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Development of magnesium alloys with exceptional mechanical properties and high thermal conductivity is a prominent subject in the field of thermal conductive magnesium alloys. Rare-earth containing magnesium alloys are known for their ability to achieve higher strength. However, they often exhibit higher density and higher cost. This study developed a high-strength and high-conductivity magnesium alloy without the need for rare earth elements through considered composition design. By utilizing the pinning effect of Mg 2 Si and solute drag effects of Zn and Cu, a fine-grained magnesium alloy with an average grain size of merely 4.5 μm was achieved. The simultaneous introduction of hard Mg 2 Si particles and ductile Cu-rich particles allow Mg-1.38Si-0.5Zn-0.5Cu alloy (SZC100) to attain a desirable combination of strength and plasticity. Althogh free of rare-earth elements, this magnesium alloy demonstrates a thermal conductivity of 141.5 W/(m·K), a yield strength of 238 MPa, and an elongation of 16.2 %. [ABSTRACT FROM AUTHOR]

In this study, the microstructure, mechanical properties, and thermal conductivity of as-extruded Mg–4Zn-0.6Zr-xCa (x = 0, 0.3, 0.6, 0.9 wt%) alloys were investigated. The results revealed a bimodal grain size distribution in all the alloys due to incomplete dynamic recrystallization (DRX), characterized by the coexistence of elongated deformed grains and equiaxed DRX grains. The bimodal grain size distribution enhanced the mechanical properties of the studied alloys. Furthermore, Ca alloying facilitated the formation of Ca 2 Mg 6 Zn 3 phases, through which the DRX extent was also enhanced. The precipitation of secondary phases, along with the increased DRX induced by Ca addition, was beneficial in eliminating the lattice distortion of the alloys, resulting in improved thermal conductivity compared to the Ca-free Mg–4Zn-0.6Zr alloy. The optimum combination of mechanical properties and thermal conductivity was achieved in the Mg–4Zn-0.6Zr-0.6Ca alloy, with yielding strength, ultimate tensile strength, tensile fracture elongation, and thermal conductivity values of 271 MPa, 318 MPa, 17.6 %, and 123.9 W/(m‧K), respectively. This work demonstrates that Mg–Zn–Zr–Ca-based alloys can be developed with high strength and high thermal conductivity, significantly expanding the industrial application of magnesium alloys. [ABSTRACT FROM AUTHOR]

Invar 36 alloy manufactured via the laser powder bed fusion (LPBF) process have attracted interest for their excellent low expansion properties. The properties of Invar 36 alloy, particularly thermal expansion, are highly sensitive to variations in process parameters. However, the effect of process parameters on microstructure and properties has not been systematically studied. This study examines the microstructure, mechanical properties, and coefficient of thermal expansion (CTE) of Invar 36 alloy under various processing parameters with different volumetric energy densities (VED). The results demonstrate that VED variations significantly impact the microstructure, mechanical properties, and CTE. Increasing VED leads to larger grain size and higher high angle grain boundaries, while geometric dislocation density and Taylor factor do not exhibit a linear relationship. At 89.29 J/mm3 VED, the Invar 36 alloy displays the optimal yield strength (405.4 MPa), tensile strength (489.3 MPa), and elongation (43.3%). The CTE meets the ASTM F1684 standard for all specimens. Lower relative density corresponds to smaller CTE, with the lowest CTE achieved at VED of 41.67 J/mm3. Furthermore, the influence of porosity on CTE diminishes with rising temperature. This research opens up the possibility of process parameters optimization for improved CTE and mechanical properties in as-printed Invar parts. [ABSTRACT FROM AUTHOR]

In this study, the effects of applied pressure (AP) and residual heat quenching (RQ) on the mechanical properties and thermal conductivities of Al-4.6Mg-3.6Zn-0.86Mn-0.48Fe alloys were investigated based on intensively microstructure analysis by scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM) and synchrotron X-ray tomography (SXT). The results indicated that AP and RQ did not change the type of intermetallic; instead, they reduced the length and quantity of lath-like Al 6 (Fe,Mn) and significantly refined the grain by increasing the cooling rate. Moreover, η′ precipitation particles were enriched near the grain boundaries, which was beneficial for the yield strength of the alloy; the AP + RQ sample exhibited the best mechanical properties of the ultimate tensile strength, yield strength and elongation of 269 MPa, 164 MPa and 11.4 %, respectively, which were 19 %, 17 %, and 83.8 % higher than those of the gravity cast (GC) sample. Moreover, the thermal conductivity of the AP + RQ sample did not show significant changes, which were attributed to the reduction in solid solute caused by the increased volume fraction of η′ precipitates, thus improving the thermal conductivity; however, the formation of numerous semi-coherent interfaces between η′ and the matrix led to increased lattice distortion, resulting in electron scattering. • Residual heat quenching can improve the strength of cast Al–Mg–Zn alloys. • The 3D morphology of the Fe-rich phases and pores has been significantly improved. • Mechanical properties enhanced by improvement of Al 6 (FeMn) and the presence of η'. • The semi-coherent interfaces between η′ and matrix reduced the thermal conductivity. [ABSTRACT FROM AUTHOR]

Abstract Nitrogen-annealed tensile specimens of a cold rolled medium Mn (9.76 wt%) steel exhibited significantly reduced ductility due to a two-zone embrittled surface layer, imparted during annealing in a nitrogen atmosphere. The embrittlement was associated with high nitrogen contents at the surface. [ABSTRACT FROM AUTHOR]

Porthole die extrusion of Mg-Al-Zn alloy was conducted using the as-cast, as-homogenized and as-extruded billets. The effects of initial microstructure on grain size, secondary particle, texture and mechanical properties of the extruded profiles were investigated. The results showed that complete dynamic recrystallization (DRX) occurred in welding zone of all profiles, and the profile extruded from as-cast billet had the smallest DRXed grains. Large un-DRXed grains with {10−12} extension twins were found in the matrix zone of the profiles extruded from as-cast and as-homogenized billets. In welding zone, all profiles have a strong basal plane texture with <0001> directions parallel to transverse direction, while the texture intensity and distribution significantly varied with initial billets. The profile obtained from as-extruded billet exhibited inferior tensile properties due to its low solid bonding degree. The hardness distribution in matrix zone of the profiles was not uniform due to the inhomogeneous microstructure. [ABSTRACT FROM AUTHOR]

