Papers by Keyword: Solidification Process

Abstract: Herein, Ti-6Al-4V alloy was remelting by high-energy laser, the influence of laser energy density of mobile laser source on the evolution of solidification structure of Ti-6Al-4V alloy was studied, and the changes of relevant service performance of Ti-6Al-4V alloy after laser-remelting were explored. The results showed that there were four distinct regions: overheated zone, melting zone, heat-affected zone and substrate zone in Ti-6Al-4V alloy after laser remelting. The overheated zone and melting zone were dominated by primary α phase and secondary α phase, and a heat-affected zone was dominated by β phase. With the increase of laser energy density, the depth of molten pool and the range of melting zone in Ti-6Al-4V alloy increased, and the crystal phase distribution and grain size changed significantly. Laser-remelting Ti-6Al-4V alloy could still maintain a good passive state in the potentiodynamic polarization curve test, and the optimal laser power during remelting was 1200 W. This study proved that the crystal phase composition and grain size during the solidification process after laser-remelting were a key factor affecting the service performance of Ti-6Al-4V alloy.

Abstract: This report outlines a succinct analysis of the contemporary casting methods in single-crystal turbine blades. Furthermore, this paper also provides an examination of the solidification procedure in mixed turbine blades. The couple cooling and heating operation system was advanced to obtain identical thermal positions for single crystal (SC) solidification in the blade group, thereby significantly diminishing the associated flaws in the contemporary Bridgman process. The chemistry science of Nickel based alloys planed for single crystal (SC) gas turbine blades has been notably improved upon, especially when considering the initial production of alloys. The second and third production within the total operation has been enhanced by the introduction of rhenium (Re). Surged density, grain flaws, and microstructural stableness have presented themselves as significant issues within this process. Additionally, it is imperative to minimize the concentrations of the different alloying components.

Abstract: The direct difference method is used for solving the heat conduction equation, and simulate the solidification process of T-type cast. The effect of the thermal resistance at cast/mold on distribution of temperature and the solidification rate of corner region is studied. The results show that during the solidification process of T-type, the riser region first solidified, followed by the right half, finally the solidified part was around the corner. With the decrease of the thermal resistance at cast/mold, the temperature of the corner area decreased more quickly and the solidification rate increased. In the actual design process, the material with the good thermal conductivity should be selected for the cast mold to accelerate the solidification rate of the corner region, so the solidification rate of the corner and riser region tend towards harmony, which reducing the formation of various types of defects, and the quality and mechanical properties of the casts were improved.

Abstract: In this study, we present a numerical technique for the improvement of computational efficiency for computation of microstructural evolution in alloy during solidification process. The goal of this technique is for the computational domain to grow around the microstructure and fixed the grid spacing, while solidification advances into the liquid region. The growth around the microstructure is controlled according with the solute diffusivity for binary alloy in the liquid region. The computation showed that the microstructure with well-developed secondary arms can be obtained with low computation time and moderate memory demand.

Abstract: The traditional method has been used to the foundry technique for the melt block mobile plate. The pouring position,the parting face and some of the casting parameters were determined, such as the allowance for finish, stripping taper, the rate of shrinkage and soon on. The commercial casting simulation software was introduced into the casting process, the filling and solidification process were calculated by it. The results shown that there are some shrinkage exists in the original technique and the filling process were inordinate. The gating system was optimized and according to the simulation results, the shrinkages in the original technique were eliminated and the filling process is smoothly which could help the designer to make a correct determination.

Abstract: It is a concerned problem that what influences of cooling rate on evolution of microstructures of the treated and untreated Cu are during solidification process after Cu’s being melted by laser grooving. Based on the embedded-atom method, molecular dynamics simulations have been performed on the cooling processes of liquid metal Cu by using crystal-liquid configuration method at six different cooling rates. Through the two-phase structural features, pair correlation function, average atomic energy and mean square displacement analysis, it is found that the cooling rate plays a critical role on the solidification process to the liquid Cu. The liquid Cu becomes its crystalline state during relatively low cooling rate, while the glass transition of the liquid Cu is performed with the relatively high cooling rate. The solidification process of the liquid Cu has effect on the solid crystal Cu and leads to form the indented interface between two-phase structures.

Abstract: In this study, the experimental measurement of the pressure distribution in a cylindrical die cavity for squeeze casting of magnesium alloy AM50A was carried out. Piezo-electric quartz pressure transducers were integrated into a die cavity for real-time pressure measurements. The experimental results revealed that local cavity pressures at various locations changed with time in the duration of squeeze casting solidification and cooling. The pressure transfer rate varied considerably within the casting geometry. The distribution of local cavity pressures was inhomogeneous in the cavity.

Abstract: Oil pump cover, as a part of the oil pump, is generally formed by adopting aluminum die casting molding, and required for good internal and external quality. In order to improve the oil pump cover forming quality, the paper first simulates the thermal equilibrium of die-casting mold in the forming process by finite element analysis, and obtains the temperature curves when mold works for 10 consecutive cycles, and determines that the thermal equilibrium temperature of die-casting mold is 260 °C. And then, based on the simulation results of filling and solidification in the forming process by ProCAST software, the shrinkage and cavity appear in the larger wall thickness of the casting. Meanwhile, by simulating the die-casting processes of the oil pump at different pouring temperatures, there are the least of shrinkage and cavity when the pouring temperature setting 640 °C. The results show that: it can take some methods to achieve the progressive solidification, and can reduce or eliminate the possible shrinkage and cavity, such as shortening the distance between sprue, runner and inner runner and die casting to reduce the casting heat loss, or adding cooling system to accelerate the cooling rate in the larger wall thickness of the casting. This analysis provides theoretical basis for the actual casting production of oil pump covers.

Abstract: In order to reduce the wear of parts caused by long-term friction, and to reduce the frequency of parts replacement, ZA alloy with low hardness and good wear resistance is chosen to replace the traditional copper alloy as the material to manufacture automotive bushing, and the semi-solid die casting is used. On this basis, the software AnyCasting is used to simulate and analyze the filling and solidification process, the filling sequence, the variation of temperature field, and the part region where defects are prone to occur in the semi-solid process. The simulation results show that under the parameters set in the simulation process, when casting filling rate reached 90%, the metal started to solidify; since the gate place is easy for heat dissipation, when the temperature of the alloy liquid reached its liquidus temperature 595°C, the phenomenon of solid-liquid phase separation appeared at the gate; the defects such as gas trapping, residual stress and deformation would appear both in the place of first filling and the parting surface; when the preheat temperature of the mold was 150°C-200°C,the alloy liquid possesses liquidity. The simulation results offer certain theoretical instruction to optimize the semi-solid casting process of ZA Alloy automotive bushing manufacturing, as well as reducing or avoiding a variety of quality defects arose in the actual casting process.

Abstract: A heavy section ductile casting (HSDIC) with dimensions of Φ590 mm×800 mm was prepared. Cooling curves at the center, at 85 mm from the center, at 170 mm from the center and at 255 mm from the center of the casting were recorded and analyzed. The results show that the precipitation of initial graphite, nucleation of eutectic cell and mass eutectic reaction at 255 mm from the center were all earlier than the other three locations. Moreover, it takes the longest time of 53 minutes of recalescence at 170 mm from the center with the highest temperature rise of 7 °C, though the cooling rate at this location is not the lowest in the casting, the mechanical properties are the worst. In addition, the largest amount of chunky graphite appears at 170 mm from the center.