استكشف المجموعة الواسعة من العناوين المتاحة.

Structural and mechanical characterization of electron beam additive manufactured stainless steel samples has been carried out. The XRD measured austenite and ferrite lattice parameters showed their sensitivity to the heat input value, which was related to the chromium atom redistribution. The ferrite content depended on the heat input too. Optimal heat input level has been detected, which allowed obtaining the tensile strength higher than that of the base stainless steel. Residual strain levels in the as-deposited metal and fusion line zone have been measured using the X-ray sin 2 ψ method. The highest tensile residual strain was determined in a fusion line zone between the first as-deposited layer and a substrate. The microstructure of the first fusion line zone contained deformation twins and entangled dislocations generated by plastic flow under thermal expansion-contraction cycles.

This is the first study ever to show the impact of high-energy 160 MeV xenon ion irradiation on the properties of 100Cr6 bearing steel. The projected range (Rp) of xenon ions is 8.2 µm. Fluence-dependent variations in the coefficient of friction and wear of the 100Cr6 steel material have been observed. These changes correlate with shifts in the crystal lattice constant and variations in the oxygen, carbon, and iron content in the wear track. Fluence-dependent changes in these parameters have been observed for the first time. Irradiation reduces stresses in the crystal lattice, leading to crystallite size increase. The modifications in the properties of 100Cr6 steel result from radiation-induced defects caused by electronic ion stopping. The degree of these modifications depends on the applied irradiation fluence. Furthermore, the use of a higher irradiation fluence value appears to mitigate the effects produced by a lower fluence.

The microstructure, phase composition and elemental composition in the α - and β -phases of the two-phase wrought Ti-5.7Al-1.6V-3Mo titanium alloy at room temperature were studied by transmission electron microscopy and X-ray energy-dispersive spectroscopy. The temperature ranges of phase transformations in the alloy during heating from 298 to 1523 K were studied by differential scanning calorimetry (DSC). Two endothermic peaks were observed on the DSC curve at the temperatures of 1078 K and 1207 K, and one exothermic peak was observed at a temperature of 1123 K. The endothermic peak on the DSC curve at a temperature of 1078 K is due to the formation of α ″-martensite, at a temperature of 1207 K is caused by α  →  β phase transformation. The exothermic peak at a temperature of 1123 K, presumably, corresponds to the polymorphic transformation of brookite → rutile in TiO 2 oxide. High-temperature synchrotron studies were carried out from room temperature to 1373 K. It was found that the increase in lattice parameters during heating is nonlinear. Possible mechanisms of the nonlinear change in the lattice parameters at temperatures above 1200 K are discussed. At T  > 1000 K α ″-martensite was formed by β  →  α ″ phase transformation. An increase in the volume fraction of α ″-phase with increase in temperature was accompanied by a decrease in the volume fraction of β -phase. An increase in microstrain of the α -phase lattice and a decrease in microstrain of the β -phase lattice were observed upon heating.

The lattice strain ε(D) function of nanocrystals within different interface environments was modeled. For nanoparticles and nanocrystals embedded in incoherent interfaces, the lattice shrinks with the decrease of size, resulting in the reduction of ε(D). For nanostructure materials and the nanocrystals embedded in the coherent interfaces, ε(D) increases due to lattice expansion. These changes in interfacial lattice parameters depend on the sign of interfacial stress fss, i.e., the lattice contracts when fss > 0 and expands when fss < 0. In addition, we also give a criterion to judge the sign of fss, fss is negative when the surface stress f of the matrix is larger than that of the embedded nanocrystals, and vice versa. The variation in the sign of fss is also applicable to explain the thermal stability of the interface.