Short term sub-glass transition annealing controls the structural reordering and nanocrystallization of CuZr − based bulk metallic glasses (BMGs). Using this method, 5 times higher resistance against strain softening as confirmed by three-point bending tests is attained. Homogenously dispersed nanoparticles in sizes of 20–50 nm accounts for the remarkable shifts and peak formations on reciprocal space together with the diffraction spots observed on 2D diffraction pattern. Real-space pair distribution function analysis reveals noticeable changes in peak shapes and positions correlated with the changes in short- to medium-range ordering. The differences in the partial coordination numbers upon annealing mark the dominant Zr − Zr pair to diminish whereas the Cu − Cu pair becomes prominent, hinting that Cu diffusion is mainly responsible for structural reordering and formation of new phases. The pursued study using hard X-ray synchrotron radiation reveals important aspects of structural changes preceding nanocrystallization, which in turn enhances the mechanical performance in BMGs. [ABSTRACT FROM AUTHOR]

The B 4 C were introduced into three-dimensional carbon fiber preform by slurry infiltration (SI), then combined with chemical vapor infiltration (CVI) and liquid silicon infiltration (LSI) to get the B 4 C modified C/C-SiC composites (C/C-B 4 C-SiC). The microstructures, oxidation resistance, mechanical and thermal physical properties of the C/C-B 4 C-SiC were investigated. The results indicated that B 4 C distributed near the fiber surface and mainly in the region of the needle punched fibers, short-cut fiber web layer, and outside of the fiber bundle in non-woven layer. The C/C-B 4 C-SiC possessed good oxidation resistance for B 4 C was easy to oxidize into B 2 O 3 and the product B 2 O 3 could fill in the defects such as pores and cracks to prevent the oxidation. The flexural strength, fracture toughness, and thermal capacity of the C/C-B 4 C-SiC were much higher than those of the C/C-SiC. The B 4 C both can enhance the interface combination with fibers and act as ceramic particles reinforcement. In addition, B 4 C had higher thermal capacity than C, Si or SiC to increase the thermal capacity of the C/C-B 4 C-SiC. [ABSTRACT FROM AUTHOR]

In this study, a high-strength and heat-resistant Al–Ce–Sc–Zr alloy was designed and fabricated by additive manufacturing. The as-built alloy shows an excellent combination of strength and ductility compared to other Al–Ce-based alloys, including an ultimate tensile strength of 445 MPa, a yield strength of 344 MPa and an elongation of 10%. Even at 300 °C, the alloy still retains a superb tensile yield strength of 233 MPa, which is the best among the high-temperature aluminum alloys reported so far. The excellent performance is mainly attributed to a significant amount of fine, homogeneous and coarsening-resistant Al 11 Ce 3 intermetallic nanoparticles formed during the rapid solidification process of laser additive manufacturing. The formation of coherent Al 3 (Sc, Zr) nano-precipitates and interfacial segregation at the interface of intermetallic nanoparticles during high temperature exposure further improve the high temperature properties of the alloy. Our work has the potential to provide design concepts for the development of novel high temperature aluminum alloys. • The rapid cooling rates during additive manufacturing produce a high volume fraction of nanoscale Al 11 Ce 3 intermetallic. • Thermal exposure promotes the precipitation of Al 3 (Sc, Zr) in matrix and the segregation of Sc/Zr at Al/Al 11 Ce 3 interface. • The combined role of Al 11 Ce 3 intermetallic and Al 3 (Sc, Zr) nano-precipitates contributes to excellent mechanical properties. • The Al–Ce-Sc-Zr alloy exhibits a high tensile yield strength of 233 MPa at 300 °C. [ABSTRACT FROM AUTHOR]

Eutectic Sn-Zn alloy is considered as one of the best lead free solder alloys in microelectronic industry. That motivates our group to select different weight percentage of Antimony (Sb) (0.5, 1.0, and 1.5 wt%) as an alloying to Sn-9.0Zn-0.5 Al solder alloy. The thermal behavior, microstructure modification as well as tensile properties of the new developed solder alloys were investigated. A slight increment of the melting temperature (∼ 1 °C) was recorded using differential scanning calorimetry (DSC) after additions of Sb. For 1.5 wt% of Sb, two endothermic peaks at 200.8 °C and 201.5 °C were observed, which are assigned as hypoeutectic Sn-Zn composition. X-ray diffraction (XRD) measurements confirm the existence of β-Sn phase, α-Zn phase, and Sb-Sn intermetallic compounds (IMCs). Scanning electron microscope (SEM) images indicate that the Sb additives refine the microstructure and form a uniform distribution of IMCs in the matrix of solder. The road-like α-Zn phase, Al 6 Zn 3 Sn and SbSn IMCs were clearly appeared in β-Sn matrix, which are responsible of the enhancement in tensile strength. Moreover, α-Zn phases in the Sn-9Zn-0.5Al-1.5Sb alloy were modified as needle-like, broken enormously, depleted, and circle shapes. Generally, The Sb-containing alloys have higher ultimate tensile strength (UTS) and lower elongation than Sb-free solder alloy due to the solid solution and second phase dispersion strengthening effect. The relationship between UTS and temperature follow the Arrhenius law. The average activation energies (Q) were found to be 44.4 ± 1.0 kJ/mol, and the average stress exponents (n) were usually around 5.3 ± 0.45, which are close to pipe diffusion controlled creep in β-Sn matrix. [ABSTRACT FROM AUTHOR]

The thermal conductivity of Mg-Sm binary alloys is relatively poor due to the severe lattice distortion introduced by the high solid solubility Sm atom in the Mg matrix, which restricts their widespread application. In this study, the viability of Al alloying (0–2.6 wt%) in permanent mold cast Mg-4Sm (wt.%) alloy was investigated to design cast Mg alloys with high thermal conductivity. It is found that the thermal conductivity significantly improved with the addition of Al content, and peaked at 136.8 W/(m·K) with an Al content of 1.5 wt%, which is attributed to the release of the Sm atoms from the Mg matrix. It is also confirmed that minimizing the lattice distortion effect is critical to achieving high thermal conductivity. The formation of Al 2 Sm and Al 11 Sm 3 phases leads to a dramatic decline in solid solution strengthening due to its strong consumption of the dissolved Sm atoms, but in the meantime enhances secondary phase strengthening and promotes stronger interactions between different strengthening components. The optimum combination of mechanical properties and thermal conductivity is obtained in Mg-4Sm-2Al alloy, which possesses a yield strength of 102.6 MPa, elongation of 6.8% and thermal conductivity of 124.5 W/(m·K), compared with several commercial as-cast Mg alloys. • The peak value of thermal conductivity (136.8 W/(m·K)) was achieved in the developed Mg-4Sm-1.5Al alloy. • Minimizing the lattice distortion effect is critical to achieving high thermal conductivity. • Excellent combination of thermal conductivity and mechanical properties was obtained in the developed Mg-4Sm-2Al alloy. [ABSTRACT FROM AUTHOR]

