Al-matrix composites have become the focus of research in the material science field today because of their excellent physical properties and mechanical properties. There are many kinds of methods for preparing aluminum matrix composites, such as common casting agitation method, powder metallurgy method, etc. However, due to technical problems such as interface reaction and particle segregation, the development and application of aluminum matrix composite materials are restricted. In recent years, research work has tried to combine spray forming technology with aluminum-based composite material preparation technology to develop a "spray co-deposition" technique that solves the segregation problem of enhanced particles well, and because The solidification time is very short, which can avoid the dissolution of the reinforcing phase particles in the matrix and the interfacial reaction; in addition, the technology combines the preparation and forming processes of the materials, simplifies the production process, and reduces the production cost.
At present, spray co-deposition preparation of aluminum matrix composites has two methods for adding reinforcing particles: (a) separate particle addition; (b) hybrid particle addition.
Split-type particle addition method: As an example of adding SiC particles to an aluminum alloy, the reinforcing phase particles are sprayed into the atomization cone through two injection pipes located below the atomizer, wherein the particle size is approximately 3 to 15 microns. The results show that the volume fraction of the reinforcing phase particles added by this method is as high as 25%. At the same time, it shows better strength and toughness and has a higher elastic modulus.
The method of mixed addition of particles: the reinforcing phase particles and the atomizing gas are mixed together, so that the cooling rate of the nozzle tip is greatly improved. The SiC particle size is 10-20 microns. This method requires increasing the superheat of the melt to ensure proper solid/liquid ratio. This method can reduce the porosity in the deposited billet and make the distribution of the reinforcing phase particles more uniform. Experiments show that the volume fraction of SiC reinforced phase particles added by this method can reach more than 20%, and shows a good overall performance.
Metal matrix composites are prepared by spray co-deposition technology. Because the matrix alloy is in the semi-solidified state and the temperature is low, the interface reaction caused by excessive contact temperature is avoided, thereby improving the interface properties of the material. At the same time, as the spray co-deposition process can refine the grain structure, increase the solid solubility of the alloy matrix, eliminate the macro-segregation and generate the characteristics of non-equilibrium metastable, it can further improve the performance of the composite material.
In recent years, on the basis of the spray co-deposition technology, a reactive spray forming technique has been developed to combine the injection molding technology with the reaction method for the preparation of metal matrix composites to enhance the phase particles in the metal. During the injection of the melt, it is directly generated by a chemical reaction, so the combination with the matrix is ​​better, so that the interface problem of the metal matrix composite material is better solved. In addition, under the condition of rapid solidification, the matrix structure is further refined, making This technology promises higher performance aluminum matrix composites.
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