Q.B. Nguyen

Microstructure and Mechanical Characteristics of AZ31B/Al2O3 Nanocomposite with Addition of Ca

The present study addresses the development of a AZ31B—Al2O 3 nanocomposite. AZ31B—Al2O3 nannocomposite is known to exhibit excellent ductility matching with that of pure aluminum but with limited strength levels. Addition of Ca is shown in this study to lead to a simultaneous improvement in 0.2%YS, UTS and hardness while the ductility was compromised. The ductility, however, stayed ~30% higher than the ductility of monolithic AZ31B. The results suggest that this alloy-composite has significant potential in diverse engineering applications when compared to AZ31B or AZ31B—Al2O3 nanocomposites.

Investigation into tensile and compressive responses of Mg-ZnO composites

Abstract In the present study, the mechanical properties of magnesium composites containing nano-ZnO particles are investigated. An increase in microhardness was observed with increasing amount of ZnO from 0·5 to 1·5 vol.-% in magnesium. The tensile and compressive yield strengths of the composites remained similar to that of Mg. This is attributed to the heterogeneous grain size distribution and the resultant weak basal texture. The tension–compression yield asymmetry was also found to be minimal due to the lack of strong basal texture. The composites showed improved ultimate tensile and compressive strengths, and this is attributed to well known strengthening mechanisms due to the presence of fine reinforcement particles. The tensile failure strain was significantly improved in composites, while there was a compromise in compressive failure strain. The improved tensile failure strain was due to non-basal slip activation through grain refinement and lack of intense basal intensity in composites.

Improving Compressive Strength and Oxidation Resistance of AZ31B Magnesium Alloy by Addition of Nano-Al2O3 Particulates and Ca

In the present study, new light weight nanocomposites (AZ311.5Al2 O3-Ca) based on magnesium alloy AZ31B are developed using disintegrated melt deposition technique. Microstructural characterization studies revealed equiaxed grain structure, minimal porosity, and good matrix-reinforcement interfacial integrity. The results also showed that addition of both nano-Al 2O3 and Ca led to a simultaneous improvement in 0.2% yield compressive strength (0.2% YCS), ultimate compressive strength (UCS), and work of fracture (WoF) of the AZ31B magnesium alloy while failure strain was slightly compromised. Moreover, excellent oxidation resistance of this composite was realized when compared to AZ31B up to 500°C. The results suggest that this composite formulation can be used in diverse engineering applications requiring light weight structural materials.

Tensile and Compressive Responses of Ceramic and Metallic Nanoparticle Reinforced Mg Composites

In the present study, room temperature mechanical properties of pure magnesium, Mg/ZrO2 and Mg/(ZrO2 + Cu) composites with various compositions are investigated. Results revealed that the use of hybrid (ZrO2 + Cu) reinforcements in Mg led to enhanced mechanical properties when compared to that of single reinforcement (ZrO2). Marginal reduction in mechanical properties of Mg/ZrO2 composites were observed mainly due to clustering of ZrO2 particles in Mg matrix and lack of matrix grain refinement. Addition of hybrid reinforcements led to grain size reduction and uniform distribution of hybrid reinforcements, globally and locally, in the hybrid composites. Macro- and micro- hardness, tensile strengths and compressive strengths were all significantly increased in the hybrid composites. With respect to unreinforced magnesium, failure strain was almost unchanged under tensile loading while it was reduced under compressive loading for both Mg/ZrO2 and Mg/(ZrO2 + Cu) composites.

Enhancing tensile and compressive strengths of magnesium using nanosize (Al2O3+Cu) hybrid reinforcements

This study investigates the microstructure and mechanical properties of magnesium (Mg) containing alumina (Al2O3) and copper (Cu) nanoparticles as hybrid reinforcements. For composite preparation, the amount of Cu was varied from 0.1 to 0.9 volume percent, whereas the amount of Al2O3 was fixed at 1 volume percent. Mg and its composites were synthesized using powder metallurgy route incorporating energy-efficient microwave sintering followed by hot extrusion. Hybrid reinforcements in Mg matrix led to a grain size reduction, and the grain size decreased with increasing presence of secondary phases (reinforcements and intermetallics). Overall distribution of secondary phases within the matrix was observed to be uniform despite the formation of clusters. A significant improvement in microhardness was exhibited by all composite formulations when compared to pure Mg. The results also showed that yield and ultimate strengths were enhanced in all composite formulations under both tensile and compressive loading while tensile and compressive failure strains were compromised.

