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Evolution for the dynamic recrystallization (DRX) volume fraction of Ti-5Al-5Mo-5V-3Cr-1Zr near β titanium alloy during hot deformation was characterized by using the Johnson–Mehl–Avrami–Kolmogorov (JMAK) equation. To determine the equation parameters, a series of thermal simulation experiments at the temperature of 1023–1098 K and strain rate of 0.001–1 s‒1 to the true strain of 0.7 were conducted to obtain the essential data about stress σ and strain ε. By further transforming the relationship of σ versus ε into the relationship of strain hardening rate dσ/dε versus σ, two characteristic strains at the beginning of DRX (critical strain εc) and at the peak stress (peak strain εp) were identified from the dσ/dε-σ curves. Sequentially, the parameters in the JMAK equation were determined from the linear fitting of the different relationships among critical strain εc, peak strain εp and deformation conditions (including temperature T, strain rate ε ˙ $\dot \varepsilon $ and strain ε). The as-obtained JMAK equation was expressed as XDRX=1-exp[-0.0053((ε-εc)/εc)2.1], where εc=0.6053εp and εp=0.0031 ε ˙ $\dot \varepsilon $ 0.0081exp(28,781/RT). Finally, the JMAK equation was implanted into finite element program to simulate the hot compression of thermal simulation experiments. The simulation predictions and experimental results about the DRX volume fraction distribution showed a good consistency. [ABSTRACT FROM AUTHOR]

AZ80 hollow profile was produced by porthole-die extrusion. The mechanical behavior and microstructure characteristic of extrusion welds in AZ80 hollow profile during different T5 heat treatments were investigated. Five kinds of morphologies of β-Mg17Al12were observed in turn in weld regions under various temperatures. Extrusion weld is not weakest region in AZ80 hollow profile in terms of hardness, the peak hardness of weld regions is roughly equal to the weld-free regions at different aging temperatures, which is attributed to similar volume fraction, morphology, and size of β-Mg17Al12precipitate in weld regions and weld-free regions. The precipitate-free zones (PFZs) usually form near the welds interface in aging process, and the hardness of PFZs is usually lower than those of weld regions and weld-free regions. Aging at 200°C for 24 h is suitable heat treatment system for AZ80 hollow profile, which can achieve excellent mechanical property and simultaneously reduce the width of PFZs. [ABSTRACT FROM PUBLISHER]

A kind of nickel–aluminum bronze (Cu–10Al–4Fe–4Ni) prepared by centrifugal casting (CC) and gravity casting (GC), respectively, were investigated. The results indicate that CC alloy, which is totally different from GC alloy, consists of α, κI, κII, κIII, κIV, and β′ phases and the microstructures of CC alloy shows nonuniformities from external to internal layer mainly because the distribution of iron and nickel are influenced by centrifugal force. Besides, it is noted that comprehensive mechanical properties of CC alloy are superior to those of GC alloy. Additionally, heat treatments were performed on CC alloy. The results demonstrate the optimal heat treatment is aging at 450 °C/1 h by air cooling after solution treated at 890 °C/1 h by water quench. The ultimate tensile strength and hardness are increased by about 10% and 56%, respectively, and wear resistance is also greatly improved. However, the elongation is decreased by 53%. [ABSTRACT FROM AUTHOR]

Abstract: The WC–9Ni–2Cr cemented carbides were prepared by ball milling method and low pressure sintering. The microstructure and properties of the cemented carbides were then investigated using scanning electron microscopy, mechanical property tester and immersion corrosion tests. The results showed that the adding method of Cr significantly influenced the microstructure and properties of the WC–9Ni–2Cr cemented carbides. Cemented carbides with Cr added in the form of chromium carbide (Cr3C2) were characterized by carburizing and showed a relative lower density, while the addition of metallic chromium and nichrome (Ni–18Cr) resulted in the formation of (W,Cr)C phase and a decrease in the bending strength. However, no defects were found in the microstructure of the cemented carbides in which Cr was added via Cr–Cr3C2 composite powder. Furthermore, cemented carbides prepared with nichrome powder and metallic Cr powder exhibited a higher immersion corrosion resistance in neutral tap water after soaking six times according to BS:6920:2000. [Copyright &y& Elsevier]

