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In the present study, Mg-9Al/MWCNTs (multi-walled carbon nanotubes) composites were synthesized using the technique of powder metallurgy followed by hot extrusion. MWCNTs were dispersed in Mg-9Al matrix using an ionic gemini dispersant. Microstructural characterization studies revealed that MWCNTs can be individually dispersed with no structural damage. Matrix-MWCNT was found to be excellent (absence of voids and debonding). Results further revealed that the addition of MWCNTs significantly affected the size of Mg17Al12 phase, which decreased from micron to nano length scale. The tensile test results revealed that the elongation and ultimate tensile strength of Mg-9Al composite with 0.4 wt % MWCNTs content were 15% and 355 MPa, respectively, showing 150% and 18% enhancement in comparison to Mg-9Al alloy. The remarkably enhanced mechanical properties were mainly attributed to the uniformly distributed nanoscale Mg17Al12 s phase in composite and the excellent interface bonding between MWCNTs and matrix.

Magnesium based micro-composites are known to have good mechanical integrity and are broadly investigated for different structural applications, however, their electromagnetic interference (EMI) protecting viability has rarely been studied. Thus, with an increasing interest in developing components made of magnesium alloys/composites for EMI SE (shielding effectiveness) applications, this study focusses on the electromagnetic shielding, electrical and magnetic properties of Mg/xTi (x = 5, 10, 15 wt %) micro-composites in correlation to the microstructure. The results indicated that there was grain refinement with progressive addition of Ti particulates in the Mg matrix. It was also found that the electrical conductivity of the composites decreased with increasing Ti amount. The magnetic characterisation performed on the samples verified that the composites are non-magnetic in nature. An interesting observation was made in this study pertaining to the SE values of the micro-composites. The SE values in the X-band microwave range (8.2–12.4 GHz) showed that with an increase in Ti wt%, the SE value remained equal among all the magnesium titanium composites, but improved in comparison to pure magnesium. This was attributed to decreased reflection (SER) (due to decrease in volume of Mg matrix with increase in amount of Ti reinforcements) and simultaneously increased absorption (SEA) (due to increase in amount of Ti which led to multiple internal reflection) coefficients of the shielding effectiveness.

In the present study, aluminum based metal matrix composites containing various amounts of boron nitride (BN) nanoparticulates (0, 0.5, 1.0 and 1.5 vol.%) were fabricated by using the powder metallurgy (PM) technique involving microwave sintering and hot extrusion process. The microstructure, physical, thermal, mechanical and damping characteristics of the extruded nanocomposites were investigated. Field emission scanning electron microscopy (FE-SEM) study shows the evenly distributed BN particles in Al matrix. Mechanical analysis indicates that the compression, hardness and tensile strength of Al-BN nanocomposites increases with increasing amount of BN content. Particularly, a significant improvement in the tensile strength (?36%) is achieved in Al-1.5 vol.% BN nanocomposite when compared to the pure aluminum (Al). This improvement strength can be attributed to the dispersion hardening of the Al matrix due to the presence of hard BN nanoparticles. Thermal analysis shows that the coefficient of thermal expansion (CTE) decreases with increasing amount of BN which may be ascribed to inherent low CTE of BN nanoparticles used as reinforcement. The addition of BN nanoparticulates enhanced the damping characteristics of pure Al with Al-1.5 vol.% BN nanocomposite exhibiting the maximum damping capacity and damping loss rate with a minimum change in elastic modulus. The improved combination of properties exhibited by Al-BN nanocomposites make them potential candidates for a wide spectrum of industries especially for weight critical applications. This publication was made possible by NPRP Grant 7-159-2-076 from the Qatar National Research Fund (a member of the Qatar Foundation). Scopus

The hot deformation behavior of hybrid SiC and CNTs reinforced AZ61 alloy composite was investigated by hot compacting at the strain rate range of 10−4–0.1 s−1 and temperature range of 250–400 °C. The constitutive equation and processing maps were successfully established and checked. The results revealed that the composite exhibited typical flow behavior of metallic materials, and the flow stress increased as the temperature decreased and strain rate increased. The flow behavior was precisely described by using hyperbolic sine constitutive equation in this work. The average stress exponent and activation energy of the composite are 4.9 and 174 kJ/mol, respectively, indicating that the dominant deformation mechanism might be dislocation climb. The processing maps of the composite exhibited two instability zones and two safe zones (250–330 °C, 0.001–0.006 s−1 and 350–390 °C, 0.0001–0.0005 s−1) for selection of optimum processing parameters. Dynamic recrystallization (DRX) occurred in the safe zones, however, cracking and twinning were observed in the instability zones. In addition, the examination of microstructure evolution revealed that DRX gradually occurred more adequately as the temperature increased and strain rate decreased, and SiC particulates could promote the DRX of the composite due to the particle stimulating nucleation (PSN) effect.

In the present study, Mg-3Al-xLa (x ∼ 1, 2.5, 4) alloys were synthesized using disintegrated melt deposition technique followed by hot extrusion. These alloys were critically investigated for microstructure, tensile and compression properties, damping properties, microhardness and fracture morphology. The grain size of Mg-3Al was significantly reduced by the addition of Lanthanum (La) and it was minimum for 2.5 La-containing alloy (∼5.8 μm, 25% of pure Mg grain size). SEM and X-ray studies revealed the suppression of β-eutectic phase ( M g 17 A l 12 ) due to the formation of A l 11 L a 3 , A l 2 L a , and A l 2.12 L a 0.88 intermetallic phases. Microhardness increased with the addition of La and it was recorded highest for Mg-3Al-4La (122 Hv). Mechanical characterization results show that the tensile yield strength (TYS), ultimate tensile strength (UTS) and ductility for Mg-3Al-2.5La alloy are the best reported values till date among all the available reports for this system of alloy (TYS ∼ 160 MPa, UTS ∼ 249 MPa and fracture strain ∼22%). Results of damping measurement revealed an increase in damping of Mg-3Al alloy due to the presence of La (2.5%). Compression results show that the addition of La to Mg-3Al caused gradual decrease in compression yield strength and elongation.

