[en] Superconducting (Hg,Re)Ba₂CaCu₂O_y ((Hg,Re)-1212) thin films have been prepared on single crystal substrates of LaAlO₃ by reacting laser deposited ReBaCaCuO precursor films with CaHgO₂ in sealed quartz tubes. The effects of the deposition parameters such as laser fluence and substrate temperature, on surface morphology and microstructure were examined by atomic force microscopy (AFM) and scanning electron microscopy (SEM). AFM observations revealed that a granular structure was seen in the precursor films deposited at lower energy (less than 200 mJ) and disappeared at higher energy (250 mJ). SEM investigation on final reacted films showed that the precursor films deposited at 250 deg. C resulted in a well-connected and uniformly dense microstructure, whereas the films deposited at lower or higher temperatures were porous and non-uniform

[en] The hot flow behaviors of interphase precipitated Ti-Mo-xNb (x = 0, 0.02) steels were investigated by conducting compression tests at higher strain rates of 0.1–10 s⁻¹ and temperatures of 800–1150 °C using a Gleeble-2000 thermo-mechanical simulator. The hot deformation behavior was modeled through combining the dislocation density based Bergstrom and the diffusional transformation based KJMA models. The results show that even small amount of Nb addition can effectively increase the activation energy for hot deformation, thus delaying the occurrence of dynamic recrystallization. However, the ascend rates in flow stress σ, peak stress σ_p and dislocation density ρ_p with Nb appeared to be more significant at higher strain rates, implying that the effectiveness of Nb in Ti-Mo-xNb steels was sensitive to strain rate. The microstructual features demonstrated that the hardening effect caused by Nb addition was offset by the softening effect of DRX at 0.1 s⁻¹, causing the weak strain-rate dependence; whereas, at the strain rate of 10 s⁻¹, the softening mechanism was considered as DRV, giving rise to a relatively large discrepancy in flow behaviors with Nb addition.

[en] X-ray photoelectron spectroscopy (XPS) has been used to investigate the evolution of surface chemistry of YBa₂Cu₃O_7-δ (Y123) films prepared by the metalorganic deposition (MOD) process using trifluoroacetate (TFA) precursors. Detailed XPS core-level spectra obtained from the samples quenched from various points during the calcining and firing stages have been reported for the first time and are used to identify surface species. The XPS data show evidence of formation of intermediate phases such as Y-O-F, BaF₂, and CuO during the calcining process, which are the decomposition products of yttrium, barium, and copper trifluoroacetates, respectively. The TFA precursors are completely decomposed at the end of calcination. The change of binding energies for Y 3d_5/2, Ba 3d_5/2, and O 1s during the firing process indicates that Y123 starts to form at 800 deg. C after 0.5 h firing. Based on the experimental results, an alternative mechanism of the chemical evolution from precursor to final film in the TFA-MOD process is proposed

[en] Recrystallization and precipitation behaviors after cold rolling and aging are investigated for Cu-0.7Cr-0.13Zr alloy. The processed alloy was characterized using the measurement of Vickers hardness, scanning electron microscopy, and transmission electron microscopy. The resultant complex microstructures are interpreted in terms of the interactions between precipitation and recrystallization. Upon aging at 500 °C for 1 h, the 45% rolled alloy exhibits a retarded recrystallization process and therefore an efficient hardening response, which are attributed to the pinning effect of fine dispersed precipitates on the dislocation. When heavily deformed and aged at high temperature, the alloy shows an accelerated process of recrystallization, and precipitates are found to coarsen.

[en] Electroplating was employed to fabricate the Ni film on the Ti substrate. Adhesion strength of Ni film on Ti substrate was determined using the three-point bend technique that was proposed in standard mechanics test. The experimental results demonstrate that the interface fracture energies obviously increase with the roughness of Ti substrates, and are independence with the thickness of Ni films. Moreover, the adhesion strength of Ni film on Ti substrate was also measured by peel test, and was evaluated by Miedema model of experiential electron theory. The intrinsic interface fracture energy measured by three-point bend test is reasonable agreement with that obtained by theoretical calculation of Miedema model, and is roughly comparable to that by peel test

[en] An enhancement of the exchange coupling and hard magnetic properties of melt-spun Nd₂Fe₁₄B/α-Fe-type nanocomposites was achieved by optimization of their nanostructured morphology via magnetic annealing. Compared with the Nd_2.4Pr_5.6Dy₁Fe₈₄Mo₁B₆ sample annealed without a magnetic field, the magnetic annealing results in a noticeable improvement in the coercivity _i H _c, the remanence 4πM_r, and energy product (BH)_max. (BH)_max at 50 K was enhanced by 43.7% after magnetic annealing in a field of 19 T. The kink in the demagnetization curve disappeared and, additionally, a much better squareness of the demagnetization curves was observed in the magnetically annealed samples. The intergrain exchange coupling was evaluated by Henkel plots. Evidence for stronger intergrain exchange coupling was found in the magnetically annealed sample, which is due to nanostructure refinement promoted by the magnetic annealing. The nanostructure refinement was confirmed by X-ray diffraction, transmission electron microscope, low-temperature demagnetization curves and a modified Brown's equation analysis. The improvement of hard magnetic properties of the magnetically annealed sample results mainly from the magnetic-field-induced exchange-coupling enhancement