5083铝合金慢应变速率拉伸下的应力腐蚀行为

采用慢应变速率拉伸(SSRT)测试法及扫描电镜(SEM)与透射电镜(TEM)分析手段,研究了预变形量及应变速率对5083铝合金在空气和3.5%NaCl溶液中应力腐蚀开裂(SCC)行为的影响。结果表明:在空气中,5083铝合金几乎不发生SCC现象,其断口均呈现韧性断裂形貌;在3.5%NaCl溶液中,5083铝合金具有SCC敏感性,其断口呈现局部沿晶界或相界断裂形貌,随着应变速率的减小,应力腐蚀敏感指数(ISSRT)增大,当应变速率减至1×10-6s-1时,其应力腐蚀断口呈现典型的解理脆断特征;(Mg5Al8)等第二相析出及预变形后位错增多是导致5083铝合金SCC敏感性增大的主要原因。     

2219铝合金母材及搅拌摩擦焊接头应力腐蚀敏感性

利用慢应变速率拉伸试验,研究2219铝合金母材及搅拌摩擦焊接头在不同腐蚀介质环境中的应力腐蚀行为.运用性能损失率指标和应力腐蚀指数评价材料的应力腐蚀敏感性.结果表明,应变速率为10-6 s-1时,2219铝合金母材和FSW接头在3.5%Na Cl介质环境中SCC敏感性小,断口由韧窝塑性区和腐蚀区组成;在剥蚀介质环境中,母材和FSW接头SCC敏感性大,断口呈冰糖状,有较深的腐蚀坑和二次裂纹,为沿晶脆性断裂.FSW接头SCC敏感性较母材大.     

新型1200 MPa级Ti-35421合金应力腐蚀敏感性的原位电化学研究

以新型1200 MPa级Ti-35421合金(Ti-3Al-5Mo-4Cr-2Zr-1Fe)为研究对象,采用慢应变速率拉伸实验结合原位电化学监测研究了不同应变速率和阴极保护电位对其应力腐蚀开裂行为的影响。结果表明：当应变速率为1.67×10^-5mm·s^-1时Ti-35421合金在3.5%NaCl溶液中应力腐蚀敏感性最高,其塑性损失和应力腐蚀指数分别为27.27%和0.273;裂纹尖端钝化膜层在应力和腐蚀的共同作用下钝化保护弱于溶解,导致了应力腐蚀加剧;当外加阴极保护电位为-600mV时Ti-35421合金在3.5%NaCl溶液中的应力腐蚀敏感性最低,其最佳阴极保护电位范围为-450～-600 mV,降低了阳极共轭反应,从而使其塑性损失和应力腐蚀指数分别降低到1.01%和0.113。     

氢对LC4高强铝合金应力腐蚀断裂的影响

采用慢应变速率拉伸试验研究了氢在LC4高强铝合金应力腐蚀断裂过程中的作用。结果表明，LC4合金在干燥空气中不发生应力腐蚀断裂，而在潮温空气中发生应力腐蚀断裂，在潮湿空气和阳极极化条件下，铝合金的应力腐蚀断裂机理是以阳极溶解为主，氢几乎不起作用，在预渗氢或阴极极化条件下，氢脆起主要作用，预渗氢时间延长可加速LC4合金的应力腐蚀断裂。     

Comparison of accelerated SCC tests performed on the aluminium alloy 2014-T651

The stress corrosion cracking (SCC) behaviour of plates of the Al-Cu-Si-Mn-Mg alloy 2014-T651 was investigated in short transverse direction performing various accelerated tests. Corrosive media used were: aqueous 3.5% NaCl solution, an aqueous solution of 2% NaCl + 0.5% Na₂CrO₄ at pH = 3 (according to LN 65666), and substitute ocean water according to ASTM D1141. C-ring and tensile specimens were loaded under constant deformation, constant load and slow strain rate conditions. Alternate immersion tests in 3.5% NaCl solution clearly indicate the low SCC resistance of the alloy 2014-T651 in short transverse direction. Under continuous immersion conditions the acidified 2% NaCl solution containing chromate is an appropriate synthetic environment, while neutral 3.5% NaCl solution does not promote severe stress corrosion cracking. The SCC susceptibility of 2014-T651 is also observed in slow strain rate tests using substitute ocean water as well as acidified 2% NaCl solution inhibited by chromate. In 3.5% NaCl solution the evaluation of slow strain rate data is complicated by pre-exposure effects.     

