Khin Sandar Tun

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.

Synthesis and Characterization of Nano Boron Nitride Reinforced Magnesium Composites Produced by the Microwave Sintering Method

In this study, magnesium composites with nano-size boron nitride (BN) particulates of varying contents were synthesized using the powder metallurgy (PM) technique incorporating microwave-assisted two-directional sintering followed by hot extrusion. The effect of nano-BN addition on the microstructural and the mechanical behavior of the developed Mg/BN composites were studied in comparison with pure Mg using the structure-property correlation. Microstructural characterization revealed uniform distribution of nano-BN particulates and marginal grain refinement. The coefficient of thermal expansion (CTE) value of the magnesium matrix was improved with the addition of nano-sized BN particulates. The results of XRD studies indicate basal texture weakening with an increase in nano-BN addition. The composites showed improved mechanical properties measured under micro-indentation, tension and compression loading. While the tensile yield strength improvement was marginal, a significant increase in compressive yield strength was observed. This resulted in the reduction of tension-compression yield asymmetry and can be attributed to the weakening of the strong basal texture.

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.

An investigation into the effect of ball milling of reinforcement on the enhanced mechanical response of magnesium

Magnesium composites containing as-received and ball-milled (B) Al particles were synthesized through powder metallurgy route using microwave-assisted rapid sintering technique followed by hot extrusion. Microstructural characterization revealed fairly uniform distribution of both as-received and ball-milled (up to 1.626 vol.%) Al particles in the matrix and reduction in average matrix grain size. Compared to monolithic Mg, Mg/Al, and Mg/Al (B) composites exhibited significantly higher strengths and failure strains. The results revealed that strength and failure strain (up to 1.626 vol.% Al) of composites containing ball-milled Al particles remained higher compared to composites containing as-received Al particles. Compared to monolithic Mg, Mg/1.626Al (B) composite exhibited the best mechanical properties improvement with an increase of 78%, 79%, 87%, and 225%, in 0.2%YS, UTS, failure strain and WOF, respectively, while for Mg/1.626Al composite, the improvement was 51%, 53%, 65% and 142%, respectively. The effects of as-received and ball-milled Al particles contribution on the enhancement of mechanical properties of Mg is investigated in this article.

Role of Microstructure and Texture on Compressive Strength Improvement of Mg/(Y2O 3 + Cu) Hybrid Nanocomposites

In this study, uniaxial compressive properties of pure magnesium and Mg/(Y 2O3 + Cu) hybrid nanocomposites are investigated. Addition of hybrid reinforcements (ceramic + metal) at nano-length scale led to grain-size refinement and the amount of porosity remained below 1%. The presence of hybrid reinforcements led to a significant increase in 0.2% compressive yield strength (CYS) and ultimate compressive strength (UCS) while the failure strain was compromised. Best improvements in 0.2% CYS, UCS, and hardness were realized when the amount of copper was increased to one volume percent for fixed 0.7% Y2O3 nanoparticulates. Comparatively low ductility of magnesium hybrid nanocomposites under compressive loading was attributed to the absence of twinning unlike pure magnesium. The variation in the mechanical properties in this study is correlated with the microstructural features and texture effects.

Enhancing Uniform, Nonuniform, and Total Failure Strain of Aluminum by Using SiC at Nanolength Scale

The present study reports a unique tensile response of pure aluminum triggered due to the presence of SiC particles at nanolength scale. Al/SiC nanocomposites were synthesized by using energy efficient microwave assisted powder metallurgy route. Characterization studies conducted on the extruded samples revealed that the increasing presence of SiC particles at nanolength scale did not affect the 0.2% yield strength but increased ultimate tensile strength and work of fracture. Most interestingly, the presence of SiC nanoparticles increased the uniform, nonuniform, and total strain of aluminum when compared with pure aluminum. An attempt has been made in this study to inter-relate the enhanced tensile response of aluminum with the ability of SiC nanoparticles to homogenize the slip process and to delay void initiation and coalescence during tensile loading.

Effect of hybrid reinforcement on the high temperature tensile behavior of magnesium nanocomposite

Abstract In the present study, results revealed that hybrid (0.7 % yttria + 0.3 % copper) nano-particle reinforcement has a significant strengthening effect on commercially pure magnesium reaching 100 °C, which gradually diminishes with further increase in temperature. Due to the presence of reinforcement particles, magnesium matrix also completely recrystallizes at 100 °C. Hybrid nano-reinforcement also assisted in the deformation process and achieved large ductility at a relatively low temperature.

Strength of Mg–3%Al alloy in presence of graphene nano-platelets as reinforcement

ABSTRACT Bulk Mg–3%Al alloy-based nanocomposites containing graphene nano-platelets (GNPs) were synthesised using the powder metallurgy technique incorporating energy efficient hybrid microwave sintering and hot extrusion. GNPs in amounts of 0.1, 0.3 and 0.5 wt-% were investigated as reinforcements. Microstructural characterisation accomplished using optical, scanning and transmission electron microscopy revealed the presence of minimal porosity (<1%), a uniform distribution of GNPs in the matrix and a reduced grain size as a result of the presence of GNPs. The results of mechanical property characterisation revealed an overall improvement in micro-hardness and compressive response, due to the presence of GNPs, with best results exhibited by the Mg–3Al/0.3% GNPs composite. The ductility under compressive loading for composite samples remained higher than 20%.