The Ca concentration dependence of microstructure, mechanical properties and thermal conductivity of Mg-2Ga-xCa (x = 0, 0.2, 0.4 and 0.8, in wt.%) alloys has been investigated at room temperature. As the Ca content increases, both the average grain size and the volume fraction of dynamically recrystallised grains decrease in the as-extruded alloys, leading to an increase in yield strength. However, the increase in the number and the size of second phase particles associated with the higher Ca content brings about the reduced plasticity. In addition, a minor Ca addition (0.2% and 0.4%) to the Mg-2Ga alloy has no significant effect on the thermal conductivity, but the 0.8%Ca addition can improve the thermal conductivity of the as-cast and as-extruded Mg-2Ga alloys significantly, which is mainly related to the reduction of solute Ga atoms in α-Mg. Meanwhile, the as-extruded alloy exhibits the higher thermal conductivity than the corresponding as-cast alloy. The as-extruded Mg-2Ga-0.8Ca alloy exhibits the tensile yield strength of 244 MPa and the thermal conductivity of 135.5 W·m-1·K-1. It is desirable to design Mg alloys with high strength and high thermal conductivity by selecting proper alloying elements for the formation of the precipitates other than dissolving in the Mg solution. [ABSTRACT FROM AUTHOR]

Thermal management materials with high thermal conductivity (TC), adjustable coefficient of thermal expansion (CTE) and excellent mechanical properties have promising applications in the electronic packaging and high-power density equipment fields. In this work, we have developed a novel strategy for tungsten-copper coated graphite flakes and aluminum nitride nanoparticles reinforced copper matrix composites (GFs(W–Cu)/AlN/Cu composites) fabricated by vacuum hot-pressing sintering. Herein, tungsten-copper coated graphite flakes (GFs(W–Cu)) were prepared by impregnation reduction and ultrasonic-assisted electroless plating, in which W–Cu coating improved interfacial bonding and realized metallurgical-physical synergy. Meanwhile, the AlN nanoparticles reinforced Cu flakes (AlN/Cu) were prepared by high energy ball milling, where AlN nanoparticles were evenly dispersed in the Cu matrix and played the role of pinning boundary and refining grain. Effects of nano-AlN with different volume fractions on the mechanical and thermal properties of GFs(W–Cu)/AlN/Cu composites were studied as well. As for the mechanical properties, the in-plane, through-plane flexural strength and tensile strength of GFs(W–Cu)/1.5AlN/Cu composite reached 276.7 ± 4.5, 390.6 ± 4.5 and 136.1 ± 3.0 MPa respectively, which increased by 96.8%, 283.7% and 120.7% than those of the GFs(W–Cu)/Cu composites. In terms of the thermal properties, the in-plane TC of GFs(W–Cu)/1.5AlN/Cu composite is 617.8 ± 12 Wm−1K−1, while the through-plane CTE ranging 25–200 °C is 4.9 ± 0.2 ppmK-1. In conclusion, the GFs(W–Cu)/AlN/Cu composites provide a huge potential for design and application in the thermal management materials. • A novel ternary copper matrix composite reinforced by tungsten-copper coated GFs and AlN nanoparticles was fabricated via hot-pressing sintering. • W–Cu coating obviously promoted the interfacial bonding to metallurgical-mechanical synergy bonding. • Uniformly dispersion of nano-AlN effectively enhanced grain refinement and higher strength. [ABSTRACT FROM AUTHOR]

Mo-0.5 wt%ZrC alloy plate with enhanced mechanical properties and thermal stability was manufactured by powder metallurgy and hot rolling. The as-rolled Mo-0.5%ZrC plate shows an ultimate tensile strength (UTS) of 725 MPa and a total elongation (TE) of 24.1% at room temperature. After annealing at 1300 °C, the UTS of Mo-0.5%ZrC alloy decreased to 676 MPa while the TE increased to 32.8%. After 1600 °C annealing, the UTS of Mo-0.5%ZrC alloy is 507 MPa and the TE increased significantly to 56.4%. Additionally, Mo-0.5%ZrC alloy exhibits a high recrystallization start temperature of about 1300 °C. The addition of nanoscale ZrC particles can enhance the strength and high temperature stability by pining dislocations and grain boundaries. Meanwhile, ZrC nanoparticles can also react with the impurity oxygen to form Zr–C–O or ZrO 2 particles, and thus alleviate the oxygen embrittlement of Mo alloy. However, the oxide particles tend to grow into larger particles at high temperatures, leading to decreased number density of dispersoids and lower dispersion-strengthening effect. • Mo-0.5%ZrC alloy plate shows enhanced mechanical properties and thermal stability. • The recrystallization temperature of Mo–ZrC alloy is 300 °C than that of pure Mo. • Recrystallized Mo-0.5%ZrC alloy shows excellent room-temperature ductility. • ZrC can react with O to form stable oxide and enhance the grain boundary bonding. [ABSTRACT FROM AUTHOR]

The demand for high-performance magnesium alloys, including high strength, high thermal conductivity, and good heat resistance, is growing rapidly in practical applications. Here, we report a high performance Mg–7Al–3Ca (AX73, wt.%) alloy with high strength, good thermal conductivity, and acceptable heat resistance via the high-pressure die casting (HPDC) method. Compared to the commonly used Mg–4Al–4RE (AE44) and Mg–9Al–1Zn–0.25Mn (AZ91D), the HPDC AX73 exhibited a much higher yield strength (YS) at room temperature (RT) and 175 °C. The high YS was attributed to the combinations of fine-grain strengthening, second phase strengthening from numerous Al 2 Ca eutectic phases, and solid solution strengthening from Al solutes. After the aging treatment, the room-temperature YS of AX73 alloy was further improved from 184 MPa to 196 MPa due to fine Al 2 Ca precipitation. Since the existence of Ca obviously reduced the Al solutes in the α-Mg matrix, the AX73 and AX73 aged alloys possessed reasonable thermal conductivity of 67 and 68.5 W(m·K)−1, respectively. [Display omitted] • A high-performance Mg–7Al–3Ca (AX73) was fabricated by the high-pressure die casting (HPDC) method. • The HPDC AX73 exhibited a much higher yield strength (YS) at room temperature and 175 °C. • The aging treatment further improved the YS due to fine Al 2 Ca precipitation. • The AX73 and AX73 aged alloys possessed reasonable thermal conductivity of 67 and 68.5 W(m·K)−1, respectively. [ABSTRACT FROM AUTHOR]