Corrosion susceptibility of peened friction stir welded 7075 aluminum alloy joints

Effects of surface treatment techniques like laser and shot peening on stress corrosion cracking (SCC) susceptibility of friction stir welded (FSW) 7075 aluminum alloy joints were investigated. This study had two parts; the first part investigated the peening effects on stress corrosion cracking susceptibility in FSW samples by slow strain rate testing in a 3.5% NaCl solution. The second part of the study investigated the effects of peening on corrosion while submerged in a 3.5% NaCl solution with no external loads applied. No signs of corrosion pitting or SCC were evident on any of the tensile samples during the slow strain rate testing. The FSW plates exposed in 3.5% NaCl solution for 60 days were inspected periodically for signs of corrosion and stress corrosion cracking in the areas expected to have residual stresses due to welding. Pitting corrosion was seen on the samples, but even after 60 day exposure no stress corrosion cracking was detected on any of the peened or unpeened samples.     

On the Stress corrosion cracking behaviour of aluminium alloy sheet in an aqueous solution of 3% NaCl + 0.3% H2O2

The stress corrosion cracking (SCC) behaviour of aluminium alloy sheet was investigated in the long transverse direction using the slow strain rate testing technique. The synthetic environment used was an aqueous solution of 3% NaCl + 0.3% H₂O₂. No indications of SCC sensitivity are observed for the alloys 2024-T351, 8090-T81, and 2091 CPHK-T8X. The alloys 2091 T8X and 6061-T4 are found to be susceptible to intergranular stress corrosion cracking. At strain rates below 4 · 10^?7 s^?1, the slow strain rate testing technique indicates a slight SCC sensitivity with alloy 6013-T6. Fractography reveals transgranular stress corrosion cracking. Transgranular stress corrosion cracking is also observed with 6061-T4 specimens which are dynamically strained at strain rates below 5 · 10^?7 s^?1. Aqueous 3% NaCl solution with hydrogen peroxide addition promotes pitting and intergranular corrosion. The loss of ductility caused by these corrosion processes interferes with the evaluation of the results of the slow strain rate testing technique.     

Spannungsrißkorrosionsuntersuchungen an Strangpreßbarren der Legierungen 8090-T851 und 2091-T851

On the stress corrosion cracking behaviour of flat extrusions of the alloys 8090-T851 and 2091-T851 The stress corrosion cracking (SCC) behaviour of flat extrusions of the Al-Li-Cu-Mg-Zr alloys 8090-T851 and 2091-T851 was investigated performing accelerated tests under constant deformation, constant load, and slow strain rate conditions. The used corrosive environments were an aqueous 3.5% NaCl solution and an aqueous solution of 2% NaCl + 0.5% Na₂CrO₄ at pH = 3. Round tensile specimens and tuning fork type specimens were alternately immersed in 3.5% NaCl solution according to ASTM G44 under constant deformation, whereas they were continuously immersed in the other tests. The investigated flat extrusions of the alloy 8090-T851 were stress corrosion resistant in the extrusion and the long transverse directions. With the alloy 2091-T851 failure was observed at 75% of the 0.2 proof stress which may be caused by stress corrosion cracking or stress assisted intergranular corrosion. In the short transverse direction the SCC behaviour of the extrusions of both Al-Li alloys is comparable with that of a 2024-T351 alloy plate revealing a high SCC susceptibility.     

Zum Spannungsrißkorrosionsverhalten rekristallisierter Bleche der AlLi-Legierung 8090-T81

On the stress corrosion cracking behaviour of recrystallized 8090-T81 Sheets The stress corrosion cracking behaviour of a recrystallized sheet of the Al-Li-Cu-Mg-Zr alloy 8090-T81 was studied performing accelerated tests under constant deformation, constant load, and slow strain rate conditions. The used electrolytes were an aqueous 3.5% NaCl solution, an aqueous solution of 2% NaCl + 0.5% Na₂CrO₄ at pH = 3, and synthetic seawater according to ASTM D1141. Alternately immersed in 3.5% NaCl solution according to ASTM G44 the investigated alloy was found to be susceptible to stress corrosion cracking was not promoted by continuous immersion in aerated 3.5% NaCl solution, 3.5% NaCl solution saturated with carbon dioxide, and in acid chromate inhibited 2% NaCl solution. Using the slow strain rate technique with continuously immersed flat tensile specimens stress corrosion cracking was only observed in synthetic seawater. Under specific environmental conditions hydrogen embrittlement can occur in the investigated material.     

On the corrosion behaviour of 8090-T6 sheet material

The exfoliation corrosion and stress corrosion cracking behaviour of an unrecrystallized sheet of the Al-Li-Cu-Mg-Zr alloy 8090-T6 was investigated. The material was highly susceptible to exfoliation corrosion in the 96 h EXCO test, whereas the intermittent salt spray test (MASTMAASIS test) revealed only a slight degree of exfoliation. The stress corrosion cracking behaviour was investigated in 3.5% NaCl solution under constant load, constant deformation, and slow strain rate conditions. Tests under constant load were also performed in an inhibited and acidified 2% NaCl solution according to the German standard LN 65666. In these accelerated tests the investigated alloy was found to be not susceptible to stress corrosion cracking in the rolling direction. The slow strain rate tests revealed a great scattering of the relative fracture energy with decreasing strain rates. This scatter is probably caused by pits acting as crack nuclei thus giving rise to scatter of the ductility.     

