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Weight reduction is one of the prime goals for auto industries to achieve fuel economy, and magnesium matrix composite offers the opportunity to assist with fulfilling those needs. The present work focuses on developing the magnesium alloy (AZ91D), AZ91D/SiCnp nanocomposite, and AZ91D/SiCnp/CNT hybrid nanocomposite via the semisolid stir casting technique incorporating the ultrasonic vibration process. The produced cast samples are subjected to physical, microstructural, and mechanical characteristics study. The evaluated results are compared and it was found that AZ91D/6wt% SiCnpnanocomposite offers high hardness (78.45 ± 0.1 Hv), yield (150 ± 1.8 MPa), and ultimate tensile strength (241 ± 1.75 MPa) as compared to the cast AZ91D alloy samples. The scanning electron microscope reveals the homogeneous particle distribution structure with reduced porosity. The density of the developed composite obeys the rule of the mixture, and the porosity is limited to less than 1%. The presence of 6 wt% carbon nanotube in AZ91D/6wt% SiCnp alloy nanocomposite facilitates superior hardness, yield, and tensile strength of 84.35 ± 0.1 Hv, 174 ± 1.5 MPa, and 271 ± 1.6 MPa. The impact strength of the composite increased, while the content of SiCnp was improved. [ABSTRACT FROM AUTHOR]

Micron‐sized graphite particles additions to Al2011 alloy were investigated to know their impact on mechanical properties. The stir cast method was used to manufacture the Al2011 alloy with 2 and 4 wt% of graphite particles reinforced composites. The microstructural analysis and mechanical properties of the synthesized composites were tested. Scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) spectrums were used to characterize the microstructure of the samples that were obtained from the casting. SEM micrographs indicated the homogeneous distribution of particles and the EDS patterns confirmed the presence of graphite particles. Al2011 alloy hardness was decreased with the addition of graphite particles. Further, with the addition of 2 and 4 wt% of graphite particles in the Al2011 alloy, the ultimate tensile and yield strengths of composites were increased with increase in elongation. SEM micrographs of tensile fractured surfaces were used to study the various fractured behaviors in the Al2011 alloy‐graphite composites. [ABSTRACT FROM AUTHOR]

The effects of various drawing parameters and annealing processes on the structure and properties of Cu-Ag wires, containing 1 wt% silver, were investigated using specialized equipment including fine wire-drawing machines, very fine wire-drawing machines, heat treatment equipment, tensile testing machines, microcomputer-controlled electronic universal testers, resistance testers, and scanning electron microscopes. The results revealed that continuous drawing of Cu-1%Ag alloy wires led to elongation of the grains, resulting in a uniform and tightly fibrous microstructure. Moreover, the tensile strength of the alloy wire increased from 670 MPa to 783.9 MPa after a single pass with a deformation of 14%. Subsequently, when the wire was drawn at a speed of 500 m/min, the tensile strength further increased to 820.1 MPa. After annealing the Փ0.08 mm Cu-1% Ag alloy wire, an increase in annealing temperature up to 500 °C resulted in the wire's tensile strength decreasing from 820.1 MPa to 377.5 MPa. Simultaneously, the elongation increased from 1.94% to 15.21%, and the resistivity decreased from 1.931 × 10−8 Ω·m to 1.723 × 10−8 Ω·m. Additionally, when annealing was conducted at a rate of 80 m/min, the wire resistivity dropped to 1.635 × 10−8 Ω·m. [ABSTRACT FROM AUTHOR]

Mg-3Sn-1Mn-xLa alloy bars were prepared using backward extrusion, and the effects of the La content on the microstructures and mechanical properties of the alloy were systematically studied using an optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and tensile tests. The results of this research show that the Mg2Sn phases were mainly formed at the α-Mg grain boundaries and within the grains in the Mg-3Sn-1Mn alloy. After adding a certain amount of La, the plate-shaped MgSnLa compounds consisting of Mg17La2, Mg2Sn, and La5Sn3 gradually disappeared in the α-Mg matrix and grain boundaries. With an increase in La content, the Mg2Sn phase in the crystal was gradually refined and spheroidized. When the content of La reached 1.5%, the tensile strength of the alloy reached 300 Mpa and the elongation reached 12.6%, i.e., 25% and 85% increases, respectively, compared to the Mg-3Sn-1Mn alloy. The plate-shaped compound of Mg-3Sn-1Mn-1.5La had an average length of 3000 ± 50 nm, while the width was 350 ± 10 nm. Meanwhile, the extruded alloy's grain size was significantly refined, and there were many small cleavage steps and dimples in the fracture surface of the alloy. When the La content reached 2%, the alloy performance showed a downward trend due to the coarsening of the grains. The formed plate-shaped MgSnLa compounds and Mg2Sn phases were consistent with the α-Mg matrix. They effectively pinned the dislocations and grain boundaries, which is the main reason for strengthening the mechanical properties of extrusion alloys. [ABSTRACT FROM AUTHOR]

Magnesium-based alloys were more prevalent in automobile applications owing to their mechanical properties, low mass, and density. However, its poor mechanical properties are restricting its applications. Therefore, the present study focuses on improving the mechanical properties of AZ31D alloy by reinforcing silicon carbide (SiC) and graphite (Gr) nanoparticles with weight fractions of 2%, 4%, and 6% using stir-casting technique. The microstructure analysis was performed using a scanning electron microscope. The elemental analysis was confirmed using energy-dispersive spectroscopy, and X-ray diffraction was used to study various phases in the nanocomposites. Further, the mechanical properties, such as microhardness, ultimate tensile strength, yield strength, and compression strength of the nanocomposites, were significantly improved by 53%, 59%, 62%, and 82%, respectively, as compared with base alloy. [ABSTRACT FROM AUTHOR]

