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The primary objective of this study is to investigate the microstructural, mechanical, and wear behaviour of AZ31/TiC surface composites fabricated through friction stir processing (FSP). TiC particles are reinforced onto the surface of AZ31 magnesium alloy to enhance its mechanical properties for demanding industrial applications. The FSP technique is employed to achieve a uniform dispersion of TiC particles and grain refinement in the surface composite. Microstructural characterization, mechanical testing (hardness and tensile strength), and wear behaviour evaluation under different operating conditions are performed. Response surface methodology (RSM) is utilized to optimize the wear rate by considering the effects of process parameters. The results reveal a significant improvement in hardness (41.3%) and tensile strength (39.1%) of the FSP-TiC composite compared to the base alloy, attributed to the refined grain structure (6–10 μm) and uniform distribution of TiC particles. The proposed regression model accurately predicts the wear rate, with a confirmation test validating an error percentage within ± 4%. Worn surface analysis elucidates the wear mechanisms, such as shallow grooves, delamination, and oxide layer formation, influenced by the applied load, sliding distance, and sliding velocity. The enhanced mechanical properties and wear resistance are attributed to the synergistic effects of grain refinement, particle-accelerated nucleation, the barrier effect of TiC particles, and improved interfacial bonding achieved through FSP. The optimized FSP-TiC composites exhibit potential for applications in industries demanding high strength, hardness, and wear resistance. [ABSTRACT FROM AUTHOR]

Magnesium (Mg) and its alloys offer promise for aerospace, railway, and 3D technology applications, yet their inherent limitations, including inadequate strength, pose challenges. Magnesium matrix composites, particularly with metallic reinforcements like titanium (Ti) and its alloys, present a viable solution. Therefore, this study investigates the impact of Ti6Al4V reinforcement on AZ31 magnesium alloy composites produced using pulse plasma sintering (PPS). Results show enhanced microhardness of the materials due to improved densification and microstructural refinement. However, Ti6Al4V addition decreased corrosion resistance, leading to strong microgalvanic corrosion and substrate dissolution. Understanding these effects is crucial for designing Mg-based materials for industries like petrochemicals, where degradation-resistant materials are vital for high-pressure environments. This research provides valuable insights into developing Mg-Ti6Al4V composites with tailored properties for diverse industrial applications, highlighting the importance of considering corrosion behavior in material design. Further investigation is warranted to establish predictive correlations between Ti6Al4V content and corrosion rate for optimizing composite performance. [ABSTRACT FROM AUTHOR]

In this research, tin was added to the AZ31/2Al2O3 magnesium metal matrix composite to investigate its influence on degradation rate in the presence of simulated body fluid (SBF) and wear behaviour in dry conditions. The AZ31- x Sn/2Al2O3 (x = 0, 2, 4, 6, 8, and 10 wt%) composites were manufactured using the bottom pouring stir casting route. The microstructure of the manufactured AZ31/2Al2O3 and AZ31- x Sn/2Al2O3 composites revealed that they were composed of the α-Mg solid solution and the intermetallic compound □-Mg17Al12, which was situated near the grain boundaries. When tin was added, the Sn-rich intermetallic compound Mg2Sn was formed, increasing the volume fraction of the Mg2Sn phase. Compared to AZ31/2Al2O3 composite, the wear test revealed that AZ31/2Al2O3 composites containing Sn particles exhibited a higher ability to generate more stable tribo-layers at higher applied loads, which protected the worn surface and reduced the wear rate. The wear resistance of composites was improved primarily by the behaviour of the tribo-layer in the wear process. The degradation rates (mm/year) of the AZ31 composites were carried out for 72 h in SBF. The degradation rate was reduced when the Sn content in the AZ31/2Al2O3 composite was increased to 6 wt% and then increased with further Sn addition. It was observed that when the amount of Sn particles increases up to 6 wt%, the severity of the degradation decreases. [ABSTRACT FROM AUTHOR]

