Effect Of Rare Earth On Creep Resistance Property Of Magnesium Alloy

Lightening the automobiles as well as other transportations and the flying vehicle's weight, and consequently reducing the energy consumption, is an effective way of environmental protection. Lately, the magnesium alloy is thought highly of its low density and high specific strength that the magnesium alloy's application in automotive industry and others is increasingly abroad. But its bad elevated temperature(120℃upwards) creep resistance property and corrosion resistance property hinder its further generalization and application. Generally, the magnesium alloy transmission components of the automobiles working in 150-250℃, so it is practical that studies magnesium alloy temperature creep resistance property in this temperature.At present, the magnesium alloy widely applying and having best combination property generally contains Al element.Mg17Al12 is the most important strengthening second phase in Mg-Al alloy. But the Mg17Al12's melting-point (mp) is low and the stability is bad, frequently existing in the magnesium alloy as reticular shape. In order to enhance the creep resistance of magnesium alloy, the content of Mg17Al12 in the alloy must be reduced, and other high melting point, more stable second phase is expected to produce. Rare earth (RE) combining with aluminum element can form high mp Al-RE second phase in the magnesium alloy, which can prevent the grain boundary slipping and the dislocation climbing under high temperature and thus can enhance the creep resistance property of magnesium alloy.The present paper has mainly studied following aspects: 1) preparing RE-bearing magnesium alloy with high creep resistance property, 2) studying the influence mechanism and mode of RE on the magnesium alloy's creep resistance performance, 3) researching the variation of magnesium alloy's creep resistance property containing different amount of RE, and discovering the optimal RE content.By the researching, the conclusion follows: The enhancement of experimental magnesium alloy's creep resistance property is mainly the result of second-phase reinforcement of Rare-Earth phase with rich aluminum. After solution treatment, the coarse (Mg,Zn)17Al12 phase in magnesium alloy before heat treatment can solute into the matrix and then precipitate with fine and disperse particles after aging, and simultaneously the Rare-Earth second phase also can distribute dispersedly. The RE second phase can enhance the creep life of experimental magnesium alloy, reduce its steady-state creep speed and eventually improve the alloy's creep resistance property. Meanwhile the RE second phase can improve the tensile strength and yield strength under room temperature of magnesium alloy. With RE content increasing, the plasticity and creep speed of magnesium alloy reduced while the rupture life of magnesium alloy increased. When the content of RE exceeded 1.6%, the acicular Al-RE phase turned up in the magnesium alloy and for its dissevering the magnesium alloy matrix, on the contrary, the creep rupture life descended and the creep resistance property reduced. With the increase of creep experiment temperature, the deformation and solution extent of (Mg,Zn)17Al12 phase both increase while the RE second phase is correspondingly stable.With increase of temperature, the deformation amount of experimental magnesium alloy increased, the creep speed improved, and the creep-rupture life becomed shorter.