Sr and Y addition can form Al4Sr, Al2Y and Al3Y phases which can impede dislocation movement and promote dynamic recrystallization during the rolling deformation and decrease the lattice resistance to dislocation motion by decreasing Al solubility in the alloy, resulting in finer grains, lower dislocation density and no twinning generating in the twin-roll casting and sequential hot rolling (TRC-HR) AZ31–1.3Sr–1.0Y alloy. The maximum stress and elongation of the alloy increase significantly after adding Sr and Y. The average cavity and grain sizes of the TRC-HR AZ31–1.3Sr–1.0Y alloy are smaller, resulting in higher elongation in the alloy. The addition of Y and Sr can effectively improve the free bulge formability and the thickness uniform of the alloy. The Al4Sr, Al2Y and Al3Y phases can inhibit the grain growth by obstructing dislocation motion or grain boundary slip, resulting in smaller grain size of AZ31–1.3Sr–1.0Y alloy bulge parts. [ABSTRACT FROM AUTHOR]

The nano-ZrO2-reinforced AZ31 alloy composites were fabricated by friction stir processing with three multi-passes and high rotation speeds. The AZ31/2.14 vol% ZrO2, AZ31/4.29 vol% ZrO2, and AZ31/6.43 vol% ZrO2 composites were designed. The fine microstructure and uniform dispersion of ZrO2 particles were observed in the AZ31/ZrO2 composites. The excellent interfacial bonding was observed between the Mg matrix and ZrO2. The hardness and tensile properties were enhanced after three cumulative friction stir processing passes. This was attributed to grain refinement and strengthening effects of ZrO2. The tensile properties and hardness of the AZ31/ZrO2 composite increased with the increase of volume fraction of the ZrO2 particles from 2.14 to 6.43 vol%.

In the friction stir welding (FSW) process, the final performance of weld joints is determined by microstructures influenced mainly by the heat input and mechanical deformation. In this research, the effects of FSW parameters, rotation speeds, and welding passes, on microstructure and mechanical properties of AZ31 alloy were systematically and comparatively studied. It was found that the microstructure at the joint center with multi-pass FSW could obtain a smaller average grain size compared with the single pass. The differences of the grain size were reduced significantly when the samples experienced the double-side FSW process. The mechanical performance results showed that the optimum strength (315 MPa) was achieved through the double-side FSW process with a rotation speed of 500 r/min and welding speed of 60 mm/min. The mechanism of the parameters and double-sided process on mechanical properties of the joint samples was elaborated.

In recent years, many researchers have been focusing on improving the discharge properties of AZ31 magnesium alloy for battery applications. In this paper, the equal‐channel angular pressing (ECAP) is used as a preferred way of refining the microstructure to enhance the discharge characteristics of AZ31 alloy as the anode for seawater batteries. The electrochemical discharge behaviors of ECAP‐processed AZ31 alloy are investigated along extrusion surfaces, normal cross‐sections, and transverse cross‐sections and compared with as‐cast and homogenized samples. On the basis of the findings, the anode efficiency is improved effectively through the ECAP method, with approximate isotropy in the discharge behaviors of refined AZ31 alloy. The enhanced discharge performance can be attributed to the refined grains, uniform grain sizes, and dispersed β‐Mg17Al12 after ECAP processing. [ABSTRACT FROM AUTHOR]

