High-temperature X-ray diffraction study of phase transformations in nitrogen-bearing steels

The phase composition, lattice parameters, and residual stresses in the α and γ phases of steels containing 0.14–1.2 wt % N are determined by high-temperature X-ray diffraction at 20–1200°C. A procedure is proposed for the in situ quantitative study of the Cr₂N nitride dissolution kinetics and austenite grain growth when diffraction patterns are taken at high temperatures. The temperature boundaries of the decomposition of the α and γ phases and the temperature of complete dissolution of nitride phases are found. The formation of interphase residual stresses during thermal treatment is considered.     

锌铝镁镀层汽车板镀层相的X射线衍射分析

为了对锌铝镁镀层汽车板镀层相进行表征,进而指导生产现场工艺调整及优化,首先采用X射线衍射仪(XRD)对测试参数进行了优化,然后根据最优测试参数,对7种不同镀层质量的锌铝镁镀层汽车板镀层相组成进行了定性定量分析。结果表明,优化后的锌铝镁镀层XRD相分析的最佳测试参数为小角掠射模式,窄狭缝,步长0.02°~0.04°,扫描速度不大于2°/min,扫描角度范围40°~51.5°。对7种不同镀层质量的锌铝镁镀层试样进行分析,发现物相组成相同,均由Zn、MgZn₂和AlMg₄Zn₁₁组成;镀层质量在50g/m²以下时,随着镀层质量的增加,镀层相中MgZn₂和AlMg₄Zn₁₁的质量分数先增大后减小,但差别不大;镀层质量从50g/m²增加到70g/m²时,镀层相中Zn的质量分数降低,MgZn₂和AlMg₄Zn₁₁的质量分数均增加,且MgZn₂的增长速率大于AlMg₄Zn₁₁。常规的XRD只能进行初步的半定量分析,而实验通过优化仪器参数提高了XRD半定量精度,进而取代了传统的化学法进行定量分析,及时了解了镀层物相组成,实验结果将为生产现场进行镀层工艺优化提供理论指导。     

X-ray diffraction study of the system tungsten-rhenium-carbon

Conclusions The system W-Re-C was studied by the method of x-ray structural analysis. Phase equilibria were established for as-cast alloys and alloys quenched from 2000, 1500, 1000, and 800°C. Rhenium and -W₂C form continuous series of solid solutions. Forthe composition W₃Re₂C, there exists a ternary compound with a cubic structure which is related to the -Mn structure (space group P4₁ 3-O⁷, a=6.859±0.002 A). At temperatures above 2500°C, there exists the ternary carbide (W, Re)C, which has a cubic face-centered NaCl type structure (space group Fm3m-O _h ⁵ , a==4.063± 0.001 A). Preliminary data were obtained on the existence of a rhombic low-temperature W₂C modification.     

X-ray diffraction study of alloys in the system Mo-Re-C

Summary An x-ray diffraction study of alloys in the system Mo-Re-C has led to the discovery of two ternary compounds. The compound Mo₃Re₂C has a structure of the -Mn type (a=6.86±0.01 A). The compound (Mo, Re)C has a structure of the NaCl type and contains a variable amount of rhenium, ranging between a few and 40 at.%. There exists a continuous series of solid solutions between Mo₂C and Re. The data obtained indicate a close relationship between the systems Mo-Re-C and W-Re-C.     

X-ray diffraction study of in vitro calcification of tendon collagen

Decalcified samples of turkey leg tendon were submitted to in vitro calcification in the presence of metastable solutions of calcium phosphate at different concentrations. The structural relationship between apatitic deposits and collagen fibrils was examined by high- and small-angle X-ray diffraction using conventional and synchrotron radiation sources. At high supersaturation the apatitic crystallites were deposited on the collagen fibrils with their crystallographic c-axis preferentially oriented parallel to the fibril axis. At lower supersaturation, a fraction of the apatitic crystallites also grew with the c-axis preferentially oriented parallel to the collagen fibril axis, whereas other exhibited a preferential orientation perpendicular to the fibril axis. The analysis of the small-angle X-ray diffraction data indicates that the deposition of the apatitic phase in the sample stored in solution at lower supersaturation induced modifications of the collagen electron density distribution in the axial direction, which can be attributed to the deposition of the inorganic crystallites inside the gap region of the collagen structure.     

Determining ternary phase diagrams with electrochemical cells and in situ X-ray diffraction

We discuss how in situ X-ray diffraction and measurements of electrochemical potential in electrochemical cells can be used to determine the phase diagrams of ternary and pseudoternary compounds. These techniques reduce the number of samples needed, and also allow the phase diagram to be presented as a function of chemical potential, a presentation that makes it easier to appreciate analogies between different systems.     

X-ray diffraction study of the dependence of the fine TiC structure on dispersion of hardening phase particles

The special features of the fine structure of the TiC—based composite were studied by the methods of X-ray diffraction, the methods of local X-ray spectrum analysis and optical microscopy. The correlation between the thin TiC structure parameter values and dispersion of TiN phase particles was established.