This study examines Mg-Y binary alloys synthesized using disintegrated melt deposition technique and secondarily processed by hot extrusion. The alloys were subjected to ignition, damping and tensile tests to determine the effect of low Y content addition on the properties of Mg. Further, the alloys were also subjected to low and high strain rates of approximately 8.33 × 10 −5 s −1 and 1.3 × 10 3 s −1 in compression to elucidate the effect of yttrium addition on dynamic response of magnesium. The results of microstructural characterization revealed a progressive reduction in grain size of magnesium with the increasing presence of yttrium. Transmission electron microscopy revealed the presence of Mg-Y phases irrespective of the limited amount of yttrium. Results of mechanical characterization revealed that increasing presence of yttrium leads to an increase in the ignition temperature, micro-hardness, tensile and compressive fracture strain, 0.2% offset compressive yield and ultimate strength and dynamic strengths with the best values obtained for Mg-1.8Y alloy. An attempt is made in this study to inter-relate the microstructural features with the mechanical response of Mg-Y alloys.

Magnesium alloys and composites have gained critical importance in several industries owing to their superior specific properties. Understanding and interpreting the influence of the processing technology, alloying and reinforcement addition on the mechanical response of magnesium is vital to improve its commercial acceptability. The presence of secondary phases in a magnesium alloy system influences the behavior of the material tremendously. The incorporation of alloying elements beyond the solubility limits using high-temperature processing technologies may result in unwanted secondary phases which might be detrimental. In this study, Mg–19Zn–1Ca alloy and Mg–19Zn–1Ca+1SiO2 nanocomposite containing an exceptionally high amount of zinc (19 wt percent) were fabricated via sinterless powder metallurgy method followed by hot extrusion by judiciously controlling temperature at each stage to minimize secondary phase formation. The addition of SiO2 nanoparticles to such alloy was further investigated. Results revealed a low incidence of secondary phase formation leading to enhanced physical and mechanical properties when compared to high weight percent Zn compositions fabricated using traditional methods and many commonly used commercial Mg alloys and stainless steel. The addition of SiO2 nanoparticles enhanced thermal stability and damping response marginally while compressive yield strength, ultimate compressive strength and fracture strain of ∼202–208 MPa, ∼380 MPa, and ∼17% were similar for both the alloy and nanocomposite.

In this study, in-situ Mg2Si reinforced AZ91 composites unmodified and modified with 2.0 wt %Sb addition were fabricated. Investigation was done on the modification mechanism of Mg2Si phase morphology, intrinsic mechanical properties of Mg2Si phase and mechanical properties of Mg2Si/AZ91 composites containing unmodified and modified Mg2Si phase. The results showed that the morphology of primary Mg2Si phases was significantly modified from coarse dendritic shape to blocky polygonal shape with addition of Sb in Mg2Si/AZ91 composite. The 3-D morphology of modified Mg2Si phases was seen as perfect octahedron, and the average size was also refined into approximately 18 μm. Microstructure analysis revealed that Sb-rich layer with the thickness of 265 nm–744 nm formed on the surface of primary Mg2Si particles and suppressed the preferred growth along direction due to Sb atoms preferentially absorbed on the {100} surfaces. Meanwhile, approximately 4.18 at. % Sb was doped into Mg2Si crystals by substituting Si sites, which reduced the surface energy and restricted the growth of Mg2Si. Additionally, the most thermodynamically stable Mg3Sb2 phase formed during the solidification process acted as effective heterogeneous nucleus thus refining the size of primary Mg2Si. The intrinsic hardness of modified Mg2Si phase was greatly improved by 36.6% due to the lattice distortion induced by Sb doping. Moreover, Sb modified Mg2Si/AZ91 composite exhibited simultaneously enhanced strength and ductility when compared to unmodified Mg2Si/AZ91 composite, which were attributed to the improved CTE strengthening, increase in hardness of Mg2Si and reduction of stress concentration resulted from modification of morphology and size.

A novel attempt is made to study and compare the effects of TiO 2 morphology in the form of nanoparticulates and nanofibers on the physical, mechanical and microstructural properties of pure magnesium. Pure magnesium and Mg (1.98 and 2.5) vol. % TiO 2 nanocomposites are synthesized by powder metallurgy technique coupled with microwave sintering followed by hot extrusion. X-Ray diffraction studies of the synthesized magnesium materials indicated that morphology of ultrafine reinforcements play a vital role in modifying the strong basal texture of pure magnesium. The microstructural characterization of Mg–TiO 2 nanocomposites indicated significant grain refinement of pure Mg with TiO 2 nanoparticulates contributing more effectively exhibiting as high as 22% reduction observed with Mg 2.5 vol. % TiO 2 nanocomposite having TiO 2 in the form of nanoparticulates. Under tensile loading, with addition of 1.98 vol. % TiO 2 nanoparticulates and nanofibers, significant improvement in the tensile fracture stain of pure magnesium of ∼14.5% and ∼13.5%, respectively was observed. Further, marginal changes in the tensile strength of pure magnesium by ∼10 MPa was observed with the addition of TiO 2 reinforcements. Under compression loading, among the synthesized magnesium materials, Mg–TiO 2 nanocomposites containing 1.98 vol. % TiO 2 nanofibers exhibited superior strength properties with a maximum 0.2% compressive yield strength and ultimate compressive strength of ∼90 MPa and ∼300 MPa, respectively. Further, decrease in the tension-compression asymmetry values was found to be more significant in Mg–TiO 2 nanocomposites where TiO 2 was used in the fiber form. The results reveal that TiO 2 nanofiber is more effective in improving the overall mechanical performance of pure magnesium.