This article presents the texture development of magnesium AZ31 alloy in the accumulative roll bonded (ARB) AZ31/AZ31 multilayer and AZ31/AA5086 laminate composite. The comparative study demonstrates that the texture evolution in AZ31 in a multilayer system is strongly influenced by the interfaces. A typical basal texture of AZ31 has been observed in AZ31/AZ31 multilayer with texture intensity increased with the rolling deformation. Presence of AZ31/AA5086 interface in the laminate composite leads to a tilted basal texture along the rolling direction (RD) in AZ31 alloy. The texture intensity of composite increased initially with rolling reduction and weakened at the higher rolling strain. Weakening of texture in AZ31 during the laminate processing at higher strain has been attributed to the development of wavy interfaces in AZ31/AA5086 laminate. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the AZ31 alloy powder production and characterization processes experimentally using the gas atomization method. For this purpose, firstly, the design and production of gas atomization units were done at Karabük University Faculty of Technology Department of Manufacturing Engineering. In this gas atomization unit, the manufacturability of AZ31 powder from magnesium alloys was investigated by the gas atomization method which is one of the production methods by powder metallurgy. The parameters and the literature used in the production of materials similar to the AZ31 alloy are taken into account as producibility parameters. In the gas atomization method, parameters such as nozzle diameter, gas pressure, and temperature must be controlled in order to produce the desired properties in metal powder production. The diameter of the nozzle is crucial because it affects the gas pressure and temperature, the size of the powder, and the shape of the powders. Experimental studies were carried out using 3 different temperatures (790, 820, and 850°C), 4 different nozzle diameters (2, 3, 4, and 5 mm) and 4 different gas pressures (5, 15, 25, and 35 bar). In the molten metal atomization process and in the process of forming a protective gas atmosphere, argon gas was preferred. Scanning electron microscopy (SEM) was used to determine the shape of the AZ31 powders produced, XRD, XRF, and SEM-EDX analyses were used to determine the phases in the internals of the produced powders and percentages of these phases. Laser measurement devices were used for powder size analysis and hardness tests were performed to determine the mechanical properties of the produced powders. The powders produced were pressed into masses at 4 different pressing pressures (300, 400, 500, and 600 MPa). The best sinterability values of the bulked powders and sintering process were performed at 3 different temperatures (500, 550, and 600°C). Density measurements were made after pressing and sintering the powders. As a result of the experimental studies, it was found that the powder size decreased with the increase of the gas pressure but the nozzle diameter, and the powder shape changed to the dripping and the spherical in the ligament and complex form. It has been observed that the temperature has no significant effect on the powder size and shape. [ABSTRACT FROM AUTHOR]

Hydrostatic tube cyclic expansion extrusion process is a newly invented severe plastic deformation technique for producing long ultrafine-grained and nanostructured tubes with higher mechanical properties. In the present research, this process was applied through two passes at room temperature on the commercial purity copper. Then, the hardness, tensile properties, fracture surface and microstructure of the samples were evaluated. The main goal of this research was to achieve a material with a simultaneous high strength and desirable ductility. In this process, the utilization of pressurized fluid between the die and the tube leads to first, the desired improvement of mechanical properties due to the effects of hydrostatic compressive stress. Second, the reduction of a required deforming force to eliminating the friction between the die and the tube leads to the facilitation of producing relatively long ultrafine-grained and nanostructured tubes. After two passes of process, a nearly equiaxed and homogeneous ultrafine-grained (UFG) microstructure was observed. The yield strength and ultimate strength increased from 75 MPa and 207 MPa to 310 MPa and 386 MPa, respectively. However, elongation to failure decreased from 55% to 37%. Also, the hardness value of the tube increased significantly from 59 Hv to 143 Hv, and the uniform distribution of hardness was obtained through the thickness of the tube. The fractography evaluations revealed that the predominantly ductile fracture happened in all samples of tensile testing. The hydrostatic tube cyclic expansion extrusion process can be utilized as a practical industrial method for producing relatively long ultrafine-grained tubes. [ABSTRACT FROM AUTHOR]

Evaluation of the possibility of substitution of steel part in the car body by the one made of AZ31 alloy was the main objective of the whole project. The objective of this paper was to determine the flow stress model, which accounts for the difference in the behavior of magnesium alloys during tension and compression. Tension tests on Zwick machine and compression tests on Gleeble 3800 were performed. Inverse analysis was applied to interpretation of the results of the tests. Separate numerical models for tension and compression were implemented into Abaqus software and simulations of the stamping were performed. Sensitivity of the results to the flow stress model was evaluated. [ABSTRACT FROM AUTHOR]

