镁合金表面DCPD涂层的制备及其界面结合机制研究  

Preparation of DCPD Coating on Magnesium Alloy and Its Interface Bonding Mechanism

作　　者：李沛[1] 李志[1] 杨建成 袁静[2] LI Pei;LI Zhi;YANG Jiancheng;YUAN Jing(Second Ward of Orthopedics,Qinghai Provincial People's Hospital,Xining 810017,China;School of Physics and Electronic Information Engineering,Qinghai Minzu University,Xining 810007,China)

机构地区：[1]青海省人民医院骨科二病区,西宁810007 [2]青海民族大学物理与电子信息工程学院,西宁810007

出　　处：《表面技术》2024年第4期193-199,210,共8页Surface Technology

基　　金：青海省卫生健康委员会指导性计划课题(2021-wjzdx-33);中国科学院西部之光人才培养计划“西部青年学者项目”。

摘　　要：目的研究CaHPO_(4)·2H_(2)O(DCPD)与Mg的界面结合机制,以提高DCPD在镁合金表面的界面结合强度。方法利用电镀法在AZ31镁合金表面制备DCPD涂层,采用SEM、XRD、XPS等对涂层形貌及结构进行表征。同时,运用分子动力学模拟(MD)对DCPD在Mg表面形成机制进行研究,通过统计界面层中不同组分的径向分布函数、密度分布、均力势、总能量等的变化,揭示DCPD/Mg的界面结合能、结合位点及结合方式。结果通过电镀法形成的DCPD涂层形貌为致密的荷花瓣状晶体,主要成分为CaHPO_(4)·2H_(2)O。模拟结果表明,CaHPO_(4)·2H_(2)O的4个晶面(010)、(-120)、(11-1)、(111)、(-120)与Mg的结合能最强(163.63 kJ/mol)。其中起“铆钉”作用的基团是HPO_(4)^(2-)和H_(2)O,结合位点主要为O与Mg,即HPO_(4)^(2-)和H_(2)O通过静电作用及范德华力与Mg形成Mg-HPO_(4)^(2-)和Mg-H_(2)O偶极对。研究发现,形成的偶极对中HPO_(4)^(2-)及H_(2)O的配位数分别为0.75和1.16,Mg-H_(2)O的解离能更大,结构更稳定。结论提出改善DCPD/Mg结合强度的方法,电镀前可将镁合金置于NH4H_(2)PO_(4)溶液中浸泡片刻,促进CaHPO_(4)·2H_(2)O(-120)晶面的形成。To improve the bonding force of the CaHPO_(4)×2H_(2)O(DCPD)coating on magnesium alloys,the work aims to propose an approach for synthesizing calcium phosphate coating on the surface of magnesium alloy via electroplating.The morphology,microstructure,and interface bonding of the calcium phosphate coating were characterized by a combination of different characterization techniques(SEM,XRD and XPS)and molecular dynamics simulation(MD).The formation of lotus-shape-like calcium phosphate coating,namely its main component,was CaHPO_(4)·2H_(2)O.MD simulation was used to analyze the interfacial morphology,radial distribution function(RDF),the potential of mean force(PMF),total energy,interface bonding energy,and relative concentration.The interface bonding energy,mutual bonding site,change in interface structure,and micro bonding mechanism between Mg and DCPD coating were further investigated.The main conclusions included three aspects:(1)Among the four common crystal planes of the DCPD coating,namely layer(010),layer(-120),layer(11-1),and layer(111),the layer(-120)had the strongest interface bonding force with Mg(001),which was 39.09 kcal/mol;(2)The main components of CaHPO_(4)·2H_(2)O could be simply divided into Ca2+,HPO_(4)^(2-)and H_(2)O.Among them,the relative contents of HPO_(4)^(2-)and H_(2)O in the interface layer were higher,indicating that the groups acting as"rivet groups"in the two-phase interface layer were HPO_(4)^(2-)and H_(2)O groups.The bonding sites were mainly effective interactions between O and Mg atoms.In other words,HPO_(4)^(2-)and H_(2)O groups could form Mg-HPO_(4)^(2-)and Mg-H_(2)O dipole pairs with Mg through electrostatic interaction and Van der Waals force;(3)The coordination number of Mg-HPO_(4)^(2-)and Mg-H_(2)O dipole pairs were 0.75 and 1.16,respectively,and their molar ratio was close to 1:1.Thus,one Mg atom on the DCPD/Mg interface was closely bound with one HPO_(4)^(2-)or one H_(2)O.The coordination number of Mg-H_(2)O dipole pair might be larger due to its higher concentration in

关 键 词：镁合金 DCPD涂层 界面结合能 界面结合位点 分子动力学模拟 

分 类 号：TG174[金属学及工艺—金属表面处理]