The microstructure, tensile property and corrosion behavior of the die-casting AlSi10Cu3 alloy with 0.6 wt% (La + Yb) addition and T6 heat treatment are discussed. The results of optical microscope (OM) and scanning electron microscope (SEM) demonstrate the main phases are refined after the alloy is treated by two modification methods, and the distribution of Al2Cu phases becomes uniform after T6 heat treatment, thus increasing the ultimate tensile strength (UTS), yield strength (YS) and elongation by 21.6%, 31.4% and 52.5%, respectively. Simultaneously, the corrosion current density (iccor) reaches the minimum value of 5.89 mA·cm-2, which is reduced by 81.1%. Meanwhile, the hydrogen evolution rate and weight loss rate also reach the minimum value of 25.5 × 10-3 ml cm-2 h-1 and 116.5 μg·cm-2 h-1, and comparing with unmodified alloy, they are reduced by 54.6% and 52.2%, respectively. The optimized corrosion behavior is attributed to the refinement of the various cathode phases in the alloy. Moreover, parts of β-Al5FeSi phases are transformed into α-Al8Fe2Si phases and the uniform distribution of Al2Cu phases avoids severe local corrosion. [ABSTRACT FROM AUTHOR]

Grain refinement of Al–Si alloys is one of the effective methods for improving the elongation (El) and ultimate tensile strength (UTS). The influences of alone adding Ni (0.5, 1.0, 1.5, and 2.0%) and complex adding Ni (0.5, 1.0, 1.5, and 2.0%) plus 0.4%Y on the evolution of α-Al, eutectic Si, as well as mechanical performance of Al–7Si alloy, were investigated. All specimens were characterized by electron probe microanalysis, transmission electron microscopy, optical microscope, and scanning electron microscope. The results indicated that the secondary dendrite arm spacing (SDAS) of primary α-Al was markedly decreased with increasing Ni content in Al–7Si alloy. When the Ni addition concentration increased to 1.5%, the developed dendritic α-Al were effectively refined into fine equiaxed dendrites. Rare earth Y (0.4%) plus Ni were together added to Al–7Si alloys. The results showed that complex addition of Ni plus Y had a more outstanding refinement effect of α-Al and eutectic Si than that of Ni alone addition in Al–7Si alloy. The coarse and needlelike eutectic Si was modified into fine fibrous shape, and the SDAS of α-Al was significantly reduced when 1.5%Ni plus 0.4%Y was simultaneously added to Al–7Si alloy. Meanwhile, the mechanical performance test illustrated that the El and UTS were improved to 10.8% and 217.8 MPa, respectively. [ABSTRACT FROM AUTHOR]

The structure and mechanical properties of non-equiatomic Al8Co30Cr18Fe9Ni31Nb4, Al8Co30Cr18Fe9Ni31Nb2Ti2 and Al8Co30Cr18Fe9Ni31Ti4 high entropy alloys (HEAs) were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), hardness and tensile testing. TEM and XRD analyses revealed the formation of γ''-Ni3Nb/γ (FCC), double FCC and γ'-Ni3Al/γ (FCC) structure for as-cast Al8Co30Cr18Fe9Ni31Nb4, Al8Co30Cr18Fe9Ni31Nb2Ti2 and Al8Co30Cr18Fe9Ni31Ti4 HEAs, respectively. The hardness and yield strength values were found to increase with the addition of Nb while the ductility of alloys increased with the increase in Ti concentration, significantly. The as-cast Al8Co30Cr18Fe9Ni31Ti4 alloy exhibited an excellent combination of ultimate tensile strength of 844 MPa and an elongation of 29.8% due to the coherent phase relation between γ' precipitates and γ matrix. The fractured surfaces of as-cast Al8Co30Cr18Fe9Ni31Nb4, Al8Co30Cr18Fe9Ni31Nb2Ti2 and Al8Co30Cr18Fe9Ni31Ti4 HEAs showed typical dimple type ductile fracture under tension test. [ABSTRACT FROM AUTHOR]

The effects of Ag content and hot-rolling on the microstructure and mechanical properties of Zn-1.5Cu-xAg-0.1Zr(x = 0, 0.1, 0.5, 1.0) alloys were investigated. The microstructure, phase composition and fracture morphology of the alloys were observed and analyzed by optical microscope, x-ray diffraction, scanning electron microscope, energy dispersive spectrometer and universal mechanical testing machine. The results show that Ag has the effect of grain refinement. After alloying, the grain size of as-cast Zn-1.5Cu-xAg-0.1Zr alloy decreased first and then increased, and the minimum grain size of as-cast Zn-1.5Cu-0.5Ag-0.1Zr alloy was refined to 64.18 μm. At the same time, new phase AgZn3 began to precipitate, the yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) of alloys were also up to 97.35 MPa, 139.25 MPa and 7.60%, respectively. After hot-rolling, the grain of Zn-1.5Cu-xAg-0.1Zr alloy was broken and new phase CuZn5 was precipitated. The mechanical properties were significantly improved, and the maximum YS, UTS and EL of as-rolled Zn-1.5Cu-1.0Ag-0.1Zr alloy were 218.14MPa, 244.83MPa, 64.50%, respectively. [ABSTRACT FROM AUTHOR]

