| With the adjustment of China's energy structure,natural gas plays an increasingly important role in people's daily life and industrialized production.The extensive application of natural gas has led to the increasing demand of LNG carrier,and currently Japan and South Korea and other countries are in a monopolistic position in the LNG liquid cargo containment system technology,therefore,it is urgent to promote the research on LNG cargo containment system in China.The bonding property of the interface between the low temperature metal-AA5083 aluminum alloy and the outer insulating material of containment system is the crucial link affecting the advance of the research,so it is of far-reaching significance to study the influence of different surface treatment of AA5083 aluminum alloy on interfacial bonding property of AA5083/cryogenic adhesive under low temperature environment.In this paper,the optimum parameters of surface lithography,sand blasting treatment and phosphoric acid-sulfuric acid anodic oxidation for AA5083 aluminum alloy were studied firstly.The optimal size parameters of the micro-pit matrix for photolithography are obtained by contrast method:the diameter of the micro-pits is 200?m,the diameter and clearance ratio is 2:1,the depth of the micro-pits is 20?m.At this moment,the contact angle of AA5083 and cryogenic adhesive is 31.46°,the roughness value is 0.710?m and the surface energy is 30.82mN/m.Under the condition of pressure 0.4MPa,angle 15°,the nozzle and the aluminum alloy surface distance 60 mm,the optimal diameter of sand grain for sand blasting treatment is 150 mesh.At this time,the contact angle of AA5083 and cryogenic adhesive is 36.19°,the roughness value is 1.472?m,the surface energy is 29.13 mN/m.The optimum technological parameters for the surface treatment of phosphoric acid-sulfuric acid anodic oxidation obtained by orthogonal experimental method are: voltage 20 V,time 20 min,electrolyte temperature 40°C.At this time,the contact angle of AA5083 and cryogenic adhesive is 28.85°,the roughness value is 1.040?m,and the surface energy is 80.34 mN/m.Secondly,surface silane assisted treatment was carried out on AA5083 after the above three optimal surface treatment processes,the surface properties of specimens were characterized,and the mechanism of silane treatment on improving the interfacial bonding strength of AA5083/cryogenic adhesive was analyzed by the test of EDS and FTIR.At the temperature of 25°C(room temperature),0°C,-60°C and-120°C,the single lap shear test was carried out separately to investigate the effect of different surface treatment methods on the interfacial bonding strength of AA5083/cryogenic adhesive.The results show that the value of shear strength of the specimens which treated by anodic oxidation and silane treatment is the largest at-60°C,that is 33.96 MPa.At last,the marine hygrothermal durability test of the AA5083/ cryogenic adhesive joint with different surface treatment was carried out with different time period(from one month to four),and the fracture failure mode of the bonding joint was analyzed.The results show that with the increaseing of durability test time,the shear strength of all specimens decreases in different degrees.Among of them,the marine hygrothermal durability of specimens treated by anodic oxidation and silane treatment is the best,the shear strength with one months,two months,three months and four months durability test are 22.87 MPa,22.37 MPa,21.74 MPa and 19.86 MPa respectively.The test strength at each stage is about 3.30 times the strength of the untreated specimen in the same period.The failure mode of AA5083/cryogenic adhesive joint treated by anodic oxidation and silane treatment is cohesion failure. |
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