In this work, magnesium ZK60 alloy is pre-processed by turning followed by compaction and extrusion of the chips. This work is aimed at studying the influence of varying turning speeds on the microstructure and properties of extruded ZK60 alloys. The findings of this study indicate that lower turning speeds resulted in generation of discontinuous chips which when consolidated led to bulk materials with lesser overall porosity. Further, the turning-induced-deformation in the chips plays a significant role in influencing the microstructure (grain size) and properties of the resultant (extruded) material. This study highlights the significance of low speed turning to obtain materials with superior mechanical properties and promotes cost and energy efficiency through recycling industrial metal swarf, which is a significant environmental and economic concern.

This work presents the use of equiatomic high entropy alloy (HEA) particles as unconventional reinforcement phase in Mg matrix. Mg-HEA composites were fabricated by powder metallurgy method incorporating microwave sintering and hot extrusion. Recrystallized fine grains (∼50% reduction) were observed in all the composites due to the capability of HEA particles to serve as nucleation sites and for grain boundary pinning following extrusion. Grain refinement coupled with intrinsic high hardness of HEA particles led to an improvement in hardness of 47%, 51% and 54% in Mg-2.5 wt% HEA, Mg-5 wt.% HEA and Mg-7.5 wt% HEA composites, respectively. In comparison with traditional micron size reinforced composites, Mg-HEA composites displayed superior hardness improvement. In addition, HEA reinforcement particles also enhanced both tensile and compressive strengths of magnesium with marginally compromised tensile ductility and marginally enhanced compressive ductility. Relatively strong fiber texture of extruded pure Mg was weakened in the composites due to the presence of HEA particles effectively reducing the yield asymmetry to near unity in Mg-5 wt.% HEA and Mg-7.5 wt% HEA composites.

The present study illustrates the structural and mechanical properties of magnesium composites containing Ni 50 Ti 50 metallic glass reinforcement particles. Novel Mg-composites containing 3, 6 and 10 vol.%Ni 50 Ti 50 amorphous particulates were synthesized using the microwave assisted rapid sintering technique followed by hot extrusion. The developed Mg-composite materials were investigated for their microstructural and mechanical properties. Microstructural studies revealed the retention of amorphous structure of Ni 50 Ti 50 reinforcement and its fair distribution in developed Mg/Ni 50 Ti 50 composites. Mechanical property evaluation under indentation and compression loads showed significant enhancement in strength properties (microhardness:+78%, 0.2CYS:+79%, UCS:+70%, 0.2TYS:+95%, UTS:+50%) without compromising the compressive ductility. For the first time, tensile properties of such amorphous particles reinforced Mg-composites were studied and the results showed ∼98% increase in 0.2TYS and ∼50% increase in UTS. The tensile ductility was adversely affected. However, the obtained values are comparable to that of conventional Mg-composites. The observed mechanical response discussed in terms of structure–property relationship highlights the efficacy of amorphous Ni 50 Ti 50 reinforcement particles and the energy efficient microwave sintering approach to produce high performance magnesium composites.

In this study, the effects of nanoscale ZnO reinforcement on the room temperature tensile and compressive response of monolithic Mg were studied. Experimental observations indicated strength properties improvement due to nanoscale ZnO addition. A maximum increment in tensile yield strength by similar to 55% and compressive yield strength by 90% (with reduced tension-compression asymmetry) was achieved when 0.8 vol.% ZnO nanoparticles were added to Mg. While the fracture strain values under tensile loads were found to increase significantly (by similar to 95%, in case of Mg-0.48ZnO), it remained largely unaffected under compressive loads. The microstructural characteristics studied in order to comprehend the mechanical response showed significant grain refinement due to grain boundary pinning effect of nano-ZnO particles which resulted in strengthening of Mg. Texture analysis using X-ray and EBSD methods indicated weakening of basal fibre texture in Mg/ZnO nanocomposites which contributed towards the reduction in tension-compression yield asymmetry and enhancement in tensile ductility when compared to pure Mg. (C) 2014 Elsevier B.V. All rights reserved.

In the present study, new light weight Mg–Ti nanocomposites with superior mechanical properties compared to pure magnesium are synthesized using disintegrated melt deposition technique followed by hot extrusion. The microstructural characterization studies revealed that the samples exhibited fairly uniform distribution of titanium nano particulates with minimal porosity and good interfacial integrity between Mg matrix and Ti particulates. The CTE results revealed that the addition of (0.58, 0.97 and 1.98) vol.%Ti reinforcements marginally improve the dimensional stability of pure magnesium. The room temperature tensile properties of the synthesized nanocomposites revealed a significant increase in the 0.2%YS (∼79% to ∼112%) and UTS (∼ 46% to ∼81%) when compared to pure magnesium, with decrease in ductility. The presence of nano-sized 1.98 vol.%Ti in pure Mg revealed the best tensile properties with an increase in 0.2%YS by ∼112% and UTS by ∼81%, while the ductility decreased by ∼49% but comparable to the other work reported on Mg–Ti microcomposites available in the literature. The room temperature compressive properties of the nanocomposites reveal that the addition of 0.97Ti increases the 0.2%CYS of Mg by ∼59% and with 0.58Ti, the UCS of Mg increased by ∼34% with an inappreciable decrease in the ductility.

