稀土Er对A356铝合金微观组织和力学性能的影响

Effect of Rare Earth Erbium on Microstructure and Mechanical Properties of A356 Aluminum Alloy

针对传统的A356铝合金,添加稀土元素是改善其微观组织并提高力学性能的有效途径。本工作通过示差扫描量热分析(DSC)、X射线衍射(XRD)、扫描电镜(SEM)等分析手段来研究稀土Er对铸态A356铝合金组织和性能的影响。结果表明,稀土元素Er是一种能够显著改善A356合金铸态组织的优良变质剂。Er的加入细化了初生α-Al相,二次枝晶间距降低,枝晶臂直径减小,同时对铸态组织中的共晶Si起到了变质作用。当Er含量达到0.4%(质量分数,下同)时,细化效果最为显著,二次枝晶间距由53.6μm减小到17.5μm,共晶硅形貌也由粗大的板条状转变为短棒或圆粒状。与A356合金相比,添加0.4%Er的合金样品的抗拉强度和伸长率分别提高了15.1%,29.8%。

For conventional A356 aluminum alloy,the addition of rare earth elements is an effective way to modify its microstructures and improve its mechanical properties.The effect of rare earth Er on microstructures and properties of as-cast A356 aluminum alloy was studied by differential scanning calorimetry(DSC),X-ray diffraction(XRD)and scanning electron microscopy(SEM).The results indicate that rare earth element Er is a good modifier for A356 aluminum alloy,which is able to improve obviously the microstructure of as-cast alloy.The addition of Er refines the primaryα-Al phase,decreases the secondary dendrite arm spacing and the dendrite arm diameter,and modifies the eutectic Si in as-cast structure simultaneously.When the amount of Er reaches 0.4%(mass fraction,the same below),the refinement effect is the most significant,secondary dendrite arm spacing decreases from53.6μm to 17.5μm and the morphology of eutectic Si transforms from thick lath-shaped to short rodlike or round granular.Compared with A356 alloy,the tensile strength and elongation of A356 aluminum alloy with the addition of 0.4%Er increase by 15.1% and 29.8%respectively.