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Combining DSC/TG–QMS analysis and dilatometry experiments at constant heating rates, the sintering behaviors of the Ti(C,N)‐based cermets with carbon additives were studied. It is found that the additives of diamond or graphite could promote the interactions among raw powders during solid‐state sintering. The outgassing behavior and endothermic effect were enhanced, thereby resulting in the increasing densification activation energy. The negative activation energy during the liquid phase sintering indicates that the dissolution–precipitation process occurs easily and provides a rapid densification path. The dissolution–precipitation process for cermets with.6‐wt% graphite or.6‐wt% diamond additive became more efficient than for cermets without additional carbon additive. The white‐core/gray‐rim grains were clustered together in the cermets with.6‐wt% graphite additive, whereas they were distributed evenly in the cermets with.6‐wt% diamond additive. Moreover, the average sizes of ceramic grains in the cermets without additional carbon additive, and with.6‐wt% graphite or.6‐wt% diamond additives, were.453, and.517, or.525 μm, respectively. [ABSTRACT FROM AUTHOR]

Fe2W-type ferrite BaFe2+2Fe3+16-xO27± (x =−0.8, −0.4, 0.0, 0.4, 0.8, 1.2) fine powders and magnets were synthesized by a facile ceramic route. The lattice and microstructure of the fine powders were studied by x-ray diffraction (XRD). The results show that a single magnetoplumbite structure is obtained under the condition of Fe change (x =−0.8, −0.4, 0.0, 0.4, 0.8, 1.2). The morphology of the sintered magnet was studied by scanning electron microscopy (SEM). The influence of iron content on the magnetic characteristics of BaFe2+2Fe3+16-xO27± was systematically studied by controlling the pre-sintering temperature of 1300°C. The change in the remanence (Br) of BaFe22+Fe16-x3+O27± magnets with different iron content first increased and then decreased, which confirmed that the change trend of the Br was consistent with the variation in the saturation magnetization (Ms). Meanwhile, the coercivity (Hcj) and (Hcb) of the magnets was consistent with the change characteristics of the coercive force (Hc) of magnetic powder. At iron change (x) = −0.4, Ms, Br, Hc, Hcj, Hcb, and maximum energy product ((BH)max) reach maximum. [ABSTRACT FROM AUTHOR]

Herein, powder metallurgy gas-solid nitriding was used to prepare a high-nitrogen Ni-free austenitic stainless steel with more than 1.0 wt.% N. Study of the microstructures and corrosion resistances of the as-prepared samples revealed that the corrosion weight loss, size, number of corrosion pits, and corrosion depth decreased as the N content increased from 1.19 to 1.37 wt.%. The self-corrosion current densities of the alloys were determined from their potentiodynamic polarization curves. The changes in the capacitive arc radius as demonstrated by the Nyquist curves were consistent with the conclusions of the immersion corrosion analysis; that is, a high N content leads to a high corrosion resistance. [ABSTRACT FROM AUTHOR]

Ti6Al4V alloy has been considered as a key component used in ultrasonic scalpels. In this series of papers, the fabrication, structure, and mechanical and ultrasonic properties of medical Ti6Al4V alloys suitable for ultrasonic scalpel are studied systemically. These alloys with low elastic modulus and present a typical bimodal microstructure with relatively high β phase content (~40%) and lamellar α thickness of ≤ 0.9 µm. In the first paper, the relationship between the microstructure and mechanical properties of hot-rolled Ti6Al4V alloys treated by heating treatment is discussed. In the second paper, the dependence of the ultrasonic properties on the microstructure of the heat-treated Ti6Al4V alloys is reported. With increasing solid solution temperature, the content and size of the primary α phase decrease. In contrast, the content and size of the lamellar α phase increase. Additionally, the β phase content first increases and then decreases. The microstructure of Ti6Al4V alloys could be slightly changed by aging treatment. When the solid solution treatment temperature increases to 980 °C from 960 °C, the average size of the lamellar α phase in the alloys increases by 1.1 µm. This results in a decrease in the average yield strength (93 MPa). The elastic modulus of alloys is mainly controlled by the β phase content. The microstructure of alloys by solution-treatment at 960 °C shows the highest β phase content and lowest average elastic modulus of 99.69 GPa, resulting in the minimum resonant frequency (55.06 kHz) and the highest average amplitude (21.48 µm) of the alloys at the length of 41.25 mm. [ABSTRACT FROM AUTHOR]