Magnesium alloys have excellent properties such as high specific strength, rigidity, good damping, electromagnetic shielding, castability, and machinability. However, corrosion, creep, and fatigue resistance are generally the properties that need to be improved. In this study, a hybrid coating was formed on AZ31 magnesium alloy with different surface roughness at different frequencies. In the hybrid coating, an oxide coating was first grown on the surface by the micro-arc oxidation method, and then, the epoxy coating was grown on this oxide coating by the dipping method. The characterization of the coatings was performed by XRD, SEM, and EDS analysis. Furthermore, the relationship between fatigue life and surface roughness was also discussed in this study. The fatigue life and strength of the coated samples were determined as a result of the tests performed on the fatigue device. It was concluded that the fatigue life and strength of hybrid coatings were much better compared to uncoated and single-layer coated samples. [ABSTRACT FROM AUTHOR]

Electrochemical micromachining (ECM) is a nontraditional method used for machining operations in hard and light materials with fixed or varying parameters. In this study, magnesium AZ31 alloy was micro machined using two types of electrolyte supply systems, namely electrolyte flooding and minimum quantity electrolyte (MQE). Experimental investigations were performed using TOPSIS and artificial neural network (ANN) techniques with types of electrolyte supply system, electrolyte concentration (EC), duty cycle (%), and machining voltage (V) as the input parameters, and material removal rate (MRR) and over cut (OC) as the outputs. Single and multi-objective parameter optimization was performed using Taguchi, TOPSIS, and ANN techniques. The machined microholes were analyzed using scanning electron microscopy. According to the TOPSIS results, under optimal conditions, a high MRR value and minimum OC of 1.282 µm/s and 66 µm, respectively, were obtained. The results of TOPSIS were verified using the developed ANN architecture. [ABSTRACT FROM AUTHOR]

This paper focuses on modeling the tribological properties of AZ31-SiC composite using an artificial neural network (ANN) fabricated through the stir casting method. The twenty-seven tests were performed with three loads (10 N, 15 N, and 20 N), three sliding speeds (0.5 m/s, 1.0 m/s, and 1.5 m/s), and three sliding distances (500 m, 750 m, and 1000 m) on wear testing machine and are used in the formation of training sets of ANN. Using the wear test data, Taguchi, Analysis of Variance (ANOVA), and regression analysis were carried out to determine the effect of the control parameters on the wear and coefficient of friction (COF). The experimental results demonstrate that the wear rate increases with an increase in load and distance and decreases with an increase in velocity. In addition, an alternative method is proposed to predict the wear and COF using ANN modeling with single and multi-hidden layer techniques. With good training, ANN gives accurate and close results to the experimental results. The results obtained using ANN modeling have a percentage of error of 4.71% and 5.79% for wear and COF respectively, when compared to experimental values. This prediction process saves time and costs for the manufacturer. [ABSTRACT FROM AUTHOR]

In recent years, a new wave of biocompatable, bioactive, bioresorbable and biodegradable metals were developed by researchers for biomedical applications because of the excellent properties of magnesium metal matrix composite. This present study aims to fabricate the AZ31-Sn/2 wt% nano-Al2O3 composites with various weight fractions (0, 2, 4, 6, 8 and 10 wt%) of micro-tin (Sn) particles using the stir casting technique. The effect of Sn particles reinforcement on mechanical properties, microstructure and wear performance was examined. The EDX analyses and scanning electron microscopy were used to study the hard particles distribution and the interface between the AZ31 alloy and reinforcement particles. The mechanical properties and wear behaviour are increased in AZ31-Sn/nano-Al2O3 composites compared with the AZ31/nano-Al2O3 composites. Furthermore, these outcomes recommend that for applications demanding high compressive strength and wear performance, the AZ31-Sn/nano-Al2O3 will be effective composites. [ABSTRACT FROM AUTHOR]