The development of magnesium alloys with superior plasticity and favorable strength is still challenging in aerospace industry. Herein, hot extruded Mg-xNd-2.0Sm-0.4Zn-0.4Zr alloys (x = 0, 0.5, 1.0, 1.5, 2.0 and 2.5 wt.%) were rationally designed and easily prepared in order to implement the favorable combination of strength and plasticity. The effects of Nd element addition on the microstructure and mechanical properties of the hot extruded alloys were systematically investigated by optical microscopy (OM), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The OM results indicated that the grain size of the hot extruded alloys decreased from 27.1 to 14.1 μm with increasing Nd addition from 0 to 2.5 wt.%. Some coarse β phases existed at the grain boundary when the addition of Nd element increased to 2.0 wt.%. The TEM results showed that the nanoscaled basal lamellar precipitates, granular precipitates and prismatic lamellar precipitates formed in α-Mg matrix. And the amount of precipitated phase increased obviously with the increase of Nd element addition. The ultimate tensile strength increased significantly from 203 ± 3.0 to 237 ± 2.5 MPa, and the elongation decreased from 30.5 to 21.2 % when the Nd elements increased from 0 to 2.5 wt.%. The fractographs of the hot extruded alloys could be classified as ductile fracture. [ABSTRACT FROM AUTHOR]

The microstructure, phase composition, precipitates evaluation, casting, and mechanical properties of the novel cast Al-4Cu-2.1Er-1Mg-0.2Zr-0.2Cr-0.15Fe-0.15Si-0.1Ti alloy were analyzed using by optical microscope, scanning and transmission electron microscopes, differential scanning calorimetry, thermodynamic calculations, hot cracking and mechanical properties measurements. The positive effect of Cr as a substitution of Mn on plasticity and precipitation strengthening was demonstrated. The 0.2Zr, 0.2Cr and 0.1 Ti as a grain refiners provide a fine grain size of 25 μm in the as-cast state due to primary Al 75–80 Cu 10–12 Er 3–4 Cr 7 phase particles formation as a nucleation centers of Al. The hot cracking index (HCI) of the AlCuErMgCr alloy was 12–14 mm which is similar with HCI of the cast Al-Si-Cu-Mg alloys. The good casting properties in the AlCuErMgCr alloy achieved due to a fine grain structure and narrow solidification range. The contribution of the Al 3 (Zr,Er) (40 nm), Al 45 Cr 7 (6 nm), and S'(θ') (100/5 nm) precipitates is 38.5 MPa, 140.4 MPa, and 198.9 MPa and the calculated contribution from dislocation and precipitates is 262.3 MPa. The ultimate tensile strength (UTS) and elongation (El.) of the AlCuErMgCr alloy are 372 MPa and 6% which is higher in 16.6% and 150%, respectively, than in the Mn-containing alloy. Novel alloy has an excellent combination of yield strength (YS) and plasticity at 20–250°C. The YS and El. are 301 MPa and 6% and 225–250 MPa and 4.6–11.5% at 20 and 200–250°C, respectively. The rupture strength at 250°C after 100 h (σ 100 250) is 106 MPa. Mechanical and casting properties of the novel alloy are superior to the properties of commercial 201.0 (Al-Cu-Mn-Mg-Ag-Ti) alloy. • Cr, replacing Mn, had a positive impact on both plasticity and precipitation strengthening. • 0.2Zr, 0.2Cr, and 0.1Ti as grain refiners resulted in the formation of primary Al 75–80 Cu 10–12 Er 3–4 Cr 7 phase particles. • The AlCuErMgCr alloy displayed an ultimate tensile strength (UTS) of 372 MPa and an elongation (El.) of 6%. • The rupture strength at 250°C after 100 hours was determined to be 106 MPa. [ABSTRACT FROM AUTHOR]

Zn alloy has attracted much attention as a biodegradable material for biomedical applications. However, due to the significant strain softening of Zn alloys, how to break the bottleneck of synergistic yield strength and uniform elongation is an urgent problem to be solved. In this work, a Zn-2.3Cu-0.8Mn (wt.%) alloy was fabricated via low-temperature extrusion and annealing at 330 °C for 1 h to attain dual heterostructures with bimodal grains and multi-scale second phases, focusing on the effect of heterostructure on the mechanical properties. Uniaxial tensile test and loading-unloading-reloading test were applied to reveal the mechanical properties of the Zn-2.3Cu-0.8Mn alloy, while scanning electron microscope, electron backscatter diffraction, and transmission electron microscope were used to characterize its microstructure. Compared with the as-extruded alloy with uniform and fine grains, 330–1 alloy achieves a better combination of strength and uniform elongation (yield strength: 287.8 ± 8.5 MPa, ultimate tensile strength: 321.4 ± 6.8 MPa, and uniform elongation: 14.2 ± 1.8%). The high strength was primarily attributed to the coordination of grain boundary strengthening, hetero-deformation induced strengthening, Orowan strengthening, and dislocation strengthening. Besides, the coarse grains, twinning, as well as the suppression of grain boundary sliding and phase boundary sliding promoted dislocation proliferation and storage capacity, thereby improving work hardening capacity. The large strain hardening capacity was responsible for excellent plasticity. This study provides a feasible strategy for the design of Zn-based alloys with an excellent combination of high strength and strain hardening capacity. [ABSTRACT FROM AUTHOR]

