NZ2锆合金碘致应力腐蚀

研究了NZ2锆合金板材在不同温度、不同浓度的碘蒸气中的力学行为,并进一步通过扫描电镜观察其断口形貌。结果表明,试验温度为400℃,其发生应力腐蚀的临界碘蒸气压约为102Pa;横向试样较轧向试样更具应力腐蚀敏感性;温度升高能够促进裂纹尖端的应力释放,有利于碘能被更有效地吸附到裂纹尖端,加快对锆合金的腐蚀作用,从而降低了应力腐蚀的临界碘浓度。在高温碘蒸气中,断口腐蚀产物主要为锆的氧化物;虽然碘蒸气对锆有较强的腐蚀作用,但是不足以穿透其表面的保护膜,而局部变形则可以促进碘对金属锆的腐蚀。     

I-SCC Behavior Evaluation of N36 Zirconium Alloy Cladding Using Ring Tensile Test

在102,103,104Pa碘蒸气压力和350℃温度条件下对N36锆合金包壳管进行I-SCC(碘致应力腐蚀)环向拉伸试验。对拉断后的环形试样进行宏观观察。碘环境下的试样表现出脆性断口,不同于无碘环境下的杯-杯形韧性断口形貌。分析试验载荷-位移曲线及力学参数,评价试样的I-SCC敏感性。碘环境下力学性能均较无碘环境下降,且下降程度随着碘浓度的升高而增大。通过对I-SCC评价参数的筛选,采用以拉伸载荷-位移曲线下面积表示的韧性作为I-SCC敏感性评价参数,结果表明包壳管韧性随着碘浓度的增加而降低。     

N36锆合金包壳管环向拉伸I-SCC行为评价(英文)

在102,103,104Pa碘蒸气压力和350℃温度条件下对N36锆合金包壳管进行I-SCC(碘致应力腐蚀)环向拉伸试验。对拉断后的环形试样进行宏观观察。碘环境下的试样表现出脆性断口,不同于无碘环境下的杯-杯形韧性断口形貌。分析试验载荷-位移曲线及力学参数,评价试样的I-SCC敏感性。碘环境下力学性能均较无碘环境下降,且下降程度随着碘浓度的升高而增大。通过对I-SCC评价参数的筛选,采用以拉伸载荷-位移曲线下面积表示的韧性作为I-SCC敏感性评价参数,结果表明包壳管韧性随着碘浓度的增加而降低。     

碘对N18锆合金应力腐蚀开裂的影响

研究了再结晶退火N18锆合金在碘气氛中的应力腐蚀开裂（SCC）行为,着重研究了350℃时碘分压对该合金SCC的影响.结果表明,随着碘分压增加,N18合金对碘致应力腐蚀开裂 的敏感性增加,开裂的临界应力强度因子KISCC降低,裂纹萌生所需的应力降低,裂纹萌生所需的时间也缩短;SCC裂纹的快速扩展也受碘分压的强烈影响,碘分压越高, 裂纹扩展过渡到快速的穿晶准解理方式时对应的应力强度因子越低;碘分压不仅影响腐蚀产物层的形成,也影响裂纹扩展方式.碘分压的影响规律可用碘的扩散机制及Zr-I-O体系的化 学平衡来解释.     

Ti-6Al-4V合金的热盐应力腐蚀

在实验室条件下研究了Ti-6Al-4V合金热盐应力腐蚀。实验表明在300—420℃温度范围内静态热盐应力腐蚀临界应力低于同温度的蠕变强度。实验还表明,经热盐应力暴露后试样的塑性对形变速度很敏感。用离子探针分析断口微区氢浓度的结果表明,氢在试样表面和断口处有明显的富集,因而可以认为钛合金热盐应力腐蚀的脆化是通过盐对试样的腐蚀而生成的氢所引起的。     

HOT SALT STRESS CORROSION CRACKING OF TITANIUM ALLOY Ti-6A1-4V

在实验室条件下研究了Ti-6Al-4V合金热盐应力腐蚀。实验表明在300—420℃温度范围内静态热盐应力腐蚀临界应力低于同温度的蠕变强度。实验还表明,经热盐应力暴露后试样的塑性对形变速度很敏感。用离子探针分析断口微区氢浓度的结果表明,氢在试样表面和断口处有明显的富集,因而可以认为钛合金热盐应力腐蚀的脆化是通过盐对试样的腐蚀而生成的氢所引起的。     

