Papers by Keyword: A356 Aluminum Alloy

Abstract: Based on the theory of grain refinement, the microstructures and simulations of A356 semi-solid aluminum alloy under different cooling mediums were studied. The experiment and simulation results show that water cooling is better than any other cooling mediums. Combined with the simulation of stirring and heat dissipation in SIT device, the changes of temperature field and solid fraction of the melt were studied to help understand the nucleation, growth and solidification behavior under the SIT process. During the process, the temperature field of the melt becomes relatively uniform from a larger temperature gradient and the continuous cooling speed is increased. The results also indicate that compared with traditional casting, the microstructure cooled by water are composed of refined rosiness and nearly spherical particles. With the increase of cooling degree, the average grain size decreased from 206μm to 186μm. The solid fraction increases from 4.4% to 12.2% under the no-cooling and air-cooling conditions, while it is more uniform, increasing from 5.1% to 8.8% due to the water cooling.

Abstract: One of the main reasons for the scrap of cast thin-wall frame aluminum alloy castings is deformation and cracking. It is an effective method for solving the problem by predicting the distribution of casting stress, clarifying the size of the deformation and the location of the crack, and taking necessary measures in the process. This paper uses the ProCAST software to simulate the thermal stress coupling of A356 thin-walled frame castings, analyzes the influence of pouring temperature, pouring speed and mold temperature on the stress field distribution of castings, predicts the hot cracking trend and deformation, and optimizes Casting process..

Abstract: To obtain an A356 aluminum alloy casting with a uniform structure and no internal shrinkage defects, ProCAST software is used to set different filling and solidification process parameters for an A356 aluminum alloy casting with large wall thickness differences, And multiple simulations are conducted to obtain optimized casting process; then, based on the process, the microstructure of the thickest and thinnest part of the casting are simulated. The size, morphology, and distribution of the simulated microstructure of the thinnest part and the thickest part of the casting are very similar. The simulated microstructure is similar to that of the actual casting. This shows that castings with uniform structure and no internal shrinkage defects can be obtained through the optimized casting process .

Abstract: A356 aluminum alloy was modified by Al-Sr master alloy, and the eutectic silicon phase was changed from long needle to short fiber. Compared with the untreated, the secondary dendrite spacing decreased by 14.37 %, the tensile strength increased by 13.0 MPa, and the elongation increased by 29.51 %. After modification treatment, more developed secondary dendrites and block inclusions can be seen in the tensile fracture of A356 alloy, which is not conducive to the plasticity and fatigue resistance of the alloy.

Abstract: Fatigue behavior of A356 aluminum alloy for motorcycle rim was experimentally investigated based on T6 heat treatment and artificial aging. The high speed of 1,100 rpm from centrifugal casting was used in this study. The pouring temperature at 750 °C was employed and the preheated temperature at 250 °C was applied on the mold. The solution heat treatment of the sample was conducted for 4 hours at 540 ^o C before it immersed into the water for rapid cooling at room temperature. This step followed by natural aging treatment at 30 °C and artificial aging treatment at 150 °C, 175 °C, and 200 °C for 2 hours, respectively. It is found that increasing centrifugal casting speed into 1,100 rpm combined with heat treatment and artificial aging temperature can significantly increase not only its mechanical properties but also the fatigue life of motorcycle wheel made of A356 aluminum alloy. This experiment proved that the lowest fatigue crack growth rate obtained with this method was at temperature of 175°C.

Abstract: In this study, A356 aluminum alloy was heated up to semi-solid state and used as a billet for forward and backward extrusion. The workpiece will undergo solidification at the contact between billet and the tools when the material flowing through the die cavity during the semi-solid extrusion. The plasticity of A356 with 0.3wt% Y at semi-solid state was investigated by performing compression test. A numerical simulation code based on thermo-viscoplastic finite element method was developed to simulate the material flow and study the yttrium-modified A356 aluminum alloy under forward and backward extrusion. A minimum average punch strain rate is proposed for semi-solid extrusion.

Abstract: The objective of this study is to investigate the effects of activating fluxes on the weld bead geometry, hot cracking susceptibility and mechanical property of A356 and 6061 aluminum alloy dissimilar welds in the gas metal arc (GMA) welding process. In this activated GMA welding process, there were nine single-component fluxes used in the initial experiment to evaluate the penetration capability of butt-joint GMA welds. The grey relational analysis (GRA) was employed to obtain the better weld bead geometry of welds that were considered with multiple quality characteristics. Based on higher grey relational grade (GRG), four single-component fluxes were selected to create mixed-component flux in the next stage. The experimental results showed that the GMA welds coated with activating flux were provided with better geometry of dissimilar welds. The experimental procedure of activated GMA welding process not only produced a significant increase in tensile strength of welds, but also improved the hot cracking susceptibility of aluminum alloy welds.

Abstract: Study the property and resistivity of Low-pressure semi-solid die casting ( LPSSDC) aluminum wheel hub after heat treatment. The Brinell hardness has reached more than 100HB in all position. Tensile properties at inner rim and outer rim are both reached 280MPa. The result of resistance analysis on LPSSDC aluminum wheel hub is below. The resistivity of the material is only influenced by the supersaturated solid solution (SSSS), GP zone, metastable phase β 'and stable phase β (Mg₂Si). The resistivity has a decline during aging 0-0.5h and 0.75-8h, and an increasing during 0.5-0.75h. The resistivity remains stably when the decomposition of the solid solution achieved a dynamic balance after 8h aging time.

Abstract: In this study, modification of aluminium silicon eutectic alloy by grain modifier, strontium was investigated on conventional and slope cast A356 alloy. A356 alloy with addition of 0 to 0.97 wt.% Sr was prepared by conventional and slope casting in melting furnace. The molten metal of A356 alloy was casted into steel mould. Microstructure was observed using SEM. Phase analysis was done using XRD. Microhardness was conducted using Vicker microhardness. Microstructure of conventional cast displayed dendritic structure whereas slope cast displayed globular structure. Addition of Sr refined eutectic structure in both conventional and slope cast alloy. Phase analysis revealed the presence of Al2Sr phase in conventional cast Al-6Si-0.97Sr. Microhardness of the conventional cast alloy decreased with increasing of Sr up to 0.97 wt.%.

Abstract: The main goal of investigations on semi-solid metal processing is to produce complex parts with enhanced mechanical properties. Flow behavior and die filling in semi-solid processing is an intrest area of researchers. A comprehensive understanding of the behavior of the under investigation metallic slurry is the design key of a successful manufacturing process. In this way the material’s transient response is very important for understanding of the rheological properties and also further commercial development of the process. The material used in this research is an Al-Si alloy which is widely used in automotive and aerospace applications. The experiments were conducted using a Searl rheometer which is specially designed for high temperature rheological measurements. For rheological tests of semi-solid alloy in different solid fractions, the isothermal holding and shear rate step change experiments were examined. Using practical rheological results, a single phase thixotropic model has been derived and adopted with measurements. The investigated alloy behavior was obviously thixotropic which is quantified in a theoretic model. Also instantaneous rheopectic behavior was observed for this alloy. The state of the microstructure has been applied through a structural parameter. The presented model for A356 alloy fits well with the experiments.