High density reduced graphene oxide (rGO) reinforced aluminum nitride (AlN) composites were successfully fabricated by the one-step spark plasma sintering (SPS) method. Raman spectra showed that the raw material of GO was thermal reduced to rGO during the SPS process, and the reduction of GO can be strongly affected by the carbonaceous atmosphere. With the rGO content increasing (0–2 wt %), the dispersion of rGO and relative density of the composites decreased, decreasing the elastic modulus and hardness accordingly. However the flexural strength had a slight increase when rGO content was ≤1 wt%, and the fracture toughness increased from 3.5 to 5.2 MPa m 1/2 with the rGO due to the crack bridging and pulling out of rGO. The thermal conductivity of the composites was low and sharply decreased from 92.5 to 37.4 W m −1 K −1 with the addition of rGO, which are attributed to the low crystalline quality and high vacancy defects in rGO and the increase of interfacial thermal resistance. [ABSTRACT FROM AUTHOR]

In order to improve the thermal and mechanical properties, CNTs were introduced into the matrix of SiC/SiC composites through electrophoretic deposition. Effect of the introduction of CNTs into CVI SiC/SiC composites was investigated. Microstructure, mechanical properties and thermal conductivity of SiC/SiC composites (SS) and SiC/SiC-CNTs composites (SSCS) were compared. Results indicated that matrix of SSCS presented a multi-layer morphology while that of SS showed a single-layer of SiC. Compared with SS, intra-bundle pores in SSCS were much smaller and fewer, which was accorded with the higher density (2.78±0.04 g/cm 3 ) and smaller porosity (5.8±0.3%). SSCS had a better performance in bending strength (484±16 MPa) and damage tolerance (19.4±0.7 MPa m 1/2 ) because of the pull out and crack bridging of CNTs. The thermal conductivity of SSCS was 1.74 times higher than that of SS. With the introduction of CNTs into CVI SiC/SiC composites, density, bending strength, damage tolerance and thermal conductivity were improved. [ABSTRACT FROM AUTHOR]

An improved thermo-mechanical processing (N-ITMT) was proposed for manufacturing fine-grained precipitation-hardening Al–Zn–Mg–Cu alloy based on cold rolling, short-period annealing and continuous rolling, and the corresponding microstructure evolution and mechanical properties were investigated. The N-ITMT processing can produce high-quality rolling sheets without edge cracks compared with the traditional RI-ITMT. The recrystallized fine-grained structures of N-ITMT samples are similar to those of RI-ITMT when the total reduction of N-ITMT reached 85% and exhibited high stability during long-period solution treatment. Moreover, the mechanical properties of N-ITMT samples are almost the same as those of RI-ITMT after peak aging (T6). It shows that cold deformation plus short-period annealing can acquire large quantities of MgZn 2 particles with diameter ≥0.2 μm, which can perform as nucleation sites for new recrystallized grains during subsequent solution treatment. It is greatly indicated that the static long-period overaging used by RI-ITMT can be replaced by cold deformation plus shot-period annealing, and the continuous rolling after short-period annealing would benefit the crack-free rolling sheets. Thus, N-ITMT would be a good alternative to RI-ITMT for efficient commercial production of different heat-treatable Al alloys to acquire fine grains. [ABSTRACT FROM AUTHOR]

The fabrication of a 2.5 dimensional silicon oxynitride fiber fabric reinforced boron nitride matrix (2.5 D Si–N–O f /BN) composites through borazine infiltration and pyrolysis routine is reported. The Si–N–O fiber exhibited an amorphous structure with high composition uniformity. The borazine-to-ceramic conversion completed at 1200 °C and generated hydrogen-free turbostratic BN ceramic. Both the density and crystalline degree of the derived BN products increased with the elevating of pyrolysis temperature. The average bending and tensile strength of the 1200 °C fabricated 2.5 D Si–N–O f /BN composites were 127.4 MPa and 78.3 MPa, respectively. Considerable fiber pull-out was observed throughout the fractured surfaces, which was mainly attributed to the appropriate bonded fiber/matrix interfaces and the relative low elastic modulus of the matrix. Meanwhile, the composites displayed low dielectric constant and loss tangent values of 3.37 and 0.0031, as well as a low thermal conductivity of 1.04 W m −1 K −1 . [ABSTRACT FROM AUTHOR]

Al matrix composites (AMCs) have gained tremendous interest in the past decades due to their lightweight, superior mechanical and other physical properties. In this study, an ultrafine-grained Al2024/1 wt% TiC/1 wt% graphene nanoplatelets (GNPs) nanocomposite was fabricated through powder metallurgy. Synergetic effects of TiC and GNPs on the microstructural characteristics, mechanical properties and thermal conductivity were investigated in comparison with those of the matrix and TiC or GNPs singly reinforced Al2024 matrix nanocomposites. The Al2024/1 wt% TiC/1 wt% GNPs nanocomposite showed significantly improved mechanical properties with the compression yield strength of 370.2 MPa, ultimate compressive strength of 615.8 MPa and fracture strain of 8.6%, indicating a superior balance in the strength and ductility over TiC or GNPs singly reinforced Al matrix composite, since the distributions of both the TiC and GNPs in Al2024/1 wt% TiC/1 wt% GNPs nanocomposite were improved significantly. The significant mechanical property improvements are attributed to the synergistic reinforcing contributions from TiC and GNPs. The thermal conductivity of Al2024/1 wt% TiC/1 wt% GNPs nanocomposite stables at 55.0 W∙m-1∙K-1 without a further decrease compared with the composite singly reinforced with GNPs. • An ultrafine-grained Al2024–TiC-GNPs hybrid nanocomposite (AlTG) was fabricated. • Introducing TiC and GNPs benefits uniform dispersions of TiC and GNPs in AlTG. • The hybrid composite (AlTG) shows a superior balance in the strength and ductility. • Improved dispersions of TiC and GNPs explain better mechanical properties of AlTG. • Excellent thermal conductivity of AlTG is remained compared with other composites. [ABSTRACT FROM AUTHOR]