Zinc ingot was added to molten ZK60A magnesium alloy to improve tensile and compressive properties after hot extrusion. In tension, Zn addition increased strength (by up to +71%) and ductility (by +109%). The addition of Zn resulted in significant grain refinement by about 1 order of magnitude, and increased alignment of the basal plane along the extrusion direction (or force axis). More importantly, the addition of Zn enabled the significant formation of rod-shaped intermetallic nanoparticles (β nanorods) responsible for significant strengthening during tensile deformation. The β nanorods were preferentially formed from hetrogenous precipitation of dissolved Zn on finer α nanorods. The observation of non-basal slip in the high strain zone (HSZ) adjacent to the β nanorod (after room temperature tensile deformation) indicated the sufficiently robust nature of the interface between the β nanorod and the alloy matrix. In compression, Zn addition increased strength (by up to +74%) but at the expense of ductility (decreased by −34%). There was buckling and fracture of the β nanorod (loss of strength) during compression but this was offset by the significant grain refinement and increased alignment of the basal plane along the force axis (gain in strength). Also, there was HSZ formation from the tip of one β nanorod to another, but the strain hardening rate was overall higher due to Zn addition, resulting in ductility loss.

In the present study, new magnesium based AZ41/Al 2 O 3 –Ca and AZ51/Al 2 O 3 –Ca nanocomposites were successfully synthesized incorporating varying amount of elemental Al (1 and 2% by wt.), Ca (1 and 2% by wt.) and 1.5 vol.% nano-sized (50 nm) Al 2 O 3 particulates into AZ31 alloy using disintegrated melt deposition technique. AZ41 and AZ51 alloys were also developed following the same processing route by adding 1 and 2 wt.% Al, respectively. All alloy and composite samples were then subsequently hot extruded at 400 C and characterized. Microstructural characterization studies revealed equiaxed grain morphology, reasonably uniform distribution of nanoparticulate and intermetallics in the matrix, good interfacial integrity and minimal porosity. Addition of nano-sized Al 2 O 3 particulates and Ca into AZ41 and AZ51 samples helped to reduce the average grain size and diameter of Mg 17 Al 12 second phase and introduced (Mg, Al) 2 Ca phase in the matrix. Microhardness test results revealed that AZ51/Al 2 O 3 –2Ca samples exhibited around 47% and 90% higher microhardness value when compared to monolithic AZ51 and AZ31 samples, respectively. Room temperature tensile test results also revealed that newly developed nanocomposites exhibited superior combination of tensile properties in terms of 0.2% yield strength, ultimate tensile strength and ductility when compared to their respective alloys and some commercially available Mg alloys.

In this study, the effect of trace additions of Ag (0.175 wt.%) and Cu (0.035 wt.%) on the microstructural evolution and mechanical behavior of extruded Mg–5Sn alloy is investigated. Microstructural studies revealed that all the alloys have fine grains (2–6.5 μm), and that the binary Mg–5Sn alloy has polygonal and submicron-sized lath/rod-like Mg 2 Sn second phase particles. While Ag addition (TQ50 alloy) induced a change in morphology from lath/rod-shaped Mg 2 Sn to short-rod/oblong-shaped Mg–Sn–Ag particles, the presence of Ag and Cu (TQC500 alloy) resulted in an additional Mg 2 (Cu, Sn) nano-sized phase. From XRD analyses, it was identified that the trace addition of Ag and Cu modified the preferred Mg-crystal orientation of the Mg–5Sn alloy that had basal planes strongly aligned parallel to the extrusion direction. Both Ag and Cu contributed to a remarkable decrease in the coefficient of thermal expansion and better static salt–water corrosion resistance. When compared to pure Mg, all the alloys showed significant improvement in hardness, tensile and compressive strength values, with Ag and Cu trace additions contributing to enhanced tensile ductility. The effect of trace additions of Ag and Cu on the material behavior was identified based on structure–property correlation.

In this work, we synthesized and investigated the mechanical performance of magnesium (Mg) nano-composites containing either B 4 C or hybrid Al–B 4 C particles (B 4 C particles hybridized with Al using ball milling) synthesized through powder metallurgy route using microwave assisted rapid sintering technique followed by hot extrusion. Compared to monolithic Mg, microstructural characterizations revealed presence of porosity along the particles boundaries and reduction in average matrix grain size. Among the different nano-composite formulations, the Mg/0.66B 4 C nano-composite exhibited the best improvement, though marginal, in tensile yield strength (0.2% YS), compressive yield strength (0.2% CYS), ultimate tensile strength (UTS), ultimate compressive strength (UCS) and tensile failure strain (FS t ) (up to +10%, +7.5%, +2%, +36%, and 12%, respectively) compared to pure Mg while compressive failure strain (FS c ) was compromised. To improve the mechanical response of Mg/B 4 C nano-composites further, the best observed B 4 C content was hybridized with Al to outcome hybrid Al–B 4 C particles. The effect of presence of hybridized B 4 C particles with Al (Al–B 4 C) in the case of hierarchical Mg/0.92Al–0.66B 4 C configuration exhibits an improvement of +8.3% (0.2% YS), +29% (0.2% CYS), +45% (UTS) and +6.2 (UCS) compared to its Mg/0.66B 4 C nano-composite counterpart whereas both FS t and FS c were compromised. Considering the crystallographic texture, the effect of presence of B 4 C particles (either solely or as hybrid particle forms) on textural evolution of Mg is also investigated here.