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A 6061 Al coating for AZ31 Mg alloy was prepared by multi-pass friction stir welding (FSW) with different travel speeds. The microstructure, mechanical properties of the interfacial region and the corrosion behavior of the coating were investigated systematically. The results indicate that the interfacial intermetallic compounds formed in the stir zone (SZ) consist of mainly Al 12 Mg 17 and Al 3 Mg 2. The intermetallic compounds in the SZ are significantly increased when the travel speed is increased from 30 mm/min to 60 mm/min. Microhardness measurements and results of shear-tensile tests show that the mechanical properties are influenced by the intermetallic compounds formed in the SZ during FSW. Corrosion tests indicate that the 6061 Al coating can significantly improve the corrosion resistance of AZ31 plate. The 6061 Al coating obtained with a travel speed of 30 mm/min has a maximum corrosion potential E corr of -0.503 V VSE. [ABSTRACT FROM AUTHOR]

Anodized AZ31 Magnesium Alloys was synthesized via electrodeposition processes. The aim of this work was to determine the mechanical and tribological response of the anodized AZ31 Magnesium alloy with different current densities immersed under cement concrete paste with different solidification times. The samples of the anodized alloy were characterized by microindentation so, the mechanical properties (micro-hardness) was increased by 32% when the magnesium alloy was anodized with a current density of 25 mA/cm2, in this sense the friction coefficient between the anodized AZ31 magnesium (MgO) obtained with the highest current density and the metallic AZ31 alloy exhibited a reduction of 54.5%. The scratch test and wear rate (abrasive sliding of cement concrete) show an increase in the critical load and a reduction of weight loss as a function of the applied current density around of 49% and 92.3%, respectively. Scanning electron microscopy was performed to analyze morphological surface changes on the anodized AZ31 alloy after tribological tests. The tribological behavior of the anodized AZ31/MgO system indicates that the AZ31/MgO coatings can have a promising future in applications for the civil construction industry. [ABSTRACT FROM AUTHOR]

Multipass friction stir processing (FSP) is an effective method to produce a homogeneous microstructure and enhance the mechanical properties of magnesium (Mg) alloys. However, few studies have concentrated on the variation of corrosion resistance of Mg alloys during multipass FSP. Electrochemical alternating current (AC) impedance, polarization behavior, hydrogen evolution, and corrosion morphology were used to investigate the effects of subsequent passes on the corrosion resistance of FSP AZ31 plates. A quasi‐in‐situ observation of the growth of corrosion products was carried out to further study the corrosion behaviors of FSP AZ31 alloy. It is found that subsequent passes could further reduce the grain size of FSP AZ31 alloy and result in an increase in the hardness compared with the first pass. Moreover, subsequent passes are beneficial to the improvement in the corrosion resistance of AZ31 alloy. Pitting corrosion occurs in FSP AZ31 plates, which has not changed after subsequent passes. [ABSTRACT FROM AUTHOR]

A multi-pass caliber rolling has attracted attentions as an alternative to severe plastic deformation processes. The present study enhanced strength and ductility of AZ31 Mg alloy simultaneously through the application of caliber rolling. The improving trends in tensile properties were interpreted with various caliber-rolling strains. The oval/circular-shaped calibers imposed a high plastic strain at the center of cross-section, leading to effective grain refinement to submicron scale. This work also confirmed the texture randomizing effect of caliber rolling. Such microstructural evolutions gave rise to the fabrication of high-strength material. Moreover, the caliber-rolled AZ31 Mg alloys exhibited an improvement in ductility as compared to the as-received sheet-rolled material. This was discussed in terms of activation of non-basal slip systems and suppression of mechanical twinning. This study successfully proved the possibility of caliber rolling to produce a bulk Mg rod with enhanced tensile properties. [ABSTRACT FROM AUTHOR]

In the present work, effects of the hot spinning process on the spinnability of AZ31 blank to a tubular shape are investigated. The hot spinning process was carried out by an electrical heating system embedded inside the mandrel. Based on the results, the hot spinning below 250 °C led to fracture. At 250 °C, although deformation imposed no fracture, localized thinning limited the spinnability of the alloy. The spinnability was, however, quite well at the temperature range of 300–450 °C. At this range of temperature, it was found that despite different initial microstructures, the initial conditions of the material, i.e., annealing and as-received conditions, have no significant effect on the spinnability. This was attributed to the complete dynamic recrystallization above 300 °C. Regarding the roller path, two paths of linear and nonlinear paths were implemented. The results show that the nonlinear path of the roller failed to produce a sound tube even above 300 °C. Finite element simulations in combination with a ductile fracture criterion were employed to analyze the low spinnability of the AZ31 blank through this path. Based on the results, this path introduces higher longitudinal strain along with the combination of intensive tensile hydrostatic and longitudinal stresses within the workpiece wall. Such deformation conditions, therefore, cause circumferential cracks at the workpiece wall. [ABSTRACT FROM AUTHOR]