Residual oxygen in wurtzite-type aluminum nitride (AlN) crystal, which significantly affects phonon transport and crystal growth, is crucial to thermal conductivity and the crystal quality of AlN ceramics. In this study, the effect of residual oxygen on the lattice of AlN was examined for as-synthesized and sintered samples. By controlling reaction time in the carbothermal reduction nitridation (CRN) procedure, AlN powder was successfully synthesized, and the amount of residual oxygen was systematically controlled. The evolution of lattice parameters of AlN with respect to oxygen conc. was carefully investigated via X-ray diffraction analysis. With increasing amounts of residual oxygen in the as-synthesized AlN, lattice expansion in the ab plane was induced without a significant change in the c-axis lattice parameter. The lattice expansion in the ab plane owing to the residual oxygen was also confirmed with high-resolution transmission electron microscopy, in contrast to the invariant lattice parameter of the sintered AlN phase. Micro-strain values from XRD peak broadening confirm that stress, induced by residual oxygen, expands the AlN lattice. In this work, the lattice expansion of AlN with increasing residual oxygen was elucidated via X-ray diffraction and HR-TEM, which is useful to estimate and control the lattice oxygen in AlN ceramics.

The lattice parameters of both the product phase and the matrix phase have determined using in situ X-ray and neutron diffraction measurements during forward and reverse transformations in steels. The lattice parameters are well known to be influenced by various factors, including temperature, internal stresses induced by transformation strains, partitioning of alloying elements, crystal defects, and magnetic strains. Therefore, it is crucial to accurately disentangle the contributions of these factors to the observed changes in lattice parameters. This review examines the evaluation of internal strain (stress) associated with ferrite, pearlite, bainite, martensite, and reverse austenite transformations, with a particular emphasis on the distinction between diffusional and displacive transformations. Additionally, the effects of plastic deformation of austenite on the bainite or martensite transformation are discussed. In this context, the roles of dislocations and vacancies are highlighted as key areas for further investigation.

Nitrides of transition metals such as iron and nickel are known to possess excellent properties relevant for technological applications. Among these, FeNhas been synthesized in zinc blende face centered cubic ( F 4 3 ¯ M ) crystal structure while NiN has not been synthesized yet. Literature search revealed that hexagonal close packed and primitive tetragonal structures of these compounds have not been investigated to ascertain their preference.Therefore, the structural stability of Zinc blende face centered cubic, hexagonal closed packed and primitive tetragonal crystal structures of the compounds were investigated in this study. Generalized gradient approximation of Perdew-Burke-Ernzerhof revised for solids (GGA-PBEsol) as implemented in Quantum espresso package was used based on density functional theory for the computation. The results revealed that FeN and NiNcompounds prefer Zinc blende face centered cubic crystal structure as their equilibrium lattice parameters occurred at the least equilibrium minimum energies in this structure. The lattice parameters of FeN and NiN compounds in thezinc blende FCC crystal structure were computed to be 4.232 Å and 4.324 Å respectively in agreement with experiment and previous computations. The preference of zinc blende FCC crystal structure by these compounds imply they may possess highly directional covalent bonds that prefer a tetrahedral arrangement of atoms, thus forming good binary semiconductor compounds. Therefore, these compounds have high possibility of been synthesized in zinc blende FCC crystal structure.

— Temperature dependences of lattice parameters for AgInSe 2 single crystals have been used to determine their thermal expansion coefficients along the a and c crystallographic axes. The results demonstrate that the thermal expansion coefficients of the AgInSe 2 single crystals in the a - and c -axis directions change sign at temperatures of 142 and 135 K, respectively. Analysis of the temperature-dependent band gap of AgInSe 2 with the use of optical absorption spectra shows that its band gap increases with increasing temperature in the range 80–120 K and decreases in the range 120–300 K.

The concentration dependences of melting temperature , Debye temperature and lattice parameter as.s. for massive high-entropy alloys based on Fe, Ni, Co, Cu and Al were analyzed within the concept of additivity of physical values of high-entropy alloys. 4- and 5-component alloys were considered in the form of single-phase solid solutions. It was established that can vary within 150 K, that is, is insensitive to changes in the concentration of individual atoms. It is even less sensitive to concentration since the maximum value is ≅80 K. The lattice parameters change in accordance with Vegard's rule.