<p style="margin: 0cm 0cm 0pt" class="MsoPlainText"><span style="mso-bidi-font-family: 宋体; mso-hansi-font-family: 宋体" lang="EN-US">Aluminum alloys have been found ever-increasing applications in marine environments. The study on the corrosion of aliminum alloys using field test was started in USA in 1940s.Such studies, however, were carried out in China untill 1980s. Although the corrosion </span><span style="mso-bidi-font-family: 宋体; mso-hansi-font-family: 宋体" lang="EN-US"><span style="mso-spacerun: yes">&nbsp;</span>behaviours of 11 kinds of aluminum alloys were investigated exposed to tide, splash and full immersion zones at Qingdao, Zhoushan, Yulin and Xiamen area of China, the corrosion behaviour of materials in deep ocean environments is different from that in shallow marine environments. In this work, the corrosion behavior of 5052 and 6061 aluminum alloys in 800 and 1200 m deep ocean environments of South China Sea was studied using field test. The morphology and composition of corrosion products were investigated using SEM, EDS and XRD. The results indicated that severe local corrosion took place in the aluminum alloys. The corrosion products were composed of Al2O3, SiO2 and a small amount of Mg3(SO4)2(OH)2 and NaCl.The crevice corrosion perforation occurred on the edge of 5052 and 6061 samples.And the groove corrosion pits formed on the cross section of 5052 sample.Pitting corrosion took place on the main area of 5052 and 6061 samples.The size and density of pits formed on 6061 aluminum alloy were higher than those on 5052 aluminum alloy.And the pitting corrosion perforation formed on 6061 aluminum alloy in 800 m deep ocean.Comparing with the data of literatures,the maximum pit depths of 5052 and 6061 aluminum alloys decreased first and then increased with depth increased. The maximum value of pit depth appeared </span><span style="mso-bidi-font-family: 宋体; mso-hansi-font-family: 宋体" lang="EN-US">at about 800 m deep ocean. This is due to the amount of dissolved oxygen is </span><span style="mso-bidi-font-family: 宋体; mso-hansi-font-family: 宋体" lang="EN-US">the lowest in 800 m deep ocean, which promotes local corrosion.<o:p></o:p></span></p>

通过实海暴露实验, 研究了5052和6061铝合金在中国南海海域800和1200 m深海环境下浸泡3 a的腐蚀行为.采用SEM, EDS和XRD技术, 分别进行了腐蚀形貌观察、腐蚀产物成分和相组成分析.结果表明: 2种铝合金在深海环境下均发生了很严重的局部腐蚀, 表面形成了白色的腐蚀产物,腐蚀产物由Al2O3, SiO2, 以及少量Mg3(SO4)2(OH)2和NaCl组成.5052和6061铝合金均在铆接区域产生了缝隙腐蚀穿孔, 其中, 5052铝合金还在截面形成了沟槽状腐蚀坑.在样品主表面, 5052和6061铝合金主要发生点腐蚀, 其中6061铝合金表面的点蚀坑深度更大,密度更高, 且在800 m深海环境下发生了点蚀穿孔. 分析表明, 随着水深的增加,5052和6061铝合金的最大点蚀坑深度先增加后降低,最大点蚀坑深度的最大值出现在水深800 m左右.这是由于800 m深海中的溶氧量最低, 促进了局部腐蚀的发生.

