(Zr55All0Ni5Cu30)0.97Ce0.03非晶合金在含Cl-介质中的腐蚀电化学行为研究

  用电化学技术方法研究了Zr₅₅Al_l0Ni₅Cu₃₀和(Zr₅₅Al_l0Ni₅Cu₃₀)_0.97Ce_0.03非晶合金在含Cl^-介质中的腐蚀电化学行为及添加稀土Ce的影响.结果表明：随Cl^-浓度增加,两种非晶合金的腐蚀速度加快;添加稀土Ce后提高合金耐蚀性;随极化电位的提高,两种非晶合金在0.05 mol/L Na₂SO₄及含Cl^-介质中均出现钝化特征,维钝电流密度随Cl^-浓度增加而减小;Zr₅₅Al_l0Ni₅Cu₃₀非晶合金的电化学阻抗谱由单容抗弧组成(Zr₅₅Al_l0Ni₅Cu₃₀)_0.97Ce_0.03非晶合金的交流阻抗谱在Cl^-浓度较低时呈单容抗弧特征,而随Cl^-浓度的增加,单容抗弧变为双容抗弧.     

Cu含量对新型AlNiZrCoYSi高熵非晶合金非晶形成能力与耐腐蚀性能的影响

采用高真空电弧熔炼喷射成形技术制备了一种新型Al_17.5Ni₂₀Zr_17.5Co₂₀Y₂₀Si₅高熵非晶合金条带,并研究了Cu元素的添加及含量变化对Al_17.5Ni₂₀Zr_17.5Co₂₀Y₂₀Si₅高熵非晶合金耐腐蚀性能的影响。利用X射线衍射仪(XRD)、差示扫描量热仪(DSC)、显微硬度计分别研究了合金材料的非晶形成能力与硬度;通过极化曲线(Tafel)和Nyquist图等电化学方法考察了高熵非晶合金室温下在3.5 wt.% NaCl水溶液中的耐腐蚀性能。结果表明：四种(AlNiZrCo)_75-xCu_xY₂₀Si₅(x=0, 10, 14, 15)近等原子比高熵非晶合金均呈现典型的非晶态衍射峰,Cu含量对AlNiZrCoYSi高熵非晶合金的非晶形成能力影响不大,但会降低合金的抗腐蚀性能,且上述合金的维氏显微硬度均超过470 HV_0.1。其中,Al_17.5Ni₂₀Zr_17.5Co₂₀Y₂₀Si₅高熵非晶合金的耐腐蚀性能最佳,其自腐蚀电位(E_corr)为-0.248 V,自腐蚀电流密度(i_corr)为1.63 μA/cm^₂,极化电阻(R_p)为24.56 kΩ.cm^₂,该材料在解决严苛海洋环境下防腐耐磨问题具有较大的应用潜力。     

EFFECT OF Gd ADDITION ON THE GLASS FORMING ABILITY AND MECHANICAL PROPERTIES IN A Zr–BASED BULK AMORPHOUS ALLOY

适量的Gd掺杂可提高Zr_50.7Cu₂₈Ni₉Al_12.3块体非晶合金的玻璃形成能力, 当Gd元素掺杂量 (原子分数) 为1%时, 即(Zr_50.7Cu₂₈Ni₉Al_12.3)₉₉Gd₁, 柱状非晶合金直径可达16 mm (不掺杂时为14 mm). 稀土Gd掺杂降低了锆基块体非晶合金的断裂强度与塑性 变形能力. 随着Gd含量的增加, 其断裂方式由单一的剪切断裂转变为剪切断裂与破碎断裂的复合形式, 且含Gd元素掺杂的非晶合金断口呈现了脉状纹络与纳米周期性条纹共存的特征.     

Mg-Cu-Y非晶合金在酸性介质中腐蚀行为研究

    利用动电位极化曲线研究了非晶和铸态的Mg_58.5Cu_30.5Y₁₁镁合金在0.005 mol/L H₂SO₄+0.25 mol/L Na₂SO₄中的电化学腐蚀行为,结果表明：开路电位下两种材料均发生活性溶解,非晶合金由于具有高反应活性,比铸态合金更容易腐蚀;但当外加阳极电位增加至一定数值后,非晶合金的阳极溶解速度低于铸态合金,这是由于非晶合金中溶解到溶液中的Cu重新沉积到合金表面形成了具有保护性能的Cu富集层;铸态合金由多种相组成,不同相之间的电偶腐蚀加速了铸态合金的溶解.     