The effect of the relative contents of Al and Ti on the equilibrium phase formation in a novel Ni 51 Co 18 Fe 5 Cr 10 Al 16-X Ti X high entropy superalloy (HESA) system was analysed using Thermo-Calc software (TCHEA-3 database). The proposed HESAs showed a broad γ+γ′ equilibrium phase field over an extended temperature range (from 660 °C to a γ′-dissolution temperature >1184 °C) without the presence of brittle intermetallic phases. The effect of Al/Ti ratio on the microstructure, mechanical properties and precipitation strengthening of the HESAs was determined. The proposed alloys showed a high volume fraction (∼60%) of a (Ni, Co) 3 (Al, Ti)-type ordered (γ′) phase in a disordered face-centered cubic matrix phase (γ). The microstructure and the thermal properties of the HESAs showed excellent correlation to the theoretical thermodynamic predictions. A lower Al/Ti ratio improved the mechanical properties of the HESA system due to the high lattice misfit between the γ and γ′ phases. The homogenised and aged Ni 51 Co 18 Fe 5 Cr 10 Al 8 Ti 8 HESA exhibited a γ′-volume fraction of 63%, γ′-dissolution temperature of 1200 °C and yield strengths of 1056 MPa and 852 MPa at room-temperature and 800 °C, respectively. The present work shows the potential to design Al–Co–Cr–Fe–Ni–Ti HESAs with a high volume fraction of γ′-phase and excellent mechanical properties. • Ni 51 Co 18 Fe 5 Cr 10 Al 16-X Ti X showed a broad γ+γ′ only equilibrium phase field over an extended temperature range (660 °C to a γ′-dissolution temperature >1184 °C). • Yield strength of Ni 51 Co 18 Fe 5 Cr 10 Al 16-X Ti X alloys increased with a decrease in Al/Ti ratio due to the increased the lattice misfit between γ and γ′ phases. • Ni 51 Co 18 Fe 5 Cr 10 Al 16-X Ti X alloys with a γ′-volume fraction of 63% and γ′-dissolution temperature of 1200 °C. • Homogenised and aged Ni 51 Co 18 Fe 5 Cr 10 Al 8 Ti 8 HESA exhibited yield strengths of 1056 MPa and 852 MPa at room-temperature and 800 °C. [ABSTRACT FROM AUTHOR]

To meet the requirements of structural and functional integration, machinability and workability of engineering materials, continuous mesophase pitch-based carbon fiber (MPCF) reinforced 2024 aluminum (Al) matrix composites with 20–50 vol % MPCF were fabricated by vacuum hot pressing method. The effects of MPCF volume fraction and T6 heat treatment on microstructure, thermal and mechanical properties of MPCF/2024Al composites were investigated. The results show that the interface of the as-sintered composite was well bonded. After T6 heat treatment, the amorphous layer at the interface changed from continuous to discontinuous and the interfacial bonding was further improved, but there was no interfacial reaction. The increase of MPCF volume fraction was beneficial to improve the thermal conductivity (TC) and elastic modulus (E) of the as-sintered composites, up to 258.3 W/(m⋅K) and 343.5 GPa respectively, while the composites with 30 vol % and 40 vol % MPCF respectively had the highest ultimate tensile strength (UTS) and a coefficient of thermal expansion (CTE) close to zero. After heat treatment, the TC and E were slightly changed, while the CTE was further reduced and UTS was significantly improved. In this work, the heat-treated composite with 30 vol % MPCF had the highest UTS of 499.3 MPa and good thermal properties, and the TC of this composite may be further improved by using MPCFs with higher TC. Therefore, this composite is expected to become a promising engineering material integrating structure and function. [ABSTRACT FROM AUTHOR]

Abstract: A new functionally graded zirconia–mullite/alumina ceramic (FGZM/A) and its constituent separated single zirconia–mullite/alumina (ZM/A) layers were designed and synthesized by reaction sintering of zircon and alumina. Influence of MgO addition, different sintering temperature and sintering time on the mineral composition, densification parameters, microstructure, mechanical and thermal properties of FGZM/A and it's separated ZM/A layers were investigated. Results showed that the tailored FGZM/A ceramic gave a continuous homogeneous structure without sharp interface. MgO addition enhanced the densification parameters in term of apparent porosity and bulk density, microstructure and compressive strength of ZM/A system with a little effect on the hardness, fracture toughness, thermal expansion and thermal shock resistance. FGZM/A in presence of MgO showed a gradient in its properties from one layer to the other. It recorded an average values of all the separated composites made from single layers through the different properties which reflect the strong interfacial bonding and homogenous distribution of powders in its different layers. [Copyright &y& Elsevier]

Abstract: This work investigates the effect of Fe addition on the microstructural, mechanical, and thermal properties of the Sn–1Ag–0.5Cu (SAC105) solder alloy. The addition of Fe leads to the formation of large circular FeSn2 intermetallic compound (IMC) particles, which produce a weak interface with the β-Sn matrix. The addition of Fe also leads to the inclusion of Fe in the Ag3Sn and Cu6Sn5 IMC particles. Moreover, Fe-bearing solders have been shown to form large primary β-Sn grains. The weak interface between the large FeSn2 IMC particles and the β-Sn matrix together with the presence of the large primary β-Sn grains results in a significant reduction on the elastic modulus and yield strength of the Fe-bearing solders. Moreover, the improved plasticity of the large primary β-Sn grains causes the Fe-bearing solders to exhibit large total elongation. The addition of Fe also significantly reduces the effect of aging. After aging at 100°C and 180°C, it has been observed that the Fe-bearing solders significantly suppress the coarsening of the Ag3Sn IMC particles; consequently, they exhibit stable mechanical properties. This effect can be attributed to the inclusion of Fe in the Ag3Sn IMC particles. In addition, fracture surface analysis indicates that the addition of Fe to the SAC105 solder alloy does not affect the mode of fracture, and all tested solders exhibited large ductile-dimples on the fracture surface. Moreover, the addition of Fe did not produce any significant effect on the melting behavior. As a result, the use conditions of the Fe-bearing solders are consistent with the conditions for conventional Sn–Ag–Cu solder alloys. [Copyright &y& Elsevier]

Abstract: Mg–3.0Al–2.2La–0.3Y–0.2Mn (wt.%) alloy was prepared by high-pressure die-casting. The microstructure, thermal stability of intermetallic phases and mechanical properties were investigated. The dominant strengthening phase is Al11La3, mainly distributed in the interdendritic regions. The Al11La3 phase exhibits good thermal stability with no significant decomposition at temperatures up to 200°C within 800h, while almost all Al11La3 intermetallics decompose to Al2La at higher temperature of 450°C for 800h. The alloy exhibits significantly improved tensile and compressive yield strengths at room temperature and 200°C. The outstanding mechanical properties are mainly attributed to the formation of Al11La3 intermetallics, which is present in a high volume fraction, and possesses fine morphology and relatively good thermal stability. [Copyright &y& Elsevier]

Abstract: 3D-orthogonal-woven-C–SiC composite blocks were fabricated using liquid–silicon-infiltration and were characterized for thermal and mechanical properties. Coefficient of thermal expansion (CTE) and thermal-diffusivity of the blocks were determined in the three mutually perpendicular directions. CTE was found to lie in the range −0.5×10−6 to 0.9×10−6/°C over the temperature range 25–1050°C while thermal diffusivity was found to be in the range 37.0–7.0mm2/s over the temperature range 25–1200°C. The composites were subjected to sudden heating at a heat flux of 0.9W/mm2 for 20s and cooling by a blast of air, upto 5 times. Three point bend test of the specimens was carried out. After five thermal shocks the composites retained about 59% of the initial strength (190MPa); after each thermal shock, the composite retained 85–90% of the previous strength. The composites showed excellent resistance to thermal shock and chemical erosion necessary for re-usable aerospace applications. [Copyright &y& Elsevier]