The present study deals with the microstructural evolution and mechanical properties of AZ31 magnesium alloy processed throughout the novel hot constrained compression (HCC) method. AZ31 core specimens constrained by steel sleeves were compressed in the temperature range of 100 to 600 °C at 0.1 s−1 strain rate, up to true strain of 0.6 mm/mm. Similarly, simple compression (SC) tests were carried out on the AZ31 specimens to compare with the HCC ones. The AZ31 specimens failed under SC while the HCC process was successfully conducted without any sign of failure. This phenomenon is attributed to the hydrostatic pressure imposed by the sleeve steel. Moreover, microstructure characterization revealed that the greater strain accommodation in the HCC case is a result of grain refinement due to severe twinning and preceded dynamic recrystallization (DRX) at low and high temperatures, respectively. Nonetheless, the HCC process beyond 460 °C led to grain growth and coarser microstructure as compared to the SC counterparts. Mechanical properties of processed specimens were investigated at room temperature using shear punch tests. Results indicated that while shear strength and formability of HCC products are premier at low temperature deformation, they are attenuated by increasing the temperature beyond 460 °C. This phenomenon is mainly attributed to the different grain size distribution and the effects of γ precipitants. [ABSTRACT FROM AUTHOR]

Abstract The influence of VN particles on the grain refinement and mechanical properties of AZ31 magnesium alloy was investigated and the refining and reinforcing mechanisms were also discussed. These particles present remarkable grain refining efficiency on AZ31 alloy. Addition of 0.5 wt% VN into AZ31 alloy led to decreasing the average grain size from 115.7 μm to 62.4 μm. X-Ray Diffraction and energy dispersive spectroscopy showed the existence of AlN, which was in situ produced through the reaction of VN and Al. Based on the phase identification and disregistry calculation, it was confirmed that the refinement of AZ31 alloy was mainly ascribed to duplex phase composed of AlN and VN acting as nucleating substrates of α-Mg during solidification. Improved mechanical properties were achieved after addition of VN. Yield strength (YS) increased from 39.5 MPa to 50.3 MPa with addition of 1 wt% VN. 0.5 wt% VN into AZ31 alloy exhibited the best mechanical properties with a YS of 47.1 MPa, an ultimate tensile strength (UTS) of 197.4 MPa and an elongation (EI) of 17.8%, enhancing the AZ31 alloy by about 19.2%, 40.3% and 67.9%, respectively. Highlights • Remarkable refinement was achieved by adding VN particles into AZ31 alloy. • AlN were in situ produced through the reaction of VN and Al. • Duplex phases composed of AlN and VN act as nucleation substrates of α-Mg. • 0.5 wt% VN into AZ31 alloy exhibited the best mechanical properties. [ABSTRACT FROM AUTHOR]

Effect of electromagnetic stirring and solution treatment on the microstructural evolution and mechanical properties of AZ31 alloy are investigated in this study. Results show that the mechanical properties of AZ31 alloy are substantially increased after electromagnetic stirring and solution treatment. The tensile strength and elongation are 178 MPa and 19.6 % for AZ31 alloy prepared by electromagnetic stirring after solution treatment. A large number of twins and low angle boundaries are observed in the specimen after heat treatment, since the compressive stress on (101‾0) crystal plane become larger during quenching. The dislocation arrays, which produced by slip or climbing of dislocations, join together to form low angle boundaries. [ABSTRACT FROM AUTHOR]