A systematic study of Mg67Zn28Ca5 amorphous alloy was made at near supercooled liquid region with strain rates ranging from 10−6 to 10−3 s−1. Compressive deformation behavior showed a transition from inhomogeneous to homogeneous flow. The strain rate sensitivity below the glass transition temperature was approximately 0.27, while in the supercooled liquid region, strain rate sensitivity approached a value of 1. Crystallinity and phase presence in material, were examined by XRD, DSC and TEM. before and after deformation.

This study is aimed at understanding the ductility enhancing function of nanoparticles in a concentrated magnesium alloy (AZ81) nanocomposite. Al2O3 nanoparticles were selected for reinforcement purposes due to the well known affinity between magnesium and oxygen. AZ81 magnesium alloy was reinforced with Al2O3 nanoparticles using solidification processing followed by hot extrusion. The nanocomposite exhibited similar grain size and hardness to the monolithic alloy, reasonable nanoparticle distribution and non-dominant (0 0 0 2) texture in the longitudinal direction. Compared to the monolithic alloy in both tension and compression, the nanocomposite exhibited higher failure strain (+66% and +18%, respectively) without significant compromise in strength, and higher energy absorbed until fracture (EA) (+71% and +12%, respectively). The beneficial effects of Al2O3 nanoparticle addition on the tensile and compressive ductility enhancement of AZ81 alloy is discussed in this paper.

In the present study, 1 and 2 wt.% of aluminum were successfully incorporated into magnesium based AZ31 alloy to develop new AZ41 and AZ51 alloys using the technique of disintegrated melt deposition. AZ41–Al 2 O 3 and AZ51–Al 2 O 3 nanocomposites were also successfully synthesized through the simultaneous addition of aluminum (1 and 2 wt.%, respectively) and 1.5 vol.% nano-sized alumina into AZ31 magnesium following same route. Alloy and composite samples were then subsequently hot extruded at 400 °C and characterized. Microstructural characterization studies revealed equiaxed grain structure, reasonably uniform distribution of particulate and intermetallics in the matrix and minimal porosity. Physical properties characterization revealed that addition of both aluminum and nano-sized alumina reduced the coefficient of thermal expansion of monolithic AZ31. The presence of both Al and nano-sized Al 2 O 3 particles also assisted in improving overall mechanical properties including microhardness, engineering and specific tensile strengths, ductility and work of fracture. The results suggest that these alloys and nanocomposites have significant potential in diverse engineering applications when compared to magnesium AZ31 alloy.

AZ31/AZ91 hybrid alloy nanocomposite containing Al2O3 nanoparticle reinforcement was fabricated using solidification processing followed by hot extrusion. The nanocomposite exhibited similar grain size to the monolithic hybrid alloy, reasonable Al2O3 nanoparticle distribution, non-dominant (0 0 0 2) texture in the longitudinal direction, and 25% higher hardness than the monolithic hybrid alloy. Compared to the monolithic hybrid alloy (in tension), the nanocomposite synergistically exhibited higher 0.2%TYS, UTS, failure strain and work of fracture (WOF) (+12%, +7%, +99% and +108%, respectively). Compared to the monolithic hybrid alloy (in compression), the nanocomposite exhibited higher 0.2%CYS and UCS, and lower failure strain and WOF (+5%, +3%, −7% and −7%, respectively). The beneficial effects of Al2O3 nanoparticle addition on the enhancement of tensile and compressive properties of AZ31/AZ91 hybrid alloy are investigated in this paper.

In this study, composites containing pure magnesium and hybrid reinforcements (5.6 wt.% titanium (Ti) particulates and 2.5 wt.% nanoscale alumina (n-Al2O3) particles) were synthesized using the disintegrated melt deposition technique followed by hot extrusion. The hybrid reinforcement addition into the Mg matrix was carried out in two ways: (i) by direct addition of the reinforcements into the Mg–matrix, Mg–(5.6Ti + 2.5n-Al2O3) and (ii) by pre-synthesizing the composite reinforcement by ball milling and its subsequent addition into the Mg–matrix, Mg–(5.6Ti + 2.5n-Al2O3)BM. Microstructural characterization revealed significant grain refinement due to reinforcement addition. The evaluation of mechanical properties indicated a significant improvement in microhardness, tensile and compressive properties of the composites when compared to monolithic magnesium. For the Mg–(5.6Ti + 2.5n-Al2O3) composite, wherein the reinforcements were directly added into the matrix, the improvement in strength properties occurred at the expense of ductility. For the Mg–(5.6Ti + 2.5n-Al2O3)BM composites with pre-synthesized ball-milled reinforcements, the increase in strength properties was accompanied by an increase/retention of ductility. The observed difference in behaviour of the composites is primarily attributed to the morphology and distribution of the reinforcements obtained due to the ball-milling process, thereby resulting in composites with enhanced toughness.

