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研究了在变形镁合金AZ31中添加稀土元素Gd对合金铸态和轧态组织与性能的影响。结果表明:加入AZ31中的Gd元素形成了稀土相Al2Gd和Al-Mn-Gd的混合相,使β-Mg17Al12相的数量减少甚至消失。铸态合金中的少量Gd元素削弱了Al的晶粒细化作用,使组织粗化;而当Gd元素的含量提高时Gd开始发挥晶粒细化作用,使合金的晶粒显著细化。对于轧态合金,加入Gd元素后形成的Al2Gd相能促进合金在轧制过程中的动态再结晶,使孪晶数量减少,加工硬化作用减弱,晶粒尺寸细化。而过量的Gd元素形成粗大的第二相,使合金组织粗化。因此,适量的Gd元素可使轧态AZ31合金的强度降低而延伸率提高,其中在350℃轧制的AZ31-0.8Gd合金的延伸率最高(为13.4%),不含Gd的合金延伸率仅为5.4%。
The effect of adding rare earth element Gd on the as-cast and as-rolled microstructure and properties of the as-cast AZ31 magnesium alloy was studied. The results show that the addition of Gd element in AZ31 forms a mixed phase of rare earth Al2Gd and Al-Mn-Gd, reducing or even eliminating the amount of β-Mg17Al12 phase. A small amount of Gd in the as-cast alloy impaired the grain refinement of Al and roughened the microstructure. When the content of Gd increased, Gd began to exert grain refinement and the grain size of the alloy was significantly refined. For the rolled alloy, the Al2Gd phase formed after adding Gd element can promote the dynamic recrystallization of the alloy during the rolling process, so that the number of twins is reduced, the work hardening effect is weakened, and the grain size is refined. The excessive Gd elements form a coarse second phase, the alloy organization coarsening. Therefore, the proper amount of Gd element can reduce the strength of the rolled AZ31 alloy and increase the elongation, wherein AZ31-0.8Gd alloy rolled at 350 ℃ has the highest elongation (13.4%), the alloy without Gd elongation only 5.4%.