关键词： 镁合金   聚苯胺   鳞片石墨   腐蚀防护  

摘要： 目的针对聚苯胺环氧涂层物理屏蔽性能欠佳的问题,通过引入具有片层结构的鳞片石墨,从而进一步提高涂层对镁合金的腐蚀防护性能。方法利用化学氧化聚合法在鳞片石墨表面合成聚苯胺,通过X射线衍射仪、扫描电子显微镜、傅里叶变换红外光谱仪,对所得到的聚苯胺/鳞片石墨复合粉末进行表征。将合成的复合粉末均匀分散于环氧树脂中后,在AZ91D镁合金表面制备涂层,通过电化学阻抗测试对涂层在3.5%氯化钠溶液中的腐蚀防护性能进行研究。结果聚苯胺可以在鳞片石墨的表面聚合,鳞片石墨的加入使聚苯胺环氧涂层的附着力略有降低,涂层硬度、柔韧性及耐冲击性能没有明显改变,但鳞片石墨的加入明显提高了聚苯胺环氧涂层的阻抗值。在浸泡前1488 h,苯胺与鳞片石墨的质量比为1∶1时,涂层的阻抗值为1.3×10^(8)Ω·cm^(2),防护性能最好。但随着浸泡时间的延长,苯胺与鳞片石墨的质量比为4∶1时,涂层的阻抗值逐渐高于其他涂层,当浸泡4008 h后,其阻抗值为1.6×10^(8)Ω·cm^(2),仍具有较优异的防护性能。结论环氧涂层中添加聚苯胺/鳞片石墨复合粉末后,通过鳞片石墨前期的屏蔽与聚苯胺长期缓蚀的协同作用达到了对镁合金较好的防护效果,而涂层的这一防护效果和苯胺与鳞片石墨比例有关。

关键词： 汽车轮毂   AZ31镁合金   液态模锻   显微组织   耐磨损性能   耐腐蚀性能  

摘要： 采用不同的浇注温度和比压对AZ31镁合金汽车轮毂进行了液态模锻成形,并进行了显微组织、耐磨损性能和耐腐蚀性能的测试与分析。结果表明:随比压和浇注温度的增加,轮毂试样的平均晶粒尺寸和磨损体积均先减小后增大,腐蚀电位先正移后负移,耐磨损性能和耐腐蚀性能先提升后下降。与30 MPa比压相比较,50 MPa比压时试样的平均晶粒尺寸和磨损体积分别减小了27.39%、41.67%,腐蚀电位正移了36 m V。与680℃浇注温度相比,700℃浇注时试样的平均晶粒尺寸和磨损体积分别减小了33.33%、47.5%,腐蚀电位正移了47 m V。AZ31镁合金汽车轮毂的液态模锻工艺参数优选为:50 MPa比压、700℃浇注温度。

关键词： AZ31B镁合金   剪切旋压   差温旋压  

摘要： 分别进行了AZ31B镁合金轧板等温剪切旋压成形和差温剪切旋压成形实验,对两种成形条件下的工件微观组织和力学性能进行了对比分析。结果表明:200~300℃变形时,镁合金轧板具有良好的等温剪切旋压和差温剪切旋压可成形性;在热旋压成形时,旋压件发生了晶粒细化,但随着旋压温度上升,两种成形方式的旋压件平均晶粒尺寸均增加。在200℃旋压成形时,差温剪切旋压件组织更加细小,力学性能优于等温剪切旋压工件,其轧向(RD)与横向(TD)方向的屈服强度分别为251、233 MPa,抗拉强度分别为304、299 MPa,伸长率分别为21.1%、21.8%;随着旋压温度增至300℃,差温旋压件与等温旋压件的组织状态和力学性能趋于一致。

关键词： magnesium alloy   cyclic plasticity   macroscopic experiments   microscopic observations   constitutive model  

摘要： Fatigue analysis has always been a concern in the design and assessment of Mg alloy structure components subjected to cyclic loading,and research on the cyclic plasticity is fundamental to investigate the corresponding fatigue ***,this work reviews the progress in the cyclic plasticity of Mg ***,the existing macroscopic and microscopic experimental results of Mg alloys are ***,corresponding macroscopic phenomenological constitutive models and crystal plasticity-based models are ***,some conclusions and recommended topics on the cyclic plasticity of Mg alloys are provided to boost the further development and application of Mg alloys.

关键词： 镁合金   筒形件   复合铸型   铸造工艺   顺序凝固  

摘要： 针对一种材质为GW63K的复杂薄壁镁合金筒形件的结构特点和工艺难点,开展复合铸型铸造工艺研究。根据铸件结构,设计了基于不同型砂的复合铸型铸造工艺,利用ProCAST软件进行数值模拟仿真,并根据模拟结果进行凝固顺序调整,优化铸造工艺,最终达到顺序凝固的目的。结果表明,复合铸型铸造工艺条件下的铸件内部品质达到了HB7780-2005中Ⅰ类铸件要求,T6态力学性能满足抗拉强度≥280 MPa,伸长率≥3%的要求。

