Y含量对汽车变速箱AK30镁合金显微组织及 力学性能的影响

采用光学显微镜(OM)、扫描电镜(SEM)、X射线衍射(XRD)、维氏硬度和拉伸-压缩试验机等手段,评价Y含量对AK30镁合金微观组织和力学性能的影响。研究结果发现,Y含量能够显著影响AK30镁合金凝固组织和力学性能。当合金中没有添加Y元素时,AK30镁合金的晶粒粗大,晶界处有大量的Mg_3Zn相分布,力学性能最差。当合金中添加1%的Y元素时,AK30镁合金的晶粒尺寸没有发生变化,依然较大;但晶界处的Mg_3Zn相却在减少,而合金的晶内却出现了少量的Mg_3Y相,合金的力学性能增加。当合金中的Y含量增加到2%时,晶粒细化,晶体内析出了大量的Mg_3Zn相与α-Mg相组成的共晶组织,力学性能达到最大值。当合金的Y含量增加到4%时,晶粒粗化,且大量的Mg_3Zn脆性相在晶界处析出,合金的力学性能下降。为了提高AK30镁合金的力学性能,应该向AK30镁合金中添加2%的Y元素。

EFFECT OF Y CONTENT ON SOLIDIFICATION MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AUTOMOBILE GEARBOX AK30 MAGNESIUM ALLOY

In this paper, the effect of Y content on the solidification microstructureand the mechanical properties of AK30 alloy was preliminarily investigated by optical microscope (OM), scanning electron microscope (SEM), X-ray diffraction (XRD), Vickers hardness, and tensile-compressive testing machine. Y content could effect on solidification microstructure and the mechanical properties of AK30 alloy. It was found that the increase of Y content could refine thesolidification microstructure obviously. At w(Y)=0, the morphology of primary phases was coarse and a number of Mg₃Zn phase existed ingrain boundary. At w(Y)=1%, size of grain did not change and there were a small number of Mg₃Zn phase ingrain boundary. However, there existed a small number of Mg₃Y phase ingrain. At w(Y)=2%, size of grain was refined, and there were many eutectic structures ingrain. At w(Y)=4%, the morphology of primary phases was coarse again, and there were many brittle phases ingrain boundary. However, with the increase of Y content, the mechanical properties of AK30 alloy increased at first, then decreased. in order to improve the mechanical properties of AK30 alloy, it should add 2% of Y content to AK30 alloy.