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The microstructures and corrosion behavior of Mg–6Gd –x Zn–0.4Zr ( x = 0.5, 1, and 2 wt%) alloys under as-cast and solution treated conditions were studied. Long period stacking ordered (LPSO) structure formed in the as-cast alloys and disappeared after solution treatment. The distribution of LPSO structure is related to Zn concentration. The corrosion rates of the as-cast and solution treated alloys increased with increasing Zn content. The as-cast alloys, which had LPSO structure located at the outer edges of grains, exhibited better corrosion resistance and a more uniform corrosion mode as compared to the alloy which had LPSO structure distributed throughout some whole grains. [ABSTRACT FROM AUTHOR]

Abstract A superhydrophobic coating based on a Mg-Mn LDHs film was fabricated on pure Mg by an in-situ growth method and chemical modification by adsorption of myristic acid (MA, CH 3 (CH 2) 12 COOH). The static contact angle of the superhydrophobic surface was about 152.2°. The structure and composition of the samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The corrosion resistant performance of the samples in simulated body fluid (SBF) was investigated by electrochemical impedance spectroscopy (EIS). The impedance of the superhydrophobic coating sample at low frequency is approximately 20,000 Ω·cm2 which is more than twice of that of the LDHs film and ten times of that of pure Mg substrate. The superhydrophobic coating can effectively protect the Mg from corrosion in SBF for a long time. Highlights • The superhydrophobic Mg-Mn layered double hydroxide coatings are formed on pure magnesium. • The corrosion behavior in simulated body fluid (SBF) is investigated by electrochemical impedance spectroscopy (EIS). • The superhydrophobic coating can effectively protect the Mg from corrosion in SBF for a long time. [ABSTRACT FROM AUTHOR]

CrNiN coatings with various Ni content were deposited by RF reactive magnetron sputtering from Cr–Ni alloy targets. The influence of Ni content on phase structure, preferred orientation, microstructure and hardness of the coatings was investigated. The results show that RF sputtered CrNiN coatings are mainly composed of CrN phase, present columnar growth, and have a nearly feature-less surface morphology. The preferred orientation changes from CrN (220) to CrN (111) as Ni content is increased from 2.92 to 8.79 at.%. The doped Ni can favor dense structure and improve coating surface smoothness, but cannot refine grains. The coating hardness is increased by adding 2.92 at.% Ni due to the effect of discontinuous Ni coverage on hindering grain boundary sliding, dense structure and smoother surface. As Ni content is increased to 8.79 at.%, the hardness is then decreased as a result of too much soft metal and larger grain size. [ABSTRACT FROM AUTHOR]

CrN and Cr–Cu–N coatings were deposited under different bias by RF magnetron reactive sputtering. The Cr–Cu–N coatings with an ultra-low Cu content of 0.53–2.1 at.% were prepared. The influence of Cu content and substrate bias on microstructure and hardness was investigated. With increasing bias both CrN and Cr–Cu–N coatings change the preferred orientation from (220) to (111), then to coexist of (111) and (200), finally to (111), and the grain refining effect is obvious. The addition of Cu is more conductive to the strengthening of CrN(111), but cannot cause an obvious decrease in the grain size. All the coating surfaces present nearly feature-less characteristic, implying a fine grain microstructure. The hardness decreases as the bias increases. The Cr–Cu–N coating containing the maximum soft metal of Cu (2.1 at.%) has the highest hardness of 27.1 GPa due to a dense structure, smoother surfaces, and the highest degree of Cu coverage. The reason of failure to get superhard Cr–Cu–N coatings is a combination of incomplete monolayer coverage due to ultra-low Cu content, (220) preferred orientation, and the grain size of CrN with less than 20 nm. [ABSTRACT FROM AUTHOR]