In this study, the ultrasonic resonance parameters of Ti6Al4V alloys under different heat treatments are measured by an impedance analyzer. The amplitude of the specimens is measured experimentally by means of optical microscope and image analysis software. These results show that the ultrasonic properties of Ti6Al4V alloys are closely related to β phase content and elastic modulus of the alloys. The highest volume fraction of the β phase appears in the specimen treated by solid solution treatment at 960 °C is 40.2%. These alloys present the lowest average elastic modulus (~99.69 GPa) and the minimum resonant frequency (55.06 kHz) and the highest average amplitude (21.48 µm) when the testing sample length is 41.25 mm. These findings can be used to guide the design of medical Ti6Al4V alloys for ultrasonic scalpels. [ABSTRACT FROM AUTHOR]

The microstructure and mechanical properties of the vacuum sintered (80- x)TiB 2 - x WC −10Co-10 Ni (x = 0, 2.5, 5, 7.5, 10, 12.5) cermets were studied by XRD, SEM, EPMA and TEM analysis. The results show that the TiB 2 -7.5 WC based cermets exhibited excellent comprehensive properties with relative density, Rockwell hardness, transversal rupture strength and fracture toughness of 99.44 ± 0.18 %, 17.50 ± 0.71 GPa, 2108 ± 29 MPa, and 12.21 ± 0.29 MPa m1/2, respectively. The XRD diffraction peaks of TiB 2 , W 2 CoB 2 , WB and CoNi binder were detected in cermets with WC addition. The HCP TiB 2 core-FCC (Ti, W, Co, Ni) (B, C) rim structure was formed in TiB 2 -WC based cermets with FCC CoNi binder. The coherent interface formed between the TiB 2 core and (Ti, W, Co, Ni) (B, C) rim phase, as well as the amorphous CoNi thin layer formed at the interface between (Ti, W, Co, Ni) (B, C) rim and CoNi binder phase, both of them were suggested to improve the interfacial bonding strength of TiB 2 -WC based cermets. [ABSTRACT FROM AUTHOR]

In this study, the effects of the addition of carbonyl nickel powder on the density, microstructure, and mechanical properties of sintered yttria-stabilized zirconia (3YSZ) were investigated. Sintering at 1300 °C resulted in the optimum comprehensive mechanical properties. The addition of 5 vol% carbonyl Ni increased the fracture toughness and flexural strength from 9.51 MPa m1/2 to 14.5 MPa m1/2 and from 747 MPa to 873 MPa, respectively. The addition of carbonyl nickel showed greater improvement than did the addition of spherical Ni powder. The dendritic morphology improved the interface bonding between the ceramic and the metal, enabling a bridging mechanism of the ductile phase. However, further Ni addition decreased the mechanical properties. X-ray diffraction results showed that the amounts of the monoclinic phase (M) and cubic phase (C) of 3YSZ increased, whereas the amount of the tetragonal phase (T) decreased. The Y segregation near the Ni particles, which was confirmed by an energy dispersive spectrometer (EDS), caused the phase changes. The segregation of Y occurred during the cooling stage, rather than the holding stage, of sintering. During the cooling stage, the heat mismatch between Ni and ZrO 2 resulted in strong elastic strain energy, which promoted Y segregation. [ABSTRACT FROM AUTHOR]

Porous NiTi-based shape-memory alloys (SMAs) were aged at different temperatures and holding times to study the effects of high O contents on the composition, microstructure, phase-transformation behaviour, and shape-recovery properties of SMAs. NiTi 2 and Ni 2 Ti 4 O x phases were precipitated during the aging process; the concentration was not significant until an aging temperature of 500 °C was applied for 2 h (O content = 1.87 wt.%). Aging the SMAs at 600 °C for 2 h produced a coarse NiTi 2 phase and an O content of 4.3 wt.%. Ti atoms were consumed during the oxidation process, which caused the excess Ni atoms to dissolve into the matrix or generate Ni-rich phases, such as Ni 4 Ti 3 or Ni 3 Ti. The presence of excess Ni atoms resulted in different phase-transformation behaviours. A high O content increased the elastic modulus of the porous NiTi-based SMAs, but decreased the shape-recovery rate. The samples aged at 600 °C exhibited inferior mechanical properties, and hence, it was concluded that high-temperature heat treatments should be avoided. [ABSTRACT FROM AUTHOR]