取向对含钪2124铝合金抗应力腐蚀开裂行为的影响

采用光学显微镜和扫描电镜等研究新型含钪2124铝合金两种不同取向试样在3.5%NaCl(质量分数)溶液中的应力腐蚀开裂行为,并对裂纹尖端形貌和腐蚀形貌进行分析。结果表明:该铝合金在应力腐蚀时首先发生阳极溶解,裂纹尖端晶界处大量聚集的腐蚀产物产生的楔入力和外加应力的共同作用促使预制裂纹在腐蚀介质中进一步沿晶界向纵深方向扩展;两种取向试样在全浸腐蚀时均发生明显的晶间腐蚀,容易发生应力腐蚀开裂;得到了不同取向试样的应力腐蚀裂纹扩展规律及应力腐蚀强度因子门槛值,并探讨取向对应力腐蚀开裂行为的影响。     

Effects of Stress Intensity Factor on Electrochemical Corrosion Potential at Crack Tip of Nickel-Based Alloys in High Temperature Water Environments

在高温水环境中,应力会提高镍基合金裂纹尖端的阳极溶解速率并加速裂纹扩展。采用弹塑性有限元方法,对高温水环境中镍基合金裂纹尖端应力和电化学腐蚀的关系进行研究。分析了应力强度因子对模拟高温水环境中600合金1T-CT试样裂纹尖端表面电化学腐蚀电位的影响,并讨论了弹性变形和塑性变形对裂纹尖端电化学腐蚀电位变化的影响。     

应力强度因子对高温水环境中镍基合金裂尖电化学腐蚀电位的影响（英文）

在高温水环境中,应力会提高镍基合金裂纹尖端的阳极溶解速率并加速裂纹扩展。采用弹塑性有限元方法,对高温水环境中镍基合金裂纹尖端应力和电化学腐蚀的关系进行研究。分析了应力强度因子对模拟高温水环境中600合金1T-CT试样裂纹尖端表面电化学腐蚀电位的影响,并讨论了弹性变形和塑性变形对裂纹尖端电化学腐蚀电位变化的影响。     

Ti-679合金热盐应力腐蚀行为

在350～500℃范围内研究了Ti-679合金的热盐应力腐蚀性能。实验表明合金的显微组织对热盐应力腐蚀的敏感性有很大的影响,在相同的热暴露条件下α+β相区热处理试样的临界应力比β相区热处理的要高。试验结果也表明,表面存在压应力的试样的临界应力高于无压应力者。用离子探针对断口表而进行的测定显示出在裂纹中有氢的大量富集,这表明钛合金在受热盐应力腐蚀过程中所产生的并随后被吸收的氢是开裂的主要原因。     

Interkristalline,Kornflächen- und Spannungsriß-Korrosion von ausgehärteten AlZnMg 1-Legierungen

Intercrystalline corrosion, grain-phase corrosion and stress-corrosion cracking of aged AlZnMg1 alloys Potentiostatic polarisation curves and stress corrosion crack propagation of a pure and a commercial AlZnMg1-alloy, both peakhardened either by warm or by double ageing, were investigated in airsaturated sodium halide and sulfate solutions at a temperature of 303 K. For this, propagation of crack tips was observed microphotographically under potentiostatic conditions and under constant stress using specimens precracked by fatique corrosion. The pure alloy contents (weight percent): Zn 4,4; Mg 1,26; Fe 0,05; Si 0,006; balance Al, the commercial alloy: Zn 5,05; Mg 1,2; Fe 0,23; Si 0,1; Mn 0,23; Cr 0,2; Cr 0,2; Ti 0,074; Zr 0,12; Cu 0,056; balance Al. In sodium halide solutions either grain boundary and grain attack or only grain attack occurs at a potential region more positive than the respective breakdown potential. At the more negative restpotential no attack can be observed. The influence of concentration of chloride ions on the velocity of discontinuous crack propagation in the pure alloy, which starts without any initiation stage, is different for both heat treatments. No crack propagation is observed in the commercial alloy and in any case in sulfate solutions. The obtained stress corrosion cracking results may be explained by hydrogen embrittlement of the area around the crack tip.     

The effects of heat treatment and zirconium on the corrosion behaviour of Mg-3Nd-0.2Zn-0.4Zr (wt.%) alloy

The corrosion behaviours of Mg-3Nd-0.2Zn (wt.%) (NZ) and Mg-3Nd-0.2Zn-0.4Zr (wt.%) (NZK) alloys were investigated in as-cast (F), solution-treated (T4) and artificially-aged (T6) conditions in 5% NaCl solution using immersion test and electrochemical measurements. The immersion test indicates that both NZ and NZK alloys exhibit better corrosion resistances in T4 and T6 states than in the F condition due to the galvanic corrosion between the cathodic Mg₁₂Nd compound and the anodic α matrix in the F condition. The NZK alloy demonstrates lower corrosion rates than the NZ alloy in three conditions, which indicates that the addition of zirconium has a beneficial effect on the corrosion resistance. It was discovered by field emission scanning electron microscope (FE-SEM) that the corrosion products of NZK-T6 formed in salt solution are composed of sandwich shape compounds, while that of NZ-T6 is composed of fine needle-like compounds and small particles. The former are more uniform and compact than the latter and can play a more protective role for the alloy. Electrochemical measurements also confirmed that the more protective film formed on the NZK than on the NZ alloy.     

