Dissolution Of Alloying Elements Research Articles

Tailoring degradation of MgZn alloy films with bioinert amorphous carbon

MgZn based amorphous alloy films were composited with diamond-like carbon (DLC) in sputter deposition to tailor their degradation and the related biological properties. Structural and compositional analyses indicate that all the films are amorphous, but the films with intermediate MgZn:C ratio exhibit nanoparticles at surface, cracks, peeling off and electric insulation. Metal carbides are possibly formed during film deposition, and the surface layer is then converted to oxides, hydroxides and carbonates during the ageing in air. After immersion in the simulated body fluid for 2 days, apatite and Mg compounds layer is formed on the alloy and the composite films. Although Cl- ions and microgavlanic coupling can accelerate dissolution of the alloy, the carbon phase effectively delays dissolution of the alloy. The films have good antibacterial activity against E. coli, which comes from the released Mg2+ and Zn2+ ions. The MC3T3-E1 cell test shows that the film with metal elements content of 22.6 at% has the highest alkaline phosphatase activity among the tested samples. The suppressed and lasting dissolution of alloy elements is beneficial for antibacterial activity and osteoblast cell behaviors of the MgZn alloy-DLC films.

Experimental study on corrosion-erosion behavior of ITER blanket structure materials in flowing Pb-17Li

Abstract A rotating corrosion test device has been developed to study the compatibility between liquid tritium breeder material and structure materials for fusion facility. The corrosion behaviors of three samples made of reduced activation ferritic/martensitic steel (RAFMS), 316 L stainless steel and oxide dispersion strengthened steel (ODS), are studied in liquid Pb-17Li at 500℃ for an exposure of 1000 h. The weight changes of the specimens are obtained before and after test. The analyses of surface morphology and component are characterized by SEM, EDS and XRD methods. Results show that weight-loss rate of RAFMS is lower than that of 316 L and ODS in the experiment. It indicates that the corrosion mechanism is governed by some or all dissolution of alloy elements (such as Cr, Ni) from the sample surface into liquid Pb-17Li and the exfoliation from the corroded surface by the flowing Pb-17Li. Specifically, the dispersed Al2O3 particles in ODS is easy to be corroded in liquid Pb-17Li and then provide corrosion points to accelerate dissolution of Ni-Fe austenite. The compatibility of RAFMS with liquid Pb-17Li is slightly better than that of 316 L and ODS in the current experimental period.

Dissolution energetics and its strain dependence of transition metal alloying elements in tungsten

We have systematically investigated the dissolution energetics of all 3d–5d transition metal alloying elements (AEs) in tungsten (W) using a first-principles method. It is found that Ti is the easiest one to dissolve with the solution energy of −0.81eV in the intrinsic bulk W, while La is the most difficult one with the solution energy as large as 3.91eV. The d-electrons play a determining role in the dissolution of AEs in W. We have demonstrated that the solution energies of AEs is a linear monotonic function of strain. The binding energy results indicate that the interaction between AEs is repulsive for the early elements and then becomes attractive for the late elements in each series. This study provides a good reference for developing W materials as a plasma facing material.

Research on Dehydrogenation and Sintering Process of Titanium Hydride for Manufacture Titanium and Titanium Alloy

In this paper, unlike the traditional powder metallurgy technology, the titanium hydride is directly used as the starting material to manufacture the titanium and titanium alloy. Thermogravimetric and dilatometric techniques are performed to study the dehydrogenation and shrinkage of TiH2 powders with different particle sizes. The process factors such as the sintering temperature, the sintering time, the heating rate, the compaction density, the compaction methods, and the alloy system, would affect the sintering densification of TiH2 powders and TiH2-Al-V alloy powder. The results shown that the dehydrogenation temperature of the starting and ending of the ball milling TiH2 is lower than that of the coarse TiH2 powders, the finer the TiH2 powder, the lower the temperature. The densification of TiH2 powders is easy due to the combination of dehydrogenation and shrinkage of α-Ti in one process, which creates the fresh dehydrided titanium uniform during sintering, thus leads to rapid densification and very high sintering relative density, higher than 99%. In contrast, it is difficult to achieve a full densification of TiH2-Al-V alloy powder during sintering, which requires dissolution of alloy elements during sintering above its beta transformation temperature. The sintered microstructure of Ti-6Al-4V shows the typical lamellar shaped α+β characteristics, with a uniform alloy element distribution.

Microstructure modifications and corrosion behaviors of Cr4Mo4V steel treated by high current pulsed electron beam

In this work, Cr4Mo4V steel was irradiated by high energy current pulsed electron beam (HCPEB) with energy density of 6 J/cm 2. Morphology and phase composition of the surface layer were analyzed using scanning electron microscopy (SEM) and glancing angle X-ray diffraction (GXRD). The crater-like morphology was observed on surface after HCPEB treatment, and the thickness of melted layer was ∼7 μm. Results from GXRD revealed that HCPEB treatment could suppress martensite transition and the content of retained austenite in the melted layer increased with irradiation number. The corrosion resistance was evaluated by electrochemical polarization tests in neutral 3.5% NaCl solution. Compared with the untreated Cr4Mo4V steel, corrosion potential of the samples treated by HCPEB improved and the corrosion current density decreased. The improved corrosion resistance is attributed to the absence of the carbide, formation of retained austenite and dissolution of alloy elements, particularly of Cr and Mo, into the matrix.