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This study investigates the effects of zinc (4 wt.%) and severe plastic deformation on the mechanical properties of AZ61 magnesium alloy through the stir-casting process. Severe plastic deformation (Equal Channel Angular Pressing (ECAP)) has been performed followed by T4 heat treatment. The microstructural examinations revealed that the addition of 4 wt.% Zn enhances the uniform distribution of β-phase, contributing to a more uniformly corroded surface in corrosive environments. Additionally, dynamic recrystallization (DRX) significantly reduces the grain size of as-cast alloys after undergoing ECAP. The attained mechanical properties demonstrate that after a single ECAP pass, AZ61 + 4 wt.% Zn alloy exhibits the highest yield strength (YS), ultimate compression strength (UCS), and hardness. This research highlights the promising potential of AZ61 + 4 wt.% Zn alloy for enhanced mechanical and corrosion-resistant properties, offering valuable insights for applications in diverse engineering fields. [ABSTRACT FROM AUTHOR]

The large differential-thermal extrusion (LDTE) process, a novel approach for efficiently fabricating a high-strength Mg-10.3Gd-4.4Y-0.9Zn-0.7Mn (wt.%) alloy, is introduced in this work. Unlike typical isothermal extrusion processes, where the ingot and die temperatures are kept the same, LDTE involves significantly higher ingot temperatures (~120 °C) compared to the die temperature. For high-strength Mg-RE alloys, the maximum isothermal extrusion ram speed is normally limited to 1 mm/s. This research uses the LDTE process to significantly increase the ram speed to 2.0 mm/s. The LPTE-processed alloy possesses a phase composition that is similar to that of isothermal extruded alloys, including α-Mg, 14H-type long-period stacking ordered (LPSO) and β-Mg5(Gd, Y) phases. The weakly preferentially oriented α-Mg grains in the LDTE-processed alloy have < 10 1 ¯ 0 > Mg//ED fibrous and <0001>Mg//ED anomalous textures as their two main constituents. After isothermal aging, high quantitative densities of prismatic β′ and basal γ′ precipitates are produced, which have the beneficial effect of precipitation hardening. With a yield tensile strength of 344 MPa, an ultimate tensile strength of 488 MPa, and an elongation of 9.7%, the alloy produced by the LDTE process exhibits an exceptional strength–ductility balance, further demonstrating the potential of this method for efficiently producing high-strength Mg alloys. [ABSTRACT FROM AUTHOR]

Magnesium matrix composites have attracted significant attention due to their lightweight nature and impressive mechanical properties. However, the fabrication process for these alloy composites is often time-consuming, expensive, and labor-intensive. To overcome these challenges, this study introduces a novel use of machine learning (ML) techniques to predict the mechanical properties of magnesium matrix composites, providing an innovative and cost-effective alternative to conventional methods. Various regression models, including decision tree regression, random forest regression, extra tree regression, and XGBoost regression, were employed to forecast the yield strength of magnesium alloy composites reinforced with diverse materials. This approach leverages existing research data on matrix type, reinforcement type, heat treatment, and mechanical working. The XGBoost Regression model outperformed the others, exhibiting an R2 value of 0.94 and the lowest error rate. Feature importance analysis from the best model indicated that the reinforcement particle form had the most significant influence on the mechanical properties. Our research also identified the optimized parameters for achieving the highest yield strength at 186.99 MPa. This study successfully demonstrated the effectiveness of ML as a valuable, novel tool for optimizing the production parameters of magnesium matrix composites. [ABSTRACT FROM AUTHOR]

This study investigates the effects of incorporating MgO into magnesium–calcium (Mg-Ca) alloy composites and subjecting them to the equal channel angular pressing (ECAP) process on the resulting mechanical and corrosive properties, as well as biocompatibility. Initially, the incorporation of MgO into the Mg-Ca alloy composites did not yield significant improvements in grain refinement, tensile strength, or corrosion rate reduction, despite exhibiting improved biocompatibility. However, upon subjecting the Mg-Ca-MgO alloy composites to the ECAP process, noteworthy outcomes were observed. The ECAP process resulted in substantial grain refinement, leading to significant improvements in tensile strength. Furthermore, a marked decrease in corrosion rate was observed, indicating enhanced corrosion resistance. Additionally, the biocompatibility of the Mg-Ca-MgO alloy composites improved after undergoing the ECAP process. These findings highlight the synergistic effect of incorporating MgO and employing the ECAP process, providing valuable insights into the development of advanced magnesium-based materials with superior mechanical properties, reduced corrosion rates, and improved biocompatibility. [ABSTRACT FROM AUTHOR]

