Papers by Keyword: Al-Li Alloy

Abstract: Solid-state Al−Li/NaBH₄ mixtures with salts have been fabricated for hydrogen evolution through a milling process, providing uniform dispersion of metals Al, Li and salts among pulverized NaBH₄ particles, in order to increase the contacts of NaBH4 with active catalytic sites. The results show that the mixture has good hydrolysis properties, especially that Al−Li−CoCl₂/NaBH₄ mixture has hydrogen yield of 1482 mL g^-1 in 40−minute hydrolysis in pure water, with 100% conversion efficiency. The catalytic effect comes from Al(OH)₃ and Ni₂B or Co₂B, which were fabricated in the hydrolysis process.

Abstract: At 953K, anodic over voltage by electrolyzing LiCl and Li₂CO₃ were measured respectively by continuous pulse oscillograph method in a mixture fused salt of LiCl-LiF in a laboratory electrolyte cell and the change of polarization curve obtained was studied as well. According to kinetics of electrode process theory, we calculated and analyzed anode reaction mechanism and reaction rate-determining step. The results indicate that when over voltage entered into the Tafel zone with current density in range of 0.1 to 0.3A·cm^-2, electrode reaction of LiCl is controlled by electrochemical polarization but electrode reaction of Li₂CO₃ is controlled by chemical polarization. With current density increase further beyond the Tafel zone (i>0.4A·cm^-2), electrode reaction is changing gradually from dual control influenced by electrochemistry or chemistry united with concentration polarization to single concentration polarization. While electrolyzing Li₂CO₃, it is complexing oxygen ions discharging on carbon anode slowly that determine the whole electrode reaction rate.

Abstract: Third generation Al-Li alloy 2195 and 2198 were studied. The material properties of these two Al-Li alloy were compared with traditional alloy 2024; damage tolerance properties was tested and compared with 2024 as well. Microstructure of parent material and welded sample was studied and compared. Crack growth rate was tested and compared. Some conclusions were drawn: Al-Li alloy had a great strength and damage tolerance; local inhomogeneities microstructure in welded samples, which created the difference of damage tolerance and the tendency of crack growth rate in welded samples.

Abstract: A three-dimensional model which takes into account Marangoni shear stress, buoyancy force, and electromagnetic force in the laser-plasma hybrid welding pool is presented. Distribution of velocity and temperature in welding pool are calculated by finite volume method (FVM). Numerical analysis shows that the Marangoni shear stress determines flow pattern and the electromagnetic force can widen bottom surface of welding pool. The simulation results agree well with corresponding experimental results.

Abstract: A three dimensional heat transfer model on laser-plasma hybrid welding has been proposed, that takes into account the interaction between laser beam and plasma arc. Through FEM computation, the temperature fields were computed and analyzed for an Al-Li alloy during laserplasma hybrid welding with different distances between the two heat sources. The simulation results are in agreement with the experimental results.

Abstract: Aluminum-Lithium alloys were developed as major replacements for existing aluminum alloys to reduce the weight of aircraft and aerospace structures. Mechanical properties of Al-Li alloys greatly depend on solidification conditions. Other than reducing the microsegregation, homogenization treatment has other effects on the microstructure of Al-Li ingots. In this research, effects of homogenization treatment at constant temperature (500°C) on the precipitation in the microstructure of Al-1Li-3Cu-0.1Zr (wt %) and Al-2Li-3Cu- 0.1Zr (wt %) specimens have been investigated. Results show that homogenization at 500°C for 24 hours not only increases the hardness and phases precipitating in grain but also reduces microsegregation of Fe in grain boundaries.

Abstract: Surface alloying is a new method of surface treatment by which an element is diffused into the surface of another element causing the formation of a solid solution on its surface. Using this method, the problems of casting methods have been eliminated. In this method, the sample is sunk into an aqueous solution and is connected to the cathode. Applying enough voltage, lithium separated from lithium sulphat-sulfuric acid solution diffuses into the aluminum surface. The depth of diffusion into the aluminum is measured to be 50 to 500μm according to the diffusion time which is selected to be 1 to 24 hours. Experiments showed that the formed layer is very uniform. It was also concluded from the experiments that hardness is increased extensively, with the maximum value of 98HV, and fatigue life is increased by the factor 4. It was also shown that the toughness, yield stress and ultimate tensile strength of samples are the same as those of pure aluminum.

Abstract: To respond the need of industries to the new materials with higher specific modulus and lower density than those of the older Al alloys, aluminum- lithium alloys have been invented and improved. Aging process is one of the most important methods to improve the mechanical properties of aluminum- lithium alloys which are in the heat treatable category of aluminum alloys. Low temperature and natural aging processes cause the "short range diffusion" of Cu atoms in the aluminum and the formation of the GP zones. In this research, stability of GP zones and the effects of these areas on physical and mechanical properties of AA2090 alloy were investigated by hardness, electrical resistance, DSC (differential scanning calorimetric) and tensile tests. Results show that endothermic effect in the DSC diagrams of AA2090 alloy at 180°C to 240°C can be related to the enthalpy of GP zones dissolution. Formation of GP zones in the structure increases hardness, tensile strength and electrical resistance of Al- Li C u (2090) alloys.

Abstract: The influence of aging process on microstructures and mechanical properties of a rapid solidification Aluminum-Lithium alloy has been analyzed in this paper. The results show that the better aging process is as follows: heating to 170oC for 4 hours and then followed by a final aging at about 190 oC for 18 hours. A lot of fine participated second phase such as δ′ in matrix and a narrow participation free band make alloy’s good performance.

Abstract: By the test of Al-Li-Cu-Mg-Zr Alloy’s mechanical property and microstructure in various kinds of extrusion technology, the effect of extrusion processing parameter on the structure and property of the alloy was analyzed, and the parameter’s range for obtaining proper compromise of strength and toughness was discussed.