长期时效N10276合金在CO2/H2S/Cl- 环境中的腐蚀行为

通过电化学阻抗与循环动电位极化的方法研究了在CO₂/Cl^-以及CO₂/H₂S/Cl^-溶液体系中、长期时效前后N10276合金的腐蚀机理。结果表明,阻抗弧的低频区间出现了一个不完整的容抗弧,并且随H₂S浓度的增加（10~100 μL/L）转变为Warburg阻抗,其主要原因是高含量H₂S相关吸附物。H₂S可以增加合金腐蚀速率。相比较而言,长期时效处理主要作用于合金点蚀的形成,其中,经过长期时效处理的奥氏体组织内存在大量的第二相（富含Mo与Ni的μ相）,而析出物周围的区域成为优先腐蚀区域,进而导致了N10276合金点蚀的发生。     

Tm对锆基块体非晶合金力学性能和腐蚀性能的影响

采用铜模负压吸铸工艺制备了(Zr_0.6336Cu_0.1452Ni_0.1012Al_0.12)_100-xTm_x（x=0~5,原子分数）块体金属玻璃（BMG）合金,研究了Tm对合金力学性能和抗腐蚀性能的影响。结果表明,当Tm含量增加到3%时,其玻璃形成能力（GFA）和压缩塑性显著提高,但过量Tm会降低GFA。x=3时合金的最大过冷液相区宽度为100 K,抗压强度为1669 MPa,塑性应变为21.01%,远高于Zr_0.6336Cu_0.1452Ni_0.1012Al_0.12 BMG的各项性能（67 K、1439 MPa和5.90%）。然而,电化学测试结果表明,x=3时的合金在3.5%（质量分数）NaCl溶液中的耐腐蚀性不佳,且其耐腐蚀性和力学性能随Tm含量的变化趋势与预期不同。可能是由于过量添加稀土元素Tm,容易形成更多的氧化物,导致点蚀加剧。进一步添加Tm可以提高Zr基BMG钝化膜的完整性和耐点蚀性能,但力学性能不理想。     

具有高非晶形成能力的高熵合金Cu29Zr32Ti15Al5Ni19

用铜模吸铸法成功地合成了由两个固溶体相构成的高熵合金(HEA) Cu₂₉Zr₃₂Ti₁₅Al₅Ni₁₉和相同成分的非晶态合金(HE-BMG)。实验结果表明该成分的高熵合金具有高的非晶形成能力。铸态高熵合金Cu₂₉Zr₃₂Ti₁₅Al₅Ni₁₉的抗压强度为1127MPa。在750℃保温2小时后的Cu₂₉Zr₃₂Ti₁₅Al₅Ni₁₉高熵合金的硬度仍高达826HV。     

RAPID SOLIDIFICATION WELDING OF ULTRA--THIN Zr55Cu50Al12Ni3 AMORPHOUS FOILS

应用微型储能焊机实现了厚度为25---35 μm的Zr₅₅Cu₃₀Al₁₂Ni₃非晶箔材的快速凝固连接. XRD测试表明, 接头仍为非晶结构. 计算的接头冷却速率高达10⁶ K/s, 远大于形成锆基非晶合金的临界冷却速率, 有效地抑制了接头区的晶化. 接头尺寸微小, 直径为60---90 μm, 未产生气孔、夹杂等焊接缺陷. 接头剪切强度高达1141 MPa. 高的电阻率特性使非晶合金的焊接能量明显低于晶态合金.     

冷-热处理对Zr基块体非晶合金结构和性能的影响

传统晶态材料构件或装备在低温环境中会出现可动部分卡死、龟裂、特性改变甚至脆性断裂等现象。低温极端条件如温度突变、高应变速率冲击等对材料性能带来的不利影响严重制约了其在低温极端环境领域的应用。块体非晶合金在低温条件下具有强度更高塑性更好的特殊性能,在极地科考以及航空航天等极端条件下具有极大的应用优势。本文以(Zr_0.6336Cu_0.1452Ni_0.1012Al_0.12)₉₇Tm₃块体非晶合金为研究对象,研究冷-热处理时间对块体非晶合金的结构、力学性能和腐蚀性能的影响。结果表明,当处理时间由30 min延长到90 min时,试样的晶化体积分数从2.3%增加到4.0%,屈服强度由1701 MPa增加到1810 MPa。在3.5 wt.% NaCl溶液中,合金具有较小的自腐蚀电流密度与较大的电化学阻抗,这意味着经冷-热处理后的块体非晶合金具有优异的耐腐蚀性能。本研究为块体非晶合金在低温极端环境领域的应用提供了强有力的理论支撑。     

