稀土离子La~(3+)、Ce~(3+)对铝合金孔蚀的缓蚀作用实验分析

用电化学方法研究了稀土离子La~(3+)、Ce~(3+)对铝合金LY12CZ在中性含Cl~-离子水溶液中对孔蚀行为的缓蚀作用,测定了孔蚀电位E_b,保护电位E_p以及诱导时间等,结果表明,两种离子对铝合金LY12CZ的孔蚀均有较好的缓蚀作用。并进行了机理分析。     

高比重钨合金的烧结成形与组织性能研究

采用液相烧结成形工艺制备了90W-Ni-Fe合金棒,通过分析烧结态钨合金的组织形貌和力学性能,观察合金的断口组织形貌,研究了烧结工艺对高比重钨合金组织性能的影响,认为减少W-W界面,增加W-W界面的结合强度,是提高烧结态钨合金力学性能的有效途径。     

Dynamic necking of a near α titanium alloy at high strain rates:Experiments and modelling

The tensile behaviour of near α Ti3Al2.5 V alloy, conceived for applications in aerospace and automotive engineering, is characterized from quasi-static to high strain rates. The material is found to present noticeable strain rate sensitivity. The dynamic true strain rate in the necking cross-section reaches values up to ten times higher than the nominal strain rate. It is also observed that beyond necking the dynamic true stress-strain curves present limited rate dependence. The experimental results at different strain rates are used to determine a suitable constitutive model for finite element simulations of the dynamic tensile tests. The model predicts the experimentally macroscopic force-time response, true stress-strain response and effective strain rate evolution with good agreement.     

Influence of magnetically constricted arc traverse speed (MCATS) on tensile properties and microstructural characteristics of welded Inconel 718 alloy sheets

The magnetically constricted arc technique was implemented to mitigate the heat input related metal-lurgical problems in Gas Tungsten Arc Welding (GTAW) of Inconel 718 alloy particularly Nb segregation and subsequent laves phase evolution in fusion zone. This paper reports the direct effect of magnetically constricted arc traverse speed (MCATS) on bead profile, tensile properties and microstructural evolution of Inconel 718 alloy sheets joined by Gas Tungsten Constricted Arc Welding (GTCAW) process. The mechanism amenable for the microstructural modification and corresponding influence on the tensile properties of joints is investigated both in qualitative and quantitative manner related to the mechanics of arc constriction and pulsing. It is correlated to the solidification conditions during welding. The relationship between MCATS and Arc Constriction Current (ACC) was derived. Its interaction effect on the magnetic arc constriction and joint performance was analysed. Results showed that the joints fabricated using CATS of 70 mm/min exhibited superior tensile properties (98.39% of base metal strength with 31.50% elongation). It is attributed to the grain refinement in fusion zone microstructure leading to the evolution of finer, discrete laves phase in interdendritic areas.     

回归再时效7A60铝合金在0.5mol/L NaCl溶液中的点蚀性能

采用腐蚀电化学的点蚀极化曲线并结合腐蚀形貌的扫描电镜分析的方法,研究了回归再时效(RRA)工艺处理7A60铝合金在0.5mol/L NaCl溶液中的点蚀行为,对其耐点蚀性能进行了评价,并探讨了RRA工艺改善该合金点蚀性能的机理。结果表明:采用120RRA工艺(120℃×24h预时效+195℃×0.5h回归+120℃×24h再时效)处理后,7A60铝合金在0.5mol/L NaCl溶液中的阳极极化曲线闭合环面积减小,再钝化电流密度Ipp降低,蚀孔较浅,RRA工艺在一定程度上改善了该铝合金在0.5mol/L NaCl溶液中的耐点蚀性能。     

