论文部分内容阅读
采用粉末原位合成工艺成功制备新型Mg-50%Al4C3-6%Ce中间合金,并利用X射线衍射(XRD)仪、扫描电镜(SEM)及能谱(EDS)分析对其进行物相鉴别和形貌分析。结果显示,中间合金主要由层片状Al4C3和细杆状Al4Ce以及Mg基体组成。在AZ91D镁合金熔体中加入Mg-50%Al4C3-6%Ce中间合金可明显细化枝晶组织,枝晶形貌由六重对称的树枝状演变为花瓣状,当加入量为1.2%(质量分数)时,平均晶粒尺寸由基体合金的360μm降至65μm。晶粒细化机制可归结为Al4C3颗粒作为初生α-Mg的异质晶核,Ce富集于固液界面,引起成分过冷,从而激活固液界面前沿潜在的Al4C3核心,提高Al4C3的形核率。
A new type of Mg-50% Al4C3-6% Ce master alloy was successfully prepared by powder in-situ synthesis and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) Morphological analysis. The results show that the master alloy consists mainly of lamellar Al4C3 and fine rod Al4Ce and Mg matrix. The addition of Mg-50% Al4C3-6% Ce master alloy to the melt of AZ91D magnesium alloy can refine the dendritic structure remarkably, and the dendritic morphology evolves from a hexagonal symmetrical dendrite to a petal-like shape. When the addition amount is 1.2% Mass fraction), the average grain size is reduced from 360 μm of the base alloy to 65 μm. Grain refinement mechanism can be attributed to the Al4C3 particles as primary α-Mg heterogeneous crystal nucleus, Ce enriched in the solid-liquid interface, causing the composition is too cold, thus activating the potential Al4C3 core in front of solid-liquid interface to improve the nucleation of Al4C3 rate.