The automobile industry uses magnesium for load-bearing components due to its low density, durability, and ductility. This study investigated a nanocomposite containing Nb2O5 (3 and 6 wt%) nanoparticles as reinforcement with AZ31 magnesium alloy made by stir casting. A severe plastic deformation was conducted on the cast samples via equal-channel angular pressing (ECAP) after homogenization at 410 °C for 24 h and aging at 200 °C for 10 h. The microstructural distributions and mechanical properties of the magnesium metal matrix composites (MMCs) reinforced with Nb2O5 nanoparticles were investigated via ECAP. With the increase in the number of ECAP passes, the grain sizes became uniform, and the size of secondary phases reduced in the pure Nb2O5/AZ31 MMC. The grain size decreased remarkably after the ECAP process from 31.95 µm to 18.41µm due to the dynamic recrystallization during plastic deformation. The mechanical properties of hardness, ultimate tensile strength, and elongation effectively improved after each ECAP pass. The maximum values achieved for the Nb2O5/AZ31 composite subjected to ECAP were 64.12 ± 12 HV, 151.2 MPa, and 52.71%. [ABSTRACT FROM AUTHOR]

In this study, the AZ31 magnesium alloy was reinforced with tungsten disulfide (WS2) nanotubes to fabricate the nanocomposite using the stir casting method. The microstructural analysis, mechanical and wear behaviors were investigated with the effect of WS2 on the AZ31 alloy. Scanning electron microscopy (SEM) was used to conduct the microstructural analysis. The microstructures are revealed to incorporate the aluminum content with the WS2 nanotube, disclose the presence of the secondary phase, which was increased compared with the AZ31 alloy and was detected by energy dispersive spectroscopy (EDS). The mechanical properties of hardness and yield strength (YS) were significantly improved with the addition of WS2 nanotubes. This is mainly due to the strengthening mechanisms of Orowan, the coefficient of thermal expansion (CTE) mismatch and the load transfer mechanism. The theoretical YS was calculated and compared with the experimental results. However, the ultimate tensile strength (UTS) and the fracture strain were decreased with the addition of reinforcement which might be owing to the clustering of nanotubes. Finally, the wear behavior of the wear weight loss and depth of cut was investigated. This test revealed that the addition of WS2 nanotubes reduced the weight loss and depth of the material cutting that was mainly due to the presence of hard WS2 nanotubes. [ABSTRACT FROM AUTHOR]

AZ61 magnesium alloy metal matrix composites (MMCs) with different weight percentages (0, 1 and 2) of micro-silicon carbide particles (SiCp) were fabricated using stir casting method. Effects of SiCp on the microstructural distributions, mechanical and fatigue properties, and fracture surfaces have been investigated. The microstructural observations of as-cast MMCs unveil the existence of primary α-Mg phase and the presence of large amount of β-Mg17Al12 secondary phase at grain boundary. The specimens are subjected to homogenization heat treatment at 410 °C for 24 h; the β-Mg17Al12 phases are significantly dissolved in the matrix grain boundaries which enhance the ductility and decrease the hardness compared with the as-cast materials. The addition of SiCp reinforcement led to improved yield strength (YS) and ultimate tensile strength (UTS) of AZ61/SiCp composite compared to the unreinforced alloy. The maximum values of YS and UTS have been attained at AZ61/1wt%SiCp composites. The enhancement of YS and UTS was due to the presence of a uniformly distributed reinforced SiCp, which depends on grain refinement of the matrix and strong interfacial bonding between the matrix and reinforcement. In the case of fatigue test results, the addition of SiCp reduced the fatigue life and strength of AZ61 alloy composite. However, addition of 1wt%SiCp showed good mechanical and fatigue properties compared to pure AZ61 magnesium alloy and AZ61/2wt%SiCp composite. Furthermore, the effects of addition of SiCp on the mechanical and fatigue properties of the composite were confirmed by using the scanning electron microscope observation of fracture surfaces. [ABSTRACT FROM AUTHOR]