This paper compares two types of polylactic acid (PLA) coating on AZ31 alloy obtained by dip coating and electrospinning. Both types of coating were loaded with gentamicin sulphate (GS) and the drug-loading efficiency and release were assessed. A higher encapsulation and release efficiency of GS was seen for dip coating (73% and 49.53%, respectively) compared to nanofiber coating (65% and 12.37%, respectively). Furthermore, the antibacterial effect of the samples with and without GS was assessed using Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria, showing that the samples with the drug encapsulated are more resistant to bacteria than the other samples. The electrochemical data reveal a higher stability in the SBF of the surface obtained by dipping than that obtained by electrospinning. The PLA coating shows a porosity of 46% for the sample obtained through dip coating and 32% for nanofibers, which is in accordance with the BET analysis results. Moreover, a higher adhesion strength was obtained for AZ31-PLA-dip (4.99 MPa) than for the AZ31-PLA-nanofibers (1.66 MPa). All samples were structurally, morphologically, and topographically characterized. [ABSTRACT FROM AUTHOR]

The use of bioabsorbable metals as temporary medical implants has attracted considerable research interest as they do not require a second surgical operation for removal after the healing process is completed. However, magnesium (Mg) and its alloys have a degradation rate that is too high in biological environments. Therefore, it must be controlled using various strategies. In this study, an AZ31-Mg-based alloy coated with CeO2 is investigated to analyse the effect of the coating on its corrosion protection and biocompatibility. The AZ31 alloy is anodised with NaOH solution, before coating to stabilise the alloy surface. The CeO2 coating is deposited on anodised AZ31 by chemical conversion treatment. The electrochemical properties of samples are evaluated using electrochemical impedance spectroscopy and cyclic polarisation curves using Hank's solution. Structural and morphological characterisation of the samples are performed using X-ray diffraction and scanning electron microscopy–energy dispersive X-ray spectroscopy. Additionally, biocompatibility is determined by live/dead assay using MC3T3-E1 pre-osteoblasts. The preliminary results indicate that CeO2 coatings exhibit higher electrochemical properties. Additionally, an increase in the ratio of live/dead cells of the AZ31OH-CeO2 surface is detected, in contrast with AZ31, thus indicating improvement in biocompatibility upon CeO2 coating. [ABSTRACT FROM AUTHOR]

Climate change has evidenced the need to reduce carbon dioxide emissions into the atmosphere, and so for transport applications, lighter weight alloys have been studied, such as magnesium alloys. However, they are susceptible to corrosion; therefore, surface treatments have been extensively studied. In this work, the influence of argon plasma pretreatment on the surface properties of an AZ31 magnesium alloy focus on the enhancement of the reactivity of the surface, which was examined by surface analysis techniques, electrochemical techniques, and gravimetric measurements. The samples were polished and exposed to argon plasma for two minutes in order to activate the surface. Contact angle measurements revealed higher surface energy after applying the pretreatment, and atomic force microscopy showed a roughness increase, while X-Ray photoelectron spectroscopy showed a chemical change on the surface, where after pretreatment the oxygen species increased. Electrochemical measurements showed that surface pretreatment does not affect the corrosion mechanism of the alloy, while electrochemical impedance spectroscopy reveals an increase in the original thickness of the surface film. This increase is likely associated with the high reactivity that the plasma pretreatment confers to the surface of the AZ31 alloy, affecting the extent of oxide formation and, consequently, the increase in its protection capacity. The weight loss measurements support the effect of the plasma pretreatment on the oxide thickness since the corrosion rate of the pretreated AZ31 specimens was lower than that of those that did not receive the surface pretreatment. [ABSTRACT FROM AUTHOR]

