Mg-15Li合金在碱性NaCl溶液中的腐蚀行为

    用电化学方法研究了Mg-15Li合金在碱性NaCl溶液中的腐蚀行为.结果表明：在强碱性pH=13及扫描电镜环境下,当Cl^-浓度低于0.4 mol/L时,合金表面形成稳定的钝化膜;随Cl^-浓度增加,点蚀电位逐渐降低.     

医用Mg-Ca和Mg-Li-Ca合金腐蚀研究

通过失重法、析氢实验、pH值测定和动电位电化学测试等方法.研究了挤压态Mg-0.54Ca和Mg-1.33Li-0.6Ca合金在模拟体液中的腐蚀降解行为,并利用OM和SEM对合金显微组织及腐蚀形貌进行了观察,采用XRD对基体及腐蚀产物的相结构进行分析.结果表明,Mg-1.33Li-0.6Ca合金的组织由α-Mg基体和Mg_2Ca及CaLi_2第二相组成,而Mg-0.54Ca合金的组织由α-Mg基体和第二相Mg_2Ca组成;Mg-1.33Li-0.6Ca合金在Hank's溶液中浸泡初期的耐蚀性能略低于Mg-0.54Ca合金,随着浸泡时间的延长,其耐蚀性能明显优于Mg-0.54Ca合金,主要原因是Li提高了Mg-1.33Li-0.6Ca合金腐蚀产物的致密性;Mg-1.33Li-0.6Ca合金的腐蚀产物为LiH.Mg(OH)_2,MgCO_3,CaCO_3,CaMgCO_3和CaMgPO_4,而Mg-0.54Ca合金腐蚀产物为MgCO_3,CaCO_3和CaMgPO_4.Mg-0.54Ca和Mg-1.33Li-0.6Ca合金在模拟体液中的腐蚀类型都为点蚀和丝状腐蚀.     

Ho对Mg-9.7Li镁合金组织和性能的影响

采用低温熔盐电解方法制备Mg-9.7Li-xHo(x=0,0.6,1.0,3.0)镁合金;通过扫描电镜(SEM)、能谱仪(EDS)、X射线衍射(XRD)和腐蚀试验等手段研究了稀土元素Ho对Mg-9.7Li镁合金组织和性能的影响.结果表明,在Mg-9.7Li镁合金中加入稀土Ho,明显改变了合金的组织,细化了α(Mg)相,合金的耐腐蚀性能得到提高;当w(Ho)=3.0%时,合金中生成了HoMg2相,细化效果最好,合金的显微硬度明显提高.     

纯镁和Mg-14Li合金耐蚀性与表面膜的对比（英文）

采用析氢实验、失重实验、电化学实验、原位电化学拉曼光谱实验以及显微组织观察(光学与扫描电子显微镜)等实验方法,对比研究密排六方结构(HCP)的纯镁和体心立方结构(BCC)的二元Mg-14Li合金(质量分数,%)在0.1 mol/L NaCl溶液中的腐蚀行为与表面膜结构。实验结果表明:纯镁的耐蚀性优于Mg-14Li合金的,并且两种材料表面膜的保护功能均随着浸泡时间(16h内)的延长而提高。通过扫描电子显微形貌分析,发现不同于纯镁表面形成的较薄且呈片状的Mg(OH)_2膜层,Mg-14Li合金表面形成较厚且呈交织针状含有Li_2CO_3的膜层;然而,两种材料的表面膜均在高的阳极过电位下发生破损。因此,两种材料的不同腐蚀抗性可归功于在其表面形成不同的保护膜。     

正挤压态Mg-1Zn-1Ca合金的显微组织及其在SBF溶液中的腐蚀行为

通过合金化、均匀化热处理和正挤压制备Mg-1Zn-1Ca(质量分数,%)合金,采用电化学方法、浸泡腐蚀法研究合金在人体模拟体液(SBF)中的腐蚀行为.采用OM和SEM观察合金组织和腐蚀产物层形貌,用SEM附带的EDS分析合金相成分和腐蚀产物成分,采用Fourier变换红外吸收光谱对腐蚀产物官能团进行结构分析,结合XRD结果确定腐蚀产物的相组成.结果表明,Mg-1Zn-1Ca合金由a-Mg,Mg2Ca和Ca2Mg6Zn3组成.在SBF溶液中浸泡72 h后,Mg-1Zn-1Ca合金的腐蚀产物为HA(Ca10(OH)2(PO4)6),Ca CO3,Mg Cl2和Mg(OH)2.在浸泡腐蚀过程中,高活性的Mg2Ca相作为阳极率先发生腐蚀,从而对周围a-Mg基体起到一定保护作用,而Ca2Mg6Zn3相活性最低,加剧了a-Mg基体的腐蚀.正挤压态合金耐蚀性能优于铸态合金的耐蚀性能.     

