AZ31镁合金包埋渗Al涂层的显微组织与性能

采用包埋渗法在AZ31镁合金表面制备Al涂层.利用X射线衍射(XRD)、背散射电子成像(BSEI)和能谱仪(EDS)等技术对Al涂层的物相、显微组织和成分进行表征分析.结果表明,包埋粉的成分对涂层的物相、显微组织和厚度有显著影响.对于以AlCl3粉末为活化剂的样品,涂层较厚,涂层从表面到内部由呈梯度分布的相和组织构成,...

Microstructure and properties of Al-coating on AZ31 magnesium alloy prepared by pack-cementation

Al-containing coatings were prepared on AZ31 magnesium alloy by pack-cementation technology. X-ray diffraction (XRD), backscattered electron imaging (BSEI) and energy dispersive spectroscopy (EDS) were jointly employed to characterize the phases, microstructure and composition of the coated samples. The results show that the feedstock composition has a significant impact on the phases, microstructure and thickness of the coatings. For the sample with AlCl₃ powder as the activator, the coating is very thick and composed of gradient phases and structures from surface to inside, including small amount of β-Mg₂Al₃, coarse eutectic-like structure of γ-Mg₁₇Al₁₂ + δ-Mg, and fine γ-Mg₁₇Al₁₂ precipitations. In contrast, for the sample with AlCl₃ and pure Al composite powders as the activator, the coating is relatively thin and contains a thin Al₂O₃ layer and a small amount of fine γ-Mg₁₇Al₁₂ precipitates. For the pack-cementation aluminizing that is not protected by high-vacuum or inert gas, the addition of pure Al powders can easily introduce the Al₂O₃ layer into the coating to prevent active Al ions further penetrating into the magnesium matrix, resulting in the thin Al-containing coating. The microhardness and corrosion behavior of the two kinds of aluminized coatings were also studied and discussed.