Ni-based alloys were prepared at different sintering temperatures in this study. The effects of sintering temperature on the volume fraction, morphology, and distribution of precipitates in Ni-based alloys, and its impact on mechanical properties were studied. The results show that the microstructure contains γ-Ni, Ni 3 Si, M 7 (B, C) 3 , M 23 (B, C) 6 , and a Si-rich multi element phase. The morphology of M 7 (B, C) 3 particles undergoes an evolution of small particles → mainly strip shape → mainly small block shape and nearly spherical shape, accompanying with the dissolution-reprecipitation process of M 7 (B, C) 3 particles caused by the diffusion of Cr element with the increasing of sintering temperature. Meanwhile, the M 23 (B, C) 6 particle is keeping aggregating and growing. The relative density, microhardness, and bending strength of Ni-based alloys also increase. Especially these properties are found to be increase quickly between 1025 °C and 1050 °C. The increase in microhardness and bending strength is attributed to the reduction in the number of residual sintering pores and the increase in the volume fraction and size of precipitates. In addition, the transition of fracture morphology from intergranular fracture mode to a combination of intergranular and partially transgranular fracture mode also contributes to the rise in bending strength. • γ-Ni, Ni 3 Si, M 7 (B,C) 3 , M 23 (B,C) 6 , and a Si-rich multi element phase. • Morphology of M 7 (B,C) 3 particles relates to dissolution-reprecipitation process. • Mechanical properties with residual sintering pores and boron carbide. [ABSTRACT FROM AUTHOR]

Ni–tungsten carbide (WC) composites were prepared using cast WC as hard particles. In this study, the thermal damage behaviour of cast WC particles and its effects on the microstructure and mechanical properties of Ni–WC composites were investigated. Results show that cast WC particles undergo edge dissolution and particle disintegration at 1600 °C and 1800 °C, respectively. The degree of thermal damage to cast WC particles increases from 30.55% to 48.84% when the melting temperature increases from 1600 °C to 1800 °C. In this process, the Ni-based melt gradually erodes the cast WC particles from the edge towards the centre. This leads to severe dissolution of the W 2 C phase, while the WC phase only dissolves partially. Notably, the degree of thermal damage to cast WC directly correlates with the W content in the melt. An increase in the W content enhances the volume fraction and nano-hardness of the M 23 (B, C) 6 compound, improving the wear resistance of the composites. • Elevated temperature rises thermal damage degree of cast WC particle. • Ni-based melt invades from particle edge towards its center during thermal damage process. • High nano-hardness and volume-fraction of block-like M 23 (B,C) 6 compound • Thermal damage behaviour improves wear resistance of composite. [ABSTRACT FROM AUTHOR]

Improving the piezoelectric activity of lead zirconate titanate (PZT) ceramics is of great importance for practical applications. In this study, the influence of Pr3+ doping on the ferroelectric phase composition, microstructure, and electric properties on the A-site of (Pb 1-1.5x Pr x)(Zr 0.52 Ti 0.48)O 3 is extensively investigated. A dense and fine microstructural sample is obtained with the introduction of Pr3+. The results show that the morphotropic phase boundary (MPB) moves to the rhombohedral phase region. The rhombohedral and tetragonal phases exhibit an ideal coexistence in the 4 mol.% Pr3+ doped (PPZT4) samples. Lead vacancy and the reduction of the potential energy barrier are considered to be the key mechanisms for donor doping, which is upheld by the Pr3+ doping. Combining the I-E hysteresis loops with the P-E hysteresis loops, it becomes apparent that both contribution maximums of the domain switching and residual polarisation are in PPZT4. Moreover, the thermal aging resistance of PZT is improved by doping, and the temperature stability is optimised from 83% in PZT to 96% in PPZT4. Hence, an appropriate amount of Pr3+ doping can effectively improve the piezoelectric activity of PZT ceramics in the MPB area and optimise the performance stability of the material under application temperatures. [ABSTRACT FROM AUTHOR]