Electrochemical Behavior of Biomedical Titanium Alloys Coated with Diamond Carbon in Hanks’ Solution

Biomedical implants in the knee and hip are frequent failures because of corrosion and stress on the joints. To solve this important problem, metal implants can be coated with diamond carbon, and this coating plays a critical role in providing an increased resistance to implants toward corrosion. In this study, we have employed diamond carbon coating over Ti-6Al-4V and Ti-13Nb-13Zr alloys using hot filament chemical vapor deposition method which is well-established coating process that significantly improves the resistance toward corrosion, wears and hardness. The diamond carbon-coated Ti-13Nb-13Zr alloy showed an increased microhardness in the range of 850 HV. Electrochemical impedance spectroscopy and polarization studies in SBF solution (simulated body fluid solution) were carried out to understand the in vitro behavior of uncoated as well as coated titanium alloys. The experimental results showed that the corrosion resistance of Ti-13Nb-13Zr alloy is relatively higher when compared with diamond carbon-coated Ti-6Al-4V alloys due to the presence of β phase in the Ti-13Nb-13Zr alloy. Electrochemical impedance results showed that the diamond carbon-coated alloys behave as an ideal capacitor in the body fluid solution. Moreover, the stability in mechanical properties during the corrosion process was maintained for diamond carbon-coated titanium alloys.     

车体用挤压态Al-6.5Zn-1.55Mg-0.25Cr-0.1Zr合金晶粒取向及应力腐蚀性分析

对含有不同显微组织形态的Al-6.5Zn-1.55Mg-0.25Cr-0.1Zr铝合金开展耐应力腐蚀表征,利用EBSD和TEM处理方法深入探讨了试样发生应力腐蚀开裂的特性。研究结果表明:晶粒形成了许多小角度晶界,大角度晶界基本都是由纤维状晶界构成。以挤压工艺制备的Al-Zn铝合金可以对再结晶过程起到抑制作用,由此减小大角度晶界的比例。有大量亚稳态球形Mg-Zn2颗粒分布于等轴晶组织以及纤维组织晶粒中,还有大量纤维组织出现在亚晶结构中;在纤维组织中还可以观察到一些非常细小的亚晶界析出相,颗粒尺寸只有12 nm。原始组织会减小应力耐腐性,在不同时间的裂纹扩展方向也存在较大差异,在临界深度处变成横向排布的裂纹。大角度晶界成为应力腐蚀裂纹的高效扩展通道,当形成小角度亚晶界后则能够对裂纹扩展发挥抑制作用。     

Beitrag zur Wachstumskinetik der interkristallinen Korrosion von ausgehärteten Al?Cu-Legierungen. Teil II: Der Einfluß mechanischer Spannungen