[Display omitted] • Y 3 Fe 5 O 12 -BaFe 12 O 19 nanocomposite film was deposited on Al 2 O 3 substrate. • High exchange spring coupling was observed between the two films. • The nanocomposite film has a high remanence ratio of 0.65. Preparation of a high remanence ratio of M-type barium ferrite film is highly desirable in self-biased microwave devices. In this letter, Y 3 Fe 5 O 12 -BaFe 12 O 19 nanocomposite film with a high remanence ratio was deposited on the Al 2 O 3 substrate. Multiple crystal structure characterizations confirm that the Y 3 Fe 5 O 12 film was grown on the orientation BaFe 12 O 19 film surface with high crystallinity and low roughness. The magnetism measurement displays that the nanocomposite film has a high remanence ratio of 0.65 for its high exchange spring coupling. Consequently, this work gives an approach to preparing ferrite film with a high remanence ratio which is applied in self-biased devices. [ABSTRACT FROM AUTHOR]

In this work, the Metal-rich phase Chromium Aluminum (CrAl)/Ceramic phase Chromium Aluminum Nitride (CrAlN) multi-layer coatings were prepared by Arc Ion Plating (AIP). The micro-structure and phase composition of CrAl/CrAlN multi-layer coatings were characterized, and the microstructure, mechanical properties, residual stress and fracture toughness of the coating were emphatically analyzed. It has been found out that the residual stress of the multi-layer coating was only −0.932 ± 0.065 GPa, which was significantly lower than that of the mono-layer coating for −1.569 ± 0.093 GPa. At the same time, it was also found that the preferred growth orientation of the coating changed from a mono-layer (111) to a multi-layer (200) crystal plane. The hardness of the multi-layer (22.74 ± 0.57 GPa) is slightly lower than that of the mono-layer (24.92 ± 0.5 GPa), and the adhesion strength (46.2 ± 3.8 N) is obviously higher than that of the mono-layer (37.4 ± 2.4 N), and the fracture toughness is also higher (8.7 ± 0.8 MPa m1/2). In addition, the mechanism of crack initiation and propagation in stress-induced coatings was studied in detail on the basis of the structure of micro-nano CrAl/CrAlN multi-layer coatings. [ABSTRACT FROM AUTHOR]

Very low-pressure plasma spray is a promising technique for preparing dense metal/ceramic coatings due to the high-speed plasma jet. However, at the same time, the low-pressure environment weakens the ability of the plasma jet to heat sprayed materials. In order to improve this shortcoming, a novel bi-cathode plasma torch was firstly designed in this study, which could enhance the plasma power from 40 kW to 81 kW and realize the axial powder feeding. By using this torch under 6 mbar, a dense and uniform yttria-stabilized zirconia coating with a porosity of 2.7% was fabricated, which had a hybrid microstructure that deposited with the form of unmelted particles, melted droplets, and vapor clusters. Meanwhile, 40% of the zirconia phase changed from the monoclinic type to the tetragonal type, indicating that the yttria-stabilized zirconia powder was melted well. The microhardness and elastic modulus of the coating was high compared with those prepared with other plasma spraying processes, which was 11.7 ± 0.6 GPa and 167.8 ± 4 GPa, respectively. The high density and mechanical property of the YSZ coating demonstrated that using the bi-cathode plasma torch at low pressure has the potential for the preparation of SOFC electrolytes. [ABSTRACT FROM AUTHOR]