Investigation of the SCC behaviour of alloy 2024 using the slow strain rate technique

The stress corrosion cracking (SCC) behaviour of 2024 plate in T351 and T851 tempers was investigated in short transverse direction performing accelerated tests under constant deformation, constant load and slow strain rate conditions. Corrosive media used were: aqueous 3.5% NaCl solution, an aqueous solution of 2% NaCl + 0.5% Na₂CrO₄ at pH 3 (according to LN 65666), an aqueous solution of 3% NaCl + 0.3% H₂O₂, and substitute ocean water according to ASTM D1141. Alternate immersion tests in 3.5% NaCl solution indicated the low SCC resistance of the alloy 2024-T351 as well as the improved SCC behaviour due to aging to T851 condition. Similar results were obtained from constant load tests under permanent immersion conditions in the acidified chloride-chromate solution, in 3% NaCl solution with peroxide, and in substitute ocean water, whereas no SCC failure was observed with specimens which were permanently immersed in 3.5% NaCl solution. Using the slow strain rate method, 3% NaCl + 0.3% H₂O₂ and substitute ocean water were found to be effective synthetic environments. The other two electrolytes did not promote severe stress corrosion cracking with alloy 2024-T351. The SCC behaviour of 2024-T851 was difficult to determine employing the slow strain rate technique. Large scatter in data, observed even in inert environment, and the low elongation of the aged material, exacerbated by a further degradation of ductility due to pitting and intergranular corrosion, precluded an evaluation.     

晶粒尺寸对Al-Zn-Mg铝合金应力腐蚀敏感性的影响

采用慢应变速率拉伸试验、扫描电镜断口观察和透射电镜晶界微观结构观察及析出相统计等方法,研究了两种晶粒尺寸的Al-Zn-Mg铝合金在3.5%(质量分数)NaCl溶液(pH=6)中的应力腐蚀行为。结果表明:晶粒度大的Al-Zn-Mg铝合金的应力腐蚀敏感性比晶粒度小的合金要高;透射电镜的统计观察分析表明,小晶粒度小的合金的晶界析出相覆盖率高于大晶粒度合金的晶界析出相覆盖率。在一定的晶界析出相面积范围之内,析出相面积分数高的Al-Zn-Mg合金应力的腐蚀敏感性小于析出相面积分数低的Al-Zn-Mg合金。     

冷轧与拉伸复合预变形对2519A铝合金板材应力腐蚀的影响(英文)

采用10-6s-1慢应变拉伸测试手段研究冷轧与拉伸复合预变形对2519A铝合金抗应力腐蚀开裂性能的影响。冷轧7%后再垂直拉伸3%的合金板材抗拉强度和应力腐蚀指数分别为481MPa和0.0429,与冷轧4%后再平行拉伸3%以及冷轧7%后再平行拉伸3%的合金板材相比表现出了更好的力学性能和抗应力腐蚀开裂性能。这主要是由于冷轧7%后再垂直拉伸3%在合金板材中生成了密度更高且分布更均匀的位错组织,使时效后合金板材晶内析出相细小、密集,晶界析出相不连续,晶界无沉淀析出带且较窄。     

Pitting and stress corrosion cracking resistance of friction stir welded AA 5083

The corrosion behaviour of friction stir welded (FSW) joints of AA 5083 has been compared to that of MIG welded joints. Pitting and stress corrosion cracking (SCC) resistance in 3.5% NaCl + 0.3 g/l H₂O₂ and in EXCO (4 M KCl + 0.5 M KNO₃ + 0.1 M HNO₃) solutions has been determined at 25°C. SCC susceptibility was evaluated by slow strain rate tests (SSRT), at a strain rate of 1 × 10⁻⁶ s⁻¹.Welds obtained by FSW technique showed a higher corrosion resistance in EXCO solution and a lower pitting tendency than the base alloy. Electrochemical measurements (corrosion potential measurements, polarization curves recording) evidenced that FSW weld was cathodic to base alloy. FSW joints were not susceptible to SCC in both test solutions, whereas MIG joints cracked in both solutions.     

The stress corrosion cracking behaviour of heat‐treated Al–Zn–Mg–Cu alloy in modified salt spray fog testing

The stress corrosion cracking behaviour of 7075 (Al–Zn–Mg–Cu) alloy have been studied in a salt spray fog chamber with two vapourised aqueous solutions (0 and 5% NaCl). The paper analyses the stress corrosion resistance of 7075 aluminium alloy with several precipitation‐ageing heat treatments. The results are compared with that obtained in 3.5% NaCl aqueous solution at 20 °C. The salt spray fog testing has permitted a good evaluation of SCC susceptibility in 7075 alloy. All temper conditions studied were susceptible to SCC in the different environments tested. 7075‐T6 temper was the most susceptible, while in all the cases studied 7075‐T73 temper was the least susceptible. Compared to 7075‐T6, 7075‐RRA temper improved the resistance against the SCC process, but the mechanical properties obtained were lower.     