In this paper, a Whale Optimization Algorithm (WOA) is proposed for the optimization of tribological parameters of AZ31-SiC metal matrix composite. Experiments were carried out by the surface of pin with the different loads of 10, 20, 30 N, velocities of 0.5, 1.0, 1.5 m s−1 and sliding distances of 500 m, 750 m, 1000 m respectively for optimization. The equations derived from the regression analysis are considered as objective functions to find the optimal parameters of wear and coefficients of friction (COF) using WOA. Considering these objective functions, the WOA is used to optimize the tribological parameters. The optimized parameters obtained from the WOA are compared with the parameters derived from PSO, DE, FFA and experimental results. The optimum wear values obtained from WOA, PSO, DE, FFA and experiment results are 3.55, 3.63, 3.60, 3.57 and 3.77 mg respectively. The optimum values of COF obtained from WOA, PSO, DE, FFA and experiment results are 0.311, 0.313, 0.314, 0.312, and 0.33 respectively. The optimum wear values obtained from WOA, PSO, DE and FFA are 6.01, 3.89, 4.69, 5.48% lower than the experimental value. The optimum COF values obtained from WOA, PSO, DE and FFA are 5.76, 5.15, 4.85, 5.45% lower than the experimental value. It is evidence from the results that WOA has provided the best wear and COF values for AZ31-SiC metal matrix composite when compared to other methods. This proposed method reduces the time and effort of the manufacturer to use the composite material in an application with the optimum operating condition for more life. The microstructural SEM micrographs reveal the distribution of reinforcement in the composite. The SEM micrographs of worn out surfaces present various wear mechanisms of the composites under variety of operating conditions. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Gazi Üniversitesi Fen Bilimleri Dergisi Part C: Tasarım ve Teknoloji is the property of Gazi University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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. [ABSTRACT FROM AUTHOR]

The microstructural and mechanical behavior of a typical HCP material (AZ31 Mg-alloy) during friction stir welding was studied comprehensively for various sets of parameters. EBSD, SEM, XRD and optical microscopy have been used to characterize the microstructural properties of the welded samples, whereas tensile, microhardness and bending tests have been performed for mechanical behavior. The results showed that a large number of twins and second-phase particles (Mg17Al12 and Mg2Si) were induced. The tendency of intermetallic compounds (IMCs) formations, where both orientations of grain and grain boundaries favored its locations. The localized stress state governed the texture variation during the tension test and it was well described by EBSD analysis in terms of the assumed welding temperature. The average grain size in the stirred zone was obtained 15, 13 and 9 µm which were reduced by 32, 41 and 59%, respectively, with increasing travel speed meanwhile, in thermo-mechanically affected zone grain size was found to be 19.6, 18.2 and 13.2 µm which were reduced by 11, 17 and 40%, respectively. The maximum and minimum bending stress was achieved as 320 and 304 MPa and the corresponding bending angle was 41° and 38°, respectively, for the lowest and highest heat input conditions. All the joints fractured in HAZ-base metal regions with the lowest hardness. The weld strength was improved with travel speed due to reduced recrystallized grains in stirred zone at lower heat input. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Superhydrophobic surfaces were prepared using a two-step method that involved the etching of AZ31 and AZ91 magnesium alloys and then modifying the etched alloys with stearic acid. Magnesium alloys etched with ZnCl2 and SnCl2 exhibited surfaces roughened with micro- and nanoscale hierarchical structures consisting of two chemically distinct regions (Zn/Zn(OH)2 or Sn/SnO2 and Mg(OH)2). An optimum etching time of ten minutes was chosen for both etchants. Superhydrophobic surfaces with the highest contact angle were prepared when stearic acid reacted with the etched alloys at 50 °C for 4 h. Stearic acid was bound as zinc stearate and magnesium stearate on Mg alloys etched with ZnCl2 and SnCl2 solutions, respectively. The superhydrophobic process on AZ31 alloys etched with ZnCl2 and SnCl2 improved the corrosion resistance in phosphate buffered saline (PBS) solution compared to bare AZ31 alloy, with the use of ZnCl2 etchant leading to better results. An improvement in the corrosion resistance of AZ91 alloy was observed when the stearic-acid-modified AZ91 alloy was etched with SnCl2. In contrast, the use of ZnCl2 etchant to pretreat AZ91 alloy resulted in a significant deterioration in corrosion properties compared to bare AZ91 alloy. The microstructure of the Mg alloy had an impact on the etching and modification process. On the basis of the findings, a characterization of the chemistry of etching magnesium alloys and the formation of superhydrophobic surfaces was proposed. Magnesium alloys were prepared with superhydrophobic surfaces, incorporating antibacterial metals, features which may increase their potential for use in medical applications. [ABSTRACT FROM AUTHOR]