This paper details the synthesis of Al7475 alloy with 8% wt. of nano B4C particulate metal matrix composites using the liquid metallurgy technique. Scanning electron microscope (SEM) of the synthesized composites demonstrates the uniform dispersion of the reinforced nano B4C particles throughout the matrix. EDS spectrums confirmed the various elements present in Al7475-B4C composites. Hardness, tensile and compression tests were carried out to find out the impact of nano B4C on various mechanical properties of the composites. Synthesized composites had a greater hardness, tensile and compression strength with the incorporation of B4C particles. Tensile failure analysis was studied using SEM images of fractured surfaces. [ABSTRACT FROM AUTHOR]

Alumnium alloy LM 25 based composites reinforced with boron carbide at different weight fractions of 4%, 8%, and 12% were fabricated by stir casting technique. The microstructures and morphology of the fabricated composites were studied by scanning electron microscopy and energy dispersive spectroscopy. Elemental mapping of all fabricated composites were done to demonstrate the elements present in the matrix and fabricated composites. The results of microstructural analyses reveal homogenous dispersion of reinforcement particles in the matrix with some little amount of clustering found in composites reinforced with 12% wt. of boron carbide. The mechanical characterization is done for both alloy LM 25 and all fabricated composites based on hardness and tensile strength. The hardness increased from 13.6% to 21.31% and tensile strength 6.4% to 22.8% as reinforcement percentage of boron carbide particles increased from 0% to 12% wt. A fractured surface mapping was also done for all composites. [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]

To obtain a robust diffusion-bonded joint at a relatively low temperature, Nb foil was applied as an interlayer to the diffusion bonding of Zr-4 alloy, and a wide process parameter involving the bonding temperature of 720–820 °C and holding time of 30–120 min was investigated to reveal the evolution of interfacial structure and mechanical properties of the joints. The β-(Zr, Nb) and Widmanstädter microstructure formed at the interface induced by the eutectoid transformation of the diffused Zr and Nb at the bonding temperatures over 740 °C. The phase structure and the thickness of β-(Zr, Nb) layer were not considerably influenced by the increase in diffusion parameters while the Widmanstädter zone thickened significantly. Moreover, the tensile strength and elongation of the resultant joints could be stabilized above 433 MPa and 7.8%, respectively, when the bonding temperature exceeded 760 °C with a holding time of 30 min. By extending the holding time to 60 min at 760 °C, the tensile strength and elongation could reach 454 MPa and 12.6%, respectively, comparable to those obtained at an elevated temperature of 820 °C for 30 min. Additionally, the samples fractured at the diffusion layer were characterized by the in-situ tensile test under the scanning electron microscope, and it was discovered that the crack initiation and propagation process occurred mainly between the β-(Zr, Nb) and Widmanstädter diffusion zone. • The well-bonded Zr-4 joints were achieved by the application of Nb interlayer. • The diffusion layer consisted of β-(Zr, Nb) and Widmanstädter microstructure. • The Nb addition lowered bonding temperature without weakening tensile properties. • The fracture occurred between the β-(Zr, Nb) and Widmanstädter diffusion zone. [ABSTRACT FROM AUTHOR]

The effect of In on melting property, microstructure and mechanical properties of Sn–40Bi–xIn (x = 0, 1, 2, 4, 6, 8 wt%, respectively) alloys was investigated by means of differential scanning calorimetry, scanning electron microscope, X-ray diffraction and tensile test. The results show that the solidus temperature and the liquidus temperature decrease with the increase in In content. The 1In, 2In and 4In alloys are composed of Sn–Bi eutectic and β–Sn dendrites with In atoms dissolved, whereas 6In and 8In alloys composed of Sn–Bi eutectics, BiIn–Sn metastable phases, Bi particles and primary β–Sn phases. At room temperature, 6In exhibits the maximum ultimate tensile strength of 77 MPa, while 4In displays a more outstanding elongation rate of 42%. Moreover, 2In alloy exhibits an even outstanding elongation behavior (above 300%) at temperatures of 100 and 120 °C. [ABSTRACT FROM AUTHOR]

The as-extruded NQZ310K (Mg-3.0Nd-1.0Ag-0.2Zn-0.4Zr, mass fraction) alloy was annealed at 300, 350, 400, 450, and 500 °C, respectively. Microstructures of the alloy were observed by an optical microscope and a scanning electron microscope equipped with an energy-dispersive X-ray spectroscope. Ambient mechanical properties were evaluated by tensile tests and nanoindentation tests, and corrosion behavior in simulated body fluid was measured by immersion test. The results show that both matrix grains and precipitates grow up with increasing annealing temperature, and the amount of the precipitates is reduced. The yield strength of the alloy under the as-extruded condition and annealed at 300 and 350 °C is 297, 313, and 298 MPa, and the ultimate tensile strength of it is 327 , 328 , and 315 MPa, respectively, indicating high yield ratio. After annealing at 400, 450, and 500 °C, the yield strength reduces faster than the ultimate tensile strength, resulting in the yield ratio decrease from 0.95 to 0.61, and the elongation improves significantly from 12.3 to 25.5%. The alloy annealed at 350 °C presents the lowest corrosion rate, and then the corrosion resistance of the alloy decreases with increasing annealing temperature. The effects of annealing on microstructure, mechanical and corrosion properties of the as-extruded NQZ310K alloy were also compared with the properties of solution treated alloy. [ABSTRACT FROM AUTHOR]

