Al-Si alloy solid-liquid mixed casting

Chen Zhenhua Institute of Non-equilibrium Materials Science and Engineering, Central South University of Technology, Changsha 410083, China Abstract A new material preparation process for solid-liquid mixed casting is proposed. That is, adding a large amount of the same alloy powder or good wettability in the superalloy melt. Dissimilar alloy powder. Stir evenly and then cast or various hot processed seed material preparation process. Through the solid-liquid mixed casting of the alloy 18, the average particle size of primary silicon precipitated in the hypereutectic alloy can be controlled when the ratio of the mass of the powder and the mass of the alloy solution is about 1 under the experimental conditions. Below 51, the average particle size of one phase in a hypoeutectic alloy can be controlled to 101 or less. Yan Ming, the process has a certain degree of advancement and superiority, there may be a definite application value, the key words solid-liquid mixed casting; powder; melt; alloys in people Category 1; 22 Document code 7 In recent years, half New technologies such as solidification and spray deposition have been widely used in the preparation of alloys and composites, and they have been shown to be large in size. Semi-solidification plus 1. Should be diverted too; gold melt into the mechanical electromagnetic mixing, so that the melt generated part of the phase particles, and then the suspension of this solution casting or a variety of heat addition of the village preparation In the process, the jets are atomized by gas or centrifugal atomization of the alloy body. A new process for producing phase or liquid phase particles and simultaneously depositing two-phase particles to form a material or directly performing thermal processing takes into consideration that both processes have the basic characteristics of solid-liquid phase mixing, leading to a new idea. The material preparation process is a solid-liquid mixed casting process. The so-called solid-liquid mixed casting process mainly involves adding a large amount of the same alloy powder or a good wettability dissimilar alloy powder to the superheated alloy solution, stirring it strongly and uniformly, and then casting or various hot processing seed material preparation processes. With semi-solidification, this cast alloy billet can also be condensed and reheated to semi-molten state for various subsequent hot workings. Through preliminary research on solid-liquid mixed casting, this process has a certain degree of advancement and applicability, and some of the results are briefly described below.

1 Experimental method Solid-liquid mixed casting experiment box 1.

In this experiment, human 120 hypereutectic quenching powders were used, adding 1203 for the superheat degree 50100, 1.73 for the hypereutectic alloy, and the melt for the eutectic alloy and the 1731 hypoeutectic alloy. The average particle diameter of the powder was 3, and the ratio of the powder addition mass to the alloy melt mass was respectively 0.21. After the powder is added, the alloy melt is cooled, stirred rapidly and evenly, and the hooks can be directly fed into the casting, or the semi-coagulated liquid can be subjected to various thermal processing. The directly cast billet can be reheated to the state of the museum and then incorporated into the hall for subsequent thermal processing to prevent oxidation. The heating and stirring can be carried out under the protection of nitrogen or other inert gas. The wood experiments are carried out using graphite clay in the furnace or outside the furnace for human agitation. Although it is impossible to achieve strong mixing and uniform distribution of the powder, the experimental results can still be determined. The degree reflects the superiority of the technology.

2 Results and Discussion 2.1. Melting of the powder In the solid-liquid mixed casting process, since the alloy solution has a certain degree of superheat, a part of the melting phenomenon occurs after the powder is added. How to make the powder evenly and minimize the amount of powder melting is the key technology of solid-liquid mixed casting. A mechanical agitation system is now being set up for strong agitation to achieve uniform mixing of the powder and the melt, and progress has been made in detailed system studies. By controlling the agitation speed and the solidification rate of the superheat of the metal melt, a state in which the powder is slightly thawed under uniform distribution can be achieved. 2 is a composite microstructure photograph of a human 13 hypereutectic alloy powder added to a human 13; eutectic alloy solution. The zone is a hypereutectic powder group with fine dispersed primary crystals of 3 phase, and zone 5 is the melting point of eutectic melt powder. Part of the reservoir porosity.

2.2 Uniform Distribution of Powders In solid-liquid mixed casting, the uniformity of powder distribution is also a key issue of the process. Since the ratio of the mass of the powder added and the mass of the alloy solution is rather large, it is difficult to achieve that the individual powders are completely separated by the liquid phase. However, from a macroscopic point of view, the uniform distribution of the powder accumulation zone and the liquid phase zone can be relatively easily achieved by mechanical rapid stirring. 3 is a solid-liquid mixed casting alloy microstructure in which agglomerates and liquid phases are uniformly distributed by several powders.

2.3 The microstructure of the solid-liquid mixed casting alloy The nucleation core in the liquid phase is greatly increased due to the addition of the powder, and due to the endothermic and slight melting of the powder, the alloy is quenched and solidified, so the powder addition amount increases. , 3 kinds of 1 3; primary alloy silicon precipitation and crystal size decreased significantly, the network dendritic structure disappears. Under this experimental condition, through the control of the process, when the quality of the powder added mass alloy solution is 1, the primary crystal silicon precipitated in the hypereutectic alloy can be controlled below 51; in the hypoeutectic alloy, the crystal grains are The degree can be controlled below 10,1, basically achieving the effect of rapid condensation. 46 are the microstructure photographs of the blanks obtained by the incorporation of the dip alloy into the solid-liquid mixed casting. The photographs show that the mixed casting microstructure of the solid liquid is essentially a mixed structure of the powder metallurgy structure and the casting structure. Most of the powders in 4 were only seldom melted, and they were still spherical or near-spherical particles. They were well combined with the liquid phase matrix. The primary phase 31 in the powder was equiaxed, fine and dispersed, and distributed evenly. Due to the partial melting of the powder in the hypoeutectic liquid phase, there is also a uniformly distributed primary crystal 5; the phase is in a polygonal shape, and the particle size is slightly larger than the primary crystal 5 particles in the powder. White crystals are phase and are equiaxed.

2.4 Reheating of the cast billet Reheating the semi-solidified cast billet to a semi-molten state for subsequent hot working is an important process for the semi-solidification process. The growth of precipitates and grains in the semi-solidified billet during the reheating process is also worth noting. Asked. In the solid-liquid mixed casting re-smelting, since a large amount of unmelted powder remains therein, in the process of heating to a semi-molten state, they will again serve to hinder the growth of primary crystals and inhibit grain growth. 7 is a photomicrograph of the microstructure when solid-liquid mixed casting is also reheated to a semi-molten state.

2.5 Ultrafine structure In the solid-liquid mixed casting, when the mass of the powder-added mass alloy exceeds 0.75, many ultrafine microstructure regions are found in the solidified structure. 8 is the microstructure photograph of the ultra-fine structure region of the solid-liquid mixed casting alloy. The ultrafine microstructure region is mainly caused by the large condensation rate in these regions.

2.6 Application Discussion The solid-liquid mixed casting process is similar to the semi-solidification process and is much simpler than the spray deposition technique, but its microstructure is better than that of the latter alloy casting method. In the preparation of multi-phase alloy dual phase steel and other types of composite materials, solid-liquid mixed casting may also be a promising method for the preparation of composite materials. In addition, it can also be considered. The cast iron scrap gold, the shoulder through the simple smashing and reduction treatment used for casting and casting in the night, described in detail. The solid-liquid immersed casting process has a certain degree of advancement and superiority, and may have a definite application value.

3 Conclusion 1 Through the same-liquid mixed casting of 3 kinds of 13 alloys, under the experimental conditions, through the control of the process, when the ratio of powder addition mass to the alloy melt mass is about 1, the hypereutectic alloy precipitates. The average primary particle size of silicon can be controlled below 51, and the average particle size of the hypoeutectic alloy can be controlled below 1.

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