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In this study, commercial AZ31 Mg alloys were processed by equal channel angular pressing (ECAP) to study the effects of processing route and numbers of passes on hydrogen storage properties of AZ31 alloys. Furthermore, Mg-based metal matrix composites (MMCs) were fabricated by gravimetric casting of AZ31 alloy, activated carbon and Ni to investigate the effect of additives on hydrogen storage properties. The results indicated that kinetics of hydrogen uptake increased with the increasing number of pass. AZ31 processed by ECAP route B c with 8 passes had hydrogen capacity of 7.0 wt%, and demonstrated the highest grain refinement and the fastest hydrogen absorption kinetics. With the addition of 5 wt% of activated carbon and 0.5 wt% Ni, the hydrogen sorption kinetics of MMCs was enhanced and was comparable to that of the AZ31 processed by ECAP with 8 passes; however, in exchange for the improved kinetics, the hydrogen storage capacity was lowered to 6.3 wt%. To enhance hydrogen absorption kinetics, adding catalysts in the casting process could be more efficient than post-casting ECAP treatment if saving processing time is the priority. [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]

Magnesium is the lightest metal and is extensive in the structural application. The metal matrix composites are developed to improve the strength of magnesium alloys. In this research, AZ91 alloy reinforced with 1 wt% WS 2 was produced using stir casting process. The composite was homogenized for 24 h at 410 °C and subsequently aged for 10 h at 200 °C. The severe plastic deformation was performed using equal channel angular pressing (ECAP). The phase composition was analyzed using X-ray diffraction techniques. The microstructure, fractography, and mechanical properties of ECAPed composites have been investigated using scanning electron microscope, and universal testing machines, respectively. The results indicate that B-phases are present in the form of particles inside and at grain boundaries in annealed composites, which are refined to needle-shaped precipitates at grain boundaries, and grains size is refined to 0.2 μm after 4passes of ECAP. Microhardness and tensile yield strength are proportional to the number of passes, and 20.45% and 103.5% are increased respectively after 4pass. The UTS was found to be maximum (324.8 MPa) for 4P WS 2 /AZ91. Fractography analysis revealed that plastic fracture in annealed and elastic-plastic fracture occurred after 4P WS 2 /AZ91 MMC. • WS 2 /AZ91 (MMCs) were manufactured by stir casting method and subsequently annealed are deformed by ECAP. • ECAP effects on microstructure and mechanical behavior of WS 2 /AZ91 MMCs have been investigated. • The relation between number of passes and strength has been established. • The investigations reveal that 4pass-WS 2 /AZ91 exhibits maximum hardness and ultimate tensile strength. [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]