In the present study, magnesium nanocomposites were fabricated using magnesium as matrix and nano-yttria as reinforcement. Nanocomposites with 0.2 and 0.7 vol.% of Y 2 O 3 particulates with an average size of 29–50 nm were synthesized blend-press-sinter powder metallurgy technique followed by hot extrusion. Conventional slow heating and microwave assisted rapid heating sintering techniques were used. Microstructural characterization of the materials revealed fairly uniform distribution of reinforcement with the presence of minimal porosity in all of the processed materials, while significant grain refinement in the cases of conventionally sintered materials. Tensile properties characterization of the conventional and microwave sintered nanocomposites revealed that significant and resembling increase in the 0.2% yield strength and ultimate tensile strength of magnesium matrix with the increasing presence of reinforcement. The ductility and work of fracture of magnesium matrix increased significantly in the case of conventionally sintered nanocomposites when compared to the microwave assisted sintered nanocomposites.

In this work, three AZ31/Al2O3 composites were synthesized and remelted using the disintegrated melt deposition solidification processing technique. Al2O3 particles of 50 nm, 300 nm and 1000 nm sizes were individually used to formulate the composites of 1.5 vol%, 5.0 vol% and 10.0 vol% reinforcement content, respectively. In each case after extrusion, the change in microstructure and mechanical properties before and after remelting was not significant. Given the strong affinity Mg has for oxygen from the Al2O3 particle, the insignificant change in mechanical properties indicated the friendly nature of AZ31/Al2O3 composites towards initial remelting. In particular, compared to the submicron and micron particle reinforced composites of limited tensile ductility, the nanoparticle reinforced composite retained its significantly higher tensile ductility (up to +400% more) after the initial remelting.

In the present study, new light weight nano-composites (AZ31B–3.3Al2O3–Cu) based on magnesium alloy AZ31B are developed using disintegrated melt deposition technique. Microstructural characterization studies revealed grain refinement and significant increase in amount of second phases as a result of increasing presence of copper. All the samples exhibited minimal porosity and good matrix-second phase interfacial integrity. The results also showed that addition of both nano-Al2O3 and Cu 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 marginally affected. The results of this study clearly illustrate the capability of AZ31B–Al2O3–Cu formulations to exhibit superior mechanical properties when compared to pure AZ31B alloy making them potential candidates as structural materials for weight critical engineering applications.

In the present study, 0.35 and 1.1 vol.% of nano-size copper were incorporated into pure tin using hybrid microwave sintering assisted powder metallurgy route. Microwave sintered samples were extruded both at room temperature and at 230 °C. Microstructural characterization studies were conducted on the extruded samples to investigate the distribution characteristics of secondary phase, grains and pores morphology. Resistivity of solder samples was also investigated and found to be not affected by the high temperature extrusion. Room temperature tensile test results revealed that hot extruded Sn–Cu samples exhibited higher strengths and ductility when compared to room temperature extruded samples. On the contrary, the tensile properties of pure tin remained independent of extrusion temperature. An attempt is made in this study to correlate the presence of copper and effect of extrusion temperature on the microstructural evolution and mechanical response of tin.

In the present study, the role of hybrid reinforcement (ceramic + metal) methodology to enhance the tensile response of magnesium is highlighted. Powder metallurgy incorporating microwave sintering was used as the processing technique. Mg/0.7 vol.%Y 2 O 3 nanocomposite was chosen as main reference point based on earlier studies. Nickel nanoparticulates in the range of 0.3–1.0 vol.% were used to hybridize the nanosize Y 2 O 3 reinforcement. Tensile results revealed an increase in 0.2% YS and UTS of Mg/(Y 2 O 3 + Ni) hybrid nanocomposites when compared to pure Mg and Mg/0.7Y 2 O 3 . Mg/(0.7Y 2 O 3 + 0.6Ni) nanocomposite showed a simultaneous improvement in both strengths (0.2%YS and UTS) and average ductility when compared to Mg and Mg/0.7Y 2 O 3 . Emphasis is placed in this study to highlight the capability of metallic and ceramic hybrid reinforcements to improve overall tensile response of magnesium when used in right amounts.

New bimetal AZ31/AA5052 macrocomposite containing millimeter-scale aluminium alloy core reinforcement was fabricated using solidification processing followed by hot coextrusion. Microstructural characterization revealed decreased intermetallic particle spacing, Mg texture change and significant interfacial interdiffusion of Mg and Al into each other. Compressive testing revealed that presence of AA5052 core increased compressive yield strength (0.2% CYS) (+51%), ultimate compressive strength (UCS) (+4%), average failure strain (+18%) and work of fracture (WOF) (+50%) of AZ31. The effect of presence of mm-scale AA5052 core on the compressive properties of the bimetal macrocomposite is investigated in this paper.

In this study, the influence of a wide range of reinforcements (SnO 2 , Cu, Y 2 O 3 , ZrO 2 + 8 mol.% Y 2 O 3 and TiB 2 ) on the electrical resistivity of Sn–3.5Ag and Sn–3.5Ag–0.7Cu solders was investigated. The electrical resistivity test was conducted on the bulk samples of composite solders at ambient temperature. Results revealed that electrical resistivities of composites containing nanometer length scale reinforcement is not compromised for the optimal amount of reinforcement required to realize best tensile properties. This behavior was not displayed by composite containing micron size particles. The results of this study are expected to pave the way to develop lead-free nanocomposites especially for the industry using solid-state bonding technique.

In this study, varying amounts of nanolength scale copper particles were incorporated into tin by microwave sintering assisted powder metallurgy route. Near dense materials exhibiting near equiaxed grains were obtained. Coefficient of thermal expansion reduced marginally due to the presence of Cu particles. Results of tensile testing revealed that with the addition of 0.35 vol.% (∼0.43 wt.%) of Cu in pure Sn, a significant improvement in yield strength (∼233%) and ultimate tensile strength (∼159%) is realized, when compared with that of commercially available Sn–0.7 wt.% Cu solder. Furthermore, Sn–Cu solder materials developed here also exhibited comparable resistivity with that of eutectic Sn–0.7 wt.% Cu commercial solder. The morphology of pores and intermetallic compounds were found to be the dominating factors affecting the strength of the materials synthesized in this study.