In the present work, AZ31 alloy is processed by WEDM process. The input machining variables of WEDM are designed according to Box-Behnken Design (BBD) of response surface methodology (RSM). The input machining variables considered in the present research are servo feed (SF), servo voltage (SV), pulse on-time (Ton), and pulse off-time (Toff), while the response characteristics evaluated in the present work are material removal rate (MRR), microhardness (MH), average surface roughness (Ra), and mean roughness depth (Rz). The analysis for each response is made with analysis of variance (ANOVA). The empirical models developed for each response are further utilized to get the Pareto fronts along various mutually conflicting process responses using improved multiobjective grey wolf optimization algorithm (MOGWO). In the present research, Levy flight algorithm has been used to improve the efficiency of MOGWO. It has been observed that the implemented multiple objective optimization approach is able to detect the uniformly distributed Pareto fronts very efficiently. The results obtained through the improved MOGWO are further validated through confirmation experiments which show a good agreement to the predicted results. The morphology of the machined surface is also evaluated using scanning electron microscopy, which depicts the microcracks, globules, micropores, and lumps. [ABSTRACT FROM AUTHOR]

In this study, graphene was incorporated into a micro-arc oxidation coating to improve the wear and corrosion resistance of AZ31 alloy. For this purpose, the different concentration of graphene particles was used as 0 g/l, 0.5, 1, and 2 g/l. The wear tests were performed under loads of 2, 4, and 8 N. The composition and morphology of the coatings were investigated by scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The coating thickness increased with increasing graphene concentration. To evaluate the corrosion performance of the coatings, potentiodynamic polarization, and electrochemical impedance spectroscopy tests were performed after immersed samples for 0.5, 16, and 32 h. The wear test results show that wear rates significantly decreases with increasing graphene concentration. Corrosion tests showed that polarization resistance increased and corrosion current density decreased for the coatings with the graphene addition compared to substrate material. [ABSTRACT FROM AUTHOR]

AZ31 alloy has excellent properties like ultra-low density, good energy absorption, and high damping performance but has poor corrosion resistance. The influence of media pH on the corrosion of AZ31 alloy in chloride and sulphate media was investigated using such electrochemical techniques as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The tests were carried out by varying pH in different concentrations (0.05–0.25M) of the media. The surface morphologies and surface compositions of the corroded alloy surfaces were analyzed using scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively. Conclusively, the recorded results reflect a trend of a higher corrosion rate at higher concentrations of the media; and an increase in the corrosion rate on decreasing the pH of the media. In the studied pH range, the alloy showed a higher corrosion resistance at pH 11 and a lower corrosion resistance at pH 3. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

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]

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. [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]

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]

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]

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]

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]