Abstract In the present study, wear and friction behaviour of Magnesium(Mg) Metal Matrix Composite(MMC) reinforced with Silicon carbide(SiC) doped reduced graphene oxide (r-GO) nanosheets is carried over. In addition, a mathematical model is developed to predict the influence of various control factors of the Mg composites fabricated through Solvent-based powder metallurgy process. Herein SiC is doped with varying wt. % (10, 20, 30) into r-GO nanosheets and its effect over dry sliding wear is studied at constant control parameters like that of load (10N), sliding distance (1000m) and sliding velocity (1 m/s). Optimal parameter for specific wear rate (SWR) is attained by Taguchi method and the mathematical model was developed using Artificial Neural Network in order to understand the wear behaviour of developed MMC under varying parametric condition. Analysis of variance result reveals that wt.% of r-GO have major influence on SWR and sliding velocity have least effect. Occurrence of delamination wear could also be notified over the worn out surface. [ABSTRACT FROM AUTHOR]

Abstract The magnesium alloys are considered to be the best structural materials, because of their advantageous weight to strength ratio. But, the limitation in their real field applications lies on the fact that magnesium alloys are highly susceptible for corrosion. The corrosion behaviour of AZ31 alloy was investigated by electrochemical methods in sodium chloride and sodium sulphate of different concentrations at different temperatures. The corrosion rate was monitored by potentiodynamic polarization technique and electrochemical impedance spectroscopy method. The surface morphology and surface composition of the freshly polished surface of the alloy was compared with that of the corroded surface by recording their SEM images and EDS, respectively. The results showed that the corrosion rate of AZ31 alloy increased with the increase in the temperature of the medium and also with the increase in the salt concentration of the medium. The activation parameters for the corrosion process were calculated and interpreted. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the performance of high purity magnesium and the magnesium-aluminum-zinc alloy AZ31 as sacrificial anodes in an electrocoagulation process with polarity change for the treatment of synthetic indigo carmine solution. It was studied the effect of the main parameters such as temperature, anodic material, current density, initial dye concentration, and agitation speed on the diminishing of indigo carmine concentration and non-purgeable organic carbon. Also, image analysis was used in conjunction with zeta potential measurements to understand the mechanism of flocs formation. The best results were 80% and 96% removal for non-purgeable organic carbon and dye content respectively at room temperature, by using turbulent regime, initial dye concentration of 100 mg L−1 and 50 A m−2 as current density with AZ31 alloy as electrodes. Particularly, high purity magnesium reached 75% in non-purgeable organic carbon removal and 86% in dye removal at the conditions described above. Finally, an additional improvement of 43% in the diminishing of the organic carbon content was observed when polarity change was used, a phenomenon that was attributed to the distribution of the oxidation reaction between electrodes, avoiding the saturation of the surface with oxide and hydroxide layers. Major areas and major fractal dimension were obtained by using a polarity change. [ABSTRACT FROM AUTHOR]

Abstract The effects of a micro-twin lamellar structure on the mechanical properties and fracture morphology of AZ31 Mg alloy have been investigated through impact test, tensile test, and SEM observation of the failure surface. A hot-rolled AZ31 Mg alloy sheet was subjected to dynamic plastic deformation with the aim of introducing a {10 1 ¯ 2} twin lamellar structure prior to tee tensile test, because dynamic plastic deformation with a high strain rate (4–6 × 102 s–1) can activate a greater number of deformation twins in AZ31. Compared with the mechanical properties of hot-rolled and annealed Mg alloy before dynamic plastic deformation, it was found that the tensile yield stress and maximum flow stress of the AZ31 Mg alloy increase after dynamic plastic deformation, and ductility improves under tension in the range 0–30°. Based on the analyses of microstructure and fracture morphology, the phenomenon can be ascribed to the fact that the micro-twin lamellar structure can refine the matrix grain and render the microstructure more homogeneous. [ABSTRACT FROM AUTHOR]