Currently, with the gradual depletion of onshore resources, more efforts are being devoted to both scientific and resource exploitation of the ocean and the deep sea. Compared with the onshore environment, marine habitats are complex and characterized by high hydrostatic pressure, high salinity, and high marine population. The ocean is a unique aquatic environment, and it has a large population of microorganisms. There is a need to exploit the ocean for new energy sources. The significant challenges of exploiting oil, gas, and minerals have forced the people to innovate and develop advanced exploration tools. Al alloys are attractive for use in marine environments due to their low densities, high strengths, good plasticity, excellent electrical and thermal conductivities, and excellent corrosion resistance. The high chloride concentrations and microorganisms in the ocean have a significant effect on the corrosion resistance of many metallic materials. In this work, the corrosion behavior of 5754 Al alloy in seawater containing B.subtilis was investigated. The corrosion rate was analyzed by the weight loss method. The morphologies of the corrosion products and the corrosion profiles were observed by SEM and white light interferometer, respectively. The corrosion products were analyzed by energy dispersive spectroscopy and XRD. Finally, the corrosion mechanism of the Al alloy was studied using electrochemical impedance spectroscopy. The results show that the corrosion rate of the Al alloy in the seawater with B.subtilis was 12.5 mg/(dm2·d), which was only 1/6 times that in the seawater without the bacteria. A protective film comprising of CaMg(CO3)2 was gradually formed on the surface of the alloy in the presence of the bacteria. The bacteria promoted the formation of the CaMg(CO3)2 film, which protected the alloy from the seawater, and consequently, inhibited the pitting corrosion of the Al alloy in the marine environment.

采用失重法分析5754铝合金在含海洋常见微生物枯草芽孢杆菌(B.subtilis)的海水中的腐蚀行为，利用SEM和白光干涉仪分别观察了表面腐蚀产物形貌及腐蚀轮廓，并用EDS和XRD分析了表面腐蚀产物成分，最后利用EIS研究该铝合金的腐蚀机理。结果表明，浸泡在含有微生物B.subtilis的海水环境中，铝合金腐蚀速率为12.5 mg/(dm2·d)，仅为浸泡在不含有微生物海水环境中铝合金腐蚀速率的1/6。浸泡在含有B.subtilis的海水环境中，铝合金表面逐渐形成一层以CaMg(CO3)2为主要成分的矿化物质膜，微生物B.subtilis的存在促进了生物矿化膜的形成，阻碍了海水对铝合金的侵蚀，从而抑制了铝合金在海水环境中的点蚀。

Environmentally enhanced fracture in smooth tensile and fatigue pre-cracked test specimens of AA5083-H131 have been evaluated as a function of sensitization time up to 7,000 h, temperature (80°C to 175°C), and test environment (dry and laboratory air, distilled water, and 0.03 M and 0.6 M NaCl). Test methods used involved slow strain rate testing of short-transverse (S-T) smooth tensile samples, typically using an initial strain rate of 5 × 10−5/s and subjecting pre-cracked S-T single edge notch specimens to monotonic loading using a range of load point displacement rates (0.0006 mm/min to 3.6 mm/min) with dK/dt ranging from 0.001 MPa√m/s to 5.12 MPa√m/s. Intergranular stress corrosion cracking (IGSCC) was only promoted when straining was conducted in a test environment capable of providing a local source of hydrogen. Exposure to an aqueous solution during sensitization at 80°C was found to increase the environment sensitive fracture susceptibility under monotonic loading, when compared to that generated after an equivalent sensitization time in the environment developed within an air oven (i.e., dry air). Initial findings using electron backscatter diffraction data are suggestive that the grain boundaries most likely suffering IGSCC are those with a sharp gradient in the Taylor Factor, and are likely to suffer an enhanced local strain/stress during global straining. Analysis of published nitric acid mass loss test degree of sensitization data for AA5083-H131 and AA5083-H116 indicates the sensitization process(es) may differ for temperatures above and below ~125°C. While thermal remediation of sensitized samples was somewhat effective in reducing the environmentally sensitive fracture, this occurred at the expense of a loss in strength. In addition, re-sensitization after remediation produced results similar to that of the originally sensitized material, but at a lower strength level.

During welding, the vibration effect of applying a pulse current on the molten pool can effectively improve weld formation and refine grains. The effect of pulse current on grain refinement and its mechanism were studied for Al-Mg alloy welds fabricated by conventional plasma welding (PAW), PAW with conventional pulse current, and PAW with composite pulse current. The grain size produced by conventional PAW was 78.2 μm, whereas the average grain size was reduced from 78.2 μm to 53.3 μm with increasing conventional pulse current frequency from 0 Hz to 100 Hz; in addition, the degree of grain refinement increased by about 30%. However, the minimum grain size was 48.2 μm, and the grain refinement effect can reach nearly 40% by combining low-frequency pulse current with conventional pulse current. The proportion of small grains and high-angle grain boundaries increased significantly after applying the composite pulse current. The additional oscillation effect of the composite pulse current can effectively eliminate coarse grains during the solidification of the weld pool. The main mechanism of grain refinement is dendrite fragmentation, which is discussed through thermodynamics and composition.