Mg-14Li-1Al-0.1Ce合金在NaCl溶液中的腐蚀行为

采用电化学方法研究了Mg-14Li-1Al-0.1Ce合金在NaCl溶液中的腐蚀行为,采用扫描电镜观察腐蚀后的表面形貌,用失重法测试腐蚀速率,用X射线衍射(XRD)分析了腐蚀层和溶液中腐蚀颗粒的组成。结果表明,Mg-Li-Al-Ce合金的腐蚀速率随溶液Cl-浓度增大而增大,由失重法所得到的腐蚀速率远大于由腐蚀电流密度(Jcorr)计算所得的腐蚀速率。扫描电镜(SEM)观察表明,合金表面随溶液Cl-浓度增加而破坏严重。腐蚀产物层没有保护作用,在腐蚀产物下有明显的蚀坑和裂纹。XRD表明腐蚀产物层和溶液中腐蚀颗粒由Mg(OH)2、Li0.92Mg4.08和Li3Mg7组成。     

Sn对Mg-8.5Li-3Al合金组织和性能的影响

采用真空感应熔炼技术制备了Mg-8.5Li-3Al和Mg-8.5Li-3Al-1Sn合金,研究Sn对Mg-8.5Li-3Ai合金组织和性能的影响,结果表明,Sn在Mg-Li-Al系合金中主要以颗粒状Mg2Sn化合物的形式存在于β(Li)相中,Mg2Sn颗粒对Mg-Li-Al合金可以起到第二相强化作用.     

Mg-1Zn-1Mn合金微弧氧化膜在SBF模拟体液中的腐蚀行为

采用微弧氧化工艺在Mg-1Zn-1Mn合金表面制备微弧氧化陶瓷膜。借助扫描电镜、激光扫描共聚焦显微镜、能谱分析仪和X射线衍射分析仪对氧化膜的微观结构和相组成进行表征,通过电化学方法和浸泡实验研究陶瓷膜在模拟体液中的耐腐蚀性。结果表明:微弧氧化5 min可在Mg-1Zn-1Mn合金表面形成光滑平整、厚度为10μm并与基体结合良好的陶瓷膜,其主要由Mg O和Mg2Si O4组成,为典型的多孔结构;微弧氧化陶瓷膜可使Mg-1Zn-1Mn合金产生钝化,显著提高合金在SBF溶液中的耐腐蚀性,腐蚀速率降低至0.026 mm/a,耐腐蚀性提高近10倍。陶瓷膜裂纹和腐蚀介质与陶瓷膜反应造成的破损使得腐蚀液渗入到合金与陶瓷膜界面,导致SBF溶液与合金接触发生反应,造成点蚀和丝状腐蚀。     

Zn对粉末冶金法制备Mg-Zn合金组织与性能的影响

以Mg粉和Zn粉为初始原料,采用粉末冶金技术制备Mg-Zn合金。研究了Zn含量对Mg-Zn合金烧结密度、显微组织、物相组成、弯曲强度和显微硬度的影响。测量了Mg-Zn合金的耐腐蚀性,探讨了Zn元素在粉末冶金过程中的作用机理。研究结果表明当添加Zn元素后,烧结产物的晶粒细小,烧结密度提高。此外,随着Zn含量的增加,烧结产物的致密度持续增加。XRD分析表明Mg-3 wt%Zn合金主要由α-Mg相组成,而Mg-4 wt%Zn合金由α-Mg 和 MgZn₂两相组成。随着Zn含量的增加,Mg-Zn合金的弯曲强度先增加而后降低,但是显微硬度持续增加。Mg-3 wt% Zn合金的抗弯强度为123.6 MPa,显微硬度为101.7 HV,分别为纯Mg样品高出58%和45%。耐腐蚀性能测试表明当添加Zn元素后,Mg-Zn合金的腐蚀速率降低,Mg-3 wt%Zn合金具有最低的腐蚀速率和最佳的耐腐蚀性能。     