In the present study, varying weight percentages of carbon nanotubes (CNTs) were incorporated into Sn–Ag–Cu solder matrix, to form composite solders. Isothermal aging study was performed on solder joints, to investigate the formation and growth of the intermetallic compound (IMC) layer at the solder/metallization interface. Shear tests were also conducted on as-soldered and aged solder joints. Results revealed that after soldering, the initial interfacial IMC thickness of the unreinforced solder joint was comparable to that of the composite solder joints. However, after aging, the interfacial IMC layer of the unreinforced solder joint was observed to grow more significantly than that of the composite solder joints. Moreover, the composite solder joints also exhibited lower diffusion coefficient and this signified that the presence of CNTs was effective in retarding the growth of the IMC layer. Shear tests results revealed that as-soldered and aged composite solder joints had better shear strength than their monolithic counterparts and the shear strength of all aged solder joints decreased with increasing aging time.

In the present study, pure magnesium and a Mg/Y2O3 nanocomposite were microwave sintered using heating rates of 49 and 20 °C/min. Results obtained from extruded rods revealed that average hardness and strengths of both Mg and Mg/Y2O3 samples were higher when they were sintered at higher heating rate. Ductility of pure Mg, however, reduced at higher heating rate while it remained similar for Mg/Y2O3 nanocomposite. An attempt is made to correlate tensile properties with the end microstructural features of the samples sintered at two different heating rates.

A new bimetal magnesium/aluminium (Mg/Al) macrocomposite containing mm-scale Al core reinforcement was fabricated via casting and hot coextrusion. Characterization revealed fairly uniform Al volume fraction along the extruded rod length attributable to mechanical interlocking between Mg shell and Al core. Major defects were absent and Mg–Al interfacial integrity was good. Thermal stability of the macrocomposite was marginally improved when compared to pure Mg. Results revealed that the presence of the Al core leads to a decrease in strength of Mg, but an improvement in stiffness as well as significant increase in failure strain (144%) and work of fracture (73%) of Mg. An attempt is made in the present study to investigate the effect of presence of mm-scale Al core on the microstructure and mechanical properties of the bimetal Mg/Al macrocomposite.

In the present study, AZ31B magnesium alloy was unified with three different volume fractions of 50-nm Al 2 O 3 particulates using the technique of disintegrated melt deposition. Composite samples were then subsequently hot extruded and characterized. Microstructural characterization studies revealed equiaxed grain structure, minimal porosity, reasonably uniform distribution of Al 2 O 3 nano-particulates and good matrix-reinforcement interfacial integrity. The presence of Al 2 O 3 particulates assisted in improving the thermal stability, microhardness and ductility of AZ31B alloy while 0.2%YS and UTS decreased. The overall tensile properties assessed in terms of work of fracture improved more than four times as a result of presence of 1.5 vol.% of Al 2 O 3 nano-particulates. An attempt is made to correlate the effect of amount of Al 2 O 3 nano-particulates on the microstructure and properties of AZ31B magnesium alloy.

In the present study, elemental and 0.3 μm size Al2O3 particulates-reinforced magnesium materials were synthesized using disintegrated melt deposition technique followed by hot extrusion. Microstructural characterization of the composite samples showed fairly uniform reinforcement distribution with good reinforcement–matrix interfacial integrity, significant grain refinement and the presence of minimal porosity. Tensile properties characterization revealed that the presence of submicron-Al2O3 reinforcement led to significant improvement in 0.2%YS, and UTS. However, ductility and work of fracture of the composites remain higher with the addition of submicron-Al2O3 particulates up to 1.1 vol%. The results further revealed that the combination of 0.2% yield strength and UTS exhibited by 0.3 μm size Al2O3 reinforced magnesium remained much superior even when compared to magnesium reinforced with nano-size Al2O3 and micron size SiC. An attempt is made in the present study to correlate the effect of submicron-Al2O3 as reinforcement and its increasing amount with the microstructural and tensile properties of magnesium.

In the present study, magnesium-based composites were fabricated with three different sizes (ranging from nanometer to micrometer scale) of 1.1 vol.% Al 2 O 3 particulates reinforcement using disintegrated melt deposition technique. Microstructural characterization of the materials revealed reasonably uniform distribution of Al 2 O 3 reinforcement with good interfacial integrity, significant grain refinement, and the presence of minimal porosity. Mechanical properties characterization revealed that the incorporation of nano and submicron size Al 2 O 3 particulates in magnesium matrix led to a simultaneous increase in hardness, 0.2% yield strength, UTS, and ductility of pure magnesium. The results further revealed that the 0.2% yield strength, UTS, and ductility combination of the magnesium containing nano and submicron size Al 2 O 3 remained much higher when compared to high strength magnesium alloy AZ91 reinforced with much higher amount of micron size SiC particulates. An attempt is made in the present study to correlate the effect of different length scales of Al 2 O 3 particulates on the microstructural and mechanical properties of magnesium.

