Papers by Keyword: Spray Deposition

Abstract: In this study, Al-8.6Zn-2.6Mg-2.2Cu (wt,%) alloy was synthesized by the spray atomization and deposition technique. Electron beam welding (EBW) joint in the spray-deposited Al-8.6Zn-2.6Mg-2.2Cu alloy is composed of fusion zone, heat affected zone and base metal region. The microstructure of the fusion zone has been found to be very fine equiaxed grains, and the microstructure of the heat affected zone is mainly composed of α-Al and Al/MgZn2 eutectic microstructure. Extensive microhardness measurements were conducted in the weld regions of the nuggets exhibited a hardness loss in the fusion zone due to the loss of strengthening phases. Tensile properties test results indicated that tensile strength of these welds approached 82.3~85.3% of the base metal. The analysis of fracture surface has confirmed that the specimen fractured within the weld region during tensile test.

Abstract: This paper described the effect of hollow jet atomization technology, under charge action, according to the spray forming process, to improve the quality of atomization. In order to deeply study the charge action on the annular molten metal of spray forming process, this paper analyzed theoretically quantity of electric charge of the annular molten metal and the surface tension of atomization droplets. The results show that the quantity of electric charge increases with the increasing of charging voltage. Under the same conditions, the hollow annular metal liquid charge is always greater than the solid cylindrical molten metal charge, but the surface tension is less than the solid molten metal. As the quantity of electric charge reduce the surface tension of the droplet, the power of atomization increases relatively. It means that the atomization quality of annular molten metal will be better than the solid cylindrical molten metal. By comparison, the structure under charge action is fine and homogeneous after experiment.

Abstract: The Al-Zn-Mg-Cu (7A04) alloys were prepared by using the method of spraying deposition and the hot extrusion. The effects of two-stage solid solution treatment and single solid solution treatment on the microstructure and mechanical properties of spray deposited 7A04 alloy were investigated. The microstructure and mechanical properties were observed and tested by optical microscopy, SEM, X-ray diffraction and other methods. It is indicated that the two-stage solid solution treatment is better than the single. After the two-stage solid solution, the sizes of recrystallization grains were small and a lot of precipitations were dissolved. And the microstructure was nice by ageing treatment. The tensile strength and elongation of the alloy can respectively reach 740MPa and 5.8 percent by the two-stage solid solution (at 450°C for 1 hour and 475°C for 2 hours) and the aging treatment.

Abstract: _{Subscript text} Nd can obviously improve the mechanical properties of spray deposited 1%Nd, 2%Nd extruded and heat treatment alloy. Nd solid solution in α-Mg matrix lead to the hardness of 2%Nd spray deposited magnesium alloy extruded is higher than that of after heat treatment. A large number of Al₂Nd particles precipitation is the key factor to the highest hardness value(139.4Hv) in 2%Nd magnesium alloy after 370°C/3h+205°C/24h heat treatment. Moreover, the precipitation of Al₂Nd accompany with Al₂Ca and Al-Mn phase increased.

Abstract: In this paper, preparation of large spray deposited aluminum alloy tube was investigated. The shape and particle size distribution of over-sprayed powders together with structure of deposits were analyzed. The results show that the over-sprayed powders resulted from particles missing, spurting and rebounding. The particle size distribution was non-standard normal distribution, the particle size of the great majority was within 150μm and the average size was 50μm. The residual pores in deposits came into being when inter-particle space could not be filled with enough liquid during spray deposition. The as-deposited preform with rough surface was a coalesced bulk of deposited particles. The rotate speed of substrate and scan speed of atomizer together with spray stripe width should satisfy any certain relationship to obtain a qualified tube preform. Substrate preheating and surface treatment and residual stress control were very important for preparing a large preform.

Abstract: In this study, Zn-30Al-1Cu alloy was synthesized by the spray atomization and deposition technique. The microstructure and mechanical properties of the alloy were studied using optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction and tensile tests. It can be seen that the microstructure of spray-deposited Zn-30Al-1Cu alloy is composed of the Zn/Al eutectoids and few compounds. The Zn/Al eutectoids were shown lamellar, particle and Chinese script morphologies. The compound phases in the microstructure of the spray-deposited alloy were examined. The property test results indicate that the spray-deposited Zn-30Al-1Cu alloy displays superior tensile strength.

Abstract: Microstructure and mechanical properties of W9Mo3Cr4V high speed steel fabricated by spray deposition have been studied. Spray deposited W9Mo3Cr4V high speed steel has a typical equiaxed structure which is finer and more homogeneous with a grain size of 20-30 micrometer compared with conventional casted counterparts. There are pores in the matrix of the deposited steel, which involve gas porosity, filling porosity and solidification shrinkage. As-deposited high speed steel is mainly composed of martensite, austenite and carbides which comprise MC carbide and M₆C carbide. Mechanical properties show that the hardness and bending strength of the as-deposited steel are higher than that of the conventionally casted ones. However, impact toughness of the high speed steel is lower than that of the conventionally casted steel, which can be attributed to the existence of porosities and M₆C carbides which reduce the impact toughness of high speed steels.

Abstract: To study the ignition-proof behavior in the spray deposited magnesium alloy with nitrogen as atomizing gas, SEM and XRD were employed to study the morphology and elements profile of nitride film formed on the Mg-5Ca alloy melt in different conditions, and the ignition proof principle was also analyzed preliminarily. The results indicated that under ordinary nitrogen (99.5%), a layer of smooth and continuous nitride film was formed on the surface of Mg-5Ca alloy after sintered at 740°C for 2 hours, and with the increasing of temperature and holding time, small cracks and cavities appeared locally on the surface film. The surface film was mainly composed of CaO、MgO、Ca₃N₂ and Mg₃N₂.The profile analysis of the nitride film indicated that Ca element collected on the surface of the nitride film, and a multiple film was formed which filled the loose and holes of single film, avoided the burning of Mg alloy during spray forming process.

Abstract: Magnesium alloy of 6% Ca and 9% Ca, produced by spray deposited method, was heat treated at different solid-solution and the same aging treatment. The microstructure and hardness were analyzed by SEM, XRD and HV tester. The experimental results showed that Ca can make the spray deposited magnesium matrix grains refine uniformly, the second phase particle Al₂Ca and CaZn are formed and the hardness value increase. With the rise of solution temperature, the hardness of 6%Ca and 9%Ca magnesium alloy rise firstly and then fall, and the hardness value of 6%Ca increase to the highest 121Hv and 9%Ca increase to the highest 128Hv after 370°C/3h+205°C/24h.

Abstract: Al-8.5Fe-1.3V-1.7Si/SiCP composite prepared by multi-layer spray deposition in different states were investigated. Ultimate tensile strengths of the composite sheets as-rolled tested at 315°C and 400°C are up to 300MPa and 186MPa respectively. The fine dispersoids and fine grains, and homogeneous SiC particles contribute to the excellent mechanical properties of the composite at elevated temperature. Specially, partial dissolution of SiC particles contributes to the stability of Al12(Fe,V)3Si phase.