Liu Riping

Tensile Strength of Zr—Ti Binary Alloy

Zr—Ti binary alloys are prepared using a nonconsumable tungsten electrode under Ti-gettered inert atmosphere (argon). Microstructures are observed mainly as α phase using x-ray diffraction. A tensile test is performed to investigate the tensile strength of a series of Zr—Ti binary alloys at room temperature. The findings indicate that increasing Ti concentration results in an initial increase (50at% of Ti) and then a decrease in tensile strength. The Zr55Ti45 (at%) component exhibits the maximum tensile strength of 1216.68MPa, which is much higher than that of pure Ti (increased by approximately 200%) or pure Zr (increased by approximately 100%). The potential mechanisms for the remarkable tensile strength are solid solution strengthening and grain refinement.

Zr-Cu Amorphous Films Prepared by Magnetron Co-sputtering Deposition of Pure Zr and Cu

ZrxCu100−x amorphous films are prepared on Si (111) substrates by magnetron co-sputtering of pure Zr and Cu. It is found that the glass forming ability (GFA) of the films increases with x when x is in the range from 35 to 65 and with the best glass forming ability at x = 65. It is therefore different from the bulk counterparts, for which only x = 35 and 50 were reported to have high glass forming ability during casting. The structure of the films is sensitive to the substrate temperature and the sputtering argon pressure.

High-Pressure Annealing Effect on Glass Transformation Temperature of Zr41Ti14Cu12.5Ni10Be22.5 Bulk Metallic Glass

Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glasses (BMG) are annealed at a temperature of 603 K under ambient and high pressures in the range of 3−6 GPa. The effect of high pressure annealing on the nanocrystallization process of compressed specimens is investigated by x-ray diffraction, differential scanning calorimetry and transmission electron microscopy. Experimental results show that the grain size of the crystalline phase decreases with the increasing pressure. For the Zr41Ti14Cu12.5Ni10Be22.5 BMG annealing at 603 K in the pressure range of 0−6 GPa, the activation energy 159.68 kJ/mol and the activation volume ΔV* = 0.94 cm3/mol are determined. The mechanism for the effects of the high pressure on the nanocrystallization process of the BMG is discussed.

Local Five-Fold Symmetry and Diffusion Behavior of Zr 64 Cu 36 Amorphous Alloy Based on Molecular Dynamics

A molecular dynamics simulation is performed to investigate the relationship between the local five-fold symmetry and the diffusion behavior involved in the rapid solidification of a Zr64Cu36 alloy melt. The Voronoi polyhedron analysis indicates that the icosahedral clusters cannot explain the total amorphous structure, while the local fivefold symmetry shows more advantage in describing the relationship between the transition of the clusters and the diffusion behavior of Zr64Cu36 amorphous alloy. It is found that when the fraction of the local five-fold symmetry is less than 0.3, the diffusion coefficient increases significantly, and when the value exceeds 0.7, diffusion behavior is inhibited. The simulation provides a new viewpoint for understanding of the glass-forming mechanism.

Effect of Sodium Dodecyl Sulphate and Sodium Bromide Additives on Ni-W Nanocoatings

Nickel-tungsten (Ni–W) coatings were fabricated by electrodeposition method with varying quantities of sodium dodecyl sulphate and sodium bromide to examine the effects of the aforesaid additives on the coatings. The obtained nanocoatings were studied by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and hardness tester. The hardness, tungsten content and grain size attained a maximum value at current density of 0.15 A/cm²,0.1 A/cm² and 0.1 A/cm², respectively. There was a pronounced impact of both the additives on the microstructure and morphology of the coatings. According to results, there are considerable difference in terms of the impact caused by the additives to the tungsten content, hardness and grain size of the coatings. The obtained results suggest that hardness of coatings is mainly contributed by W content in the deposits.

The structural, elastic, and electronic properties of ZrxNb1?xC alloys from first principle calculations

The structural, elastic, electronic, and thermodynamic properties of ZrxNb1−xC alloys are investigated using the first principles method based on the density functional theory. The results show that the structural properties of ZrxNb1−xC alloys vary continuously with the increase of Zr composition. The alloy possesses both the highest shear modulus (215 GPa) and a higher bulk modulus (294 GPa), with a Zr composition of 0.21. Meanwhile, the Zr0.21 Nb0.79C alloy shows metallic conductivity based on the analysis of the density of states. In addition, the thermodynamic stability of the designed alloys is estimated using the calculated enthalpy of mixing.

AG/SI MULTILAYERS WITH NANOMETER SIZED PARTICLES OF SILVER DURING ANNEALING PROCESS

Thein situ low angle X-ray diffraction and transmission electron microscopy were used to monitor the interdiffusion characteristics as well as the microstructure in Ag/Si multilayers with modulated wavelength 7. 64 nm when annealing from 323 to 573 K. The interdiffusion mechanism of Ag/Si multilayers with immiscibility is different from that of other metal/Si multilayers which are miscible. Phase separation takes place at 323 K, then silicon atoms diffuse into silver sublayers through silver grain boundaries and separate silver sublayers into nanometer sized silver particles gradually at higher temperature. The mean size of silver particles is about 5 nm. The activation energy and frequency factor are determined to be 0.24 eV and 2.02 x−20m2/s, respectively.