In the present study, effect of ZrC vol.% on mechanical properties of AA6061 metal matrix composites (MMCs) produced via stir casting technique was investigated. The vol.% of ZrC particles was varied as 5,10 and 15. The composites were characterized for its microstructure and mechanical properties and their relationships were obtained. The scanning electron microscope (SEM) images revealed uniform distribution and good bonding between the AA6061 alloy and the ZrC particles. The mechanical properties of the AA6061 alloy was found to significantly improve with the addition of ZrC particles from 5 to 15 vol.%, the hardness increased from 32 to 68 HV, yield strength increased from 50 to 86 MPa and the ultimate tensile strength increased from 118 to 165 MPa. However, the % of elongation of the composite samples decreased with 15 vol.% addition of ZrC particles. Sliding wear behaviour of the composites was investigated using a pin-on-disc wear tester at a load of 9.8 N and addition of ZrC particles was significantly found to reduce the wear rate of AA6061 alloy. [ABSTRACT FROM AUTHOR]

Brass alloys are used in many applications. However, improving their surface properties would help to increase their service life. For that, this study proposed to deposit using high velocity oxygen fuel (HVOF), nickel-chromium-boron-silicon (NiCrBSi) alloy, and 316L stainless steel (SS) coatings on brass substrates and investigate the mechanical properties and corrosion resistance of the coatings. The surface–interface morphologies, phases, and porosity of the coatings were analyzed using a scanning electron microscope and 3D profilometer. The adhesive strength and microhardness of the NiCrBSi and 316L SS coatings were also studied. Corrosion investigations were carried out using the salt fog test in an acetic acid salt spray atmosphere according to the NF EN ISO 9227 standard. This work showed that the 316L SS coatings presented a lower microhardness and higher adhesion strength than the NiCrBSi coatings despite their lower corrosion resistance. This could be explained by the microstructure of the coatings, the 316L SS coatings exhibiting more defects such as pores, un-melted particles, and oxides. [ABSTRACT FROM AUTHOR]

The effect of δ-Al 3 CuNi phase and thermal exposure on microstructure and mechanical properties of Al-Si-Cu-Ni alloy is investigated by optical microscopy, scanning electron microscope, and tensile test. The alloys with different volume fractions of δ-Al 3 CuNi phase are designed according to the thermodynamic calculation, which is confirmed by the microstructure characterization. The mean diameter of primary Si increases while the eutectic Si decreases with increasing the volume fraction of δ-Al 3 CuNi phase. The eutectic Si is coarsening during thermal exposure at 350 °C. Both strip-shape and fishbone-shape δ-Al 3 CuNi phase are observed in the as-cast alloys. In addition, the fishbone-shape δ-Al 3 CuNi phase is composed of many independent short rods. Parts of the thin short rods of δ-Al 3 CuNi phase change into γ-Al 7 Cu 4 Ni phase after thermal exposure at 350 °C for 200 h. The ultimate tensile strength and yield strength increase while the elongation decreases with increasing the volume fraction of δ-Al 3 CuNi phase. Comparing with the as-cast alloys, the ultimate tensile strength and yield strength are reduced after thermal exposure at 350 °C for 200 h, but the elongation of the alloys is increased. The failure mechanism of the alloys tested at 25 °C is quasi-cleavage fracture and ductile fracture is the dominant fracture mechanism tested at 350 °C. • The Al 3 CuNi with thin short rods shape changes into Al 7 Cu 4 Ni at 350 °C for 200 h. • The eutectic Si is coarsening during thermal exposure at 350 °C. • The Al 3 CuNi phase with strip-shape is thermal stable at 350 °C. • The ultimate tensile strength and yield strength increase with the Al 3 CuNi phase. [ABSTRACT FROM AUTHOR]

Three kinds of high-performance as-extruded Mg-Gd-Zn-Zr alloys were successfully prepared by controlling Zn and Gd contents and atomic ratio. The microstructure, mechanical properties and corrosion resistance of the three alloys were studied by optical microscope (OM), scanning electron microscope (SEM), X-ray diffractometer (XRD), electron backscattering diffraction (EBSD), tensile-compressive experiment and electrochemical experiment. The results showed that the coarse grains and continuous second phase of as-cast alloys were refined and broken after hot extrusion, and the main components were α-Mg, W–Mg 3 Gd 2 Zn 3 , I–Mg 3 Zn 6 Gd and MgZn 2 phases. The mechanical properties and corrosion resistance tests revealed that the as-extruded GZ22 alloy had the highest ultimate tensile strength (UTS) of 362 ± 6 MPa and the lowest corrosion rate of 0.94 mm/year, which was attributed to the fine grains and a small amount of dispersed second phase. The strength of as-extruded GZ56 alloy decreased due to excessive hard and brittle W-phase. Meanwhile, a large amount of second phase content made the alloy had the lowest corrosion resistance. In addition, the as-extruded GZ26 alloy with high Zn/Gd atomic ratio had good comprehensive mechanical properties, and its UTS and elongation (EL) were 332 ± 3 MPa and 24.5 ± 0.6%, respectively. The unique feature of this alloy was that weak texture intensity led to good tension-compression yield symmetry, and its corrosion resistance was second only to that of the as-extruded GZ22 alloy. [ABSTRACT FROM AUTHOR]

