Microstructure-fracture toughness relationships and toughening mechanism of TC21 titanium alloy with lamellar microstructure

The independent influence of microstructural features on fracture toughness of TC21alloy with lamellar microstructure was investigated.Triple heat treatments were designed to obtain lamellar microstructures with different parameters,which were characterized by OM and SEM.The size and content ofαplates were mainly determined by cooling rate from singleβphase field and solution temperature in two-phase field;while the precipitation behavior of secondaryαplatelets was dominantly controlled by aging temperature in two-phase field.The content and thickness ofαplates and the thickness of secondaryαplatelets were important microstructural features influencing the fracture toughness.Both increasing the content ofαplates and thickeningαplates(or secondaryαplatelets)could enhance the fracture toughness of TC21alloy.Based on energy consumption by the plastic zone of crack tip inαplates,a toughening mechanism for titanium alloys was proposed.

Serrated magnetic properties in metallic glass by thermal cycle

Fe-based metallic glasses（MGs） with excellent soft magnetic properties are applicable in a wide range of electronic industry. We show that the cryogenic thermal cycle has a sensitive effect on soft magnetic properties of Fe78Si9B13 glassy ribbon. The values of magnetic induction（or magnetic flux density） B and Hc coercivity c show fluctuation with increasing number of thermal cycles. This phenomenon is explained as thermal-cycle-induced stochastically structural aging or rejuvenation which randomly fluctuates magnetic anisotropy and, consequently, the magnetic induction and coercivity. Overall,increasing the number of thermal cycles improves the soft magnetic properties of the ribbon. The results could help understand the relationship between relaxation and magnetic property, and the thermal cycle could provide an effective approach to improving performances of metallic glasses in industry.

Characterization of CuInS_2 thin films prepared by sulfurization of Cu-In precursor

CuInS2 thin films were prepared by sulfurization of Cu-In precursors.The influences of the deposition sequence of Cu and In layers,such as Cu/In,Cu/In/In,and In/Cu/In,on structure,topography,and optical properties of CuInS2 thin films were investigated.X-ray diffraction results show that the deposition sequence of Cu and In layers affects the crystalline quality of CuInS2 films.Atomic force microstructure images reveal that the grain size and surface roughness are related to the deposition sequence used.When the deposition sequence of precursor is In/Cu/In,the CuInS2 thin films show a single-phase chalcopyrite structure with (112) preferred orientation.The surface morphology of CIS films is uniform and compacted.The absorption coefficient is larger than 104 cm-1 with optical band gap Eg close to 1.4 eV.

Effect of Alumina Micropowders on Properties of Calcium Hexaluminate

Calcium hexaluminate （ CA6 ） was synthesized by mixing light-weight calcium carbonate and Al2O3 mi- cropowder （calcined α-Al2O3, activated α-Al2O3 or α-Al2O3） according to the stoichimetric ratio of CA6, and reaction sintering at 1 200, 1 300, 1 400 and 1 500 ℃fin 3 h, respectiely. Efcts of the three alu- mina micropowders on the phase composition, micro- structure and properties of CA were investigated. The re- sults show that ： （ 1 ） for the three Al2O3 micropowders, the reaction to generate CA6 in specimens basically com- plete. at about 1 500 ℃ ; CA6 generated in all specimens is planar, bat the array modes are slightly different; （2） the specimel＇s prepared from, calcined α-Al2O3or ρ-Al2O3 shrink almost, while the specimens prepared from activated α-Al2O3 expand ; （ 3 ） the cold crushing strength of the specimen prepared from activated α-Al2O3 is the highest, reaching 42.5 MPa when only CA6 exists （ after firing at 1 500 ℃ ） ; （ 4 ） the specimen prepared from ρ-Al2O3 has the lowest generation temperature of CA6 and the highest apparent porosity, reaching 70. 1% when only CA exists （after firing at 1 500 ℃）; （5） the specimen prepared from calcined α-Al2O3 has the biggest bulk density.

Fabrication of Ti-Ni-Mo-Si composite coating by reactive braze coating process

Ti-Ni-Mo-Si composite coating was fabricated on mild steel by reactive braze coating process with Ti61. 9Ni24. 6Si4. 411409.1 （ wt. % ） powders as the raw materials. Microstr^cture of the coating was characterized by optical microscopy, scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy and micro-hardness tester. Results indicate that the Ti-Ni-Mo-Si composite coating is metallurgically bonded to the mild steel substrate and has high hardness. The microstructure of the coating consists of the reinforcement of Ti5 Si3 and Mo9 Ti4 particles and the matrix of eutectic NiTi2. Due to the poor wettability of NiTi2 liquid at low temperature, TisSi3 and Mo9 Ti4 do not uniformly distribute in the NiTi2 matrix.