关键词： 空化   纳米粒子   强化   扫描电镜   X射线光电子能谱  

摘要： 通过空化泡溃灭产生的微射流促使Al_(2)O_(3)纳米粒子对镁合金进行冲击强化。采用显微硬度仪、扫描电镜(SEM)、X射线光电子能谱(XPS)对强化后的样品硬度、表面形貌、元素含量与化学态等参数进行分析。结果表明,强化5 min后,通过SEM发现在样品表面出现纳米级颗粒,结合XPS测试、发现样品中Al_(2)O_(3)含量明显增多,表明Al_(2)O_(3)粒子渗入表面,将其硬度提高了29.1 HV。推测强化作用机制为空泡溃灭的能量传递给Al_(2)O_(3)粒子,继而由Al_(2)O_(3)粒子冲击样品表面,因此样品承受的冲击更加柔性,且Al_(2)O_(3)纳米粒子自身的强度、硬度等性能较好,渗入样品表面后能够进一步提升强化效果。

关键词： Zerilli-Armstrong   Orthogonal cutting   Flow stress   Magnesium   HCP   AZ31B  

摘要： This work reports on a methodology to extend Oxley's analysis of the thick shear zone to account for HCP materials. Ultimately, the work extracts Zerilli-Armstrong (ZA) constitutive equation' material parameters for AZ31B, an HCP crystal structure magnesium-based alloy. The methodology for accomplishing this utilizes three tasks namely: 1) Extension of thick shear zone approach for machining force simulation to account for Zerilli-Armstrong HCP material model, 2) measure cutting and thrust edge forces from orthogonal cutting tests (uncut chip thickness and cutting speed values varying between 0.05 and 0.4 mm/rev and 50-400 m/min, respectively), and 3) numerically determine updated material model parameters for AZ31B by minimizing the difference between the methodology-predicted forces and those experimentally measured. Comparing numerical data with the experiments, the determined AZ31B material model with updated parameters yielded predictability of R-2 of 0.94 and 0.91 for cutting and thrust forces, respectively. Additional validations were conducted by favorably comparing flow stress numerical predictions for AZ31B with literature-published histories at wide operating ranges of temperature, strain, and strain rate values. The presented methodology for finding HCP Zerilli-Armstrong material model parameters based on orthogonal cutting tests may serve as complementary alternative to time-consuming tension-compression flow stress experiments.

关键词： electrodeposition film   magnesium alloy   quantum chemical calculations   superhydrophobic surface  

摘要： In this study, the superhydrophobic surface with SiO2 nanoparticles and corrosion-resisting property was prepared on magnesium alloy substrate by a simple one-step sol-gel electrodeposition. The influence of electrodeposition time on hydrophobicity and morphology of the magnesium alloy surface was discussed. The molecular dynamics simulations were conducted to provide an insight into the interactions between the C16H33Si(OH)(3) molecules and the magnesium surface. The results of frontier molecular orbital and Fukui function distributions indicated that the silicon hydroxyl of C16H33Si(OH)(3) was the probable reactive site via sharing electrons with metal atoms for the adsorption on the magnesium surface. Quantum chemical calculations indicated that the coordinate bonds could be formed between C16H33Si(OH)(3) molecule and unoccupied orbital of metal atom, which led to the active adsorption on the magnesium surface and generate the superhydrophobic surface. The results showed that the superhydrophobic surface could significantly improve the corrosion resistance compared with the pristine magnesium alloy in 3.5 wt.% NaCl solution.

关键词： electroless Ni-P coating   F   O ratio   magnesium alloy   pickling time  

摘要： In this study, a simple pickling process in H(3)PO(4)and NH(4)HF(2)solution was used for electroless Ni-P plating on AZ61 magnesium alloy. It is found that the corrosion rate of magnesium alloy during pickling significantly decreased because NH(4)HF(2)was added into H(3)PO(4)pickling solution. Ni-P coating plated only with pickling process shows poor adhesion because of the low F/O ratio of the substrate surface. However, F/O ratio, adhesion, and corrosion resistance of Ni-P coating are obviously enhanced after pickling followed by activation. The optimal pretreatment process is pickling for 120 s and activation for 4 min, under which the Ni-P coating has an optimum F/O ratio of 1.8 and the coating gets a dense structure, better adhesion, and higher corrosion resistance.

关键词： Magnesium alloys   fine grains   hardness   tensile strength   wear  

摘要： ZE41 magnesium alloy was successfully produced by friction stir processing and grain refinement was achieved from a starting size of 107 mu m +/- 6.7 mu m to 3.5 mu m +/- 1.5 mu m. MgZn intermetallic which was appeared as network like structure at the grain boundaries before friction stir processing was greatly affected due to the severe plastic deformation and broken as small particles as observed from the microstructural studies. Higher hardness (approximate to 30 %) was measured for the fine grained ZE41 magnesium alloy compared with the base alloy due to the grain refinement. From the tensile tests, yield strength and ultimate tensile strength was significantly increased at the cost of decreased ductility reflected in lower strain for the fine grained ZE41 compared with the base alloy. Wear studies showed higher coefficient of friction and lower mass loss for the grain refined ZE41 magnesium alloy. From the results, it can be understood that the grain refinement achieved by friction stir processing has a profound influence on enhancing the mechanical and tribological properties of ZE41 magnesium alloy.