Al–Si base composites reinforced with different mixtures of Ni and nano-Al 2 O 3 particles have been fabricated by squeeze casting and their metallurgical and mechanical characterization has been investigated. A mixture of Ni and nano-Al 2 O 3 particles of different ratios was added to the melted Al–Si piston alloy at 700 °C and stirred under pressure. After the Al-base-nano-composites were fabricated by squeeze casting, the microstructure and the particle distribution inside the matrix have been investigated using optical and scanning electron microscopes. Moreover, the hardness and the tensile properties of the resulted Al-base-nano-composites were evaluated at room temperature by using Vickers hardness and universal tensile testers, respectively. As a result, in most cases, it was found that the matrix showed a fine eutectic structure of short silicon constituent which appeared in the form of islands in the α-phase around some added particle agglomerations of the nano-composite structures. The tendency of this structure formation increases with the increase of Ni particle addition. As the ratio of the added particles increases, the tendency of these particles to be agglomerated also increases. Regarding the tensile properties of the fabricated Al-base-nano-composites, ultimate tensile strength is increased by adding the Ni and nano-Al 2 O 3 particles up to 10 and 2 wt.%, respectively. Moreover, the ductility of the fabricated composites is significantly improved by increasing the added Ni particles. The composite material reinforced with 5 wt.% Ni and 2 wt.% nano-Al 2 O 3 particles showed superior ultimate tensile strength and good ductility compared with any other added particles in this investigation. [ABSTRACT FROM AUTHOR]

• The addition of boron can effectively refine the grain size and improve the tensile strength of the alloy at room temperature. • With the increase of boron content, the complex permittivity and permeability of the material are significantly improved, and the microwave absorption performance at low frequency is improved. • When the boron content is 0.06 at%, the minimum reflection loss peak reaches −10.7 dB at 1.9 GHz. Flaky FeSiAlB alloy powders were prepared by melting, quenching and milling. The effects of boron on the microstructure of FeSiAl alloy powders, the element distribution on the grain boundary of parent alloy, and the room temperature tensile properties of as-quenched sheet were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS) and tensile testing machine, respectively. With the addition of boron, the grain size of the master alloy was refined, and the tensile strength of the quenched sheet at room temperature was significantly improved. And obvious boron-rich regions were observed at grain boundaries. Soft magnetic properties were measured by vibrating sample magnetometer (VSM). Based on the electromagnetic parameters measured by vector network analyzer (VNA), the microwave absorption properties of flaky powder were calculated. The particles with high flake have high permittivity and permeability. Reflection loss (RL) shows that when B content amount was 0.06 at%, the absorption performance of the original FeSiAl absorbing material is improved in L and S bands, and the absorption peak moves from high frequency to low frequency. Excessive B element will lead to impedance mismatch, and the absorption performance in L and S bands will gradually decrease. For FeSiAlB flaky powder with 0.06 at % B content, the RL is −10.7 dB at 1.9 GHz and the matching thickness is 3 mm. [ABSTRACT FROM AUTHOR]

Zn alloy has attracted much attention in recent years as a new biomedical degradable material. However, how to simultaneously achieve its high strength and high ductility is a bottleneck problem to be solved. In this study, the Zn-2.0Cu-0.1Ti alloy with ununiform heterostructure, consisting of the barren areas without CuZn 5 phase and the regions enriched with CuZn 5 phase, was designed and successfully fabricated through controlled stir casting and hot extrusion. Uniaxial tensile test and Vickers hardness test were applied to reveal the mechanical properties of the Zn-2.0Cu-0.1Ti alloy, while electrochemical test and immersion test were used to characterize its degradation properties. The novel heterostructure was systematically examined by optical microscope (OM), scanning electron microscope (SEM), and transmission electron microscope (TEM). It was found that the yield strength and ultimate tensile strength of the present Zn-2.0Cu-0.1Ti alloy reach 241.2 ± 4.7 MPa and 265.8 ± 1.3 MPa, showing 294.4% and 230.3% improvement over those of pure Zn. Even more surprising is that the improved strength can be achieved without sacrificing ductility. The substantially increased strength can be mainly attributed to the strengthening mechanisms of grain refinement and Orowan looping, and the maintenance of good ductility thanks to the excellent dislocation storage ability of the present heterostructure. At the same time, the corrosion rate of the alloy in simulated body fluids also reaches the industry standard for orthopedic implants. This study not only sheds light on the design and fabrication of Zn-based material for surgical implantation application but also provides a feasible route to improve the mechanical properties of other precipitates reinforced alloys. • Heterostructure with ununiform dispersion of CuZn 5 was constructed in Zn-2.0Cu-0.1Ti alloy. • The significant strength improvement over pure Zn was achieved without sacrificing ductility. • The involved strengthening and toughening mechanisms were deeply discussed. • The slightly increased corrosion rate was explained in terms of the heterostructure. [ABSTRACT FROM AUTHOR]

