Development of Warm Sheet Forming of Magnesium alloys

Up to now, more than 90% of magnesium alloy products are still produced by die casting processes, only very small proportions are produced by plastic forming processes. Magnesium alloys have rather poor formability at room temperature, which makes it difficult for applications of the plastic forming technology in engineering. Sheet forming technology seems a very prospective technology as many Mg sheet parts have been developed for automotive bodies and electronics appliance parts (the so-called 3C products). Warm sheet forming of magnesium alloys has been attracting more and more attention in recent years due to the development of magnesium alloys in engineering applications. Many investigations have been reported in recent years regarding the research work on warm sheet forming of magnesium alloy parts. Some new advances have been made in the laboratory of the authors. A suitable temperature range is very important for plastic forming of Mg alloy sheets. The authors have tried to find a temperature range as low as possible for plastic forming of Mg alloy sheets, it has been found that Mg alloys can be warm formed in the temperature range of 120 to 170 with the limit drawing ratio of 1.4 to 2.6, on the condition that the Mg alloy sheets have been properly rolled and annealed. To find the suitable sheet rolling process conditions and annealing conditions, EBSD method has been used to find the microstructure evolution rules of the Mg sheets on some specified grains in a suitable zone at room temperature and the warm temperature ranges. The rules of the slip deformation and twinning during forming have been revealed quantitatively. The effects of the evolution of the grain orientation and texture evolution are discussed. Some new sheet warm forming technologies have been introduced in the present paper. Warm sheet forming process and warm forming with temperature gradient on the blank are discussed first, some Mg products such as mobile phone covers, MP3/MP4 covers and MD covers have been developed with the warm sheet forming technology. Warm hydroforming process is investigated to form complicated shaped Mg parts with only one pass, such as Camera covers. Press forging technology has been investigated to form 3C parts like notebook computer parts.