Strengthening Effects of Niobium on High Strength Rebars

It is well known that the strengthening mechanisms of Nb microalloying on low carbon flat product have been widely studied and recognized since microalloying 75, but the application research and strengthening effects of niobium on middle carbon steel like rebars have been incomplete and under argument due to some factors like limited solubility of Nb（CN） in reheating stage, dominant application of vanadium in rebars, as well as uncertain strengthening effect resulted from high rolling temperature and fast rolling speed in finishing rolling stage. Combining with new version of GB1499.2-2018： Steel for the reinforcement of concrete-Part 2： Hot rolled ribbed bars, it is very necessary to clarify the strengthening effects of niobium on high strength rebars for cost saving. In this paper, some new phenomena have been presented and discussed based on industrial trial results of Nb-bearing HRB400E, HRB500E and HRB600（E）, and then strengthening effects of niobium on high strength rebars were discussed.

Multi-phase structure and electrical properties of Bi_(0.5)Li_(0.5)ZrO_3 doping K_(0.48)Na_(0.56)NbO_3 lead-free piezoelectric ceramics

(1–x)K_(0.48)Na_(0.56)NbO_3–xBi_(0.5)Li_(0.5)ZrO_3(KNN–x BLZ, x = 0–0.06) lead-free piezoelectric ceramics were prepared by the conventional solid-state sintering method, and their phase structures and electric properties as well as T_C were systematically investigated. The orthorhombic–tetragonal(O–T) two phases were detected in all(1–x)K_(0.48)Na_(0.56)NbO_3–xBi_(0.5)Li_(0.5)ZrO_3 ceramics at 0.01 ≤ x ≤ 0.05. Due to the appropriate ratio between O phase and T phase(CO/C T= 45/55), high piezoelectric properties of d 33= 239 pC/N, k_p= 34%, and P_r = 25.23 μC/cm^2 were obtained at x = 0.04. Moreover, a high T_C = 348 ℃ was also achieved in KNN–x BLZ ceramic at x = 0.04. These results indicate that (1–x)K_(0.48)Na_(0.56)NbO_3–xBi_(0.5)Li_(0.5)ZrO_3 system is a promising candidate for high-temperature piezoelectric devices.

The electrical property of MnCo_2O_4 and its application for SUS 430 metallic interconnect

The conductivity of MnCo2O4 spinel,the best route to form the MnCo2O4 protective coating applied by the sol-gel process,and its effect on the intermediate temperature oxidation behavior of SUS 430 alloy,a typical material for the interconnect of solid oxide fuel cell(SOFC),was investigated.The phase structure and surface morphology of the coating and surface oxides were characterized by XRD,SEM and EDS;the "4-probe" method was employed to determine the conductivity of MnCo2O4 spinel and the area specific resistance(ASR)of the surface oxides.The conductivity of MnCo2O4 spinel is excellent,which is 2 orders of magnitude better than that of MnCr2O4 spinel.Long-term thermally cyclic oxidation at 750°C in SOFC cathode atmosphere and ASR measurement have shown that calcined in reducing atmosphere followed by pre-oxidation in the air is the best technique for forming the MnCo2O4 protective coating,which enhances the oxidation resistance,and improves the electrical conductivity and adherence of coated SUS 430 alloy significantly.As a result,the MnCo2O4 spinel is the most potential candidate for SOFC metallic interconnect protective coating application.

Dy gradient and coercivity in grain boundary diffusion processed Nd-Fe-B magnet

By controlling Dy vapor deposition process, the amount of Dy that diffused into the magnet was increased gradually from 0.1 wt.% to 0.3 wt.%. Compared with the original status, the coercivity increment was not proportional to the Dy diffusion amount. Subsequent H（cj） and Dy content gradient data showed that slope of the 0.3 wt.% sample gradient was bigger than that of 0.1 wt.% one, and the gaps between outer flakes and inner flakes enlarged with the increasement of Dy diffusion amount. Although Dy mostly enriched in triple-junction regions in electron-probe microscope analysis（EPMA） images, the following Auger depth graph showed that Dy content was as high as 3.0 at.% in 1.5 mm deep center. It proved that Dy tended to get into the main phase rather than stayed in the grain boundary during the diffusion process, and over-diffusion of Dy in the main phase was unhelpful for the coercivity enhancement.

Ultrasound-Assisted Transient Liquid Phase Bonding of Magnesium Alloy Using Brass Interlayer in Air

The microstructure evolution and oxide film behavior in ultrasound-assisted transient liquid phase（U-TLP） bonding of Mg alloy were investigated by applying different ultrasonic time at 460？C with brass interlayer in air. The results indicated that with increasing ultrasonic time, brass interlayer disappeared gradually and the Mg-Cu-Zn eutectic compounds were formed. The eutectic compounds in the joint decreased as the ultrasonic time increased further. The oxide removal process was divided into four steps. Continuous oxide film at the interface was partially fractured by ultrasonic vibration,and then suspended into liquid by undermining eutectic reaction. After that, the suspended oxide film was broken into small oxide fragments by ultrasonic cavitation effect, which was finally squeezed out of the joint by ultrasonic squeeze action. In addition, the mechanical properties of the joints were investigated. The maximum shear strength of the joint reached 105 MPa, which was 100% of base metal.