Abstract: Poly (ether ether ketone) (PEEK)/fly ash (FA) composites were prepared using melt blending technique. To improve the interfacial interaction of fly ash with the PEEK matrix, fly ash was chemically modified with calcium hydroxide, at different concentration. Various characterization studies like dynamic mechanical thermal analysis (DMTA), modulated differential scanning calorimetry (MDSC) and scanning electron microscopy (SEM) have been carried out to evaluate the storage modulus, tan δ, crystallinity, and morphology in the composites. SEM micrographs showed more uniform dispersion and interaction in the modified composites than unmodified counterpart. Surface modified fly ash improved the interfacial adhesion between fly ash and PEEK which is confirmed also through improved mechanical strength. The dynamic modulus of PEEK composites exhibited over 133% increment at 100–250°C, indicating improvement of elevated temperature mechanical properties. The modified fly ash reinforcements also showed improvement in glass-transition and crystallization temperature. [Copyright &y& Elsevier]

Abstract: ZA27 alloy based composites were synthesized by stirring method, followed by squeeze casting. Stir casting was employed successfully to incorporate 5vol.% of various reinforcement particulates, namely, SiC, ZrO2 or C. The porosity in the composites was decreased by squeeze pressure. The presence of particles and/or application of squeeze pressure during solidification resulted in considerable refinement in the structure of the composites. The microstructures, X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDXA) results indicated that no significant reactions occurred at the interface between the SiC or C particles and ZA27 alloy. However, in case of ZrO2 reinforced ZA27, the ZrO2 reacted with Cu present in the molten ZA27 alloy, forming Cu5Zr. Thermal analysis showed that both α and β nucleation and growth temperatures of the composites were lower than those of the ZA27 alloy. The presence of particles in the as-cast or squeezed composites led to not only an accelerated age hardening response, but also an increase in the peak hardness of the composites. The values of coefficient of thermal expansion (CTE) of the composites were drastically lower as compared to those of the ZA27 alloy. The tensile properties of the composites decreased as a result of the addition of the particles. Scanning electron microscope (SEM) pictures of the composites indicated that cracks mainly initiated at particle–matrix interface, propagated through the matrix and linked up with other cracks leading to failure of the composites. [Copyright &y& Elsevier]

Abstract: Reinforced carbon foam materials were produced with phenolic resole resin as precursor and K2Ti6O13 whiskers as additives. Effects of the content of whiskers on microstructure, compressive strength and thermal properties of carbon foams were investigated. The results showed that the carbon foams had a spherical and closed cell structure, and the distribution of cells was relatively uniform. The specimens with less than 4wt% K2Ti6O13 whiskers exhibited a higher compressive strength than neat foams. When the content exceeded 4wt%, the irregular openings on the cell walls revealed in microstructure images led to decrease in compressive strength. The thermal conductivity went down with increasing the content of whiskers as expected, which ranged from 0.24 to 0.40Wm−1 K−1 at room temperature. [Copyright &y& Elsevier]

Abstract: In this study, the effect of carbon nanotube (CNT) modification on the tensile and thermal properties of CNT/basalt/epoxy composites was investigated. CNT/basalt/epoxy composites were fabricated by impregnating woven basalt fibers into epoxy resin mixed with CNTs. Three groups of composites were fabricated, consisting of unmodified, acid-modified (oxidized), and silane-modified (silanized) CNTs, each at 1wt.%. Tensile tests and dynamic mechanical analysis (DMA) were performed on each group of composites to determine the mechanical and thermal properties of the CNT/basalt/epoxy composites, depending on the surface modification of CNTs. The tensile strength and Young''s modulus of silanized CNT/basalt/epoxy composites were 34 and 60% greater, respectively, than that of unmodified CNT/basalt/epoxy composites. Also the silanized composites had a higher storage modulus and T g than unmodified and oxidized composites. The enhancement of the mechanical and thermal properties of silanized CNT/basalt/epoxy composites is attributed to improved dispersibility and strong interfacial interaction between the silane functionalized CNTs and the epoxy in the basalt fabric/epoxy composites. [Copyright &y& Elsevier]

Abstract: In the present work, the characteristics of thermoplastic polyurethane (TPU) material exposed to artificial weathering environment for different durations were studied. The influence on (i) appearance and morphology, (ii) thermal properties and (iii) mechanical properties evolution of the material were investigated during aging. For this purpose, ultraviolet (UV) chamber was used as accelerated aging technique. Optical and scanning electron microscopy (SEM) observations revealed changes in appearance and morphology of TPU material after UV-exposure. From differential scanning calorimetry (DSC) analysis, it was mainly found that thermal properties, in terms of glass transition temperature (T g), were affected. Changes in mechanical behaviour were equally discerned using both computer-controlled tensile testing and abrasive wear tester. The mechanical properties in bulk of the studied material displayed tow steps. The elastic modulus and the stress at 200% of strain initially decreased and then increased progressively revealing an increase in crosslink density. The tribological properties, in terms of wear resistance, were affected and this degradation became more important with UV-exposure. Furthermore, our experimental results displayed prominently that there was a competition between chain scission and crosslinking mechanisms. [Copyright &y& Elsevier]

Abstract: This paper reports on the introduction of sol–gel prepared nano-silica into low-density polyethylene (LDPE) and maleic anhydride grafted LDPE (LDPE-g-MA), as well as on the blending of these nanocomposites with different amounts of oxidized paraffin wax as a possible compatibiliser. LDPE/wax and LDPE-g-MA/oxidized wax blends were also investigated in comparison. The FTIR results indicated interactions between LDPE-g-MA, oxidized wax and nano-silica, and these interactions influenced the thermal and mechanical properties of the samples in a complex way. There are strong indications of a stronger interaction between the nano-silica and the oxidized wax, which caused the wax to preferably crystallize around the nano-silica. The melting and crystallization behaviour, thermal stabilities, tensile properties and rheological behaviour, described in this paper, could be explained in terms of these observations. [Copyright &y& Elsevier]