In this research, solvent based powder metallurgy is used to develop Silicon Carbide (SiC) doped reduced Graphene Oxide(r-GO) reinforced magnesium composite. SiC was doped with r-GO with varying wt.% (10 & 20) by adopting hydrothermal method. Influence of SiC doping over r-GO in wear resistance of developed composite was investigated by pin on disc method. Taguchi based Artificial neural network (ANN) was used to attain optimal wear parameter and to study the influence of wear parameter by developing a mathematical model. From ANOVA results it has been observed that wt.% of reinforcement play an important role in governing the wear loss of fabricated MMC. The developed ANN model exhibits accuracy of about 99.9% when subjected to predict the wear loss. Formation of tribolayer and plastic deformation were notified from worn surface morphology, thus evidencing for the occurrence of delamination and oxidation wear. [ABSTRACT FROM AUTHOR]

High strain rate biaxial forging (HSRBF) was performed on AZ31 magnesium alloy to an accumulated strain of ΣΔε = 1.32, the related microstructure, texture and mechanical properties were investigated. It was found that the microstructure evolution can be divided into two steps during HSRBF. In the early forging processes, the refinement of the grain is obvious, the size of ~10 μm can be achieved; this can be attributed to the unique mechanisms including the formation of high density twins ({1012} extension twin and {1011}-{1012} secondary twin) and subsequently twining induced DRX (dynamic recrystallization). The thermal activated temperature increases with the increase of accumulated strain and results in the grain growth. Rolling texture is the main texture in the high strain rate biaxial forged (HSRBFed) alloys, the intensity of which decreases with the accumulated strain. Moreover, the basal pole rotates towards the direction of forging direction (FD) after each forging pass, and a basal texture with basal pole inclining at 15–20° from the rolling direction (RD) is formed in the full recrystallized HSRBFed alloys. The grain refinement and tiled texture are attributed to the excellent strength and ductility of HSRMBFed alloys with full recrystallized structure. As the accumulated strain is ΣΔε = 0.88, the HSRMBFed alloy displays an outstanding combination of mechanical properties, the ultimate tensile strength (UTS) is 331.2 MPa and the elongation is 25.1%.

High strain rate multiple forging (HSRMF) with pass strain ranging from 0.1 to 0.35 was carried out on the AZ31 magnesium alloy, and the microstructure, texture and mechanical properties were examined. The initial grain can be refined through the formation of high density {102} and {101(-)1}-{101(-)2} twins and subsequently twining induced dynamic recrystallization (DRX). The grain refinement of the HSRMFed alloy was affected by the lamellar thickness of the twin. Lower pass strain (Δε = 0.1) during HSRMF leads to the thick twin lamellae and consequently results in coarse DRX grain, meanwhile, an incomplete DRX occurs. While the twin lamellae thickness decreases with increasing pass strain, and a saturate thickness can be achieved with higher pass strain (Δε = 0.16–0.35), which results in the finer DRX structure. Homogeneous DXR structure can be obtained only at a proper accumulated strain (∑Δε = 0.96–1.4) during HSRMF, under lower accumulated strain, the DRX is insufficient, while higher accumulated strain leads to abnormal grain growth. A double peak basal texture was achieved at lower pass strain (Δε = 0.1), which developed into titled basal texture, and the texture intensity increases with the pass strain. HSRMFed alloys with homogeneous fine DRX grain and relatively weak texture show high strength and excellent ductility, therefore, and it is inferred that the optimum pass strain and accumulated strain range are 0.16–0.35 and 0.96–1.4 respectively.

High strain rate multiple forging (HSRMF) was successfully carried out on AZ31 magnesium alloy at a temperature range of 250–400 °C, and the microstructure, texture and mechanical properties were examined. Full recrystallized structure developed at a relatively lower strain due to the twining induced dynamic recrystallization (TDRX) mechanism, which is also responsible for the feasibility of HSRMF deformation at relative low temperature. The average grain sizes of the alloys high strain rate multiple forged (HSRMFed) to the accumulated strain of ∑Δε = 1.32 increased from 7.07 to 9.99 μm as the temperature ranged from 250 to 400 °C, i.e., the grain sizes of the HSRMFed alloy were less sensitive to temperature. The weakened basal texture characteristic of titled or double peak achieved was ascribed to the alteration of forging direction. The HSRMFed alloys demonstrated both excellent strength (UTS > 300 MPa) and good ductility (δ > 20%), which resulted from the combined effects of grain refinement and weakened basal texture. Therefore, HSRMF was an efficient technique to produce strong and ductile wrought AZ31 alloy.