利用气化冲击焊接技术，制备了力学性能良好基于中间层的5A06铝合金与0Cr18Ni10Ti不锈钢气化冲击焊接接头，中间层3003铝合金与飞板5A06铝合金和靶板0Cr18Ni10Ti界面焊接良好，接头结合区域呈圆环状。通过信号采集系统分析了铝箔气化时间和电流随能量输入的变化，采用OM和SEM分析了接头界面的微观形貌和元素分布。研究了能量输入对铝箔气化的时刻和接头力学性能的影响。结果表明，随着能量输入的增加，铝箔气化所需时间减小，最终碰撞速率增大，从而使焊接区域直径增大；接头的抗拉力和抗剪力随能量输入的增大而增大。当能量输入为9 kJ时，接头的最大抗拉力为44.0 kN，抗剪力为2.1 kN；5A06/3003界面呈中间对称波状结合，3003/0Cr18Ni10Ti界面以金属间化合物连接，结合区域错位分布。

5356 aluminum alloy has been widely applied in transportation, aerospace and other fields owing to its low density, excellent fatigue property, and superior corrosion resistance. Aluminum alloy is widely manufactured by the arc additive technique that operates at a fast manufacturing speed with simple equipment and high material utilization. The property of 5356 aluminum alloy is closely related to its microstructure. To better control the property of this alloy for the additive manufacturing of forming parts, it is necessary to study the evolution of its microstructure. In this work, 5356 aluminum alloy forming parts were produced by tungsten inert gas welding (TIG) arc additive manufacturing, and their microstructures and mechanical properties were analyzed. The 5356 aluminum alloy formed by TIG additive manufacturing was composed of α-Al matrix and β(Al3Mg2) phase. As the deposition height increased, the layer microstructure transformed from equiaxed grains to columnar grains and tended to stabilize at thermal equilibrium. The top layer exhibited a dendritic microstructure with serious segregation of the Mg element. The middle and lower microstructures were varied and included equiaxed grains, columnar grains, and a mixture of these, with improved Mg-element segregation. As the deposition height increased, the microhardness in the layer first decreased and then stabilized. The microhardness was larger in the interlayers than in the deposition layers. The pores gathered in the interlayers might explain the lower yield strength of the thin-walled parts than the theoretically calculated value. The tensile strength, yield strength, and elongation were all anisotropic, and the tensile property was better in the transverse than in the longitudinal direction. This result was attributable to pore accumulation between the layers of the thin-walled parts and to the uneven microstructure.

采用钨极惰性气体保护焊(TIG)电弧增材制造工艺制备5356铝合金成形件，并对成形件的组织和力学性能进行研究。结果表明，5356铝合金增材制造的相组成为α-Al基体和β(Al3Mg2)相；随沉积高度增加，沉积层显微组织由等轴晶向柱状晶转变，达到热平衡状态后趋于稳定，这是因为增材制造具有热积累效应；最顶层组织呈现树枝状，且Mg元素偏析严重；中下部组织形态多样，包括等轴晶组织、柱状晶组织及其混合组织，同时Mg元素偏析得到改善。力学性能测试结果显示，随沉积高度的增加，层内显微硬度先降低后趋于稳定，这是因为沉积层组织在增材制造过程中经历逐渐粗化的过程，导致显微硬度下降，达到热平衡状态后显微组织相对稳定，显微硬度也趋于稳定。沉积层层间位置的硬度大于层内，这是因为层间结合处为细小的等轴晶组织。聚集在层间的气孔可能是导致薄壁件屈服强度低于理论计算值的原因。抗拉强度、屈服强度以及伸长率都表现了各向异性，横向拉伸性能优于纵向，这是因为薄壁件层间气孔聚集以及显微组织不均匀。