Abstract: New type of aromatic–aliphatic polyamide/montmorillonite nanocomposites were produced using solution intercalation technique in dimethylacetamide. The modification of clay was carried out with ammonium salt of long chain alkyl amine. The nanocomposites were probed for organoclay dispersion, mechanical, thermal and water absorption measurements. Formation of delaminated and intercalated nanostructures was confirmed by X-ray diffraction and TEM studies. Improvement in tensile strength and modulus was observed for nanocomposites with optimum organoclay content (8-wt.%). Thermogravimetric analysis indicated an increase in thermal stability of nanocomposites as compared to pristine polyamide. Differential scanning calorimetric results revealed increase in glass transition temperatures (T g ) with augmenting organoclay in the nanocomposites. Water uptake of the nanocomposites reduced than the neat polyamide rendering decreased permeability. [Copyright &y& Elsevier]

Fe-based bulk metallic glasses (BMGs) with broad application prospects often exhibit good comprehensive properties. However, they are facing the bottleneck problem of structural instability during the long-term service process due to their own metastable state. In this work, a new ternary system of Fe–W–B BMGs with ultrahigh thermal stabilities, where the glass transition temperature of Fe 59 W 23 B 18 BMG reached to 923 K and the onset crystallization temperature above 970 K, were successfully developed. In addition, the Fe–W–B BMGs exhibit very high micro-hardness of 1280–1380 HV and high density about 9.6 g/cm3. The ultrahigh thermal stability and hardness are closely related to the prominent covalent bonds in the Fe–W–B BMGs. The ternary Fe–W–B BMGs with outstanding thermal properties and simple chemical components are promising materials for use in extreme service environment and model materials to understand the glass formation mechanism of Fe-based BMGs. [ABSTRACT FROM AUTHOR]

Abstract: Mechanical and thermal properties were characterized for two AlN:BN:SiC composite ceramics produced from BN with different particle sizes. The ceramics were hot pressed at temperatures from 1950 to 2100°C to ∼97% relative density. For both materials, the matrix (90:10vol% SiC:AlN) had a grain size of ∼0.4μm, and the BN grains (10vol%) were crystallographically aligned. Microhardness values were between 20 and 22GPa, while fracture toughness values were between 2.5 and 3.1MPam1/2. Other properties were found to be dependent on testing direction. Elastic moduli were between 260 and 300GPa and strengths were ∼630MPa for small particle BN additions. Thermal conductivity was calculated to be between 25 and 37W/mK at room temperature and 17 and 25W/mK at 900°C. The low values compared to traditional SiC ceramics were attributed to AlN–SiC solid solution formation and sub-micron matrix grain sizes. [Copyright &y& Elsevier]

In the trend of integration of structure and function, novel thermal management materials are urgent to be developed owning good mechanical properties as well as excellent thermal properties. In this work, a complete and dense copper (Cu) coating with a thickness of 400 nm was deposited on the surfaces of graphite films (GFs) by ultrasonic-assisted electroless plating, which can improve the surface roughness of GFs and interfacial bonding between GFs and Cu foils. Cu-coated and uncoated GFs reinforced copper matrix laminated composites (noted as GFs(Cu)/Cu and GFs/Cu) were fabricated by optimized vacuum hot-pressing sintering. Based on the scratch test and microstructures of GFs(Cu) and GFs(Cu)/Cu composites, addition of Cu coating can improve the interfacial adhesion and element diffusion behavior, and intuitively explains the mechanical interlocking effect at the C–Cu interface. On basis of the nanoindentation mechanical properties across GFs(Cu)/Cu and GFs/Cu interfaces, the interfacial transition region with Cu coating of ~3 μm is three times of that without Cu coating. Flexural strength of 27.6 vol% GFs(Cu)/Cu laminated composite is 45.9 MPa, which is 56% higher than that of the corresponding GFs/Cu laminated composite. In-plane thermal conductivity (TC) and out-of-plane coefficient of thermal expansion (CTE) of 69.4 vol % GFs(Cu)/Cu laminated composite are 1177.8 W/m·K and −2.5 ppm/K respectively, which could be explained on the theoretical calculations and interfacial structures. In conclusion, the Cu coating on surfaces of GFs can generally improve the interfacial bonding, mechanical properties and thermal properties of GFs(Cu)/Cu laminated composites. It provides an effective way to develop novel structural and functional materials for thermal management. [ABSTRACT FROM AUTHOR]

Abstract: The functionalized multi-walled carbon nanotubes (MWNTs) with amino groups were prepared after such steps as oxidation, the addition of carboxyalkyl radicals, acylation and amidation. Besides oxidated-MWNTs/epoxy nanocomposites, amino-functionalized MWNTs/epoxy nanocomposites, in which MWNTs with amino groups acted as a curing agent and covalently attached into the epoxy matrix, were fabricated. Subsequently, the effects of MWNT content on the mechanical and thermal properties for the two systems were investigated. It is found that both the tensile strength and impact strength enhance with the increase of MWNT addition, and the most significant improvement of the tensile strength (+51%) and especially impact strength (+93%) is obtained with amine-treated MWNTs at an 1.5wt.% content. Moreover, the thermal stability of the nanocomposites also distinctly improves. The improvement of the properties of the amine-treated MWNTs system is more remarkable than those of o-MWNTs system. The reasons for these changes were discussed. [Copyright &y& Elsevier]

Abstract: Three series of SiO2/S composite coatings were prepared on HP40 alloy substrates by atmospheric pressure chemical vapor deposition (APCVD). The morphologies, components and chemical structures were analyzed by means of scanning electronic microscope (SEM), energy dispersive spectroscopy (EDS) and Raman spectroscopy, respectively. Thermal shock properties, thermal stability properties, microhardnesses and tensile strengths of three samples were performed. The results show that the particles of SiO2/S composite coating reduce with the increase of sulfur content. However, thermal shock cycles by water quenching from 900°C increase with the increase of sulfur content. The microhardness and thermal stability property reduce with the decrease of sulfur content, and the microhardness of SiO2/S composite coating can reach HV0.1890. There are a small amount of sulfur losses for three samples after thermal stability tests. The tensile strength of SiO2/S composite coating can reach 39.5MPa. SiO2/S composite coating prepared on HP40 alloy substrate can meet the needs of ethylene cracking production. [Copyright &y& Elsevier]

Abstract: Microstructures and mechanical properties of Ti40 alloy thermal exposures at 550°C for different times were studied. The results show that there are only a few precipitates during thermal exposure, most of which distribute on grain boundaries and weakens its mechanical properties. By systematic analysis on its microstructures and mechanical properties, the thermal exposure at 550°C can be divided into three stages and the formation and growth of the precipitates were different at each stage. During the third stage, the main reason of un-matched properties between strength and hardness is due to the formation of continuous precipitated zones along grain boundaries. [Copyright &y& Elsevier]