Magnesium alloys have been used in a wide range of lightweight applications in industries such as aerospace, automotive, and personal computing due to their high strength to weight ratio; however, high chemical reactivity, poor corrosion and wear resistance limit their widespread uses in many fields. The plasma electrolytic oxidation (PEO) process can produce a protective oxide layer on the magnesium alloy to improve the mechanical properties that limit more widespread application of magnesium alloys. In this work, molybdenum disulphide (MoS 2 ) nanoparticles in concentrations ranging from 0 to 10 g/L were added into the PEO electrolyte. The aim of this study is to investigate the influence of incorporating MoS 2 nanoparticles on the microstructure, phase, as well as short- and long-term corrosion resistance, and other mechanical properties of PEO grown oxides. While the MgAl 2 O 4 phase was formed for all PEO grown oxide, the addition of MoS 2 nanoparticles in the electrolyte reduced the formation of MgAl 2 O 4 phase and enhanced the growth of MgO phase in the oxide coating. A higher hardness, 16.6 GPa, was obtained for the oxide layer grown with 10 g/L MoS 2 nanoparticles added. The corrosion resistance, wear resistance, and adhesion of the PEO grown oxide layer were strongly influenced by the porosity defect, phase, and microstructure of the coating. It appears that the addition of 2.5 g/L MoS 2 nanoparticle in electrolyte provided an oxide layer with the best short-term corrosion resistance, excellent adhesion, and the lowest wear rate; however, the addition of MoS 2 nanoparticles to the PEO electrolyte was disadvantageous to the long-term anticorrosion performance of an oxide layer because of its reduced formation of MgAl 2 O 4 phase. [ABSTRACT FROM AUTHOR]

The effects of Sm on the corrosion and microstructure behavior of hot-extruded AZ31 magnesium alloy were investigated by SEM, TEM, weight loss analysis, and electrochemical measurements. The results indicated that granular Al2Sm phase ~ 4 μm in size in the hot-extruded AZ31 magnesium alloy modified with 1.5 wt.% Sm leads to significant grain refinement. The corrosion rate decreased from 15.98 × 10−4 to 11.19 × 10−4 g cm−2 h−1 in the transverse section and from 8.57 × 10−4 to 6.20 × 10−4 g cm−2 h−1 in the longitudinal section. Compared to the unmodified alloy, the corrosion potential of the Sm-modified alloy in the transverse and longitudinal sections increased by 98 and 62 mV, respectively, and the Rct value (charge transfer resistance) in the transverse and longitudinal sections of the modified alloy increased from 1764 and 1756 to 2928 and 2408 Ω cm2, respectively. The results showed that the corrosion resistance of hot-extruded AZ31 magnesium alloy was significantly improved by Sm addition due to the grain refinement, the decreased dislocation density, and the suppression of micro-galvanic corrosion caused by Al-Sm-(Mn) intermetallic compounds. [ABSTRACT FROM AUTHOR]

The main goal of this study is achieving thin-walled AZ31 magnesium alloy tubes with high ductility at elevated temperature. For this purpose, a combined severe plastic deformation method, including parallel tubular channel angular pressing (PTCAP) and tube backward extrusion (TBE) was used. First, PTCAP process was applied on tubular samples at 300°C and then, TBE process was performed at 300°C. After PTCAP, a necklace like microstructure, large gains surrounded by a large number of tiny recrystallized ones, was observed and the average grain size of the material decreased from 520 µm to 11.1 µm. At the next stage, After TBE, an ultra-fine grain microstructure with an average grain size of 8.6 µm was formed. After performing this combined method, the hardness value of the PTCAP and TBE processed sample increased from 37 HV to 69 HV. Hot tensile testing studies at 300°C revealed an elongation to failure value of 181% for the PTCAP and TBE processed sample, while this value for as-received sample was 55%. Fractographic SEM images showed that predominately ductile fracture was occurred in all hot tensile specimens due to nucleation of microvoids and their subsequent growth and coalescence with each other. [ABSTRACT FROM AUTHOR]