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

AZ31镁合金包埋渗Al涂层的显微组织与性能

作　　者：Jian-jun HU Jing LIAO Xian YANG Jing ZENG Hui LI Bo SONG Hong-bin XU Ning GUO Yan JIN 胡建军;廖菁;杨显;曾敬;李晖;宋波;许洪斌;郭宁;金艳(重庆理工大学材料科学与工程学院,重庆400054;汽车零部件先进制造技术教育部重点实验室,重庆400054;西南大学材料与能源学院,重庆400715)

机构地区：[1]College of Materials Science and Engineering,Chongqing University of Technology,Chongqing 400054,China [2]Key laboratory of Advanced Manufacturing Technology for Automobile Parts,Ministry of Education,Chongqing 400054,China [3]School of Materials and Energy,Southwest University,Chongqing 400715,China

出　　处：《Transactions of Nonferrous Metals Society of China》2022年第2期493-502,共10页中国有色金属学报（英文版）

基　　金：the National Natural Science Foundation of China(No.51575073);International Cooperation Special Project in Science and Technology of China(No.2015DFR70480);Scientific and Technological Research Program of Chongqing,China(Nos.cstc2017jcyjBX0031,cstc2018jszx-cyzdX0126).

摘　　要：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 ofb-Mg2Al3,coarse eutectic-like structure ofγ-Mg17Al12+δ-Mg,and fineγ-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 fineγ-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.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AlCl_(3)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,包括少量的β-Mg_(2)Al_(3)、粗大的γ-Mg_(17)Al_(12)+δ-Mg类共晶结构和细小的γ-Mg_(17)Al_(12)沉淀相。相比之下,以AlCl_(3)和纯Al复合粉末为活化剂的样品,涂层相对较薄,且含有一层薄的Al_(2)O_(3)层和少量细小的γ-Mg_(17)Al_(12)沉淀相。这是因为对于不受高真空或惰性气体保护的包埋渗铝,以纯铝粉为渗源材料易在涂层中引入Al_(2)O_(3)层,从而阻碍活性Al离子进一步渗入到Mg基体中,最终导致形成的富Al涂层较薄。此外,还对两种不同铝涂层样品的显微硬度和腐蚀行为进行研究和讨论。

关 键 词：AZ31 magnesium alloy Al-coating pack-cementation surface aluminizing corrosion resistance 

分 类 号：TG174.4[金属学及工艺—金属表面处理]