The M2 coatings on medium carbon steel were prepared using a laser cladding process, and the microstructure and microhardness of the coatings were studied. The results show that the microhardness of the coating shows an increasing trend from the coating top to the bonding interface. The microhardness is 694 HV 1 at the surface of the coating, which reaches 836 HV 1 in the bottom regions of the coating. The wear rate of the coating is 0.32 mm3/N·m, which shows lower wear rate and better wear resistance. The coating microstructure is also different, and the coating consists of overlapping and non overlapping regions. The microstructure of overlapping region is a dendritic solidified crystalline structure encapsulated on α - Fe phase primary crystals with a dispersed carbide. The microstructure of non overlapping zone is composed of columnar crystal zone, basket crystal zone, and dendritic zone from the bottom of the coating to the surface, respectively, with the carbides distributed along the grain boundaries in the form of a network. Near the coating interface, needle-like high-carbon martensite forms in the coating. The carbides in the coating are relatively coarse. • Differences on hardness and microstructure of M2 coating. • Microhardness increasing from top to interface. • Columnar, basket, dendritic from bottom to surface. [ABSTRACT FROM AUTHOR]

This study explored the effect of diamond content (0, 0.3, 0.6, and 0.9 wt%) onTi(C 0.5 ,N 0.5)-based cermets prepared via vacuum sintering with respect to their final mechanical properties and microstructures, characterized using X-ray diffractionand scanning electron microscopy. After liquid phase sintering, all cermets exhibited a 'black core/grey rim'and partial 'white core/grey rim'structure. The cermet with 0.6 wt% diamond exhibited optimal mechanical properties with a Vickers hardness of 1795 ± 32 H V, transverse rupture strength of 2026 ± 45 MPa, and plane strain fracture toughness of 12.95 ± 0.3 MPa m1/2. This is due to grain refinement and the uniformly distributed 'white core/grey rim'grains. During the incipient liquid formation stage,a higher carbon activity arising due to diamond graphitization may shift the equilibrium towards the product, thereby yielding additional white cores due to the consumption of heavy elements in the binder. Excessive diamond introduction inhibited the dissolution of Ti(C 0.5 ,N 0.5) into the binder, resulting in fewer white cores. [ABSTRACT FROM AUTHOR]

In TiC- and Ti(C,N)-based cermets, the wettability of the ceramic phase with the metallic binder is commonly increased through supplementation with Mo in the form of pure Mo powder or Mo 2 C. Herein, TiC–high Mn steel cermets were fabricated by conventional powder metallurgy techniques using Fe–Mo pre-alloyed powders as binders to guarantee uniform Mo distribution, and the cermet preparation process was optimized and investigated in detail. The microstructures of the thus obtained cermets were observed by scanning electron microscopy and compared to those of a Mo-free cermet and a cermet prepared using pure Mo powder. The grain size of Fe–Mo powder cermets exceeded that of the Mo-free cermet but was much smaller and more homogeneous than that of the Mo powder cermet. For Fe–Mo powder cermets, angular and tetragonal TiC particles were observed at Mo contents of <1.2 wt%, while round shapes became dominant at higher Mo contents. The hardness of Fe–Mo powder cermets increased with increasing Mo content, as did transverse rupture strength, which was maximal (2264 MPa) at a Mo content of 2.4 wt%, while impact toughness was maximal (11.2 J/cm2) at a Mo content of 1.2 wt%. The above values exceeded those reported for similar conventional cermets, and the use of Fe–Mo pre-alloyed powder as a metallic binder was therefore concluded to be an attractive strategy of increasing the strength and toughness of TiC–high Mn steel cermets. [ABSTRACT FROM AUTHOR]

Fe-Co-Cu alloys were prepared by pressureless sintering at 875 °C. The effects of pre-alloyed Cu-15Sn sintering aids on the microstructure and mechanical properties of Fe-Co-Cu alloys were investigated. The results show that the Cu-15Sn aids makes the sintering densification process of Fe-Co-Cu alloy changes from solid phase sintering to instantaneous liquid phase sintering, which improves atomic diffusion rate and relative density of alloys, and also makes the matrix grains grow up. The relative density, hardness and bending strength of Fe-10 wt% Co-15 wt% Cu alloy can be significantly improved by adding 7 wt% Cu-15Sn, which can reach 96.34 %, 85 HRB, and 1857 MPa, respectively. The volume fraction of Cu-rich phase, the relative density of the alloy and the grain size have great influence on the hardness and bending strength of the alloy. When there are too many liquid phases, the relative density of the alloy decreases, making it difficult to continue to improve the strength of the alloy. Intergranular brittle fracture occurs mainly in α-Fe phase grains, but dislocation slip deformation occurs in Cu-rich phase grains. With the increase of volume fraction of Cu-rich phase and relative density, the alloy gradually exhibits macroscopic plasticity. • Cu-15Sn aids improves relative density, hardness and bending strength. • Intergranular brittle fracture change to macroscopic plasticity. • Solid phase sintering changes to liquid phase sintering. [ABSTRACT FROM AUTHOR]