In this study, AZ61 alloy processed by equal channel angular pressing (ECAP) method, is presented. This research seeks to find out the relationship that exists between the microstructure of the AZ61-magnesium alloy doped with SiC and Ni and processed by ECAP in terms of hydrogen storage properties. The results indicate that grain size reduces nearly 10 times after 4 passes of ECAP. Homogeneous distribution of the SiC in the metal matrix composite (MMC) and dynamic recrystallization are also observed. There is a gradual reduction in the grain size when the number of ECAP passes are increased. This microstructural refinement induced by ECAP improves the storage capacity and reaction kinetics of the alloy. Besides, the addition of Ni catalyst achieves faster absorption and desorption kinetics. However, it does not change its capacity. Ni reacts with Mg to form an intermetallic, which is hydrogen-absorbing, which in turn, catalyzes the reaction. Apart from introducing defects, the ECAP process also produces Mg/Al intermetallic, which acts catalytically. It is shown that SiC-doped AZ61-magnesium alloy can absorb and desorb 6.8 wt% H 2 at 648 K and 50 atm. • AZ61 with SiC and Ni additives prepared by gravity stir casting method. • Dispersion characteristics of the particles influences the rate limiting factors. • AZ61-1 wt%SiC achieves a hydrogen capacity of 6.8 wt%. • Performance declines to 6.5 wt% when Ni catalyst is added. • Combining SiC and Ni shows improved kinetics. [ABSTRACT FROM AUTHOR]

In this research, magnesium alloy AZ31 reinforced with CNTs (0 wt.%, 0.1 wt.%, 0.5 wt.%, 1 wt.%) was produced by a stir casting method followed by aged heat treatment. Composites were investigated using x-ray diffraction and scanning electron microscope techniques. The microstructure of the CNTs/AZ31 has been qualitatively and quantitatively evaluated. The results show that stir casting is a suitable method for uniformly distributing CNTs and maintaining the integrated structure. The concentration of CNTs and aged heat treatment affects the crystallite size, crystallinity degree, precipitates and phase composition of the CNT-reinforced AZ31 alloy. An increase in the concentration of CNTs results in a decrease in the degree of crystallinity and dissolution of the secondary phase. In 0.1 wt.% CNTs, the crystallite size decreases and then increases. The aged heat treatment affects the composition of the phase and creates a new secondary phase to refine the microstructure and grain size. The compressive strength is linearly related to the concentration of CNTs. Bramfitt disregistry and precipitation strengthening play an important role in qualitatively and quantitatively refining and altering the microstructure of CNTs/AZ31. [ABSTRACT FROM AUTHOR]

Abstract The response surface methodology in the design of experiments (DOE) wizard and Gurson-Tvergaard-Needleman (GTN) model were employed to estimate the optimum GTN damage parameters and to validate their significant effects respectively on the ductile fracture behavior of ECAP deformed AZ61 magnesium alloy. Hollomon's flow stress was applied to identify uniform deformation and non-uniform deformation regions to investigate the void nucleation and coalescence processes separately. The significance of statistical results was evaluated with the analysis of variance (ANOVA) based on P-values and coefficients of determination (R 2). Correspondingly, the contributions of ECAP plastic deformation and the corresponding local plasticity (damage progresses) on the progress of GTN ductile fracture damage parameters were studied. Desirability function was used to show the significance of individual and interaction effects of optimum initial damage parameters on the respective response variables. By using response surface methodology, the optimum GTN damage parameters were determined at the corresponding positions of each critical response variables. Results also showed that varying both stress triaxiality and damage variables simultaneously can greatly affect the curve fitting process of experimental, simulation and GTN model curves. However, at constant stress triaxiality condition, the GTN model curve was observed perfectly fitting with the tensile test curve. [ABSTRACT FROM AUTHOR]

Cast commercial AZ61 magnesium alloys were processed through equal channel angular pressing (ECAP) and were comminuted into chips by filing with a rasp in order to measure their hydrogen storage properties. The effects of the number of ECAP passes and the processing route of ECAP on the hydrogen storage properties of AZ61 magnesium alloys were investigated. ECAP processing led to severe dynamic recrystallization and grain refinement of the AZ61 alloys. Of the analyzed samples, the AZ61 alloy processed via the Bc ECAP route with eight passes exhibited the smallest grain size, the fastest hydrogen absorption and desorption rates, and the highest gravimetric hydrogen storage capacity of 6.2 wt%. [ABSTRACT FROM AUTHOR]

