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In this study,in situ50 vol.-% TiCx/2014Al composites with different C/Ti molar ratios (0.6, 0.7, 0.8, 0.9 and 1) were successfully produced by the method of combustion synthesis and hot press consolidation. The microstructure and the mechanical properties of the composites were investigated. Microstructure characterisation of the TiCx/2014Al composites showed relatively uniform distribution of the TiCxparticles with the particle size in the range of 200–900 nm. With the increase of the C/Ti molar ratio, the yield strength (σ0.2) and the ultimate compression strength (σUCS) increased first then decreased, and the fracture strain (εf) increased. Theσ0.2,σUCSand the abrasive wear resistance of the 50 vol.-% TiCx/2014Al composites reached the highest value when the value of the C/Ti molar ratio comes to 0.8. Theσ0.2,σUCSandεfof the 50 vol.-% TiCx/2014Al composites with the C/Ti molar ratio of 0.8 are 1094 MPa, 1454 and 6.13%, respectively. [ABSTRACT FROM PUBLISHER]

The dual phase nanosized (TiB2-Ti5Si3)/TiAl composites were successfully fabricated using in situ method of combustion synthesis and hot press consolidation. The effects of proportions of the in situ dual phase nanoparticles (TiB2 and Ti5Si3) on microstructures and compression properties of the composites were investigated. Compared with the monophase TiB2 and Ti5Si3 particles, dual phase TiB2-Ti5Si3 particles exhibit more obvious grain refinement effect. The grain size of TiAl alloy was refined from ∼66 to ∼12 μm with the the generation of dual phase TiB2-Ti5Si3 particles. Moreover, the TiAl matrix composites reinforced with dual phase nanosized TiB2-Ti5Si3 particles exhibit better comprehensive compression properties. When TiB2:Ti5Si3 = 2:1[Σ(TiB2 + Ti5Si3) = 4 vol.-%], the TiAl matrix composite has a high true fraction strain of 26.1%, a true yield strength of 761 MPa and an ultimate compression strength of 1647 MPa. [ABSTRACT FROM AUTHOR]

Among refractory metals, tantalum has long been the primary material of use in high strain rate applications. Hot pressing (HP) is a technique to produce specimens with high density and homogeneous microstructure. The individual effect of the HP or annealing heat treatment on high strain rate properties of tantalum powder compacts has been investigated, but little attention has been paid to the combined effect of subsequent annealing. In this study, the effect of annealing on the microstructure and mechanical properties of tantalum subjected to hardness and Split Pressure Hopkinson Bar (SHPB) test was investigated. After annealing at 1100°C, the grains are coarsened, thereby hardness and upper yield strength decreased to value 199 VHN and 1833 MPa, respectively. Moreover, an obvious increase in plasticity and toughness is detected at this temperature, indicating subsequent annealing is beneficial to improve the deformation properties of HPed powder compacts; the maximum plasticity of tantalum was 31.74% after annealing. [ABSTRACT FROM AUTHOR]

The objective of the present work was to determine the suitability of a new iron-based Mn–Cu–Sn matrix alloy for the manufacture of diamond-impregnated tool components. A number of specimens were consolidated by the hot press route from ball-milled powders. Density, microstructural features, phase composition, bending properties and hardness were evaluated. The results revealed excellent mechanical properties, includingσ0.2 > 850 MPa in 3-point bending and HK0.5 > 300. A commercial Co-WC reference matrix alloy was also produced for comparison purposes. Diamond-impregnated specimens with different matrices were tested for wear rate on abrasive sandstone using a test rig specially designed to simulate tool application conditions. The tests that involved 3- and 2-body abrasion ranked the alloys in different orders. Statistical analysis showed that the wear rate of diamond-impregnated composites was mainly affected by diamond concentration, but statistically significant contribution of the matrix resistance to 3-body abrasion was also found. [ABSTRACT FROM PUBLISHER]

Effects of TiB2/TiCx ratios on compression properties and abrasive wear resistance of 50 vol.-% (TiB2–TiCx)/Al–Cu composites fabricated via the combustion synthesis (CS) method assisted with hot press from the Al–Ti–B4C system were studied. With decrease in the TiB2/TiCx ratio from 3:1 to 1:3, the shape of TiB2 changed from platelike to clubbed while the size of TiCx particles increased, which directly led to different mechanical properties. The 50 vol.-% (TiB2–TiCx)/Al–Cu composite with the TiB2/TiCx ratio of 2:1 exhibited good compression strength without sacrificing the fracture strain, while the composite possessed the highest abrasive wear resistance when the TiB2/TiCx ratio was 3:1. The appropriate TiB2/TiCx ratio was recommended to be 2:1 in this research. [ABSTRACT FROM AUTHOR]

This work fabricated CoMoNiTa3 medium-entropy alloys using the vacuum hot pressing process of powder metallurgy technology. Micron-grade cobalt (6.3 μm), molybdenum (13.2 μm), nickel (2.4 μm) and tantalum powders (25.0 μm) were combined using ball milling. The experiments utilised various hot pressing temperatures (1000, 1050, 1100, and 1150 °C) and hot pressing pressures (20, 35, and 50 MPa) to identify the optimal parameters for CoMoNiTa3 alloys, while simultaneously investigating the differences in microstructures. The experimental results reveal that the optimal hot pressing parameters of this alloy were 1100 °C at 50 MPa for 1 h. The sintering density was enhanced to 9.65 ± 0.01 g cm−3, while the hardness, transverse rupture strength, and flexural modulus reached 85.5 ± 0.1 HRA, 1370.3 ± 90.1 MPa and 168.6 ± 12.7 GPa, respectively. Moreover, the electrical conductivity was 6.53 ± 0.13 × 104 S cm−1. Furthermore, the electron probe microanalyser, electron backscatter diffraction, and transmission electron microscopy results confirmed the face-centred cubic solid solution, Ni3Ta, and μ phases of the CoMoNiTa3 structure, and no preferred grain orientation was found. [ABSTRACT FROM AUTHOR]

