摘要
鉴于试样厚度对2024-T351铝合金材料的应力腐蚀开裂门槛值KISCC的影响及实际工程应用中厚壁构件的应力腐蚀敏感性评价等问题,选取能够代表实际工程应用中构件壁厚的40 mm厚双悬臂梁(DCB)试样和标准(GB 15970.6-2007)中规定的26 mm厚DCB试样,进行了应力腐蚀断裂特性研究。结果表明,40 mm厚试样得到的材料的应力腐蚀开裂门槛值KISCC值大于26 mm厚试样得到的KISCC。对S-L取向试样,40 mm厚和26 mm厚试样的应力腐蚀开裂门槛值KISCC差别不大,差异在4%左右;对S-T取向试样,40 mm厚和26 mm厚试样的KISCC值差别明显,差异在24%左右。在DCB试样应力腐蚀断口表面发现有纤维状的腐蚀产物生成,经过能谱仪(EDS)及X射线衍射(XRD)分析,纤维状的腐蚀产物是氢氧化铝。纤维状腐蚀产物的生成降低了DCB试样裂纹尖端腐蚀产物的积累,从而减轻了腐蚀产物楔形作用对应力腐蚀开裂门槛值KISCC的影响,提高了材料抗应力腐蚀的能力。并且40 mm厚DCB试样应力腐蚀断口表面的纤维状腐蚀产物明显多于26 mm DCB试样,这也是40 mm厚试样的应力腐蚀开裂门槛值大于26 mm试样的一个原因。在应力腐蚀开裂过程中,由于DCB试样裂纹尖端发生阳极反应,与主体溶液形成小阳极大阴极体系,使试样裂纹尖端呈酸性,而主体溶液呈碱性。40 mm厚试样的裂纹尖端pH约3.0,26 mm厚试样的裂纹尖端pH约3.6,厚板试样裂纹尖端处溶液酸化更严重。
In view of the influence of specimen thickness on the critical stress corrosion intensity of aluminum alloys materials and how to evaluate stress corrosion sensitivity of thick wail components in practical engineering application, the preerack DCB （ double cantilever beam） specimens with 40 mm in thickness were used to represent the thick wall of parts in practical engineering application, and 26mm thick specimens specified in GB 15970.6-2007 standard were used for studying the stress corrosion fracture characteristics of 2024-T351. The results showed that the critical stress corrosion intensity KISCC of 40 mm thick DCB specimen was bigger than that of 26 mm thick specimen. The influence of the thickness of DCB specimen with S-L direction was not obvious and the difference was about 4%. For S-T direction, the influence of the thickness of sample was significant and the difference was about 24%. Fibrous corrosion products were discovered at stress corrosion fracture surface of DCB specimen. By energy disperse spectroscopy （EDS） and X-ray diffraction （XRD） analysis, the fibrous corrosion products were aluminum hydroxide. Fibrous corrosion products reduced the accumulation of corrosion products at the crack tip of DCB specimen, so as to reduce the influence of corrosion products wedge effect on stress corrosion cracking threshold value Kiscc and improve the stress corrosion resistance of materials. Fibrous corrosion products on the stress corrosion fracture surface of 40 mm thick DCB specimen were significantly more than those of 26 mm thick DCB specimen＇ s. It was one of the reasons that the stress corrosion cracking threshold value of 40 mm thick specimen was greater than that of 26 mm thick specimen. In the process of stress corrosion cracking, the crack tip of DCB specimen got acidic and the body solution got alkaline, owing to the anode reaction at the crack tip of DCB specimen and forming small anode and big cathode system with the body solution. In the process of stress corrosion cracking, pH value at the crack tip was about 3.0 for 40 mm thick specimen and 3.6 for 26 mm thick specimen. Acidification at the crack tip of 40 mm thick DCB specimen was more serious.
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2014年第4期581-588,共8页
Chinese Journal of Rare Metals
基金
国家自然科学基金项目(51101010)资助