In this paper, solution and ageing heat treatment processes were used to improve microplastic deformation behaviors of as-cast SiCp/AZ61 magnesium metal matrix composites (Mg MMCs) fabricated by stir casting method. Higher percentages of SiC particle reinforcements showed higher microhardness values. Ageing heat treatment process was seen significant on the 12 h aged 2 wt% SiCp/AZ61 Mg MMC which induced lower microhardness value. At the 12 h ageing of 2 wt% SiCp/AZ61 Mg MMC the formations of particle free regions and discontinuous secondary phases were observed. For a higher ageing time, the secondary phases distribution became continuous and laminar structure. The addition of 5 wt% SiC particles resulted in the formation of Mg 2 Si phase throughout the whole heat treatment processes. The addition of SiC particles reinforcements increased the phase heterogeneity during ageing heat treatment processes. XRD patterns revealed the presence of nanocrystalline MgSiO 3 phase on the 12 h aged 2 wt% SiCp/AZ61 Mg MMC. Using reference intensity ration (RIR) method a 51.6% of MgSiO 3 phase was determined which can cause the formation of microplastic deformation behavior. And also, the maximum average crystallite size, compressive microstrain and microcrack-free phase boundaries were observed on the 12 h aged 2 wt% SiCp/AZ61 Mg MMC. [ABSTRACT FROM AUTHOR]

This study analyzes the effect of substitution of Ni for Zn on microstructure and mechanical properties of Mg–Gd–Y–Zn–Mn alloy. Our results show that the volume fraction of Mg5(Gd, Y) and (Mg, Zn)3RE phase decreased and LPSO phase increased with more substitution of Ni. After homogenization, only α-Mg and LPSO phase existed. In Mg–Gd–Y–Zn–Mn alloys, the LPSO phases mainly consisted of the 14H type. While in Mg–Gd–Y–Ni–Mn alloy, the LPSO phases consisted of the 18R type. In addition, compared with Mg–Gd–Y–Zn–Mn alloy, the mechanical properties of as-extruded Ni-substitution alloys were improved due to the better refinement of the size of grains and LPSO phases. The tensile strength in as-extruded Mg–Gd–Y–Ni–Mn alloy could reach up to 400 MPa with 18% of the elongation to failure. [ABSTRACT FROM AUTHOR]

We studied the hydrogen storage properties of commercial AZ31 and AZ91 magnesium alloys with refined microstructure. Various processing techniques, such as equal channel angular pressing (ECAP) and high energy ball milling (HEBM), were utilized to modify the microstructure and phase composition of the alloys. X-ray diffraction (XRD), scanning electron microscopy (SEM), and optical digital microscopy (ODM) were utilized to characterise the microstructure and phase transformations during the hydrogen absorption/desorption processes. The isothermal kinetics are measured by a Sieverts'-type apparatus at the temperature of 350 ℃. In the ECAP process, the AZ31 alloy had a slightly higher storage capacity and faster absorption kinetics, absorbing 6.0 wt% (6.6 wt% - maximum) of hydrogen in less than 12 min. In the HEBM process, AZ91 absorbed 6.5 wt% of hydrogen and desorbed it in 347 ± 13 s, a faster rate than AZ31. The pressure–composition isotherms of all studied alloys at a temperature of 300 °C were determined. The processed alloys exhibited no pressure hysteresis. The microstructure of bulk samples and the morphology of prepared powders were shown to affect their hydrogenation behaviour. The activation energies for hydrogen desorption were 119 ± 2 kJ/mol for AZ31 alloy processed by ECAP and 128 ± 3 kJ/mol for AZ91 alloy processed by HEBM, which are significantly lower than the activation energy values of pure Mg hydride. • Hydrogen storage properties of commercial AZ31 and AZ91 alloys are studied. • The ECAP and HEBM processes were employed to enhance hydrogen storage performance. • Both processes significantly improved the kinetic and thermodynamics properties. • The processed alloys exhibited no pressure hysteresis • The activation energies reduced to 119 ± 5 kJ/mol for AZ31-ECAP and 128 ± 5 kJ/mol for AZ91-HEBM. [ABSTRACT FROM AUTHOR]

