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51.
镁合金作为最轻的金属结构材料,具有比强度高、比刚度高、减震性能好、电磁屏蔽等优点。随着海洋强国战略的实施,先进镁合金结构材料逐步在海洋装备上开始应用。已列装的新型高强AZ80镁合金,通过与QBe1.7铍青铜紧固件连接,共同构成整体在典型海洋大气环境中服役。在高盐、高湿的海洋环境环境中,镁合金与电位更正的QBe1.7铍青铜偶接后,极易发生电偶腐蚀。电位相对更负的高强AZ80镁合金,作为电偶腐蚀的阳极被加速溶解。本研究对高强AZ80镁合金电偶腐蚀样品经过12个月青岛海洋大气暴露试验,发现空白对照组、电偶1组(紧固件铍青铜直径Ψ=10mm)和电偶2组(紧固件铍青铜直径Ψ=20mm)的平均腐蚀速率分别为108.1071、133.8929、173.6250g/(m~2·a)。电偶对表面的主要腐蚀产物为:Mg(OH)_2、MgSO_4和MgCl_2。空白样品、电偶1组和电偶2组平均腐蚀深度分别为:0.175、0.330、0.315mm/a。样品中部腐蚀深度最大,边部腐蚀深度则相对较小。不同样品在青岛试验站的腐蚀产物对基体保护能力的量度(n值)分别为1.1337、1.1378、1.0895,表明随着暴露时间的延长,试样在海洋大气环境中的腐蚀速率会加快,试样表面的腐蚀产物对基体根本起不到保护作用。通过灰色关联分析法,计算了青岛海洋大气腐蚀站点的环境因素与AZ80镁合金腐蚀深度和腐蚀失重之间的关联度,结果表明:青岛海洋大气环境因素对高强AZ80镁合金空白样品腐蚀失重影响前三位分别为:SO_4~(2-)非水溶性硫酸盐转化率;对电偶1组样品影响前三位的环境因素分别为:SO_2硫酸盐转化率NO_2;对电偶2组样品影响前三位的环境因素分别为:水溶性降尘SO_2NH_3。对比电偶对2组和1组,唯一的差别是电偶对的面积比,但决定镁合金腐蚀速度的大气成分完全不同,相关机制会在未来工作中详细研究。 相似文献
52.
The phase transformation activation energy of the Cu61.13Zn33.94Al4.93 alloys, which were treated at 4 GPa and 700 °C for 15 minutes, was calculated by means of differential scanning calorimetry curves obtained at various heating and cooling rates. Then, the effects of high-pressure heat treatments on the solid-state phase transformation and the microstructures of Cu61.13Zn33.94Al4.93 alloys were investigated. The results show that high-pressure heat treatments can refine the grains and can change the preferred orientation from (111) to (200) of α phase. Compared with the as-cast alloy, the sample with high-pressure heat treatment has finer grains, lower β' → β and β → β ' transformation temperature and activation energy. Furthermore, we found that high cooling rate favours the formation of fine needle-like α phase in the range of 5--20 °C/min. 相似文献
53.
This paper investigates the effect of atomic disorder on the electronic structure, magnetism, and half-metallicity of full-Heusler Co2FeSi alloy by using the full-potential linearized augmented plane wave method within the generalized gradient approximation (GGA) and GGA+U schemes. It considers three types of atomic disorders in Co2FeSi alloy: the Co--Fe, Co--Si, and Fe--Si disorders. Total energy calculations show that of the three types of disorders, the Fe--Si disorder is more likely to occur. It finds that for the Co--Si disorder, additional states appear in the minority band-gap at the EF and the half-metallcity is substantially destroyed, regardless of the disorder level. On the other hand, the Co--Fe and Fe--Si disorders have little effect on the half-metallicity at a low disorder level. When increasing the disorder levels, the half-metallcity is destroyed at about 9 % of the Co--Fe disorder level, while that stays at 25 % of the Fe--Si disorder level. 相似文献
54.
