虽然镁在地壳中的含量在一些结构元素中占第三位,镁可以从一些分布很广的菱镁矿,白云石和含量丰富的氯化镁盐卤中提取,但是镁至今还没有广泛地被应用来作结构材料,和与镁相接近的结构金属-铝来比,镁的年产量仅为铝的3％左右,而其中的1/3是用于配制铝镁合金用的。产生这种现象的主要原因,除 Although the content of magnesium in the crust is third in some structural elements, magnesium can be extracted from some widely distributed magnesite, dolomite and abundant magnesium chloride brine, but magnesium has not been widely used so far Structural materials, magnesium and magnesium are close to the structural metal - aluminum, the annual output of magnesium is only about 3% of aluminum, and of which 1/3 is used for the preparation of aluminum-magnesium alloy. The main reason for this phenomenon, except