Properties, structure and phase relations in the systems magnesium - rare-earth metals.

摘要

Magnesium alloys containing rare-earth metals (RE) as alloying elements are known and used as attractive light structural materials for a long time. Addition of the rare-earth metals to magnesium enables to obtained magnesium alloys with higher strength properties both at near room and elevated temperatures. Actually, there is the only disadvantage of the rare-earth metals as alloying element to magnesium. This is its enough high cost which limits practical use of Mg-RE alloys. The specific feature of the rare-earth metals influence on properties of magnesium is significant difference between every of them. The cost of every of them is also significantly different. These two factors cause the choice of the separate rare-earth metals for alloying of magnesium in order to meet the reasonable balance between high strength and cost of the materials for industry. In according with this rule, only a few rare-earth metals were used for development of commercial magnesium alloys. These rare-earth metals are cerium, neodymium and yttrium. In order to diminish cost of the rare-earth metals added to magnesium they are used together some contents of other rare-earth metals. So, cerium is used commonly as mishmetal which is a mixture of the rare-earth metals of cerium subgroup with prevail contents of cerium, neodymium is used with significant contents of praseodymium, yttrium is used with some contents of rare-earth metals of yttrium subgroup (gadolinium, terbium, dysprosium and other). Such a form of use of the rare-earth metals results from intention to short expenditure of their production during separation from each other, but not from wish to improve somehow properties of the alloys.