In the present study, the damping capacity of a metal matrix composite is predicted using a micro-mechanical modelling approach. The model is based on finite element analysis of an axisymmetric unit cell, which mimics a pure metallic cylinder with a stiff reinforcing spherical particulate placed at the center. The energy dissipated by the composite is numerically predicted using the unit cell by applying a harmonic load, taking into account the viscoplastic behavior of the processing induced residual plastic strain at the matrix–reinforcement interface of the composite. The model shows that the plastic zone size increases with volume fraction of Ti added which results in a proportional increase in the damping capacity of the composite. The model was validated by comparing the numerical results against an impact based suspended beam experiment conducted at low strain amplitude on Al/Ti samples with different volume fractions of Ti particulates.

A new idea of using a stiffer metallic element, such as copper, to enhance the damping of AZ91 magnesium alloy is successfully attempted. The study focuses on the relationship between the damping capability of the composite with the weight percentage of copper added to the matrix. Results of this study show that addition of about 8.1, 15.5 and 20.6 wt.% of copper increases the overall damping capacity of the AZ91 matrix by 64%, 78% and 107%, respectively. Particular emphasis is placed on rationalizing the increase in damping in terms of the increase in dislocation density and presence of plastic zone at the matrix–particulate interface.

In the present study, elemental and titanium particulate reinforced magnesium materials were synthesized using an innovative disintegrated melt deposition technique followed by hot extrusion. Microstructural characterization of the composite samples showed reasonably uniform distribution of titanium particulates in the matrix material, strong interfacial integrity of magnesium matrix with titanium particulates, and the presence of minimal porosity. Physical property characterization revealed that addition of titanium as reinforcement marginally improves the dimensional stability of pure magnesium. Tensile behavior characterization revealed that the presence of titanium reinforcement led to an improvement of 0.2% yield strength and ductility while the UTS was adversely affected. An attempt is made in the present study to correlate the effect of titanium as reinforcement and its increasing amounts with the microstructural, physical and tensile properties of magnesium.

In the present study, commercially pure magnesium reinforced with 3.2 vol% of nickel, where 1.3 vol% percentage remained in elemental form, was fabricated using an innovative disintegrated melt deposition technique followed by hot extrusion. Microstructural characterization of the composite samples showed uniform distribution of nickel particulates in the matrix material, minimal porosity and defect free Nip/Mg interface associated with Mg–Ni based intermetallics. Mechanical properties characterization revealed that the presence of nickel as reinforcement lead to a significant increase in elastic modulus, 0.2% yield strength and UTS of pure magnesium while the ductility was adversely affected. An attempt is made in the present study to correlate the effect of nickel as reinforcement with the microstructural and mechanical properties of magnesium.

In this study, an aluminum alloy, AA1050, was reinforced with an interconnected, axisymmetrical, galvanized iron wire preform. The composite was synthesized using disintegrated melt deposition technique followed by hot extrusion. Micro structural characterization conducted on the composite samples showed good interfacial integrity and low volume percent of non-interconnected porosity. Physical property characterization showed that the coefficient of thermal expansion of the composite decreased below the values predicted by the theoretical models. Hardness test conducted on the materials revealed that the composite matrix exhibited a higher hardness when compared to the monolithic aluminum alloy. Tensile property characterization revealed that, even with a low volume percentage (0.896%) of the reinforcement, the elastic modulus of the composite material increased beyond the value predicted by the Rule-of-Mixture model. The 0.2% yield strength and the ultimate tensile strength of the composite material and the monolithic aluminum alloy remained within each other’s standard deviation while the ductility of the composite material decreased. An attempt is made in this study to correlate the presence of interconnected-wires as reinforcement with the unusually superior coefficient of thermal expansion and elastic modulus exhibited by the composite material.

In the present study, three aluminum–silicon alloys containing 7, 10 and 19 wt % silicon were synthesized using a novel technique commonly known as disintegrated melt deposition technique. The results following processing revealed that a yield of at least 80% can be achieved after defacing the shrinkage cavity from the as-processed ingots. Microstructural characterization studies conducted on the as-processed samples revealed an increase in the volume fraction of porosity with an increase in silicon content. Porosity levels of 1.07, 1.51 and 2.65% attained in the case of Al–7Si, Al–10Si, and Al–19Si alloys indicates the near-net shape forming capability of the disintegrated melt deposition technique. The results of aging studies conducted on the aluminum–silicon alloys revealed similar aging kinetics irrespective of different silicon content. Results of ambient temperature mechanical tests demonstrate an increase in matrix microhardness and 0.2% yield stress and decrease in ductility with an increase in silicon content in aluminum. Furthermore, the results of an attempt to investigate the effect of extrusion on Al–19Si alloy revealed that the extrusion process significantly assists in reducing porosity and improving microstructural uniformity, 0.2% yield strength, ultimate tensile strength and ductility when compared to the as-processed Al–19Si alloy. The results of microstructural characterization and mechanical properties of aluminum–silicon alloys were finally correlated with the amount of silicon in aluminum and secondary processing technique.

In the present study, an Al-4.5 wt. % Cu alloy was synthesized using a casting technique and a new disintegrated melt deposition technique. Microstructural characterization studies conducted on the samples taken from disintegrated melt deposition technique revealed a relatively more equiaxed grain morphology when compared to the cast samples. Microporosity, which is unavoidable for the columnar-equiaxed matrix microstructure was found to be less in case of disintegrated melt deposited samples when compared to the cast samples. Results of ambient temperature mechanical tests demonstrate that disintegrated melt deposited samples exhibited similar 0.2% yield stress, 1.52 times ultimate tensile strength and 3.69 times ductility when compared to the cast samples. All attempt is made to correlate the results of microstructural characterization and mechanical testing with the nature of processing technique employed to synthesize Al-4.5 wt. % Cu alloy.