In the current study, combined parallel tubular channel angular pressing (PTCAP) and tube backward extrusion (TBE), as a recently developed severe plastic deformation (SPD) method, were applied at 300 °C on a commercial Mg-3Al-1Zn alloy tubes to achieve an ultrafine grained structure. Then, the microstructure, hardness, tensile properties, and fractography evaluations were done at room temperature on the SPD-processed samples. Also, to study the hot tensile ductility of the SPD-processed samples, tensile testing was performed at an elevated temperature of 400  °C, and then, the fractured surface of the tensile samples was studied. It was observed that a bimodal microstructure, with large gains surrounded by many tiny ones, was created in the sample processed by PTCAP followed by TBE. This microstructure led to reach higher hardness and higher strength at room temperature and also led to reach very high elongation to failure (~ 181%) at 400 °C. Also, the value of elongation to failure for this sample was ~ 14.1% at room temperature. The fractographic SEM images showed the occurrence of predominately ductile fracture in the samples pulled at 400 °C. This was mostly due to the nucleation of microvoids and their subsequent growth and coalescence with each other. [ABSTRACT FROM AUTHOR]

In this study, the effect of Parallel tubular channel angular pressing (PTCAP) as a severe plastic deformation (SPD) process on the microstructural, mechanical properties and superplasticity of AZ31 magnesium alloy were investigated. PTCAP method at 300°C was performed for production of ultrafine grained (UFG) tube with a high superplasticity. After the first pass of PTCAP a bimodal microstructure, large gains surrounded by a large number of tiny recrystallized ones, was observed. The grain refinement and homogeneity of the microstructure increased by applying subsequent passes of PTCAP. After four pass of PTCAP, the average grain size of the material decreased from 43 μm to 6.8 μm. Vickers microhardness measurements revealed that by applying more PTCAP passes and consequently, more grain refinement, the value of hardness increased. Fractographic SEM images showed that predominately ductile fracture was occurred in all hot tensile specimens. A higher elongation to failure of 256% was achieved at a higher tensile testing temperature of 450°C and a strain rate of 10-3 1/s, due to grain boundary sliding as a dominant deformation mechanism, while this values for the as-received sample is 116% at the same tensile testing condition. Finally, it was observed that the four-pass PTCAP processed sample has higher room temperature microstructural and mechanical properties and also higher elevated temperature superplasticity than the as-received sample. Also, the grains thermal stability test was done on the four-pass PTCAP processed sample at 5 different temperatures. [ABSTRACT FROM AUTHOR]

The extrusion experiments were carried out under various temperatures to study the formation of longitudinal weld seams (L-seams) during porthole die extrusion process of AZ31 alloy. Moreover, 3D transient numerical modeling was established to verify the experimental findings. The results indicated that the cross section of profile can be divided into three distinct zones, namely, welding zone, transition zone, and matrix zone, and the fraction of dynamic recrystallization varied in these zones. The average grain size in welding zone increased with increasing temperature, and the profile front had coarser grains in comparison with the other parts. The profile extruded at 380 °C exhibited the highest tensile strength and elongation. Moreover, the profile front always had poor tensile properties in comparison with the other parts. Q criterion is inadequate to describe the welding quality of L-seams, while J criterion shows higher prediction accuracy. Finally, it was demonstrated that the mechanical properties of profile containing L-seams were determined not only by the welding quality but also by the microstructure near L-seams. [ABSTRACT FROM AUTHOR]

The electrochemical polymerization of polypyrrole (Ppy) films on AZ31Mg alloys was carried out using cyclic voltammetery in 0.5 M sodium salicylate solution containing 0.25 M pyrrole and different concentration of sodium fluoride (NaF). Corrosion performance of the Ppy film was assessed by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests in 3.5 % NaCl solution. It was observed that Ppy coatings doped in the presence of 100 ppm NaF provide the best corrosion protection for magnesium and the corrosion potential shifted about 290 mV toward nobler potentials and decrease the corrosion current density about one order of magnitude. The surface analysis of the coatings showed that the addition of F dopant anions led to an improvement in the smoothness, thickness, and adhesion quality of the synthesized Ppy coating on the Mg surface. The scanning electron microscopy (SEM) studies of the fluoride-doped Ppy films revealed that the synthesized coating has a closely packed globular structure which was composed of nanoparticles of Ppy. [ABSTRACT FROM AUTHOR]