损伤铝合金表面超声焊接界面断口分析与结合机理

采用超声焊接铝合金箔材的工艺修复处理表面腐蚀受损的2A12CZ基体,并利用Quanta200型环境扫描电子显微镜分析了截面形貌及箔材与基体之间界面表面断口的微观形貌。结果表明：从截面来看,箔材与基体之间大部分发生了焊合,界面分界线大部分消失;从机械脱开的界面断口来看,其表面微观形貌表现为鳞片状及韧窝状的典型金属型断口形貌。这说明在给定条件下,焊接部位大部分呈冶金结合。最后对铝台金箔材与铝合金基体之间超声焊接机理进行了探讨。     

复合铝基润滑脂制备与性能

复合铝基润滑脂是性能优良的多效润滑脂,尤其是泵送性能良好,适用于集中润滑系统,已在冶金等行业获得广泛应用。考察了组成、工艺和添加剂对复合铝基润滑脂性能的影响,复合铝皂对环烷基油的稠化能力优于对石蜡基油的稠化能力,增大基础油黏度有利于改善润滑脂的性能,采用异丙醇铝三聚物比采用异丙醇铝制备复合铝基润滑脂的工艺可靠,产品性能更稳定。通过配方和工艺条件优化,制备的复合铝基润滑脂具有高滴点,良好的胶体安定性、机械安定性、氧化安定性、抗水性、防腐性和抗磨性。     

TA2-B10管不同电偶腐蚀防护方式对B10管腐蚀特性的影响

为研究TA2-B10合金管在不同电偶腐蚀防护方式下对B10管腐蚀特性的影响,在青岛小麦岛海水试验场设置TA2-B10管直接连接、电绝缘连接、电绝缘＋涂层连接三组不同电偶腐蚀防护方式对照管道,依次进行1m/s、3m/s、4m/s流动海水与浸泡交替腐蚀试验。对试验后的三组B10管道线切割,通过管道内表面电位分布试验分析不同电偶腐蚀防护方式下B10管道的腐蚀类型;采用动电位极化曲线、电化学阻抗谱和微观表征,分析不同电偶腐蚀防护方式下距离法兰接头250mm处B10管试样的腐蚀特性。结果表明,直接连接TA2-B10管处于电偶腐蚀状态,B10端内电位正移腐蚀加速,电绝缘连接和绝缘＋涂层连接TA2-B10管均处于自腐蚀状态,但电绝缘＋涂层连接具有更好的绝缘效果;电绝缘＋涂层连接防护下的B10试样,腐蚀电流密度最小,自腐蚀电位最负;三组B10试样阻抗谱均呈现单容抗弧特征,电绝缘＋涂层连接防护下的B10试样具有更大的传递电阻和膜层电阻;电绝缘＋涂层连接能有效减缓点蚀、坑蚀和晶间腐蚀三种腐蚀倾向。以上结果综合说明,绝缘＋涂层防护方式具有更好的电偶腐蚀防护效果。     

陆军航空兵直升机编制分形结构的验证与分析

从陆航直升机编制和陆航体系作战的实际需求出发,利用分形理论的信息维数定义,提出了定量验证陆航直升机编制分形结构的基本方法。以两个历史时期的美军陆航部队编制为例,建立了各型直升机分布的δ-覆盖,并分别测定了相应的信息维数,对比分析了两个历史时期美军陆航旅直升机编制的优劣。结果表明,利用信息维数可以定量说明陆航直升机编制的合理程度。     

军用装备镁合金表面微弧氧化层SEM微观形貌及耐蚀性分析

利用微弧氧化技术的恒电流方式,在含有Na：SiO,和KF等电解质的溶液中制备了AZ91D镁合金微弧氧化层,通过扫描电镜观察分析及Cu加速盐雾腐蚀试验,研究了电解液中Na：SiO,和KF质量浓度对微弧氧化层结构及耐蚀性的影响。结果表明：在相同反应条件下,微弧氧化层厚度和表面粗糙度随Na：SiO,和KF质量浓度的增加而增加,微弧氧化层的耐蚀性取决于其表面粗糙度和厚度,粗糙度小、具有一定厚度的致密微弧氧化层耐蚀性好。