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The isothermal compression tests were performed over the ranges of temperatures 820∼1060 °C and strain rates 0.001∼1 s −1 on a Gleeble-3800 simulator. The constitutive equation of Ti-6Al-3Nb-2Zr-1Mo alloy has been established to describe the changing rule of flow stress with the strain rate and deformation temperature. The apparent activation energies have been calculated to be 764.71 kJ/mol in the dual phase region and 126.94 kJ/mol in the single phase region. The processing maps have been constructed based on the dynamic material model (DMM) and the Prasad's instability criterion at strains of 0.4 and 0.7. The maps exhibit a stable domain in the temperature range of 840∼1060 °C and strain rate range of 0.001∼0.1 s −1 with two peaks in power dissipation of 51%, occurring at 940 °C/0.001 s −1 and 880 °C/1 s −1 , respectively. The high efficiency values of power dissipation indicate dynamic recrystallization (DRX)/globalization in these fields. Based on the constructed processing maps, the optimal hot processing window of this alloy corresponds to the temperature range of 840∼1060 °C and the low strain rate range of 0.001∼0.1 s −1 . The microstructures of the specimens deformed at different conditions were analyzed and connected with the processing map. It is found that in processing of the alloy at 820 °C and a higher strain rate (≥1 s −1 ) an instability deformation will take place easily.

We investigated the effect of counterface of ZrO2, Si3N4 and SiC ceramics on the tribological behavior of 1Cr18Ni9Ti steel in 90% hydrogen peroxide solution. The results show that the tribological properties of 1Cr18Ni9Ti steel are strongly dependent on the counterfaces. The adhesion behavior affects the tribocouple of 1Cr18Ni9Ti/ZrO2, leading to a high coefficient of friction (COF) fluctuating from 0.17 to 0.27 and the highest wear loss of 1Cr18Ni9Ti steel. The oxidation and hydrolysis protect the worn surface of 1Cr18Ni9Ti/SiC, inducing a low COF 0.035 and the lowest wear loss of 1Cr18Ni9Ti steel. Both the adhesion behavior and the reactions play important roles in the wear behavior of 1Cr18Ni9Ti/Si3N4, leading to a complex COF and intermediate wear loss of 1Cr18Ni9Ti steel. As for the counterparts, ZrO2 ceramic shows the most severe wear, SiC ceramic shows relatively low wear volume, and Si3N4 ceramic presents the lowest wear volume.

The microstructure evolution of titanium alloy is decided by deformation degree in cold-deformation process, and substructures resulting from different cold deformations significantly influence phase transformation behavior in isothermal aging treatment. The microstructure evolution in cold-deformation and the followed aging behavior of TB8 alloy were investigated by X-ray diffraction (XRD), Vickers hardness (HV), field emission scanning electron microscope (FESEM) and differential scanning calorimeter (DSC). Results show that the high value of FWHM results from the combination of the grain distortion and dislocations, and the enhancement of the distortion and dislocations is accompanied by increasing of HV value. The phase transformation of the present investigation exhibits the effect of cold-deformation on transformation behavior of α phase precipitation in the β matrix. It is suggested that there is a distinctive behavior in the aging transformation of cold-deformed titanium alloy.

The effect of annealing temperature on the microstructure evolution of Zr 48 Cu 36 Ag 8 Al 8 bulk metallic glass was investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). Results show that the as-cast Zr 48 Cu 36 Ag 8 Al 8 alloy by rapid solidi?cation exhibits a typical characteristic of an amorphous structure. After annealed at 703 K for 20 min, a homogeneous amorphous matrix is separated into two different glassy phases, namely, phase separation occurs. Because phase separation structure will compete with the amorphous matrix during isothermal annealing, this structure is easily decomposed and transformed into the crystalline phases AlZr 2 and AlAg 3 with annealing temperature increasing. The microstructure of Zr 48 Cu 36 Ag 8 Al 8 bulk metallic glass undergoes the local structure transformation, phase separation and nano-crystallization transformation during heat treatment in the supercooled liquid region, which implies that the microstructure of Zr 48 Cu 36 Ag 8 Al 8 bulk metallic glass is sensitive to the annealing temperature. In addition, the formation of phase separation will accelerate the formation of nano-crystals.

A multiscale three-dimensional (3D) mathematical model has been established for simulating the temperature field, the fluid flow and the solidification structure of Ti-6Al-4V alloy ingot during vacuum arc remelting (VAR) process, which consists of the macroscopic mass, the momentum and energy conservation equations and the macroscale model of the nucleation and growth of grains. On the basis of heat transfer and fluid flow calculation, the 3D solidification structure formation of the ingot during whole VAR process has been obtained. Comparing the simulation result with the experimental observation, a reasonably qualitative agreement is achieved on grain structure and grain growth pattern. In particular, when taking the heat radiation into consideration during the calculation, the columnar grains on the ingot top are predicted well. Furthermore, a sensitivity study of the effect of natural convection on the grain structure has been carried out. The results show that the natural convection has a great influence on columnar-to-equiaxed transition (CET) and grain size, expressing as promoting the CET and refining the grain.

Four groups of transmission electron microscopy (TEM) specimens of Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 metallic glass were prepared by double-jet electropolishing, dimpling and ion milling. TEM observations indicate that the microstructures in electron-transparent areas change sensitively with ion milling conditions. Detailed comparisons between the selected area electron diffraction patterns of TEM specimens and the X-ray diffraction patterns of thermally annealed samples of the same composition show that significant heating effects exist in some severe milling processes, resulting in the formation of various ordered structures in thin areas. In TEM specimens prepared by intentionally long time ion milling, the peak temperature locally reached is estimated as high as 780 K, far above the glass transition temperature of this metallic glass. The results suggest that precautions must be taken to prepare TEM specimens of amorphous alloys by ion milling, particularly when the induced microstructure changes may lead to invalid judgments.

Top-seeded power melting process (TSPMP) is an effective melting processing technique for the preparation of high J c bulk YBCO. The directional solidification is also a quite common technique used to produce well-oriented cylinder grains. The two processes were combined (named Directional Top-Seeded Power melting Process, DTSPMP) to fabricate good YBCO bulk with well-oriented domains. The seed transferring effect and the change of the solute concentration in liquid were analyzed. The effects of temperature gradient (TG) on the orientation and continuous growth of large grains were also investigated. The microstructure dependence on pulling rate was analyzed through scanning electric microscopy(SEM), and it is found that the large domains can be obtained and the fine dispersive 211 particles are entrapped at a slower pulling rate.