Contribution to the growth kinetics of the intergranular corrosion of age-hardened Al? Cu alloys. Part II: Influence of mechanical stress The influence of constant uniaxial tensile stresses on the growth kinetics of the intergranular corrosion (IC) of age-hardened Al? Cu-alloys in aqueous chloride solutions under potentiostatic conditions has been investigated using the foil penetration technique. Two systems have been tested, a pure binary Al-4% Cu-alloy (sheet thickness 0.5 mm) in 0.01 m NaCl, pH 11, and a commercial AA 2024 type alloy (various sheet thicknesses from 0.2 to 1.0 mm) in 0.1 m NaCl, pH 7, respectively. Both alloys were tempered to maximum IC susceptibility and have been tested at potentials where selective anodic dissolution of the grain boundary regions occurs. For comparison, the influence of tensile stresses on the pit growth kinetics in commercial pure aluminum (sheet thicknesses ranging from 0.2 to 1.0 mm) in 0.01 m NaCl + 0.01 m Na₂SO₄ (as pit initiation inhibitor), pH 11, has been investigated at an applied potential considerably higher than the pitting potential. All measurements have been carried out under various tensile stress levels ranging from 25 to 88% of the 0.2% proof stress (R_p0.2). The results show a significant reduction of the penetration times by a factor of 2 to 10 for all applied stress levels when only a few parallel cracks are growing (coarse-grained pure binary alloy and thin sheets of the fine-grained commercial alloy). For systems with large numbers of cracks (thicker sheets of the fine-grained alloy), no influence of the tensile stresses on the growth kinetics of the IC could be found. The penetration times for pits growing in pure aluminium have been reduced by a factor of 1.2 to 1.7 in presence of tensile stresses. The basic assumption for the discussion of the results is that even the highest mean crack growth velocities observed in this work can be expained by pure anodic dissolution of the grain boundary regions at the crack tips. The increase of the dissolution current density at the crack tips is due to the mechanical widening of the cracks. This widening of the cracks may cause a change of the crack geometry and, therefore, of the integral electrical resistance of the system (primary current distribution). Additionally, the mass transport conditions between the cracks and the bulk electrolyte may als be improved (changes of the composition of the electrolyte and, therefore, of the ohmic potential drop inside the cracks). The widening of the cracks depends on the mechanical stress distribution in the whole specimen and not only on the stress intensity at the crack tips. This allows to explain why tensile stress does not have any influence when a large number of parallel cracks are present (mechanical stress relief). The comparatively small increase of pit growth velocity is based on the weak influence of tensile stresses on the geometry of circular pits.     

微合金化元素Zr对5083铝合金组织和性能的影响

在实验室中用井式坩埚炉熔炼铸造了5083和5083+0.1Zr两种铝合金,轧制后在100～450℃范围内退火。通过金相显微镜、显微硬度计、扫描电镜、电子万能试验机、透射电镜对合金的铸态组织、板材纤维组织、力学性能、耐蚀性能、第二相粒子成分进行了分析,研究了微量元素Zr对5083铝合金组织性能的影响。结果表明,添加微量元素Zr能够细化合金组织,与未添加Zr相比,添加0.1Zr的5083合金的铸态晶粒尺寸从123μm降至73μm,并使第二相粒子Al₆Mn(Fe)尺寸变小;同时使晶间腐蚀坑变小,合金耐蚀性得到提高。添加微量元素Zr还能抑制合金板材再结晶,300℃退火1 h无明显再结晶现象;尤其是5083+0.1Zr合金经250℃退火1 h,抗拉强度为389.50 MPa,屈服强度为215.62 MPa,伸长率为18.2%,仍完全满足使用要求。     

Zr含量对Mg-3Zn-1Y合金显微组织和腐蚀行为的影响

采用传统重力铸造法制备了Mg-3Zn-1Y-xZr (x=0,0.2,0.4,0.6)合金,并通过光学显微镜(OM)、扫描电镜(SEM)、失重和电化学实验研究了Zr含量对Mg-3Zn-1Y显微组织和腐蚀行为的影响.结果 表明:Mg-3Zn-1Y主要由α-Mg基质和Mg3YZr6(Ⅰ)相组成,Zr的加入没有改变第二相的类...     

微量Zr、Er对Al-Zn-Mg合金组织与性能的影响

采用硬度、拉伸性能、电阻率和抗应力腐蚀性能测试及金相组织观察等方法,研究了微量Zr、Er对Al-4.4Zn-2.4Mg(质量分数,下同)合金组织与性能的影响.结果表明,单独添加Zr的细晶作用优于单独添加Er以及Er、Zr复合添加,Er、Zr复合添加能显著抑制合金的再结晶行为,Er、Zr复合添加后合金的力学性能和单独添加微量Zr的基本相当,但Er、Zr复合添加后合金抗应力腐蚀性能优于单独添加微量Er、Zr,Er、Zr复合添加的Al-Zn-Mg合金综合性能最好.Er、Zr复合添加提高应力腐蚀抗力是通过抑制再结晶获得纤维组织间接实现的.     

Sc、Zr对Al-Zn-Mg-Cu合金组织与性能的影响

制备了成分Al-5．8Zn-2．5Mg-1．6Cu-0．2Cr和Al-5．8Zn．2．5Mg-1．6Cu-0．2Cr-0．23Sc-0．12Zr的两种合金。通过金相显微镜及电镜观察、力学性能及腐蚀性能测试,分析了两种合金不同处理状态的显微组织及其不同状态下的力学性能和腐蚀性能。结果表明,添加Sc、Zr能显著细化合金的铸态组织,对合金的力学性能及腐蚀性能也起到极大的提高作用。添加Sc、Zr的2#合金与1#合金相比较,经T6处理后,前者的抗拉强度提高110N／mm^2,屈服强度提高91N／mm^2,伸长率也略有提高。