【摘要】 本文报道了对MB26镁合金显微组织的研究结果及其对力学性能的影响。研究结果表明,在Mg-Zn-Zr合金中添加钇混合稀土可使铸态镁合金晶界变窄,并细化晶内析出物。随着钇稀土含量的增加,合金金相组织从等轴晶粒向亚共晶组织转变。钇稀土含量的增加,不会导致钇稀土元素向晶界大量富集,使晶界宽化。在含Z相的MB26合金中经挤压后,大致发生以下反应:Mg₆Y（Re）Zn₆（?）Mg₃Y（Re）₂Zn₃+MgZn₂,MgZn₂是镁合金的强化相。在挤压后的MB26镁合金中,沿压缩的原始晶界,有颗粒的Y（Re）-Zn相生成,这对合金力学性能有不良影响,在晶内有弥散细小的Mg-Y（Re）相生成,这是合金的强化相。在挤压状态下,钇稀土含量较小的MB26合金则产生亚晶界,并伴有细小析出相沿亚晶分布而强化合金;在钇稀土含量较大（2.65％wt）则没有亚晶形成,但晶内析出大量细小弥散强化质点,使合金得到强化。含钇稀土在（0.79～2.65％wt）范围内均能得到约370MPa的抗拉强度,比不添加钇稀土的Mg-Zn-Zr合金高出30MPa左右。更多还原

【Abstract】 The microstructure of magnesium alloy MB26 and its influence on the mechanical property of magnesium alloy MB26 were studied in this paper. Results show that adding mixed yttrium rear-earth elements to as-cast magnesuim alloy can narrow the grain boundary and fine the deposit phase in the grain. With increase in the content of yttrium rear-earth elements, the metallurgical microstructure of the alloy will change from isometric to hypoeutectic. The increase of content of yttrium rear-reath elements will not cause heavy enrichment of yttrium rear-reath elements on the grain boundary and the widening of the grain boundary. Following reaction may occure in MB26 alloy that contains Z phase during extruding process: Mg₆Y（re）Zn₆extruding Mg₃Y（Re）₂Zn₃+MgZn₂. MgZn₂phase is a strengthening phase of magnesium alloy. In extruded MB26 alloy, there are big particles of Y（Re）-Zn phase distributing along the compressed original grain boundaries. This will have bad influence on the mechanicil property of the alloy. The small dispersion Mg-Y（Re） phase depositting in the grain is a strengthening phase of the alloy. Under the condition of extruding, subcrystalline grain boundaries are formed in the MB26 alloy that has less content of yttrirm rear-earth elements, and the small deposit phases are deposited along the subcrystalline grain boundaries to strengthen the alloy. Although none of the subcrystalline is formed in the MB26 alloy that has more content of yttrirm rear-earth elements （2.65％wt）, a Large amount of small dispersive strengthening particles are deposit in the grain and strenthen the alloy. When the content of yttrirm rear-earth elements is in the range of 0.79％wt to 2.65％wt, the tensile strength of MB26 alloy is about 370 Mpa. This is about 30 Mpa higher than the tensile strength of Mg-Zn-Zr alloy which does not contain yttrium.更多还原