Zr-1.0Fe-0.2Cu合金在400 ℃/10.3 MPa过热蒸汽中的腐蚀行为

以高纯锆为母材制备Zr-1.0Fe-0.2Cu合金,并在400 ℃/10.3 MPa过热蒸汽中进行腐蚀实验。用SEM和TEM对合金基体及其腐蚀后生成氧化膜的显微组织进行研究。结果表明：Zr-1.0Fe-0.2Cu合金中只存在底心正交的Zr₃Fe第二相,Cu元素易偏聚在Zr₃Fe相内,使其不易以Zr₂Cu相的形式析出,Cu元素的添加能够细化合金中Zr₃Fe第二相。Zr-1.0Fe-0.2Cu合金在 400 ℃/10.3 MPa过热蒸汽中腐蚀100 d后,耐腐蚀性能优于Zr-1.0Fe以及Zr-4重熔合金,表明添加少量的Cu元素有利于改善合金的耐腐蚀性能。在腐蚀氧化过程中,含Cu的Zr₃Fe相会滞后于合金基体α-Zr相氧化而进入氧化膜。随着氧化进程的加深,第二相中的Zr元素氧化后会以t-ZrO₂的形式存在,Fe元素则氧化成m-Fe₃O₄。伴随着第二相的氧化进程,合金元素Cu和Fe会在氧化膜中扩散流失,不再呈现聚集状态。     

Electrochemical behavior of multicomponent amorphous and nanocrystalline Zr-based alloys in different environments

Electrochemical behavior of multicomponent melt spun Zr-based amorphous as well as nanocrystalline alloys have been studied in three different corrosive media (neutral NaCl, basic NaOH and acidic H₂SO₄ solutions). Due to the presence of strong passivating elements, (Zr and Ti) melt spun ternary alloys (Zr₅₅Ti₂₅Ni₂₀) have shown complete passivation in NaCl solution even as they contain a small amount of crystallinity. Amorphous multicomponent alloys containing Cu (Zr₅₈Cu₂₈Al₁₀Ti₄ and Zr₆₅Cu_7.5Al_7.5Ni₁₀Pd₁₀) show active nature in NaCl solution and this is strongly related to selective dissolution of base metal (Zr) and enrichment of Cu in the pit region. In NaOH and H₂SO₄ solutions, all the alloys have shown complete passivation irrespective of the alloy composition.     

Electron irradiation induced nano-crystallization in Zr66.7Ni33.3 amorphous alloy and Zr60Al15Ni25 metallic glass

Electron irradiation induced phase transformation behavior of an amorphous phase in Zr_66.7Ni_33.3 alloy, and an amorphous phase or supercooled liquid in Zr₆₀Al₁₅Ni₂₅ alloy was investigated. The amorphous phase could not maintain the original glassy structure under electron irradiation at 298 K, and f.c.c.-solid solution precipitated under electron irradiation in both alloys. The precipitation of C16-Zr₂Ni, big-cube (metastable f.c.c.-based Zr₂Ni intermetallic compound), Zr₆Al₂Ni and Zr₅AlNi₄ crystalline phases from an amorphous phase was not observed during electron irradiation induced crystallization. The amorphous phase in Zr₆₀Al₁₅Ni₂₅ metallic glass shows the highest phase stability against electron irradiation induced crystallization among Zr_66.7Cu_33.3, Zr_66.7Ni_33.3, Zr₆₅Al_7.5Ni_27.5, Zr₆₀Al₁₅Ni₂₅ and Zr₆₅Al_7.5Ni₁₀Cu_17.5 alloys. In Zr₆₀Al₁₅Ni₂₅ metallic glass, electron irradiation promoted the precipitation of f.c.c.-solid solution and Zr₆Al₂Ni crystalline phases from the supercooled liquid.     