Mg-9Li-5Gd-1Zr合金的组织转变及力学性能

采用常规熔炼工艺制备Mg-9Li-5Gd-1Zr合金,考察了合金元素、均匀化热处理及ECAP挤压对Mg-9Li双相合金组织转变与力学性能的影响.结果表明,合金元素Gd和Zr能显著细化Mg-9Li双相合金中的α-Mg相,使其成为细小的条状,并均匀分布于基体中;与形成的具有取向分布的针状Mg3Gd对铸态合金起主要强化作用.均匀化热处理使β-Li基体晶粒明显长大;β-Li基体内的针状Mg3Gd相发生部分溶解、数量急剧减少;条状α-Mg相沿晶界偏聚长大,形成块状;合金强度较铸态略有下降,伸长率显著提高.ECAP一道次挤压在细化基体组织,改善组织均匀性的同时,导致均匀化处理合金中条状α-Mg相和针状Mg3Gd相破碎细化,诱导回溶的Mg3Gd相沿流变方向再次析出,合金较均匀化处理的强度、塑性均有所下降.     

Corrosion characterization of Mg-8Li alloy in NaCl solution

The corrosion mechanism of Mg-8Li alloy in NaCl solution was investigated by electrochemical testing and SEM observation. The electrochemical results indicated that the corrosion resistance of Mg-8Li alloy in 0.1 M NaCl solution gradually deteriorated with increasing of immersion time expect for 2 h immersion, which was consistent with the SEM observation of corrosion morphology. Mg-8Li alloy exhibited filiform type of attack under significant anodic control of magnesium solution reaction. The cathodic reaction was driven by hydrogen evolution reaction. The presence of filiform corrosion also proved a resistant oxide film naturally formed on the surface of Mg-8Li alloy.     

Corrosion behavior of SiC reinforced magnesium composites

The corrosion behavior of two SiC reinforced Mg-based metal matrix composites, Mg-6SiC and Mg-16SiC (in volume percent), has been studied in freely aerated 1 M NaCl solution and compared with that of pure Mg. The presence of SiC particles deteriorated the corrosion resistance of magnesium. Corrosion resistance decreased with increasing SiC volume fraction. The galvanic corrosion current density between pure SiC and pure Mg has been experimentally measured using zero resistance ammeter technique and theoretically determined using mixed potential theory. Galvanic corrosion between Mg matrix and SiC reinforcement in the composites did not contribute significantly to the overall corrosion rate. Electrochemical impedance spectroscopy indicated that the higher corrosion rates for the composites could be related to the defective nature of surface film.     

A novel phosphate conversion film on Mg-8.8Li alloy

The super light Mg-Li alloys exhibit excellent formability due to the addition of lithium, but the corrosion resistance is deteriorated. A novel conversion film is developed to improve the corrosion resistance. The surface morphology of conversion film was observed using scanning electron microscopy (SEM). The chemical composition was analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The corrosion behaviors of Mg-8.8Li alloy and conversion film were investigated with electrochemical and immersion tests. The experimental results indicated that the Mg-8.8Li alloys with and without the protection of conversion film can both be used in NaOH solution safely. But the Mg-8.8Li substrate was susceptible to corrode in NaCl and Na₂SO₄ solutions, and the conversion film can prevent them from corroding. Compared with the NaCl solution, the Na₂SO₄ solution was a strong corrosive medium to the conversion film.     

Influence of Ca on mierostructure and corrosion resistance of Mg-14Li alloy

In order to improve the corrosion resistance of magnesium lithium alloy, Mg-14Li alloy with different content of Ca (0, 3, 5, 10wt.%) was prepared with a induction melting furnace. Electrochemical test and corrosion test were carried out in NaCI solution with different Cl^- concentrations. The results indicate that the microstructure of the Mg-14Li alloy with Ca consists of dendritic β phase and eutectic structure (β+CaMg₂). With the increase of Ca addition from 0, to 3, 5, 10wt.%, the corrosion resistance of the Mg-14Li alloy initially increases first and then decreases, and that of alloy with 3% Ca is the best. Therefore, the corrosion resistance of Mg-14Li alloy in NaCI solution can be effectively improved by adding proper amount of Ca. In addition, the concentration of Cl^- was one of important factors affecting the corrosion resistance of the Mg-14Li alloy, and the influence of Ca was slighter than that of Cl^-.