Abstract The effects of solution temperature and cooling rate on microstructure and micro-hardness of a hot compressed Ti-6Al-4V alloy are investigated. The microstructure observations reveal the occurrence of static recrystallization during solution treatment. The lamellar α phases firstly decompose into the short-rod phases, and then gradually spheroidize. The increased solution temperature can accelerate the transformation of α grain boundary from the low-angle grain boundaries (LAGB) to the high-angle grain boundaries (HAGB). So, the growth and spheroidization of α grains become more and more obvious. Meanwhile, the precipitation of secondary α phases is promoted. The micro-hardness is significantly improved after the solution treatment, i.e., the micro-hardness undergoes the rapid decrease and slow increase with raising the solution temperature. In addition, the cooling rate has great impact on the microstructures and micro-hardness. With reducing the cooling rate, the mean size of equiaxed α grains and the thickness of lamellar α phases obviously increase. Highlights • Effects of post-deformation heat treatment on microstructures and micro-hardness of Ti-6Al-4V alloy are studied. • Lamellar α phases firstly decompose into the short-rod phases, and then gradually spheroidize. • The increased solution temperature accelerates the transformation of α grain boundary from LAGB to HAGB. • Micro-hardness undergoes the rapid decreases and slow increase with the increase of solution temperature. • The mean size of equiaxed α grains and the thickness of lamellar α phases increase with reducing cooling rate. [ABSTRACT FROM AUTHOR]

Cu-15Ni-8Sn coatings were prepared using atmospheric plasma spraying. The influences of arc current and aging treatment on the microstructure, mechanical and tribological properties were investigated. The coating microstructure, the wear track and the wear debris were observed and analyzed. The melting state of the particles is improved by increasing of arc current. The hardness of the aged coatings is higher than the as-sprayed coatings. The wear resistance of the aged coatings is 3–4 times higher than the as-sprayed coatings. The continuous smooth tribolayer formed on the wear tracks contributes to the low wear rate of aged coatings. The dominant wear mechanism of the coatings is delamination coupled with spalling under dry sliding condition. This work provides an effective method for producing spinodal alloy coatings with enhanced mechanical and tribological properties. [ABSTRACT FROM AUTHOR]

In the present work, two types of thermo-mechanical treatments were performed to enhance the mutually contradictory strength and electrical conductivity of Al–Mg–Si alloy. The microstructures, conducting and mechanical behavior of the alloy during conventional artificial aging treatment (solution treating, aging) and thermo-mechanical treatments (solution treating, cold rolling, aging and solution treating, pre-aging, cold rolling, re-aging) were investigated. The results indicate that the Al–Mg–Si alloy after 70% cold rolling and aging at 180 °C for 6 h reveals higher ultimate tensile strength and electrical conductivity (being 267 MPa and 58.2% IACS) than the conventional peak-aged alloys do (being 248 MPa and 54.8% IACS). Further simultaneously enhanced ultimate tensile strength and electrical conductivity, as high as 301 MPa and 58.9% IACS, respectively, can be acquired for the alloy after pre-aging at 180 °C for 2 h and then 70% cold rolling followed by re-aging at 180 °C for 6 h. With the aid of the microstructure evolution, the factors which lead to the simultaneously enhanced strength and conductivity of the alloy are discussed in detail. [ABSTRACT FROM AUTHOR]

