Squeeze casting, also known as liquid die forging, is a method to obtain castings by applying high pressure on the liquid metal poured into the mold cavity and forming the liquid metal under the pressure. This process combines the advantages of pressure casting and forging, which can effectively refine the grain and reduce the porosity and shrinkage defects. The technology has a wide application prospect in high-performance, thick wall magnesium alloy castings, and has been used in the production of magnesium alloy motorcycle wheel hub (Fig. In recent years, more and more researchers use squeeze casting technology to prepare magnesium alloy materials. The research status is summarized in the following.
The effects of pressure, pouring temperature and holding time on the microstructure and mechanical properties of Mg – 12zn – 4Al – 0.5ca alloy were studied. The results show that the microstructure of squeeze casting alloy is significantly refined, the porosity and shrinkage defects are significantly reduced, and the hot cracking tendency of the alloy is reduced. The mechanical properties of the alloy are better than that of metal mold casting. Zhu et al. Showed that the grain size of mg-6zn-4al-0.5cu alloy was refined after squeeze casting, and the porosity and shrinkage cavity decreased significantly with the increase of pressure, so the mechanical properties of mg-6zn-4al-0.5cu alloy were significantly improved. Zhang et al. Showed that the grain size of flame retardant AZ91 CA alloy decreased with the increase of pressure and the decrease of pouring temperature, while the elongation increased, which inhibited the adverse effect of ca. The effects of pressure and heat treatment on the microstructure and mechanical properties of squeeze cast mg94ni2y4 alloy were studied. The results show that the phase composition and the type of lpso remain unchanged under different forming pressures. With the increase of pressure, the microstructure is refined, the volume fraction of lpso decreases and the eutectic structure increases. In the process of heat treatment, the phase of lpso transforms from massive phase to rod phase, and it is not easy to separate during fracture. Han et al. Studied the solidification behavior and aging precipitation process of AZ91D alloy in squeeze casting process, and found that the nucleation temperature and end temperature of primary α – Mg phase of the alloy increased, but the temperature range remained unchanged; the solidification start temperature of eutectic phase increased, the end temperature decreased, and the eutectic reaction temperature range increased. The refined structure and high volume fraction eutectic phase were obtained. Miroslava et al. Found that the fatigue property of Squeeze Casting AZ31 alloy is better than that of traditional casting alloy.
Yang Yanling studied the process and solidification behavior of squeeze casting Mg nd Zr alloy. It was found that the main reason for the change of solubility of solute atoms in α – Mg matrix under pressure may be the change of atomic radius under pressure. Based on this, an empirical formula for the change of solubility with pressure was proposed. It can be predicted that with the increase of pressure, the solubility of Nd atom in α – Mg matrix will increase, which is also proved by the experimental results. When the temperature of the alloy melt is higher than that of the liquidus under pressure, increasing the pressure can increase the critical nucleation free energy of the alloy, reduce the critical nucleation density and decrease the nucleation rate. With the increase of the pressure, the grain size of the alloy increases gradually. On the contrary, when the temperature of the alloy melt is lower than that of the liquidus under pressure, increasing the pressure will reduce the critical nucleation free energy of the alloy, Increasing the critical nucleation density can increase the nucleation rate and reduce the grain size of the alloy. In addition, the increase of pressure increases the attachment velocity of atoms to the solid-liquid interface and reduces the unstable wavelength of solidification front, thus increasing the solidification rate of alloy melt. Wang et al. Prepared mg-gd-y-zr alloy by squeeze casting, and studied the effects of pouring temperature and pressure on the microstructure and mechanical properties of the alloy. The results show that the microstructure of Mg-10Gd-3Y-0.5Zr alloy solidified under pressure is fine and compact. The yield strength, tensile strength and elongation of squeeze casting T6 alloy are 9%, 19% and 114% higher than those of metal mold casting alloy, respectively. The above results show that the mechanical properties of squeeze casting magnesium alloy with or without rare earth are better than those of gravity casting.