High strength and toughness are achieved in the Mg-4.96Gd-2.44Y-0.43Zr alloy by multidirectional impact forging (MDIF). The forged sample has a fine-grained microstructure with an average grain size of ~5.7 µm and a weak non-basal texture, and it was characterized by an optical microscope (OM), scanning electron microscope (SEM), and electron back-scattering diffraction (EBSD). Tensile results exhibit the tensile yield strength (TYS) and static toughness (ST) of as-homogenized alloy dramatically increased after forging and aging, i.e., the TYS increased from 135 − 5 + 4 MPa to 337 − 2 + 2 MPa, and the ST enhanced from 22. 0 − 0.5 + 0.3 MJ/m3 to 50. 4 − 5.4 + 5.3 MJ/m3. Specifically, the forged Mg-Gd-Y-Zr alloy owns higher TYS than that of commercial rolled WE54 (Mg-5.25Y-3.5Nd-0.5Zr) and WE43 (Mg-4.0Y-3.0Nd-0.5Zr) alloys. [ABSTRACT FROM AUTHOR]

Abstract: A soft buffer layer (BL) between the weld metal (WM) and the parent metal (PM) was introduced in this study. To study the effect of a BL on mechanical properties, two types of joints made from welded high-strength low-alloy (HSLA) specimens with or without a BL were prepared. To investigate the influence of the notch location, the welded HSLA specimens machined with a U-notch in the WM or the PM. These conditions were examined to determine the effects of the BL and the notch location on the fatigue characterizations and the microscopic features of the fatigue-fractured surface. Extended-compact tension (E-CT) specimens were used for all tests. Paris fatigue curves and hardness distributions of the welded HSLA specimens with or without a BL were measured, and relevant scanning electron microscope (SEM) images were taken. The results showed that the presence of a BL significantly improved the fatigue crack growth behavior when a U-notch was in the WM. The notch location greatly influenced the fatigue behavior and the surface features of the fatigue-fractured specimens. [Copyright &y& Elsevier]

In the present paper, the Mg-11Gd-2Y-1Zn alloys with different Al addition were fabricated by the gravity permanent mold method. The effect of Al content on microstructure evolution and mechanical properties of as-cast Mg-11Gd-2Y-1Zn alloy was studied by metallographic microscope, scanning electron microscope, XRD and tensile testing. The experimental results showed that the microstructure of as-cast Mg-11Gd-2Y-1Zn alloy consisted of α-Mg phase and island-shaped Mg3 (RE, Zn) phase. When Al element was added, Al2RE phase and lamellar Mg12REZn (LPSO) phase were formed in the Mg-11Gd-2Y-1Zn alloy. With increasing Al content, LPSO phase and Mg3 (RE, Zn) phase gradually decreased, while Al2RE phase gradually increased. There were only α-Mg and Al2RE phases in the Mg-11Gd-2Y-1Zn-5Al alloy. With the increase of Al content, the grain size decreased firstly and then increased. When the Al content was 1 wt.%, the grain size of the alloy was the minimum value (28.9 μm). The ultimate tensile strength and elongation increased firstly and then decreased with increasing Al addition. And the fracture mode changed from intergranular fracture to transgranular fracture with increasing addition. When Al addition was 1 wt.%, the maximum ultimate tensile strength reached 225.6 MPa, and the elongation was 7.8%. When the content of Al element was 3 wt.%, the maximum elongation reached 10.2% and the ultimate tensile strength was 207.7 MPa. [ABSTRACT FROM AUTHOR]

To enhance the mechanical properties (e.g., strength and elongation) of the face-centered cubic (fcc) α-phase in the Au-Cu-Al system, this study focused on the introduction of the martensite phase (doubled B19 (DB19) crystal structure of Au2CuAl) via the manipulation of alloy compositions. Fundamental evaluations, such as microstructure observations, phase identifications, thermal analysis, tensile behavior examinations, and reflectance analysis, have been conducted. The presence of fcc annealing twins was observed in both the optical microscope (OM) and the scanning electron microscope (SEM) images. Both strength and elongation of the alloys were greatly promoted while the DB19 martensite phase was introduced into the alloys. Amongst all the prepared specimens, the 47Au41Cu12Al and the 44Au44Cu12Al alloys performed the optimized mechanical properties. The enhancement of strength and ductility in these two alloys was achieved while the stress plateau was observed during the tensile deformation. A plot of the ultimate tensile strength (UTS) against fracture strain was constructed to illustrate the effects of the introduction of the DB19 martensite phase on the mechanical properties of the alloys. Regardless of the manipulation of the alloy compositions and the introduction of the DB19 martensite phase, the reflectance stayed almost identical to pure Au. [ABSTRACT FROM AUTHOR]

There are many means and mechanisms to strengthen alloys, but often at the cost of plasticity. Strength or plasticity? In practice, the two often appear as contradictory relationships. In the current work, the ZrSn 1.5 Al x (x = 6, 8, 10, 12, 14 at. %) alloy obtained by controlling the Al content was smelted and hot-rolled at 890 °C, and then immediately quenched to obtain an alloy containing α + β + AlZr3 multiphase structure. Compared with ZrSn 1.5 Al 6 alloy, ZrSn 1.5 Al 14 alloy reaches a high ultimate tensile strength (1080.84 MPa) and a large elongation at fracture (28.59%) at room temperature, an increase of 27.6% and 86.3%, respectively. The formation of AlZr3 particles pins dislocations, promotes cross-sliding of dislocations, and improves the dislocation nucleation rate by changing the dislocation sliding mode, which increases the dislocation density and promotes uniform plastic deformation, enhance the strain-hardening ability of the alloys, thereby improve its plasticity and strength simultaneously. Optical microscopy (OM) and scanning electron microscope (SEM) were used to observe the metallographic structure and tensile fracture morphology. The transmission electron microscope bright field (TEM-BF) image and scanning transmission electron microscope high-angle annular dark field (STEM-HAADF) image of the sample were observed for detailed analysis. The samples were taken in the rolling direction and the mechanical properties were evaluated by uniaxial tensile tests at room temperature. In summary, the machining process is simple, the cost is low, and it is suitable for large-scale industrial-grade applications. It may have reference significance to other alloy systems. • The strength and plasticity have been improved simultaneously. • ZSA14 shows high ultimate tensile strength (1080.84 MPa) and a large elongation at fracture (28.59%). • FCC AlZr3 phase formed when Al content is over 8 at. %. • AlZr3 particles hinder dislocations, dislocation nucleation rate was increased by changing the dislocation slip mode. • The strain-hardening ability of the alloy improved. [ABSTRACT FROM AUTHOR]