The process engineering of Mg alloys is nevertheless compromised due to their relatively poor mechanical properties. To address some of these difficulties, metal-matrix composites (MMCs) of Mg-alloys have been investigated for sometime. In the present work, small amounts (up to 1 wt%) of WS 2 nanotubes are mixed with Mg-alloy (AZ31) using melt-stirring process above 700 °C. The new MMC nanocomposites exhibit much superior mechanical properties vis a vis the pristine alloy. Metallographic investigation demonstrates that the average grain size has been reduced in inverse proportion to the added amounts of nanotubes up to 1 wt%. Physical considerations suggest that the main mechanism responsible for the reinforcement effect lies in the mismatch between the thermal expansion coefficients of the metal and the nanotubes. This mismatch induced large density of dislocations in the grain boundaries in the vicinity of the nanotube-matrix interface, which obstruct the crack propagation. [ABSTRACT FROM AUTHOR]

The mechanical properties and internal friction (damping capacity) of Mg–Zn–Y alloys with a long-period stacking ordered (LPSO) structure at different Y/Zn atomic ratios (2/1, 3/2 or 4/3) in cast and extrusion were investigated. It was found that the as-cast Mg–Zn–Y alloys with different Y/Zn atomic ratios possess a single LPSO phase with the same stable 18R-type structure. Among the three alloys, the alloy with 3/2 atomic ratio yields the highest damping capacity in low- and high-strain amplitude stages. Two damping peaks particularly P1 and P2 are detected in the Mg–Zn–Y alloy with 3/2 atomic ratio at approximately 108 and 220 °C, respectively. These results may be attributed to few solute atoms in Mg matrix and grain boundaries. In addition, the studied alloy with 3/2 atomic ratio exhibits excellent comprehensive properties in as-cast and as-extruded states; this alloy yields an ultimate tensile strength of 346 MPa and maintains a certain damping capacity (Q−1 > 0.01) in extrusion. [ABSTRACT FROM AUTHOR]

The effect of equal channel angular extrusion (ECAE) on the mechanical behavior of AM60/Al2O3p magnesium metal–matrix nanocomposites was investigated. ECAE is a useful technique to produce bulk nanostructured materials through severe plastic deformation. The present magnesium metal–matrix composites (Mg MMCs) with 1 wt% nanosized Al2O3 particles for ECAE were fabricated using stir-casting method. The significantly enhanced mechanical behavior of AM60/Al2O3p magnesium metal–matrix nanocomposites at room temperature, for instance, yield strength (YS), ultimate tensile strength (UTS), and ductility, can be obtained after ECAE process. The AM60/Al2O3p MMC after 4 passes of ECAE exhibited greater YS, UTS, and ductility (+135%, +107%, and +245% increase, respectively) than those of as-cast AM60. Experimental results show that the AM60/1wt %Al2O3p MMC after 4 passes of ECAE exhibits the superior mechanical behavior. [ABSTRACT FROM AUTHOR]

The influence of trace amounts of Sn on the formation of the LPSO phase and mechanical properties of Mg–RE–Zn alloys is discussed. Results show that trace Sn has no effect on the phase category of the alloy. After annealing, however, Sn-doped alloys show a high density of the lamellar-shaped LPSO phase. After Sn addition, the strength of the alloy is enhanced but its elongation is reduced. [ABSTRACT FROM AUTHOR]

Magnesium alloys are attractive for the production of lightweight parts in modern automobile and aerospace industries due to their advanced properties. Their mechanical properties are usually enhanced by the incorporation with reinforcement particles. In the current study, reinforced AZ31 magnesium alloy was fabricated through the addition of bulk Al and the incorporation of SiC nanoparticles using a stir casting process to obtain AZ31-SiC nanocomposites. Scanning electron microscope (SEM) investigations revealed the formation of Mg17Al12 lamellar intermetallic structures and SiC clusters in the nanocomposites. Energy dispersive spectroscopy (EDS) detected the uniform distribution of SiC nanoparticles in the AZ31-SiC nanocomposites. Enhancements in hardness and yield strength (YS) were detected in the fabricated nanocomposites. This behavior was referred to a joint strengthening mechanisms which showed matrix-reinforcement coefficient of thermal expansion (CTE) and elastic modulus mismatches, Orowan strengthening, and load transfer mechanism. The mechanical properties and wear resistance were gradually increased with an increase in SiC content in the nanocomposite. The maximum values were obtained from nanocomposites containing 1 wt% of SiC (AZ31-1SiC). AZ31-1SiC nanocomposite YS and hardness were improved by 27% and 30%, respectively, compared to AZ31 alloy. This nanocomposite also exhibited the highest wear resistance; its wear mass loss and depth of the worn surface decreased by 26% and 15%, respectively, compared to AZ31 alloy. [ABSTRACT FROM AUTHOR]