An analytical densification model describing the final stages of hot pressing and sintering has been developed and found to be consistent with empirical findings. The behaviour of composite powders for the matrices of diamond tools has been studied under hot pressing conditions. Differential scanning calorimetry was used to determine the heat capacity at constant pressure Cp of pure Co, 663Cu, and composite iron- and cobalt based powders (also containing WC, Ni and 663Cu). The relationship between Cp and composite densification has been analysed, and it has been found that optimised rare earth additions to the iron based composite powders can produce Cp characteristics close or equivalent to that of pure Co powders. This modified composite powder has been used to hot press diamond drill and saw bits that show good properties. Employing a densification regime guided by the dynamic model has been found radically to improve stability in service (bend strength, hardness, impact, ductility and porosity). [ABSTRACT FROM AUTHOR]

In this study, copper powders with dendritic morphology were produced by the electrolysis method, and then silver coating was applied to these powders by an electroless coating method. The bulk samples were fabricated by hot pressing method using different ratios of copper and silver-plated copper powders. The results showed that the electroless silver coating layer provided a strong bond at the particle boundaries of the samples, significantly improving the physical and mechanical properties of the materials. Accordingly, the hardness, tensile strength, electrical and thermal conductivity values of the samples produced from silver-plated dendritic copper particles were determined to be approximately 98 HB, 185 MPa, 102 IACS% and 402 W mK−1, respectively. In addition, the oxidation resistance of the sample produced from completely silver-coated copper powders is 4 times higher than that of pure copper. [ABSTRACT FROM AUTHOR]

This study fabricated Ni–35Mo–15Cr alloys by the vacuum hot pressing technique. The experiments utilised various hot pressing temperatures (1050°C, 1100°C, 1150°C, and 1200°C) and pressures (20, 35, and 50 MPa) to determine the optimal parameters for Ni–35Mo–15Cr alloys. The experimental result showed that the optimal hot pressing parameters of this alloy were 1150°C at 35 MPa for 1 h. Among them, the sintering density reached 8.92 g·cm−3, and the hardness and TRS increased to 77.1 HRA and 1218.2 MPa, respectively; while, the electrical conductivity was 7.08 × 103 S cm−1 and the polarisation resistance was 294.65 Ω·cm2. Furthermore, the TEM observation identified the HCP structures of the Mo2C that precipitated in the Ni–35Mo–15Cr alloys, and the [02 2 ¯ 1] and [01 1 ¯ 2] crystal axis of Mo2C can be found. Overall, the properties of Ni–35Mo–15Cr alloys were effectively improved through the hot pressing process. [ABSTRACT FROM AUTHOR]

Different approaches to take advantage of powder metallurgy in the manufacturing of diamond-impregnated components were studied. Three different powders were used as starting materials; two pre-alloyed powders, based on Fe–Cu and Fe–Cu–Sn systems, and one pre-mixed Fe-based powder. Different manufacturing routes as a strategy to obtain tailored mechanical properties were studied, with the influence of alloying elements such as graphite, iron phosphide and Mn–Ni–B master alloy to reinforce the iron-based powders. Both uncoated and coated commercial synthetic diamonds were introduced in the systems to analyse the surface reactions that depend on both metallic matrix and processing parameters. Hardness values from 88 to 105 HRB were obtained with a wide range of transverse rupture strength values from 1250 to 1640 MPa. An appropriate combination of metallic matrix, alloying elements and processing parameters makes the materials analysed here suitable powders for the manufacturing of diamond-impregnated tools. [ABSTRACT FROM AUTHOR]

In situ TiB2 and TiC reinforced copper matrix composites with tailored heterogeneous structure were fabricated via high-energy ball milling of Cu, TiH2 and B4C powders followed by hot pressing. The microstructures of both ball-milled powders and hot-pressed composites were compared. Although the dislocation density of Cu matrix was changed after hot pressing, the mode of distribution of ceramic phases in the Cu matrix was noted to transmit from the ball-milled powders to hot-pressed composites in case of the TiH2 particles synthesised by the in situ reactions. The structural inheritance between the ball-milled powders and hot-pressed composites could be used to control microstructural features and thus to tune properties. The hot-pressed TiB2–TiC/Cu composites with tailored heterogeneous structure exhibited better performance than those of homogeneous counterparts. [ABSTRACT FROM AUTHOR]

In this study, two different compositions of submicrometre copper and chromium powders were mixed and the Cr50Cu50 alloys were fabricated via the powder metallurgy technique. The research imposed various hot pressing pressures, while the temperature was maintained at 1050°C for 1 h, respectively. The experimental results showed that the Saint Venant's effect obviously appeared in 1050°C, 48 MPa, 1 h hot pressing Cr50Cu50 alloys, which led to differences in the surface and internal hardness of the specimens. As a result, the optimal parameters of hot pressing of Cr50Cu50 alloys were 1050°C, 36 MPa for 1 h possessing the highest transverse rupture strength value (921.69 MPa). Moreover, the surface hardness increased to HV0.2221.78 (HRB 95.4), the relative density reached 97.15% and apparent porosity decreased to 0.10%, respectively. Furthermore, the resistivity decreased to 5.28 × 10−6 Ω cm, and ICAS was enhanced to 32.65% after the optimal procedure. [ABSTRACT FROM PUBLISHER]