Gas atomized FeCuCo (Cu 28.7 wt% Cu, 12.1 wt% Co) prealloyed powder was used as matrix of diamond tools, and CuSn (15. wt% Sn) prealloyed powder was used as sintering aids. The content of diamond particles was 0.35 wt%. The alloys were prepared through pressureless sintering. Effects of CuSn addition on mechanical properties, microstructure, and holding force of diamond particle were studied. The results show that the FeCuCo alloy is mainly composed of α-Fe phase and Cu-rich phase. Co and Sn are solid solution atoms of α-Fe phase and Cu-rich phase respectively. The fracture morphology of FeCuCo alloy mainly fine dimple and quasi cleavage fracture, as well as sintered pore surface and crack. With the increase of CuSn addition, the density, hardness, bending strength and diamond particle holding force of the alloy increase first and then decrease. The hardness, bending strength, and relative density of FeCuCo alloy with 8 wt% CuSn reach the peak. The bending strength of this alloy added with diamond particles reaches 871 MPa, and the strength loss rate is only 21.7%. There is an obvious gap between the diamond particles and the matrix, indicating that the holding mechanism is mainly mechanical encapsulation. After the addition of CuSn, there are more attachment on the surface of diamond particles, resulting in metallurgical bonding. • Co solid solute in α-Fe phase and Sn solid solute in Cu-rich phase. • Diamond particles holding force increase. • Metallurgical bonding between diamond particles and matrix produce. • Hardness, bending strength, relative density of matrix reach to HRB 105, 1113 MPa, 97.5%, respectively. • Adding 8% CuSn, the bending strength of diamond tool is 871 MPa, the strength loss rate is only 21.7%. [ABSTRACT FROM AUTHOR]

The components as well as the formation and heat treatment processes of the Al–Mg–Si–Cu aluminum alloy have been investigated in detail. However, only a few reports have considered the effects of solid solution treatment on the microstructure and properties of 6013 aluminum alloy during the aging process. In this study, the effects of solid solution temperature on the microstructure and properties of the 6013 aluminum alloy were studied via mechanical property testing, intergranular corrosion testing, electrochemical testing, and scanning and transmission electron microscopy. The results indicated that when the solid solution temperature of the alloy increased from 530 to 570 °C, the residual Mg 2 Si phase gradually decreased and the quantity of residual Al(FeMn)Si phase did not significantly change. As the solid solution temperature increased, the tensile strength, micro-hardness, and corrosion resistance of the alloy after T6 aging gradually increased, and the elongation and electrical conductivity, in turn, gradually decreased. Transmission electron microscopy depicted that the GP Zones and L phases of the alloy in the T6 state were observed. As the solid solution temperature increased, the quantity of the GP Zones and L phases increased, thereby increasing the material strength. The number of precipitates in the grain boundary gradually decreased, and the distribution distance gradually increased, which attenuated intergranular corrosion. • Effects of solid solution temperature on 6013 aluminum alloy properties investigated. • Mechanical, electrical, and physical properties gradually improved after T6 aging. • Improved properties of the alloy can contribute to aerospace applications. [ABSTRACT FROM AUTHOR]

Abstract: This work investigated the effects of reaction temperature on Eu(III) interaction mechanism and microstructure at the titanate nanotubes (TNTs)/water interface by batch and spectroscopic (FTIR, XPS, XAFS) technique. Batch adsorption results showed that the adsorption of Eu(III) onto TNTs is promoted at higher temperature, and is an endothermic and spontaneous interfacial process. The adsorption isotherms at three different temperatures can be described by the Freundlich model better than the Langmuir model did. The spectroscopic analysis results suggested that Eu(III) interaction with TNTs is mainly controlled by outer-sphere surface complexation at T =293K, which is a reversible adsorption process, whereas Eu(III) interaction is mainly controlled by inner-sphere surface complexation at T =313K and T =343K, which is an irreversible adsorption process. The findings in this work can help us to better understand the physicochemical behavior of Eu(III) and related radionuclides in natural environment. The results of this work also show the great potential importance of TNTs as novel nanomaterials in the near future of nuclear waste management. [Copyright &y& Elsevier]