Abstract: The effects of Mn substitution for Mg on the microstructure, mechanical properties, and corrosion behavior of Mg69−xZn27Ca4Mnx (x=0, 0.5 and 1at.%) alloys were investigated using X-ray diffraction, compressive tests, electrochemical treatments, and immersion tests, respectively. Microstructural observations showed that the Mg69Zn27Ca4 alloy was mainly amorphous. The addition of Mn decreases the glass-forming ability, which results in a decreased strength from 545MPa to 364MPa. However, this strength is still suitable for implant application. Polarization and immersion tests in the simulated body fluid at 37°C revealed that the Mn-doped Mg–Zn–Ca alloys have significantly higher corrosion resistance than traditional ZK60 and pure Mg alloys. Cytotoxicity test showed that cell viabilities of osteoblasts cultured with Mn-doped Mg–Zn–Ca alloys extracts were higher than that of pure Mg. Mg68.5Zn27Ca4Mn0.5 exhibits the highest bio-corrosion resistance, biocompatibility and has desirable mechanical properties, which could suggest to be used as biomedical materials in the future. [Copyright &y& Elsevier]

This study involves the investigation of the mechanical properties of the extruded tube products with reinforced silicon carbide particulates (SiCp). Finite element analyses are firstly conducted to analyze the plastic flow of the magnesium alloy AZ61 within the die and to investigate the effects of initial billet temperatures on the extrusion loads and final product temperatures. AZ61/SiCp composite ingots reinforced with different weight fractions of SiCp are fabricated by a melt stirring technique. A specially designed die set is used in the extrusion experiments to obtain tubes with uniform thickness distribution in the circumferential direction. The extruded tubes are also heat treated to obtain even better mechanical properties. Finally, tensile tests, Vickers microhardness, tests and microstructure observation are performed on the billets and extruded tubes of AZ61 monolithic alloys and AZ61/SiCp composites. A much smaller grain size and higher tensile strength and hardness are achieved for the extruded AZ61/SiCp composite tubes. [ABSTRACT FROM AUTHOR]

Gravitational melt-stir casting produced hybrid nano-reinforcements (β-SiCp) and micro-reinforcements (Bi and Sb) of AZ91 composites. SiCp-diffused discontinuous β-Mg17Al12 precipitation with a vital factor of SiC was exhibited at the grain boundary region, formulated Mg3Si throughout the composite and changed the present Mg0.97Zn0.03 phases. The creation of Mg2Si (cubic) and SiC (rhombohedral axes) enhanced the microhardness by 18.60% in a 0.5 wt.% SiCp/AZ91 matrix. The microhardness of 1 wt.% SiCp/AZ91 was slightly reduced after Mg0.97Zn0.03 (hexagonal) reduction. The best ultimate tensile value obtained was about 169.33 MPa (increased by 40.10%) in a 0.5 wt.% SiCp/AZ91 matrix. Microelements Bi and Sb developed Mg3Bi2, Mg3Sb2 and monoclinic C60 phases. The best peak yield strength of 82.75 MPa (increased by 19.85%) was obtained with the addition of 0.5 wt.% SiCp/1 wt.% Bi/0.4 wt.% Sb. The mismatch of the coefficient of thermal expansion of segregated particles and the AZ91 matrix, the shear transfer effect and the Orowan effect, combined with the quantitative value of phase existence, improved the compressive strengths of the composites with 0.5 wt.% β-SiCp, 1 wt.% β-SiCp and 0.5 wt.% SiCp/1 wt.% Bi/0.4 wt.% Sb by 2.68%, 6.23% and 8.38%, respectively. Notably, the Charpy impact strengths of 0.5 wt.% and 1 wt.% β-SiCp-added AZ91 composites were enhanced by 236% (2.89 J) and 192% (2.35 J), respectively. The addition of Bi and Sb with SiCp resulted in the formation of a massive phase of brittle Al6Mn. Al–Mn-based phases (developed huge voids and cavities) remarkably reduced impact values by 80% (0.98 J). The discussion covers the quantitative analyses of X-ray diffraction, optical microscopy and scanning electron microscopy results and fracture surfaces. [ABSTRACT FROM AUTHOR]