Hot compression features of Ti-55511 alloy are investigated by high-temperature compression tests in α+β region. It is found that the flow stress and softening mechanisms are obviously influenced by deformation conditions. The true stress decreases with the reduced strain rate or the raised temperature. The spheroidization of α phase and dynamic recrystallization (DRX) of β phase easily occur at low temperatures such as 973, 1003 and 1033 K, while the dynamic recovery (DRV) of β phase mainly occurs at high temperatures such as 1063 K because of the transformation from α phase to β phase at relatively high temperatures A dislocation density-based constitutive model, which is associated with DRV, work hardening mechanisms and the spheroidization of α phases, is established and validated to describe flow behavior. The correlation coefficient (R) and average absolute relative error (AARE) of the established model are 0.9924 and 6.8%, respectively. 3D power dissipation efficiency maps and processing maps are established to determine the appropriate processing window, i.e., too low temperatures (lower than 973 K) or too high strain rates (higher than 1 s−1) easily induce flow instability. Therefore, the medium temperature (1003–1063 K) and the low strain rate (0.001–0.1 s−1) are applicable for thermal compression of the studied titanium alloy. • Hot compression features of Ti-55511 alloy is investigated by high-temperature compression tests in α+β region. • DRX easily occurs at low temperatures, while DRV mainly occurs at high temperatures. • A accurate dislocation density-based constitutive model considering the spheroidization of α phases is established. • The optimal forming temperature and strain rate are 1003–1063 K and 0.001–0.1 s−1. [ABSTRACT FROM AUTHOR]

Spheroidization and dynamic recrystallization (DRX) mechanisms of a Ti-55511 alloy during hot compression in α+β region is investigated. It is found that the spheroidization of lamellar α phases and DRX of β phases, which are obviously influenced by deformation conditions, are the main softening mechanisms. The spheroidization fraction of lamellar α phases first increases with the raised temperature or strain rate. However, the spheroidization fraction of lamellar α phases begins to drop at about 700 °C as the strain rate is higher than 0.01 s−1, and the maximum spheroidization fraction of lamellar α phase is about 2.3%. This phenomenon is attributed to the Implanting-Mechanism, which is induced by the common or close orientation relationships of the spheroidized and equiaxed α phases, as well as few dislocations between the spheroidized and equiaxed α phases. Contrarily, the lamellar α phases are obstructed from equiaxed α phases by a mass of dislocations. Additionally, the DRX degree of β phases increases with the reduced temperature or the raised strain rate. • Spheroidization and DRX mechanisms of a Ti-55511 alloy during hot compression in α+β region is investigated. • Spheroidization fraction of lamellar α phase first increases then drops with the raised strain rate. • The maximum spheroidization fraction of lamellar α phase is about 2.3% near 700 °C and 0.01 s−1. • Implanting-Mechanism, induced by the close orientation relationships of spheroidized and equiaxed α phases, is proposed. • The DRX extent of β phases increases with the reduced temperature and raised strain rate. [ABSTRACT FROM AUTHOR]

The hot deformation behavior and microstructural evolution of a Ti-55511 alloy in α+β region are investigated by uniaxial compressive tests at elevated temperatures. Transmission Electron Microscope (TEM) and Electron Backscattered Diffraction (EBSD) are employed to observe the microstructures. The spheroidization of lamellate α phases and the dynamic recrystallization (DRX) of β grains are analyzed. It is observed that the flow characteristics are prominently affected by deformation parameters, i.e., the flow stress, peak stress and flow softening stress decrease with the reduced strain rate or the increased deformation temperature. When the deformation temperature is slightly raised or the strain rate is properly reduced, the fraction of spheroidized α phase greatly increases. The substructures are formed in the lamellate α phase, and the β phase wedges into the lamellate α phase. Then, the lamellate α phase is fragmentized and spheroidized. The DRX of β grains is promoted with the raised strain rate or the reduced deformation temperature. Additionally, the higher dislocation density and obvious dislocation pile-ups can be noticed at the α/β interface, which induces the DRX nucleation of β grains at the α/β interface. • Hot deformation behavior and microstructure evolution of a Ti-55511 alloy in α+β region are investigated. • The fraction of spheroidized α phase increases with increasing deformation temperature or reducing strain rate. • The substructures are easily formed in the lamellate α phase, and the β phase wedges into the lamellate α phase. • The DRX of β grains is promoted with the raised strain rate or the reduced deformation temperature. • The obvious DRX of β grains easily nucleate at the α/β interface. [ABSTRACT FROM AUTHOR]