Stress Corrosion Cracking Behavior of Peened Friction Stir Welded 2195 Aluminum Alloy Joints

The surface treatment techniques of laser and shot peening were used to investigate their effect on stress corrosion cracking (SCC) in friction stir welded (FSW) 2195 aluminum alloy joints. The investigation consisted of two parts: the first part explored the peening effects on slow strain rate testing (SSRT) in a 3.5% NaCl solution, while the second part investigated the effects of peening on corrosion while submerged in a 3.5% NaCl solution with no external loads applied. For the SSRT, the laser-peened samples demonstrated superior properties to the other samples, but no signs of corrosion pitting or SCC were evident on any of the samples. For the second part of the study, the FSW plates were inspected periodically for signs of corrosion. After 60 days there were signs of corrosion pitting, but no stress corrosion cracking was noticed in any of the peened and unpeened samples.     

LC4高强铝合金的腐蚀性能研究

利用慢应变速率拉伸试验方法研究了LC4铝合金在空气和3．5％NaCl溶液中的应力腐蚀断裂行为；利用HB5455－90标准研究了LC4铝合金的剥蚀行为；利用HB5255－83标准研究了LC4铝合金的晶间腐蚀行为。结果表明：LC4铝合金具有应力腐蚀敏感性，应力腐蚀的断口形貌受应变速率ε的影响较大；LC4铝合金对剥蚀很敏感，对晶间腐蚀不是很敏感。     

Gefügeabhängigkeit des Spannungsrißkorrosionsverhaltens an handelsüblicher Al-Zn-Mg-Cu-Legierung

Microstructural dependence of stress-corrosion cracking behaviour in commercial Al-Zn-Mg-Cu alloy (AA 7075) The stress corrosion cracking (SCC) behaviour of commercial Al-Zn-Mg-Cu alloy (AA 7075) has been investigated by measuring the relative fracture energy under constant strain rate as a function of microstructural parameters such as precipitate free zone (pfz) width, precipitate (ppt) size in the grain boundaries (gbs) and coherency of ppts in the grain. The SCC specimens were so aged that a given variation in one feature could be produced nearly without a concomitant change in the other variables. The respectively obtained change in microstructural variables was identified by transmission electron microscopy (TEM). SCC tests were conducted in an aqueous 3.5 wt.% NaCl solution of pH = 1 at the temperature of 30°C with an applied corrosion potential of the specimen. It is suggested from the present experimental results that the effect of coherency of ppts in the grain on the resistance to SCC is stronger than the influence of ppt size in the gbs, while pfz width scarcely influences any resistance to SCC. The effects of ageing stages on the SCC behaviour have been discussed in terms of change in slip mechanism due to the interaction between the dislocations and the ppts in the grain.     

Si含量对7050铝合金显微组织和抗应力腐蚀开裂的影响

分别研究Si含量为0．094％、0．134％和0．261％的3种T7651态7050铝合金的组织和应力腐蚀开裂敏感性。结果表明：随着Si含量从0．094％增加到0．261％,Mg2Si相的面积分数从0．16％增加到1．48％,并且尺寸粗化;而其它粗大相（包括Al2CuMg、Mg（Al3Cu,Zn）2和Al7Cu2Fe）的面积分数从2．42％减小到0．78％。合金的电导率随Si含量的增加而增加。合金在空气中进行慢应变速率拉伸时,抗拉强度和伸长率随Si含量的增加而降低;而在3．5％NaCl溶液中进行慢应变速率拉伸时,随Si含量增加,合金应力腐蚀开裂敏感性降低。     

微量Zn对Al-4.2Cu-1.4Mg合金应力腐蚀与微观组织的影响

通过慢应变速率拉伸、动电位极化曲线测试、透射电子显微分析(TEM)、背散射电子衍射(EBSD)等实验较系统地研究了微量Zn对Al-4.2Cu-1.4Mg合金应力腐蚀与微观组织的影响规律。结果表明,微量Zn的添加显著影响合金的腐蚀性能,且随着Zn含量增加,合金的抗应力腐蚀敏感性以及其对应的开路电位均呈峰值变化,含Zn量0.29%合金的抗腐蚀能力最佳。EBSD研究表明,含0.29%Zn的Al-4.2Cu-1.4Mg合金与其它合金相比存在较多的低能量小角度晶界,这可能是微量Zn显著影响该合金抗应力腐蚀性能的主要原因。