In this work, AZ91 magnesium alloy reinforced with a low fraction (0–1) wt.% tungsten disulfide(WS 2) microparticles have been fabricated using stir casting method. Effects of WS 2 microparticles on mechanical properties, microstructure, and their correlation have been analyzed. The microstructure of composites has been investigated by scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS) and X-ray diffractometer. Results indicate that density, hardness, ultimate tensile strength (UTS), and tensile ductility have a direct relation with reinforcement (WS 2) contents and has optimal value for 0.6 wt% WS 2 /AZ91 composites then slightly decrease afterward. The UTS and hardness of 0.6 wt%WS 2 /AZ91 were increased by 23.23% and 10.65% respectively with respect to monolithic AZ91. The ultimate compressive strength(UCS) is directly related with WS 2 concentration and 10.07% enhancement in UCS for 1 wt%WS 2 /AZ91 composites have been noted. The trend is interlinked with density and hardness of composites. SEM images depict, WS 2 micro-particles suppress β-Mg 17 Al 12 precipitates, refine the microstructure and enhance the grain size resulting in an increase in mechanical properties. The improvement in microstructure and mechanical properties is attributed to the dispersion of WS 2 particles which hinder the grain growth. The increase in porosity has causes the decrease in mechanical behavior of 1 wt%WS 2 /AZ91. Twin boundary fracture has been found major fracture phenomenon in fractured WS 2 /AZ91 surfaces. • WS 2 /AZ91 metal matrix composites have been manufacture by stir casting method. • Density and porosity of WS 2 /AZ91 composites has been assessed. • Mechanical behavior under compression and tension has been analyzed. • Effect of WS 2 on microstructure has been investigated. • Fracture behavior of composites has been studied. [ABSTRACT FROM AUTHOR]

The tribological behavior of AZ31 Mg alloy reinforced with multiwall carbon nanotubes (MWCNTs) was studied through experiments on a ring-on-block wear testing apparatus against 45C steel. The composites were successfully fabricated using stir-casting processing with different percentages of MWCNTs and then age hardened for 10 h. The effect of the various concentrations of MWCNTs on the microstructures, tribological properties, and wear mechanisms of the composites were systematically examined by scanning electron microscopy (SEM). With increasing percentage content of MWCNTs, the wear rate and the coefficient of friction decreased, which is attributed to the microhardness and self-lubricating properties of the MWCNTs. The microstructure characterization results established different mechanisms—specifically, abrasion, oxidation, and delamination—and very small plastic deformation. • Magnesium alloy AZ31 reinforced with multiwalled carbon nanotubes was fabricated using stir casting method. • Samples were homogenized for 24 h at 400C0 and then aged for 10 h at 200C0 temperature. • Wear tests for as-cast and aged composites were performed using Ring on Block wear apparatus under dry and wet conditions and mass wear loss and coefficient of friction was determined. • Worn surfaces were analyzed using scanning electron microscope for wear mechanism analysis. [ABSTRACT FROM AUTHOR]

A high-strength Mg-8.8Gd-3.8Y-1.0Zn-0.7Mn (wt%) alloy hollow profile with complex cross-section was successfully fabricated through porthole die extrusion, and its weld seam was analyzed for microstructure and element distribution to investigate the impact of solid-state bonding. The weld seam displayed a homogeneous magnesium grain structure and a precipitation-free zone. The diffusion behavior of alloying elements during solid-state bonding significantly affected the microstructure of the weld seam, with Gd and Y atoms diffusing towards the outside of the weld region. The hollow profile exhibited favorable mechanical properties, with an ultimate tensile strength (UTS) of 470 MPa, a tensile yield strength (TYS) of 309 MPa, and an elongation (EL) of 7.4%, and showed a minor negative effect from the weld seam. • High-strength Mg-Gd-Y-Zn-Mn alloy hollow profiles showed a favorable metallurgical bond in the weld seam with a homogeneous magnesium grain structure and no microvoids. • Alloying element diffusion influenced the weld seam microstructure, resulting in lower concentrations of Gd and Y in the weld region, while Zn and Mn showed a more uniform distribution. • The presence of the weld seam had minimal impact on the overall mechanical properties of the hollow profiles, which retained superior mechanical performance. [ABSTRACT FROM AUTHOR]