Magnesium alloys have found widespread applications in diverse fields such as aerospace, automotive, bio-medical and electronics industries due to its relatively high strength-to-weight ratio. However, stress corrosion cracking of these alloys severely restricts their applications in several novel technologies. Hence, it will be useful to identify the corrosion mechanics of magnesium alloys under external stresses as it can provide further insights on design of these alloys for critical applications. In the present study, the corrosion mechanics of a commonly used magnesium alloy, AZ31, is studied using finite element simulation with a modified constitutive material damage model. The data obtained from the finite element modeling were further used to formulate a mathematical model using computational intelligence algorithm. Sensitivity and parametric analysis of the derived model further corroborated the mechanical response of the alloy in line with the corrosion physics. The proposed approach is anticipated to be useful for materials engineers for optimizing the design criteria for magnesium alloys catered for high temperature applications. [ABSTRACT FROM AUTHOR]

The mechanism of grain refinement in a AZ31 Mg alloy subjected to hot groove rolling is investigated up to large strain (ε ~ 2.5). The alloy shows enhanced yield strength without compromising ductility. The change in strain path during rolling has resulted in significant weakening of basal texture. The microstructure analyses show that dynamic recrystallization (DRX) contributed significantly to grain refinement and hence to the observed mechanical properties. The combined effects of DRX and texture evolution on mechanical properties have been addressed. [ABSTRACT FROM AUTHOR]

Deep drawing process of AZ31 alloy sheet was conducted under crank press, which is different from conventional drawing on hydraulic press with a lower speed. The optimum drawing condition was determined by the orthogonal test to improve the drawability of AZ31 alloy. Good formed specimens were obtained and their mechanical behaviours after drawing were investigated from the point of view of microstructure evolution, texture evolution and fracture appearance. The results showed that fine grain microstructure and weaken basal texture after deformation is attributed to the twin induced dynamic recrystallisation. [ABSTRACT FROM AUTHOR]

Dry sliding wear tests were performed on AZ31 alloy using a pin-on-disc configuration under the loads of 5-360 N and sliding speeds of 0.1-1.5 m/s. Friction and wear characteristics of AZ31 alloy were investigated as a function of the load and sliding speed. Wear mechanisms for AZ31 alloy were characterized by scanning electron microscopy. The wear behavior in mild and severe wear regimes was described in terms of plastic deformation and microstructure evolution in subsurface, and surface hardness change and temperature rise of worn surfaces. The results revealed that surface strain hardening caused by large plastic deformation played an important role in maintaining a low slope of wear rate in mild wear regime, while surface thermal softening originating from dynamic recrystallization and surface melting were responsible for a rapid wear in severe wear regime. [ABSTRACT FROM AUTHOR]

Semisolid rheoforming (SSR) is a promising technology for the production of Mg wrought alloy in foundry settings. In order to realize SSR, it is necessary to characterize the grain structure evolution during slurry preparation. In this paper, slurry of AZ31 alloy was produced by a novel rheocast process known as self-inoculation method (SIM). Interrupted quenching technology was applied to investigate the primary a-Mg evolution during continuous cooling and isothermal holding. Results indicate that the initial microstructure of slurry produced by SIM is a mixture of irregular grains, which becomes ideally globular when the slurry slowly cools to 620 °C and isothermally held for at least 30 s. The local solute diffusion leads to dendritic fragmentation and forms separated particles. During prolonged holding, the particle surface gradually becomes smooth because of protuberance melting and groove advancement. Coarsening of a-Mg grains in isothermal holding was analyzed using Lifshitz-Slyozov-Wagner theory. Results suggest that coalescence is most likely the dominant coarsening mechanism in the early stage while Ostwald ripening tends to be the principal one later. The EDS results indicate that a longer holding time leads to Al solute element segregation at the grain boundaries, but Zn distribution within liquid matrix has no obvious change. [ABSTRACT FROM AUTHOR]