Abstract: The effects of crystallization on the thermal and mechanical properties of Zr41.2Ti13.8Cu12.5Ni10Be22.5 (number indicate at.%) bulk metallic glass (BMG) have been systematically studied by varying annealing times at 400°C. An icosahedral quasicrystalline phase was identified in the specimen annealed for 30min at 400°C by using differential scanning calorimetry, X-ray diffraction, and (high-resolution) transmission electron microscopy. Embrittlement behavior due to nanocrystallization has also been examined by carrying out hardness and compression tests for specimens annealed for various times. The fracture strength at room temperature was found to decrease as the annealing time increased. The hardness was, on the other hand, observed to increase due to the increase in nanocrystalline volume fraction with the progress of annealing treatment. [Copyright &y& Elsevier]

Abstract: In this study, the effects of the content and the average diameter of potassium titanate whiskers (PTW) on the mechanical strength, thermal properties, tribological performance and chemical stability of PTW/PTFE (polytetrafluoroethylene) composites were investigated. For the small size PTW at 5wt%, the tensile strength, elongation at break, notched impact strength, thermal deformation temperature and wear resistance were simultaneously increased by 35.6, 46, 3, 11.1 and 1000% over pure PTFE, respectively. When filler size was increased, the tensile strength, elongation and hardness were decreased, while the wear resistance and thermal deformation temperature were improved. The range of PTW in PTFE for optimal integrative properties is 5–10wt%, which is similar to the behavior of nanoparticles. SEM analysis shows that, comparing to glass fiber/PTFE composites, the internal structure of PTW/PTFE composites is more uniform and dense. [Copyright &y& Elsevier]

Abstract: The effects of starting powder morphology on the thermal and mechanical properties of stand-alone plasma-sprayed 7wt.% Y2O3–ZrO2 (YSZ) coatings were studied. Two powder morphologies were investigated: an agglomerated and sintered powder (referred to presently as “AS”) and a powder manufactured using plasma spheroidization to create hollow spheres (referred to presently as “HS”). Coatings made from AS powders contained 0.21wt.% SiO2 impurity, twice as much as observed in coatings made from HS powders. Properties of coatings made from each powder type were compared in the as-sprayed state and after 50h heat treatments at temperatures ranging from 1000 to 1400°C. SEM microstructural investigations revealed significant differences in the porosity and distribution of pores in the coatings. In coatings made with AS powders the majority of the high aspect ratio pores were located between lamella (interlamellar porosity). In addition to interlamellar pores, coatings made with HS powders demonstrated 1.5 times more spherical-shaped globular pores by number located within lamella. Globular pores were shown to still exist in coatings made with HS powders after 50h heat treatments at 1400°C. Archimedes porosity measurements showed that coatings made with AS powders typically contained 4–5% less total porosity than coatings made with HS powders. Thermal conductivity experiments using laser flash showed that there was no difference in the thermal conductivity of coatings made from either powder type in the as-sprayed state despite higher porosity in the coatings made from HS powders. After a 50h heat treatment at 1000 and 1200°C, coatings made from both powder types still demonstrated statistically similar thermal conductivities. However, after a 50h heat treatment at 1400°C the thermal conductivity of coatings made from AS powders was found to be 0.3W/m/K higher than coatings made from HS powders. Microstructural differences in the coatings made from the two powder types that affected sintering rates, including the increased level of SiO2 impurities and fewer globular pores, were used to explain variations in properties. In uniaxial compression tests on stand-alone samples at 1000, 1100, and 1200°C, coatings made from AS powders typically relaxed more stress than coatings made from HS powders. Differences in coating relaxation became more apparent as the test temperature increased through 1200°C. The higher percentage of impurity SiO2 in the AS coatings is believed to contribute to increased relaxation via formation of a glassy phase at the grain boundaries which assists grain boundary sliding during elevated temperature deformation. [Copyright &y& Elsevier]

A new class of high entropy carbide (NbTaMoW)C was fabricated by reaction synthesis at temperatures as low as 1800 °C using metal powders and graphite as raw materials. Phase formation, compositional uniformity, and microstructure of the (NbTaMoW)C were investigated. The experimental results showed that partial solid solution phase was formed when sample sintered at 1600 °C, according to XRD peak fitting and deconvolution. The as-prepared (NbTaMoW)C with relative density of 97.3% possessed a single-phase rock-salt crystal structure, in which the four metal elements are randomly distributed on the cation sublattice while C occupies the anion sublattice. It was further revealed that (NbTaMoW)C had a high compositional uniformity and the average grain size is 9 ± 0.5 μm. By taking the advantage of these characteristics, the microhardness of (NbTaMoW)C was significantly improved as compared with the base monocarbides. The increase in hardness was attributed to the solid solution strength mechanism. Meanwhile, (NbTaMoW)C exhibited high flexural strength and a relatively low thermal conductivity of 3.19 ± 0.04 mm2/s at room temperature. With temperature increasing, the thermal conductivity of (NbTaMoW)C increases over the entire temperature range from 25 to 1000 °C. [ABSTRACT FROM AUTHOR]

Using transmission electron microscopy, tension and indentation tests we studied commercially pure aluminum processed by severe plastic deformation through accumulative roll bonding (ARB Al) and equal-channel angular pressing (ECAP Al) up to 8.0 von Mises equivalent strain to find the structural features providing improved mechanical properties and their enhanced thermal stability in the former case. It is revealed that the average size of the elements of the grain-subgrain structure is 23% lower and the strength properties are 19 – 27% higher in ARB Al with respect to ECAP Al. The physical reason for more refinement of the grain-subgrain structure and enhanced mechanical properties is the presence of dispersed alumina nanoparticles introduced into the bulk of ARB aluminum from the surface of the bonded stripes during ARB. The thermal stability of microhardness of ARB Al exceeds the respective value of ECAP Al in the temperature interval of 473 – 513 К, where the recrystallization starts to occur. The improved thermal stability of ARB Al is related to the higher resistance to recrystallization due to the presence of alumina nanoparticles on grain boundaries formed during ARB and precipitation of Si from the solid solution on these nanoparticles. [ABSTRACT FROM AUTHOR]

The influence of the substitution of metalloid element P for Fe in Fe-P-C-B amorphous system on phase constituent, thermal properties, tensile mechanical properties and bending ductility were evaluated. The transition behavior from brittleness to ductility for the amorphous ribbons can be controlled through the alloy design. Moreover, the atomic and electronic structures of the typical Fe-P-C-B metallic glasses were simulated by the ab–initio calculations. Combining with experimental and theoretical results, it provides a possible understanding of the brittle-ductile transition caused by the chemical element tailoring in Fe-P-C-B metallic glasses. [ABSTRACT FROM AUTHOR]