Research status of rheological squeeze casting

Squash casting is one of the typical casting processes which can eliminate the porosity defects, and a new material processing technology, that is, semi-solid squeeze casting, is produced by combining it with semi-solid pulp processing technology. Rheological squeeze casting (RCG) is divided into Rheological direct squeeze casting (RCG) and Rheological indirect squeeze casting (RCG) according to the classification method of RCG by adopting various semi-solid pulping processes. Through the analysis of the development status of rheological forming technology, the main rheological forming technology in the world is rheological die casting, rheological rolling and rheological squeeze casting. The rheological die-casting process is mainly used in the production of thin-walled components with low density and low safety strength requirements. Rheological rolling mainly produces semi-finished products of bars and plates. Rheological extrusion casting (RCF), which combines the advantages of squeeze casting and semi-solid processing, can produce mechanical structures with good compactness and high mechanical properties, and is the focus of RCF research.

Guo Hongmin et al. from Nanchang University conducted an experimental study on rheological squeeze casting of 7075 and 2024 deformed aluminum alloy cup parts by combining the LSPSF process independently developed by the laboratory team with the direct squeeze casting process. Of deformation aluminum alloy semi-solid slurry squeeze casting forming process parameters such as pressure, temperature, microstructure and mechanical properties of the product and its forming performance are analyzed, the results show that the rheological of squeeze casting parts for small spherical or nearly spherical microstructure, increasing pressure to make the parts more dense microstructure, the microstructure in forming temperature is too high in poor; The defects such as cold interlayer, cold isolation and crack were found in the rheo-extrusion casting cup. At the same time, there are also microsegregation in the metallographic structure and macroscopic liquid phase segregation in the section. Compared with ordinary squeeze casting, the mechanical properties of 2024 alloy are greatly improved. The maximum tensile strength of 2024 alloy is 306MPa and the elongation reaches 10.4%. The mechanical properties of 2024 alloy reach the level of thixotropic die forging after heat treatment. At the same time, the indirect squeeze casting of A356 alloy was simulated and compared with experimental results. The results show that the combination of LSPSF process and squeeze casting process can achieve a good effect. A356 has fine grains, tensile strength of 328MPa and elongation of 10.6% after heat treatment. Zhao Shengdun et al. simulated and optimized the semi-solid squeeze casting of A356 alloy connecting rod, and obtained the relevant reasonable process parameters.

Xuan-pu dong huazhong university of science and technology such as semisolid forming end of the paper, the rheological casting by rotating bubble mixing design and mechanical vibration for semi-solid pulping, the pressure on the mold modification increased the rheological casting forming device, the results show that the development of pulping device has the function of composite pulp, can be rotation of bubbles, also can undertake of mechanical vibration; The rheological casting and forging experimental device designed and manufactured can realize pouring, casting and forging as well as mold opening and taking parts in the same process and in the same set of die. The mechanical properties of rheological castings and forgings are higher than those of liquid metals except composite pulping. The optimum rheological casting and forging process parameters were explored, but there were still some defects such as liquid phase segregation. Kim, H. H. et al. studied the manufacturing of A356 rheo-extrusion forging parts, and improved the slurry quality with the aid of vacuum auxiliary device. The results showed that the semi-solid rheo-extrusion forging process could reduce the pinhole and porosity of the parts with the aid of vacuum. Jung, Hong – Kyu rheological is studied by using general servo hydraulic press forging forming technology was studied, the results point out that the exhaust system and the design of the gate way are the key factors that affect alloy products cold insulation defects, one of the filling velocity and pressure by controlling the size, the holding time, get the best organization and performance, as well as quantitative analysis of the grain size and shape factor and other indicators.

According to the analysis of the rheological squeeze casting research closely connected to behind the pulping process of semi-solid extrusion casting equipment development and research is very few, the rheological study of squeeze casting research is much less than the rheological die casting, in this paper, the rheological squeeze casting equipment must be explored, the rheological squeeze casting forming technology on the basis of a systematic and comprehensive study.

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