     

Mg-1lLi-3AI-O. 5RE合金在酸性NaCI溶液中腐蚀特性研究

为研究Mg-11Li-3Al-0.5RE合金在酸性NaCl溶液中的腐蚀特点,采用静态失重法和电化学方法对合金的腐蚀行为进行测试,并用SEM、XRD分别分析了腐蚀形貌和腐蚀产物.结果表明:在酸性NaCl溶液中,随着Cl-含量的升高,合金的平均腐蚀速率增大,腐蚀电位负移,体系中Rsol、Rt、Rf减小,腐蚀越严重; pH值减小时,合金的腐蚀电流增大,线性极化电阻减小,加快了腐蚀的进行.在酸性环境中,Mg-11Li-3Al-0.5RE合金腐蚀后形成较大、较深的蚀坑,腐蚀产物主要为Mg(OH)2和Al2O3.     

In vitro degradation and cytotoxicity of Mg-5Zn-0.3Ca/nHA biocomposites prepared by powder metallurgy

Mg-5Zn-0.3Ca/nHA biocomposites were prepared from pure Mg, Zn, Ca and nano-hydroxyapatite (nHA) powders by powder metallurgy method. The effect of various mass fractions of nHA (1%, 2.5%, 5%) as reinforcement on the corrosion properties of Mg-5Zn-0.3Ca alloy was investigated. The corrosion resistance of biocomposite samples was investigated by immersion tests and electrochemical techniques in SBF solution. The results showed that the corrosion resistance of Mg alloy was improved by adding 1% and 2.5% nHA. Bioactive nHA motivated the formation of stable phosphate and carbonate layers on surface and improved corrosion resistance of nanocomposites. However, addition of large contents of nHA in Mg alloy as reinforcement increased the density of this precipitated layer, so gases produced from localized corrosion were accumulated underneath this layer and decreased its adhesiveness and lowered its corrosion resistance. Indirect cytotoxicity evaluation for Mg alloy and its nanocomposites also showed that their extraction was not toxic and nanocomposite with 1% nHA indicated almost similar behavior as negative control.     

镁锂合金表面高锰酸盐转化膜的研究

采用化学转化法在镁锂合金表面制得了结构致密、耐蚀性能较好的高锰酸盐转化膜,研究了转化液中高锰酸盐溶液浓度对成膜效果的影响.实验采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)和X射线光电子能谱(XPS)对所制得转化膜的表面形貌、结构和组成进行了测试.同时,使用动电位极化曲线、电化学交流阻抗谱和腐蚀失重3种方法对镁锂合金及其转化膜的耐腐蚀性能进行了深入研究.结果表明:高锰酸盐转化膜较均匀、平整,间隙较小,转化膜主要由锰的氧化物组成.提高了镁锂合金的耐腐蚀性能,当高锰酸盐溶液浓度为4.0 g/L时,转化膜的腐蚀电流密度小、容抗弧大、腐蚀速率低,耐腐蚀性能佳.     

Electroless Ni-P plating on Mg-10Gd-4.8Y-0.6Zr magnesium alloy with a new pretreatment process

A new pretreatment process for electroless Ni-P plating on Mg-10Gd-4.8Y-0.6Zr was investigated in this paper. The morphology, component, chemical composition and structure of the pretreatment layers and Ni-P coating were analyzed by scanning electronic microscopy, energy dispersive spectroscopy and X-ray diffraction spectroscopy. The structure of Ni-P coating was also detected by transmission electron microscopy (TEM). Potentiodynamic polarization analysis and salt spray test were used to test the corrosion resistance of the Ni-P coating. Experimental results indicate that: metal Cr generated in the new pretreatment process, which provided active points for later zinc immersion process, was beneficial to nickel deposition. The subsequent Ni-P coating was amorphous, in which the content of P was 9.43 wt.%. It was uniform and its thickness reached about 50 μm at 2 h deposition. Compared to Mg-10Gd-4.8Y-0.6Zr alloy substrate, the corrosion potential of the coated alloy shifted by 1090 mV positively and the corrosion current density decreased one order of magnitude in 3.5 wt.% NaCl solution. The salt spray test time of Ni-P coating was 210 h. All of these results suggest that the electroless nickel plating procedure researched in this paper is suitable for Mg-10Gd-4.8Y-0.6Zr alloy.