Corrosion performance of high pressure die-cast Al-6Si-3Ni and Al-6Si-3Ni-2Cu alloys in aqueous NaCl solution

The corrosion performance of high pressure die-cast Al-6Si-3Ni (SN63) and Al-6Si-3Ni-2Cu (SNC632) alloys in 3.5% (mass fraction) NaCl solution was investigated. X-ray diffraction (XRD) and microstructural studies revealed the presence of single phase Si and binary Al₃Ni/Al₃Ni₂ phases along the grain boundary. Besides, the single Cu phase was also identified at the grain boundaries of the SNC632 alloy. Electrochemical corrosion results revealed that, the SNC632 alloy exhibited nobler shift in corrosion potential (?_corr), lower corrosion current density (J_corr) and higher corrosion resistance compared to the SN63 alloy. Equivalent circuit curve fitting analysis of electrochemical impedance spectroscopy (EIS) results revealed the existence of two interfaces between the electrolyte and substrate. The surface layer and charge transfer resistance (R_ct) of the SNC632 alloy was higher than that of the SN63 alloy. Immersion corrosion test results also confirmed the lower corrosion rate of the SNC632 alloy and substantiated the electrochemical corrosion results. Cu addition improved the corrosion resistance, which was mainly attributed to the absence of secondary Cu containing intermetallic phases in the SNC632 alloy and Cu presented as single phase.     

The corrosion behaviour of Zr-based bulk metallic glasses in 0.5 M NaCl solution

The corrosion behaviour of eutectic Zr₅₀Cu₄₀Al₁₀ and hypoeutectic Zr₇₀Cu₆Al₈Ni₁₆ bulk metallic glasses (BMGs) was studied by electrochemical measurements, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Zr₅₀Cu₄₀Al₁₀ BMG was highly susceptible to pitting corrosion in naturally aerated 0.5 M NaCl solution at 30 °C. In contrast, Zr₇₀Cu₆Al₈Ni₁₆ BMG passivated spontaneously under the same condition. EDX results for Zr₅₀Cu₄₀Al₁₀ indicated that enrichment of Cu, Cl and O occurred in the pitted region, while for Zr₇₀Cu₆Al₈Ni₁₆ BMG, no significant difference was found in the surface composition from the specimens before and after immersion in the solution. XPS analysis including angle-resolved measurements for Zr₇₀Cu₆Al₈Ni₁₆ BMG revealed that zirconium cation (Zr⁴⁺) was highly concentrated in both air-formed and passive films. Furthermore, the concentration of Zr⁴⁺ ions after immersion for 24 h or more showed tendency to increase with decreasing take-off angle, indicating that the exterior part of the passive film consisted exclusively of zirconium oxyhydroxide. The high corrosion resistance of Zr₇₀Cu₆Al₈Ni₁₆ BMG was attributed to the formation of homogeneous and stable passive film enriched with zirconium.     

Zr-based bulk glassy alloy with improved resistance to stress corrosion cracking in sodium chloride solutions

In order to evaluate stress corrosion cracking (SCC) susceptibility of Zr-based bulk glassy alloys and develop the BGAs with low susceptibility to SCC, the SCC behaviour of Zr₅₀Cu₄₀Al₁₀, Zr₅₀Cu₃₀Al₁₀Ni₁₀ and hypoeutectic Zr₇₀Cu₆Al₈Ni₁₆ BGAs in various environments including sodium chloride solution has been investigated using a slow strain rate technique at an initial strain rate of 5 × 10⁻⁶ s⁻¹. It is found, for the first time, that the Zr₇₀Cu₆Al₈Ni₁₆ BGA has no susceptibility to SCC in a 0.5 M NaCl solution. On the other hand, Zr₅₀Cu₄₀Al₁₀ and Zr₅₀Cu₃₀Al₁₀Ni₁₀ BGAs are highly susceptible to SCC in the NaCl solution, although they are not susceptible to SCC in de-ionized water, phosphate buffer, 0.5 M Na₂SO₄ and 0.5 M NaNO₃ solutions. The possible cause of the high susceptibility to SCC in the NaCl solution for the Zr₅₀Cu₄₀Al₁₀ and Zr₅₀Cu₃₀Al₁₀Ni₁₀ BGAs is discussed.     

Corrosion of anodically polarized Zn-Al alloys in saturated Ca(OH)2 containing Cl-

Cast Zn-Al alloys containing 0%, 20%, 40%, 55%, 80% and 100% aluminium have been anodically polarized in saturated Ca(OH)₂ containing Cl^- and the conditions for corrosion and for pitting with respect to alloy composition, chloride concentration and alloy microstructure broadly defined. Pure zinc has a large passivation range which shows an etch-pitting-passivation process above about 0.02 M Cl^-. Pure aluminium has a poorly defined passive region with a large passive current and the presence of Cl^- reduces the passive current substantially. All the alloys contain a large amount of a primary aluminium-rich phase which is preferentially corroded and the corrosion behaviour of the alloys reflects the behaviour of the aluminium-rich phase.     