Simultaneous effect of nano-Al2O3 and micrometre Cu particulates on microstructure and mechanical properties of magnesium alloy AZ31

Abstract In the present study, magnesium composites are synthesised through the addition of nano-alumina and micrometre copper particulates in AZ31 magnesium alloy using the technique of disintegrated melt deposition. Nano-alumina and micrometre size copper particulates are known to significantly enhance the ductility and strength of magnesium materials respectively. The simultaneous addition of Cu and nano-Al2O3 particulates led to an overall improvement in both microstructural characteristics in terms of distribution and morphology of intermetallics/particulates and mechanical response of AZ31. The 0·2% yield strength increased from 180 to 300 MPa (67%), while the ductility increased by almost 24%. The overall tensile properties assessed in terms of work of fracture improved by 66%. An attempt is made to correlate the tensile response of composites with their microstructural characteristics. The results suggest that these alloy composites have significant potential in diverse and wider engineering applications when compared to AZ31 alloy.

Synthesis and Properties of Light Weight Magnesium-Cenosphere Composite

Significantly light weight magnesium composite foams are synthesised by addition of fly ash cenosphere particles (waste from coal-fired power plants) in biocompatible pure magnesium using solidification-based disintegrated melt deposition technique. The density of the composite foams synthesised in this study approaches that of plastics- and polymer-based composites. Microstructure development of Mg/cenosphere composite foams was favourable as they exhibited better dimensional stability (reduced coefficient of thermal expansion) and remarkable improvements in tensile strengths, compressive strengths, compressive total strain and microhardness. The present study highlights the processing, microstructure and mechanical properties of Mg/cenosphere composite foams which hold great potential as light weight metal-based green materials for diverse weight critical applications spanning from engineering to biomedical sector.

Enhancing hardness, CTE and compressive response of powder metallurgy magnesium reinforced with metastable Al90Y10 powder particles

In the present study, magnesium composites containing pre-milled metastable Al90Y10 particles were synthesised using powder metallurgy route incorporating microwave-assisted sintering and hot extrusion. The results of X-ray diffraction reveal that the pre-milled powder changed from crystalline structure to metastable structure after 200 hours ball milling and the particle retained its metastable state in all composite samples. Microstructural characterisation shows that metastable particles were fairly distributed in the magnesium matrix and located along the grain boundaries. Further, when the amount of metastable particles increased, microhardness, 0.2%yield compressive strength and ultimate compressive strength increased significantly, coefficient of thermal expansion reduced gradually, while the compressive total strain remained almost the same. Work of fracture that indicates damage tolerance increased up to 66%. The interrelationship between microstructure and properties is discussed. Results suggest that the developed composites exhibit superior strength levels and are promising for compressive strength and damage tolerance-based engineering applications.

Microstructure and damping characteristics of Mg and its composites containing metastable Al85Ti15 particle

This paper reports for the first time the damping behavior of Mg-Al85Ti15 metastable composites synthesized using near dense blend-press-microwave sinter-hot extrusion methodology. Optical microscopy results show that the metastable particles were located along the grain boundaries and the formation of twins within the grains. In addition, scanning electron microscopy reveals reasonable distribution of particles, good matrix-particle interfacial bonding and minimal presence of microvoids. The damping test results show an increment in damping capacity and damping loss rate with the presence and increasing amount of particles. The effect of microstructure on damping characteristics of magnesium and damping mechanisms are discussed.

The ability of cast composite technology to enhance ductility of wrought magnesium and alloys

Abstract At ambient temperature, hexagonal close packed magnesium has limited ductility due to low availability of active slip systems. In this work, 3 methods of enhancing the ductility of wrought magnesium are discussed, namely: (1) addition of microparticles such as Ti, Mo and SiC (Method 1), (2) addition of various oxide nanoparticles as well as carbon nanotubes (Method 2) and (3) use of aluminium based core as continuous reinforcement (Method 3). In Method 1, the magnesium matrix is softened (Ti microparticle case), delocalized in deformation (Mo microparticle case) or in a reduced state of stress around the microparticle after heat treatment (SiC microparticle case). In Methods 2 and 3, the basal plane in magnesium is sometimes tilted from 0° to 45° (to the force axis), enabling basal slip to occur more easily in the composite. In the cases where the basal plane is oriented parallel to the force axis, non-basal slip at room temperature occurs more easily between the aligned basal planes. In Method 2, the nanoparticles present also provide sites where cleavage cracks are opened ahead of the advancing crack front. An attempt is made to correlate the ductility enhancement of wrought magnesium as a function of the way it is reinforced.