The forming process of magnesium alloy can be divided into liquid forming process and solid forming process. Liquid forming mainly includes gravity casting, die casting, squeeze casting and semi-solid forming. Solid state forming, also known as plastic forming, includes extrusion, rolling, forging, stamping, drawing and so on. In addition, there are some new forming technologies, such as rapid solidification / powder metallurgy, spray deposition and so on.
At room temperature, there are only two independent slip systems and three geometric slip systems, which can not meet the von Mises criterion, so the deformation ability of magnesium crystal is poor. The liquid forming process can produce castings with complex shape, high precision and high performance requirements, which is an important development direction of magnesium alloy forming. The following is a brief introduction of gravity casting and die, focusing on the research status of magnesium alloy squeeze casting and semi-solid casting.
Magnesium alloy can be produced by different gravity casting methods, including metal mold casting,, semi metal mold casting, investment casting, shell mold casting, etc. Sand casting is suitable for small batch production of large castings because of its low cost, low production efficiency, large grain size and low performance. The production efficiency of metal mold casting is relatively high, and the cooling speed of molten metal is fast during the solidification process of casting, which is conducive to obtain parts with fine grains and high performance.
Although the traditional metal mold casting has the advantages of simple equipment and easy operation, it is difficult to effectively control the casting defects such as porosity, shrinkage cavity and hot crack. How to improve the melt fluidity is also a great challenge when forming complex thin-walled castings. Therefore, die casting and other new casting methods are widely used in magnesium alloy castings.