In this paper, the temperature sensitivity of mechanical properties and microstructure of the additive manufactured Ti-6Al-4V alloy via selective laser melting was investigated in the deformation temperature range between room temperature (RT) and 550 °C. Mechanical properties and microstructure were characterized by the means of tensile testing, optical microscope, scanning electron microscope and transmission electron microscope. The results show that the ultimate tensile strength (UTS) of the experimental Ti-6Al-4V alloy exhibits two-stage temperature sensitivity, which is reflected in the fact that the temperature sensitivity of UTS below 500 °C is conventional, whereas, the UTS decreases drastically from 834 MPa to 562 MPa as the temperature increases from 500 °C to 550 °C. Compared with the Ti-6Al-4V alloys prepared by conventional processing methods and other additive manufacturing methods, this experimental Ti-6Al-4V alloy exhibits a competitive strength below 500 °C and possesses excellent comprehensive mechanical properties at RT. The analysis shows that the microstructure is composed of α′ martensite with plenty of twinning structures when the as-built samples are deformed below 500 °C. However, above 500 °C, martensite gradually transformed into equilibrium α phase, the microstructure changed from acicular to lamellar, and β and α 2 (Ti 3 Al) appear due to the elemental distribution homogenization and martensite decomposition, which account for the dramatic decrease of the tensile strength of the experimental Ti-6Al-4V alloy above 500 °C. Unlabelled Image • SLM Ti-6Al-4V samples deformed below 500 °C had excellent tensile strength. • α′ martensite, twins and dislocations played a significant role on tensile properties. • The ultimate tensile strength of the alloy exhibited two-stage temperature sensitivity. • β phase and α 2 phase precipitated in the samples which were deformed above 500 °C. [ABSTRACT FROM AUTHOR]

Grain refinement is one of the effective methods to improve the yield strength and toughness of Al-Cu alloys. The effects of Sc addition (0.2%, 0.4%, 0.6%, 0.8% and 1.0 wt%) on the microstructural evolution and mechanical properties of as-cast Al-5%Cu alloys were studied. The as-cast samples were characterized by optical microscope (OM), transmission electron microscopy (TEM), scanning electron microscope (SEM) and electron probe microanalysis (EPMA). The results revealed the primary α-Al occurred to obvious change from developed dendrites to fine equiaxed grains with the increasing Sc content in Al-5%Cu alloy. When the addition concentration of Sc reaches 0.8%, the developed α-Al dendrites were significantly refined and the average size of α-Al decreased from 218.3 μm to 29.6 μm. Moreover, the morphology and size of θ-Al 2 Cu phases of Al-5%Cu alloy caused noticeable changes with the increase of Sc concentration. Mechanical properties test illustrated that the ultimate tensile strength (UTS), yield strength (YS) and elongation (El) increased by 61.59%, 66.82% and 57.20%, respectively, which could be attributed to microstructure refinement and fine Al 3 Sc particle precipitate. • Sc can significantly refine the α-Al phase from coarse dendrites to uniform fine equiaxed grains in Al-5%Cu alloy. • The addition of Sc change the morphology of θ-Al 2 Cu from discontinuous to continuous tissues. • The YS and UTS was improved by 61.59% and 66.82% and the El was enhanced by 57.20% when the addition of Sc reached 0.8%. [ABSTRACT FROM AUTHOR]

In this paper, Ti–6Al–4V alloy was fabricated by selective laser melting (SLM) with different build orientations, namely SLM-1 and SLM-2, respectively. Microstructures of SLM-1 and SLM-2 were characterized by X-ray diffraction, optical microscope, scanning electron microscope and transmission electron microscope. The results show that the α and α′ phases in the hexagonal close-packed (hcp) structure, as well as the residual β phase in the body centered cubic (bcc) structure, exist in both samples. However, different SLM build orientations led to varied cooling rates and α/α′ ratios in the final materials. The SLM-1 alloy with build orientation along its thickness direction had higher cooling rate and thus lower α/α′ ratio than the SLM-2 alloy with build orientation along the length direction. Besides, minor martensitic (α'') phase was observed in the SLM-1 alloy and acted as an intermediate phase between β and α′ phases. The low α/α′ ratio and existence of α'' phase in the SLM-1 alloy result in a relatively high tensile strength but deteriorated plasticity. Comparatively, the higher α/α′ ratio in the SLM-2 alloy without α'' martensite leads to a much better plasticity regardless of the slightly reduced tensile strength. [ABSTRACT FROM AUTHOR]