Mg–5Gd–1Zn–0.6Zr (wt.%, GZ51K) alloy was prepared by gravity casting in order to develop a novel, biodegradable magnesium alloy. The microstructure and corrosion behavior of the alloy exposed to simulated body fluid (SBF) were investigated under as-cast, solution and aging-treated conditions. The microstructure of the as-cast alloy consists of α-Mg, lamellar phase with long period stacking ordered (LPSO) structure, and eutectic phase. The LPSO phase disappears after solution treatment at 535 °C for 12 h, and the microstructure of the alloy after solution and aging treatment is composed of α-Mg and needle-like precipitates. The as-cast GZ51K alloy with LPSO structure exhibits slower corrosion rates and more uniform corrosion morphology as compared to the alloy without LPSO structure, and is thus desirable for use as a degradable biomaterial. [ABSTRACT FROM AUTHOR]

Abstract: The mechanical, thermo-physical properties and electronic band structures of SnS and SnSe have been calculated using density-functional theory (DFT). The elastic constants of SnS and SnSe obtained from calculations meet their mechanical stability conditions. The shear elastic properties of the {001} plane are both anisotropic for SnS and SnSe. Both compounds exhibit brittle behavior due to their low B/G ratio. The values of thermal capacity are close to 200J/molK at about 300K, and the thermal expansion coefficients decrease with increasing pressure at same temperature. The entropy is variable by power-exponent, and the internal energy is almost linear with increasing temperature for SnS and SnSe. The Gibbs energy of SnS is lower than that of SnSe under same temperature and pressure. Debye temperatures are 218K and 215K, and Grüneisen parameters are 3.25 and 2.98 for SnS and SnSe at 300K, respectively. Main anion (S, Se)p orbitals and a few cation (Sn)p and cation (Sn)s orbitals make the major contribution to the formation of the top of the valence band, and a broad structure as the conduction band, mainly due to both the cation (Sn)p and the anion (S, Se)p. [Copyright &y& Elsevier]

Abstract: The potential damage during the pyrolysis of phenol–formaldehyde (PF) resin in the manufacturing of carbon/carbon components is serious. Accurately modeling the kinetics of the pyrolysis reaction can lead to improvements in processing. To study the pyrolysis kinetics of PF resin, non-isothermal pyrolysis kinetics is investigated using thermogravimetric analysis (ТGA) at controlled heating rates. The research indicates that the pyrolysis process consists of three consecutive and overlapping stages. PEAKFIT was employed to separate overlapping regions, and then pyrolysis kinetic triplet of PF resin is calculated. With the determined apparent activation energies, the most probable mechanism functions and the corresponding pre-exponential factor, the model agrees well with the experimental data. [Copyright &y& Elsevier]

Low cycle fatigue tests for P92 heat-resistant steels (P92 HRS) were conducted at room temperature (RT) and elevated temperature (873 K). The fatigue test results showed that P92 steel showed softening characteristics during fatigue at RT and 873 K, and the increase of temperature and strain amplitude was the main reason for the decrease of uniaxial fatigue life. The specimens before and after fatigue test at two temperatures were observed and analyzed by transmission electron microscope (TEM) coupled with energy-dispersive X-ray spectroscopy (EDS) and selected area electron diffraction (SAED). Microstructure observations revealed that the cyclic softening was caused by the annihilation of dislocations, as well as the fragmentation and polygonization of lath structure. High temperature promoted the formation of subgrains by accelerating the motion of dislocations and migration of low-angle grain boundaries (LABs). With the continuously decreasing of dislocation density, the growth of equiaxed subgrains and the weakening of the precipitation strengthening, the softening rate of the material was further increased until the final fracture occurs. Therefore, the evolution of microstructure of 9Cr martensitic steel during the low cycle fatigue process was deduced and described. • The initial lath structure is changed into equiaxed subgrains with reduced dislocation density. • High temperature promotes the formation and growth of subgrains by accelerating dislocation movement and boundary migration. • The cyclic softening is suppressed by the interactions between dislocations and the precipitates. • At high temperature, this interactions effect is weakened. [ABSTRACT FROM AUTHOR]