Papers by Keyword: Spray Forming

Abstract: Porosity, hardness and microstructural studies of cold rolled spray cast Al-6Si-20Pb alloy for different percentage of thickness reduction were conducted from top to bottom and from centre to periphery of the deposit. Porosity was found to decrease and hardness was found to increase with the increase in percentage of thickness reduction. Aluminum grains were observed to become coarser with the increase in percentage of thickness reduction.

Abstract: In order to improve the atomization quality of spray forming, the cylindrical hollow jet technology was applied in the atomization process of spray forming, and a numerical simulation for the structure of hollow flow field in front of jet outlet was carried out, the distribution of hollow jet flow field was simulated under different inlet velocities and outflow technologies, and then the experimental verification was performed. The simulation results of single-phase flow field show that with increasing the liquid inlet velocity, the back flow are a can get enlarged, and the lower negative pressure can be generated, which is beneficial for the out flow of liquid metal. The simulation results of two-phase flow field show that the hollow jet can be produced a hollow part. The conclusion basically accords with the experimental result of water flow.

Abstract: The Al-Zn-Mg-Cu (7A04) alloys were prepared by using the method of spraying forming and the hot extrusion. The changes of microstructure and mechanical properties of the spray deposited Al-Zn-Mg-Cu alloy underwent ageing, regression and reageing treatment (RRA) was studied by scanning electron microscopy, X-ray diffraction and other methods. The results show that the tensile strength of the alloy aged at 120°C for 24 hours can reach the peak value (760MPa), but the elongation is only 4.8 percent. The toughness of the alloy regression treated at 160°C for 2 hours can increase to 9.0 percent, but its tensile strength decreases greatly (680MPa). The reaging treatment at 120°C can make the tensile strength up to 740MPa, while the elongation which is 8.2 percent still keeps a higher level.

Abstract: Abstract: Spray forming UHCS-1.6Al material has a refined equiaxed pearlitic structure, which was necessary for high-train-rate superplasticity. During deformation, the cementite particles pin the grain boundaries and prevent the grains growing up. As a result it exhibited excellent high-strain-rate superplasticity, with a peak ductility of 187% occurring at a strain rate of 5*10-3s-1.

Abstract: To analysis the microstructure and properties of super-high strength Al-Zn-Mg-Cu alloys containing Zr ,Ni and Mn, the apparatus of SEM、TEM、and Tensile machine was used. The results show that the microstructure was fine and homogeneous, the phases became finer for the alloys with adding Zr, Mn, Ni than the alloy with Zr only after solid solution. The ultimate tensile strength of the alloy was 850MPa and the elongation was 5% respectively at peak aging.

Abstract: The M3 type high speed steel billets with / without Nb addition were prepared via spray forming. The effects of cooling rate and Nb on the microstructures and property of the M3 type high speed steel were investigated. The results show that the as-cast steels contain coarse primary dendrites and M₂C eutectic carbide, but the equiaxed grains and fine carbides are formed in the spray-formed steels. It can be seen that carbide precipitation and grain growth were suppressed by high cooling rate. The Nb additions can change the types of primary carbides. The solidified carbide microstructure was effectively changed from M₂C to M₆C type during the cooling of hot spray-formed billet. Niobium improves the microstructural thermostability of the M3 type high speed steel during heat treatments.

Abstract: Low cycle fatigue behavior of spray formed superalloy GH738 at 650°C has been investigated under fully reversed total strain-controlled mode. When strain amplitude (Δε_t/2) is between 0.32% and 0.4%, cyclic stress response is stable under fully reversed constant total strain amplitude. The stabilized hysteresis loops narrowing sharply to a straight line indicates that the alloy exhibits typical elastic strain. The crack initiates single site from the surface. When strain amplitude is between 0.6% and 1.0%, cyclic hardening is observed until fracture. The tendency for hardening is found to increase with strain amplitude. The hyperesis loops expand gradually, which indicates that plastic deformation happens during cyclic deformation process. The crack initiates multi-sites from the surface. The cyclic strain-stress relationship of spray formed GH738 at 650°C can be illustrated by Δσ/2 =2017(Δε_p/2)0.1489.The total strain-life function can expressed by Δε_t/2=0.0071(2N_f) _-0.0781 +0.0647(2N_f) ) _-0.4914.

Abstract: The Mg-9Al-3Zn-0.6Mn-xNd alloys, preformed with φ300mm size, has been prepared by spray forming technology under a protective atmosphere. The microstructure and mechanical properties have been investigated by XRD, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and strengths tested mechine. As a result, the precipitate phases in the alloys were the finest when the Nd content was 1% compared the alloys with the Nd content were 2% and 3%, the size of precipitation phases are between 1-2um and there are phases like Mg₂Ca，Al₂Ca，and MgZn₂ in the alloys. After extrusion, recrystallization microstructures were found in the alloys. The tensile strengths are between 400-450MPa and the yield strengths are between 350-370MPa respectively as the differences content of Nd in the alloys after heat treatment.

Abstract: FGH95 superalloy cylindrical billet was prepared by spray forming, The yield is 73.6%, porosity is 0.6%, the oxygen content is only 20ppm. Spray forming preparation method and technological parameter were illustrated. The microstructure on the different positions of billet were observed. The results show that the difference of γ′ phase size, feature and distribution depend on different cooling velocity and local temperature difference during the spray forming process. SEM of nonmetallic inclusions were observed, and XPS of nonmetallic inclusions, nozzle and adhesive were analysed, the results show that the nonmetallic inclusions were from nozzle and adhesive.

Abstract: CPM9V high speed steel(HSS) ring billet was prepared by spray forming(SF), the yield is 83.5%, porosity is 0.8%, spray forming preparation method and technological parameter were illustrated. The microstructure and carbide morphology on the different position of billet were observed. The results show that carbide particles have small size, regular shape and uniform distribution, alloy element without segregation. There are some pores and defects in the position of ring billet closed to deposition substrate, come from spray forming instability beginning stage.