本文对镍基合金中Si在弱氧化环境下表面氧化成膜特性进行了研究。利用XRD、SEM、EDS等检测手段对试样进行了检测分析,结果发现:合金表面氧化膜的形成动力学对镍基合金的Si含量非常敏感。当合金元素Si的含量较高时,由于连续的非晶SiO2膜在表层氧化铬与奥氏体基体之间的富集阻碍了Cr离子的向外扩散,导致在奥氏体区之上形成了较薄的氧化铬膜;共晶组织区域由于不会形成连续的SiO2非晶膜,仍然可以作为Cr离子的快速扩散通道,使得在该组织区域形成大量的脊状氧化物。奥氏体组织之上的氧化膜厚度与基体的Si含量成反比。 相似文献
55.
This paper presents the seismic behaviour of a concentrically braced frame system with self‐centring capability, in which a special type of bracing element termed reusable hysteretic damping brace (RHDB) is used. The RHDB is a passive energy dissipation device with its core energy‐dissipating component made of superelastic Nitinol wires. Compared with conventional bracing in steel structures, RHDB has a few prominent performance characteristics: damage free under frequent and design basis earthquakes in earthquake prone areas; minimal residual drifts due to the self‐centring capability of RHDB frame; and ability to survive several strong earthquakes without the need for repair or replacement. This paper also includes a brief discussion of the RHDB's mechanical configuration and analytical model for RHDB. The seismic performance study of RHDB frame was carried out through a non‐linear time history analysis of 3‐storey and 6‐storey RHDB frame buildings subjected to two suites of 20 earthquake ground motions. The analysis results were compared with buckling‐restrained brace (BRB) frames. This study shows that RHDB frame has a potential to outperform BRB frames by eliminating the residual drift problem. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
56.
以镁、铝、锌为主要合金元素的镁铝合金材料是轻合金的基础,评述了镁合金和铝合金的优缺点及应用概况,介绍了Zn、RE、Mn、Cu等主要元素对合金微观组织、铸造性能、力学性能和抗腐蚀性能的影响。随着轻合金综合性能不断提高和改进,其应用前景更加广阔。 相似文献
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59.
Yoshikazu Araki Kshitij C. Shrestha Nao Maekawa Yuji Koetaka Toshihiro Omori Ryosuke Kainuma 《地震工程与结构动力学》2016,45(2):297-314
Shaking table tests are performed on a one‐bay one‐story steel frame with superelastic Cu–Al–Mn shape memory alloy (SMA) tension braces. The frame is subjected to a series of scaled ground motions recorded during the 1995 Kobe earthquake, Japan. The test results demonstrate that the SMA braces are effective to prevent residual deformations and pinching. It is also shown that the time history responses observed from the shaking table tests agree well with the numerical predictions using a rate‐independent piecewise‐linear constitutive model calibrated to the quasi‐static component tests of the SMA braces. This suggests that the loading rate dependence of Cu–Al–Mn SMAs as well as the modeling error due to the piecewise linear approximation can be neglected in capturing the global response of the steel frame. Numerical simulations under a suite of near‐fault ground motion records are further performed using the calibrated analytical models to demonstrate the effectiveness of the SMA braces when the variability of near‐fault ground motions is taken into account. A stopper, or a deformation restraining device, is also proposed to prevent premature fracture of SMA bars in unexpectedly large ground motions while keeping the self‐centering capability in moderate to large ground motions. The effectiveness of the stopper is also demonstrated in the quasi‐static component and shaking table tests. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
60.
形状记忆合金橡胶对高架桥梁碰撞减震效果的试验研究 总被引:2,自引:0,他引:2
地震作用下,高架桥梁相邻主梁间的碰撞会引起结构位移和加速度响应增大、应力提高,导致混凝土开裂、脱落和伸缩缝被挤压破坏,甚至引发桥梁落梁和倒塌等,因此采取减轻或者避免桥梁结构在地震作用下碰撞的措施显得尤为必要。设计制备了具有变形自恢复能力的形状记忆合金橡胶碰撞缓冲器,通过桥梁地震碰撞的振动台试验,研究了形状记忆合金橡胶缓冲器对桥梁碰撞的控制效果,提出了碰撞缓冲器吸能效率和结构自身耗能控制率指标。研究表明,形状记忆合金橡胶碰撞缓冲器具有稳定的吸能效率,能够大幅度降低桥梁结构碰撞加速度和碰撞力,这对于提高城市交通网络的地震安全性能具有重要意义。 相似文献