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Magnesium is the lightest metal on the earth and a promising material to reduce the weight of automobile end electrical parts. As a the largest magnesium manufacturer in the world, investigating new magnesium forming process is imperative to us. Following is my point of view on Magnesium forming and welcome to share your thoughts on this topic.
As a HCP metal, Magnesium has very limited ductility at the room temperature. Presently, die casting is the major process to form the magnesium parts. However, the casting parts have lower mechanical properties and intrinsic die casting shortcomings, such as pin holes, porosity, cold shuts. Although semisolid methods, such as thixomolding or rheomolding, can decrease the scrap rate of castings, the high temperature caused die erosion and part problems still need to be solved for the industrial practice.
In recent years, forming processes, such as stamping and forging, are investigated for improving the mechanical properties of magnesium parts by offering fine-grained microstructure without porosity. However, the thermally improved formability is sensitive to strain rate, temperature and grain size. Complex magnesium components can only be manufactured from sheets or rods at low strain rates ( super plastic forming (SPF)) and/or at a fine grain size (grain refining technique). When the forming speed increases to the industrially accepted level (forming time less than 1 min, strain rate higher than 10-2 s-1) only simple geometries (round and rectangular) formed by sheet drawing or hot forging are reported. Due to the difficulties mentioned above, these parts are still prevailingly formed by steel or aluminum sheets. |
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