Rapid Ultrasonic-Assisted Soldering of AZ31B Mg Alloy/6061 Al Alloy with Low-Melting-Point Sn–xZn Solders Without Flux in Air

A novel ultrasonic-assisted low-temperature soldering was developed to join AZ31B Mg alloy and 6061 Al alloy with a series of Sn–x Zn solders. The average maximum shear strength of the joints reaches up to 87.5 MPa at soldering temperature of 300 °C under ultrasonic assistance for only 5 s using Sn–20 Zn solder. The fracture path propagates completely in the soldering seam. The results indicate that the microjet generated by ultrasonic pressure in liquid solder could strike and splinter the Mg_2Sn intermetallic compounds into small pieces, which contributes to the enhancement of the joint strength. In addition, the primary Al(Zn) solid solution phase formed during cooling stage could also strengthen the joint due to the prevention of microcracks propagation.

Time-stability of sintered Nd-Fe-B permanent magnet with lower oxygen content

Time-stability of sintered Nd-Fe-B magnet with lower content of oxygen at different temperatures and humidity conditions for 400 d was investigated.Results showed that the magnetic flux loss was-0.68% for the non-electroplating samples and-0.43% for the electroplating samples at room temperature and average humidity was 25% during 400 d,respectively.The magnetic flux loss of the plated samples was lower than non-plated samples under the conditions of room temperature and with the average humidity of 54%,but the magnetic flux loss of the plated samples was larger than that of the non-plated sample at 80 oC.The magnetic flux loss of electroplated and non-electroplated sintered Nd-Fe-B magnets was less than 1% for 400 d,which showed that the N40SH grade magnets have good time stability.

Mechanism of broadening of slab in continuous casting

The mechanism of broadening of slab in continuous casting was studied by numerical simulations and experimental measurements in factories. The mechanism is derived by gradual exclusion of various factors related to the broadening of slab. It is concluded that the slab exposes to no constraint at the direction of narrow face. Because of the static pressure of molten steel, the slab deforms creepily in the direction that consequently results in the broadening of slab. The broadening of slab increases with casting speed and static pressure of molten steel. The decrease of secondary cooling intensity and strength of steel at high temperature also contribute to the broadening of slab. The micro-alloying plays an important role in improving the strength of steel and in reducing the broadening of slab.

Physics prospects of the Jinping neutrino experiment

The China Jinping Underground Laboratory（CJPL）, which has the lowest cosmic-ray muon flux and the lowest reactor neutrino flux of any laboratory, is ideal to carry out low-energy neutrino experiments. With two detectors and a total fiducial mass of 2000 tons for solar neutrino physics（equivalently, 3000 tons for geo-neutrino and supernova neutrino physics）, the Jinping neutrino experiment will have the potential to identify the neutrinos from the CNO fusion cycles of the Sun, to cover the transition phase for the solar neutrino oscillation from vacuum to matter mixing, and to measure the geo-neutrino flux, including the Th/U ratio. These goals can be fulfilled with mature existing techniques. Efforts on increasing the target mass with multi-modular neutrino detectors and on developing the slow liquid scintillator will increase the Jinping discovery potential in the study of solar neutrinos,geo-neutrinos, supernova neutrinos, and dark matter.

Effect of carbon nanotubes addition on electrochemical performance and thermal stability of Li_4Ti_5O_(12) anode in commercial Li Mn_2O_4/Li_4Ti_5O_(12) full-cell

Li4Ti5O12（LTO）/carbon nanotubes（CNTs） composite material is synthesized based on a solid-state method by sand-milling, spray-drying and calcining at 850 8C under N2 flow. The LTO/CNTs samples with1 wt% and 3 wt% weight ratio of CNTs addition and the pristine LTO sample are prepared. The rate performance and the thermal stability of these samples are investigated based on Li Mn2O4（LMO）/LTO full-cell. The results show that the weight ratio of CNTs addition has distinct effect on LTO performances.The composite materials of LTO composited CNTs have better performance at high-rate due to the intercalation enhancement by conductive network of CNTs. At second, the overcharging temperature response of the cell＇s surface with 1 wt% CNTs addition is the lowest. The particle size distribution is measured and the most uniform particles are obtained with 1 wt% CNTs addition. This trend could explain that the medium quantity of CNTs is optimal to improve the heat and mass transfer and prevent the problems of crystallite growing interference and aggregation during the calcination process.

Fe-based multi-phase nanocrystalline ribbons with hierarchically flowerlike structured metal oxides after modified by Orange II for Cr^VI absorption

Three-dimensional flowerlike nanostructured metal oxides attached on the surfaces of Fe-based multi-phase nanocrys- talline ribbons （Fe-MNRs） were prepared by a simple way （through immersing the Fe-MNRs in Orange II solution）. It has been found that the as-prepared Fe-MNRs with 3D flowerlike nanostructures （Fe-MNRs ＋ FNs） exhibit good absorption property for a typical heavy metal ion （Cr^VI） in wastewater, while Fe-MNRs do not possess such properties. The Fe-MNRs ＋ FNs could remove 99% CrvI ions from the solution in 40 min, and this adsorption property can be attributed to the ion exchange between Cr^VI and surface hydroxyl groups （O-H） of 3D flowerlike nanostructures. The present result suggests that the Fe-MNRs ＋ FNs, prepared by facile way, possess great potentials in removing heavy metallic ions in wastewater.