Advanced Materials Research Vol. 1088

Abstract: Isothermal crystallizations in the supercooled liquid metal metastable state at progressively increasing temperatures above the Glass Transition of the Zr44-Ti11-Cu10-Ni10-Be25 metal glass Alloy (cold crystallization attained by heating the samples from the glassy state) have been investigated in this study.Complex crystallization behaviours showing multiple exothermic peaks and selective crystallization of the alloy higher mobility atoms induced by the isothermal annealing, has been observed to lead to experimentally observed increase of the temperature needed to induce the glassy metal relaxation (glass transition). DSC dynamic investigation indicated that only two atomic species that are present in the metastable liquid are involved in recrystallization process below 450-470°C. Isothermal annealing in the range of temperatures between 400° and 450°C has been chosen for further investigation on thermal events kinetics occurring in the super-cooled liquid. The activation energies associated to the two crystallization processes are, respectively, -181 kJ/mol and-262 kJ/mol

Abstract: The liquidus temperature in the [NaF-AlF₃(30 mol.%)]-Sc₂O₃ molten system with the Sc₂O₃ additions up to 12 wt% was measured by the thermo analysis. The effect of the cathode current density (0, 0.25, 0.50, and 1.0 A∙cm^-2), the Sc₂O₃ content (1, 2, 4, and 8 wt%) in the NaF-AlF₃(30 mol.%)-Al₂O₃-Sc₂O₃ electrolyte, the rate of the molten aluminum agitation (0, 100 rotates/min), the synthesis duration (30-210 min) on the Sc content in the aluminum alloy at 980 °С was studied. The Al-Sc alloys with the scandium content of 0.15-1.30 wt%, depending on the synthesis conditions, and with the uniform Sc distribution throughout the aluminum matrix were produced.

Abstract: Microstructure evolution of a nickel-base single crystal superalloy during thermal exposure at 982°C was investigated. The SEM studies revealed that the size of γ' phase increased and some of which linked together with the elongation of the exposure time. There is acicular phase precipitation after the long-term ageing treatment. The TCP phase is not increased by the increment of ageing time after reaching a certain amount. There are skeleton shape carbides precipitate after 100h and 300h. The amount of precipitated carbides decreases by the elongation of ageing time.

Abstract: The Microstructure and mechanical properties of as-cast and as-extruded Mg-12Gd-2Er-1Zn-0.6Zr alloy are investigated in the present paper. The microstructure is analyzed by OM, SEM and TEM with SAED, and the mechanical properties are valued by the room temperature tensile test. The result shows that the coarse Mg5(Gd, Er, Zn) phase in the as-cast alloy was broken during hot extrusion process, and it was distributed at the grain boundary along the extrusion direction. The enhancement in mechanical properties of the extruded alloy is mainly ascribed to the refinement of these grains. The sizes of dynamical recrystallized grains are homogeneously, which was about 7 μm. Stacking fault existed in the as-cast alloy, which has a little effect on the dynamic recrystallization because of its tiny thicknesses.

Abstract: The microstructure and compressive behaviors of the Mg-Zn-Er alloy reinforced by I-phase were investigated. The XRD results suggested that the as-cast alloy was composed of -Mg and I-phase. During compress test, the deformation mechanism was depended on the test temperature and strain. It indicated that basal plane slip played an important role in deformation at both low and high temperature. However, the main deformation mechanism of the as-cast alloy includes grain boundary sliding and twins forming at the strain of 20% at a moderate temperature (225oC) besides the basal plane slip. Moreover, the DRX occurred at the moderate temperature after the strain of 50%. At high temperature (more than 300oC), the cavity was present, and the volume fraction of the cavities increases with the temperature increasing. At the high temperature, the deformation mechanism of the as-cast alloy is mainly dislocation sliding and climbing.

Abstract: Aluminum cables are playing an increasingly important role in power transmission system, in which the “rare-earth high-iron aluminum alloy power cables were developed in China. In this paper, the effects of B on grain refinement of high-iron aluminum alloy were studied by using OM (optical microscopy), SEM (scanning electron microscopy), EDX (energy dispersive X-Ray spectroscopy) and XRD (X-ray diffraction). And the conductivity of high-iron aluminum alloy was also tested. The results showed that B could take significant effects on grain refinement and promote the increase of conductivity. The refinement may be mainly due to the eutectic reaction in solidification process and the formation of AlB₂ particles. The optimal concentration of B was determined as 0.06 wt. %.

Abstract: Numerical simulations based on a new regularized phase field model were presented, simulating the solidification of magnesium alloy. The effects of weak and strong interfacial energy anisotropy on the dendrite growth are studied. The results indicate that with weak interfacial energy anisotropy, the entire dendrite displays six-fold symmetry and no secondary branch appeared. Under strong interfacial energy anisotropy conditions, corners form on both the main stem and the tips of the side branches of the dendrites, the entire facet dendrite displays six-fold symmetry. As the solidification time increases, the tip temperature and velocity of the dendrite and facet dendrite finally tend to stable values. The stable velocity of the facet dendrite is 0.4 at ε₆ is 0.05 and this velocity is twice that observed (0.2) at ε₆ is 0.005.

Abstract: To increase the industrial applicability of hypereutectic Al-Si alloys, various methods have been used to refine primary silicon. The addition and refinement effects of phosphorus (P), rare earth metals (RE) on primary Si have been studied widely, But they have been testified be with some disadvantages, that is, the pollution to the environment of P and the high cost of RE, etc. Now, a new refiner - ZnS and the corresponding processing technology were researched. Microstructures of hypereutectic Al-Si alloy (Si wt. 24%) with fine primary Si were successfully obtained. And the primary Si can be refined from more than 80μm to 20μm. And the distribution of primary silicon is getting more uniform.

Abstract: The possibilities of forming submicroporous and nanoporous structures in metallic materials by laser thermocycling as eutecticis reached were determined. With the implementation of the selected modes of laser treatment on L62 brass samples with a thickness of 50 µm leads to the formation of wrinkled relief, which indicates an increment of alloy volume in this area, that is, a porosity increment in the metallic material. Submicroporous and nanoporous structures are formed in the copper-zinc L62 alloy sample, which appear on the surface of the sample. Nanopores have a shape similar to equiaxial. Submicropores are formed as a result of nanopores merger. A relief is formed on the surface consisting of depressions having a shape similar to that of a hemisphere and a linear structure, oriented along the direction of rolling process.

Abstract: A multilayer intermetallic coating on low-carbon steel was obtained during aluminum electrodeposition in NaF-KF-AlF₃ melt at 920 °C. The current density effect on morphology and intermetallic layer composition was investigated. Electrolytically aluminized steel samples represented a good oxidation resistance at 900 °C.