Corrosion resistance of Ni/Al2O3 coatings in NaCl solution

Abstract

This paper presents results of a research on the corrosion resistance of composite Ni/Al₂O₃ coatings electrochemically deposited from Watts baths containing different amounts (0, 20, 100 g dm^?3) of Al₂O₃ particles. Potentiodynamic tests and electrochemical impedance spectroscopy (EIS) measurements were carried out in a 3% solution of NaCl. The coatings with about 6 wt-% of corundum, deposited from a bath with 100 g dm^?3 of a powder, showed the best protective properties. The rate of corrosion of such coatings after 7 days of exposure in the NaCl solution was over two times slower than that of coatings containing 2 wt-% of Al₂O₃ and six times slower than that of a standard nickel coating. Two equivalent circuits: one consisting of two RC circuits and the other one made up of three RC circuits were used for the analysis of the impedance spectra. Regardless of the presence and amount of the Al₂O₃ particles in the nickel coating, during first day of exposure in the NaCl solution a layer of nickel oxides and hydroxides forms on the surface of the coatings increasing their corrosion resistance. In the case of coatings with 6 wt-% of Al₂O₃, the passive layer is least vulnerable to the aggressive action of Cl^? ions.     

Electrochemical behaviour of amorphous and nanoquasicrystalline Zr-Pd and Zr-Pt alloys in different environments

The corrosion behaviour of melt spun amorphous and nanoquasicrystalline Zr₇₀Pd₃₀ and Zr₈₀Pt₂₀ alloy ribbons has been investigated using potentiodynamic polarization study in NaCl, H₂SO₄ and NaOH solutions at different concentrations. The amorphous and nanoquasicrystalline alloys show better corrosion resistance than Zr in all the solutions studied. Both the alloys are susceptible to chloride attack and pitting has been observed. Complete passivation has been observed in H₂SO₄, while gradual break down of passivating layer occurs in NaOH. In general, nanoquasicrystalline state in both the alloys shows better corrosion resistance than amorphous state in all the solutions studied.     

Electrochemical investigations on the bulk glass forming Zr55Cu30Al10Ni5 alloy

The electrochemical behaviour of the Zr₅₅Cu₃₀Al₁₀Ni₅ amorphous alloy prepared as cylindrical bulk samples with 7 mm diameter has been investigated. Cyclic potentiodynamic polarization measurements carried out on the cross section areas of the samples in air-saturated and nitrogen-purged sulphate and hydroxide solutions, respectively, show that the alloy rapidly forms protective passive layers with low electron conductivity which are stable in a wide pH-value and potential range. Anodic layer formation reactions are characterized. In chloride containing electrolytes a pitting corrosion susceptibility of the bulk material exists. The effect of crystalline defects as active sites for the initiation of localized corrosion processes is critically discussed.     

Microstructure and electrochemical behavior of Ti-coatedZr55Al10Ni5Cu30 bulk metallic glass

In this study, pure Ti was coated on Zr₅₅Al₁₀Ni₅Cu₃₀ bulk metallic glass (BMG) using a physical vapour deposition (PVD) technique with magnetron sputtering. Microstructures of Ti coating, BMG substrate and interface were investigated by conventional and high-resolution transmission electron microscopy (TEM and HREM). The electrochemical behavior of Ti-coated Zr₅₅Al₁₀Ni₅Cu₃₀ BMG was studied by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) in Hanks' solution. Scanning electron microscopy (SEM) was used to characterize the surface morphology of the coating after electrochemical testing. HRTEM observation reveals that the sputtering Ti coating consists of α-Ti nano-scale particles with the size about 10 nm. The polarization curves revealed that the open-circuit potential shifted to a more positive potential and the passive current density was lower after Ti coating was applied in comparison with that of the monolithic Zr₅₅Al₁₀Ni₅Cu₃₀ BMG. Electrochemical impedance spectroscopy (EIS) measurements showed that the Bode plots of Ti-coated Zr₅₅Al₁₀Ni₅Cu₃₀ BMG presented one time constant for 1 h and 12 h immersion and two time constants after 24 h immersion. The good bonding condition between Ti coating and Zr₅₅Al₁₀Ni₅Cu₃₀ BMG substrate may be responsible for the high corrosion resistance of Ti-coated Zr₅₅Al₁₀Ni₅Cu₃₀ BMG.