High-performance as-extruded and peak-aged Mg-9.2Gd-3.3Y-1.2Zn-0.9Mn (wt%) alloys have been fabricated by semi-continuous casting, heat-treating, extruding and ageing processes. The effects of different heat treatments on the microstructure and mechanical properties have been investigated. Lamellar and bulk-shaped 14H-type long-period stacking ordered (LPSO) phase and few RE-rich (RE: rare earth element) particles form by different heat treatments. After hot extrusion, the heat-treated alloy with bulk-shaped LPSO phase exhibits an equal-axial microstructure, while the heat-treated alloy with lamellar LPSO phase across the grains shows bimodal grain microstructure consisting of fine equal-axial grains and coarse deformed grains. The more profuse lamellar LPSO phase in heat-treated alloy generates higher volume fraction of deformed grains and finer equal-axial grains, hence leads to higher strength but lower ductility. After ageing, the alloy with profuse LPSO and β′ phases achieves the superior mechanical properties with ultimate tensile strength (UTS) of 525 MPa, tensile yield strength (TYS) of 420 MPa and elongation to failure (EL) of 6.3%. The alloy strengthening is mainly attributed to the bimodal grain microstructure, LPSO phase, Mg 5 Gd (β) phase and β′ phase. [ABSTRACT FROM AUTHOR]

The Mg-8Gd-4Y–1Zn–Mn (wt%) alloys prepared by semi-continuous casting and homogenizing treatment were extruded using different extrusion ratios and subsequent cooling processes. The microstructure, texture and mechanical properties of extruded alloys were investigated. The dynamic recrystallization process is promoted by increasing the extrusion ratio, while the static recrystallization process is suppressed by subsequent water cooling rather than air cooling. When the recrystallization ratio is relatively low, the non-recrystallized region showing a fiber < 10 1 ‾ 0 > Mg //extrusion direction (ED) texture component dominates the texture characteristic. With the increase of the recrystallization ratio, the recrystallized region exhibiting an abnormal <0001> Mg //ED texture gradually dominates the texture characteristic. The grain boundary energy anisotropy and the grain boundary mobility anisotropy are assumed to be changed by the Gd and Y addition, which affect the preferential growth of the abnormal <0001> Mg //ED oriented grains and eventually lead to the formation of abnormal texture component. The as-aged alloy extruded at the extrusion ratio of 6 followed by air cooling shows the highest strength. The extruded alloys with an intensive abnormal texture component exhibit the best mechanical isotropy in both as-extruded and as-aged conditions. The differences in strength along different directions are mainly resulted from the fiber strengthening. [ABSTRACT FROM AUTHOR]

Abstract: The microstructure and mechanical properties of Mg–8.40Gd–5.30Y–1.65Zn–0.59Mn (wt%) alloy were investigated in this study. The phase composition of the alloy involved an α-Mg matrix and long-period stacking ordered phases of Mg12Zn(Y,Gd) with some eutectic phases. After aging at 200°C for 50h following extrusion (extrusion ratio= 11:1, extrusion temperature=400°C), the alloy achieved high strength (ultimate tensile strength=∼500MPa, tensile yield strength=∼322MPa) and good ductility (elongation=∼10.0%) and exhibited excellent comprehensive mechanical properties. These properties could be attributed to the numerous plate-shaped β′ phase precipitates in the α-Mg matrix, as well as the small dispersed block-shaped long-period stacking ordered phases along the grain boundaries. [Copyright &y& Elsevier]

Abstract: This study investigates the effects of heat treatment on the morphology of long-period stacking ordered phase (LPSO) and the corresponding mechanical properties of Mg–9Gd–xEr–1.6Zn–0.6Zr (1–4wt%) using optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectrometry, X-ray diffraction, transmission electron microscopy, and tensile tests. The microstructure analysis of the as cast alloys showed that the volume fraction of the (Mg, Zn)3(Gd, Er) phase increased with increasing Er content. The (Mg, Zn)3(Gd, Er) phase in grain boundaries transformed into the 14H-LPSO phase Mg12Zn(Gd, Er) after heat treatment between 400°C and 515°C. The bulk shaped LPSO phases distributed along the grain boundaries produced isometric crystal grains in and enhanced the ductility of the as-extruded alloys. However, the lamellar LPSO phases precipitating in the grain interior induced strip-shaped grains in and improved the strength of the as-extruded alloys. [Copyright &y& Elsevier]