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。     

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。     

关于不定方程x3=Dy2+1

本文对方程x3=Dy2+1中一般情形的D进行了讨论,对0相似文献   

7B04铝合金孔壁超声振动抛光抗疲劳性能分析

针对7B04铝合金孔结构机加质量差、易腐蚀的问题,采用超声振动抛光技术,对原始机加孔和腐蚀孔分别进行了抛光处理,旨在改善和提高7B04铝合金原始机加孔和腐蚀孔的表面完整性。从孔壁处理前后的表面形貌和粗糙度变化情况可知:超声振动抛光可有效去除表面加工刀痕,去除腐蚀产物,同时表面粗糙度降低了43%以上,孔壁局部应力集中系数降低了24%以上,这有利于提高孔的抗疲劳性能。超声振动抛光技术为飞机孔结构的加工和维修提供了新的思路和方法。     

新型航空铝合金材料复杂形貌点蚀损伤应力集中效应分析

根据7B04铝合金材料试件模拟加速点蚀试验检测结果,并结合铝合金材料点蚀行为机制、微观结构特征与随机性过程本质,构建由多个微观椭球体合成的楔入型与合围型两种典型复杂形貌点蚀损伤模型。采用ANSYS有限元方法建模并基于线弹性断裂力学,对上述两种点蚀损伤模型的应力集中效应进行计算与分析。研究发现:两种复杂形貌特征的点蚀损伤模型产生的应力集中系数数值基本相当,各个微观椭球体蚀坑分别对应力分布产生影响并相互干涉与叠加,造成复杂形貌点蚀损伤模型的应力集中系数数值增大;两种复杂形貌点蚀损伤模型的应力主要集中在各个微观椭球体蚀坑交会的位置,大都位于宏观点蚀损伤的侧边;两种复杂形貌点蚀损伤模型的应力集中效应作用区域的尺寸与铝合金材料微观晶粒尺寸、点蚀萌生的短裂纹初期尺寸基本相当。     

装备内孔零件的堆焊修复与滚压强化工艺研究

阐述了一种修复损伤内孔零件的精密脉冲等离子粉末堆焊+滚压强化复合处理工艺,通过试验对修复层的组织性能进行了观察与测试。结果表明:修复的薄壁内孔零件试样基体变形小,修复层与基体属于冶金结合,修复层和基体过渡区域(包括熔合区和热影响区)较窄,堆焊质量良好;堆焊修复内孔零件试样经车削+滚压强化处理后表面光滑、平整,粗糙度明显降低,且形成了高值残余压应力,这些都有利于改善修复零件的抗疲劳性能。该修理工艺简单可靠、经济实用,可实现损伤内孔零件控型与控性的有效结合,为重载装备的内孔零件修复提供了一种方法。     

氯酸钾对不锈钢在硫酸和盐酸混合溶液中的缓蚀行为

研究了缓蚀剂ＫＣｌＯ３在７０％Ｈ２ＳＯ４和０．２％ＨＣｌ溶液中对１８—８不锈钢的缓蚀行为。运用线性极化技术测定了缓蚀剂的缓蚀效率为９６％。动电位极化曲线、循环极化曲线及交流阻抗的测量表明,缓蚀剂ＫＣｌＯ３是一种阳极钝化型缓蚀剂,添加缓蚀剂ＫＣｌＯ３后,不锈钢表面氧化膜进一步加强,从而有效地抑制不锈钢的均匀腐蚀和孔蚀。     

低碳钢的点蚀诱发敏感性研究

选择 3种冶金因素有代表性的低碳钢 ,通过极化试验比较了它们之间的点蚀诱发敏感性 ,同时利用电子探针分析了不同夹杂物在诱发点蚀过程中的腐蚀特征 ,并利用Flade电位比较了不同钢之间的钝化膜稳定性的差异 .结果表明 :沸腾钢的点蚀诱发敏感性显著低于镇静钢 ,稀土处理镇静钢则介于两者之间 ;夹杂物是钢中主要点蚀诱发源 ,钢基体与夹杂物交界处的钝化膜保护作用最弱 ,点蚀均从该处诱发 ;同类夹杂物在不同类型钢中的点蚀诱发敏感性差异较大 ,同一钢中的不同类型夹杂物的点蚀诱发敏感性差异很小 ,硫化物夹杂较其它夹杂物的点蚀诱发敏感性稍强 .     

在单晶硅片上直接电化学沉积制备镍反opal光子晶体

采用电化学沉积工艺直接向组装在单晶硅片上的聚苯乙烯胶体晶体中填充金属Ni,成功制备了Ni的反opal光子晶体。采用线性扫描伏安法研究了单晶硅表面的化学刻蚀对Ni的电化学沉积过程的影响,并采用扫描电子显微镜(SEM)、X射线衍射等对Ni反opal光子晶体的形貌和结构进行了观察分析,对其光学性能进行了初步研究。研究结果表明,对单晶硅片表面进行化学刻蚀有利于金属Ni的电化学沉积;在PS胶体晶体模板中电化学生长的金属Ni呈多晶状态,去除模板后形成了金属Ni的有序多孔结构。     

铝合金表面微弧氧化技术研究与应用进展

铝合金表面微弧氧化技术具有工艺简单、适用范围广、节能环保等优点,其氧化陶瓷膜具有阳极氧化膜和陶瓷喷涂层的双重优点,能够克服铝合金硬度低、耐磨性能差的缺点,在军工、机械、电子、航空、航天等诸多领域具有广阔的应用前景.简要介绍了铝合金表面微弧氧化技术的发展历程,分析了铝合金微弧氧化陶瓷膜性能、生长机理及技术工艺的最新研究进展,指出了该技术实际应用中尚待解决的问题,并提出了该技术的发展趋势.     

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。     

Microstructure,mechanical and corrosion behavior of high strength AA7075aluminium alloy friction stir welds-Effect of post weld heat treatment

High strength aluminium alloy AA7075(Al-Zn-Mg-Cu) is a precipitate hardenable alloy widely used in the aerospace,defense,marine and automobile industries.Use of the heat treatable aluminium alloys in all these sectors is ever-increasing owing to their excellent strength-toweight ratio and reasonably good corrosion resistance.The shortage in corrosion resistance,however,usually poses negative concern about their reliability and lifetime when they service in the variable marine environments.These alloys also exhibit low weldability due to poor solidification microstructure,porosity in fusion zone and lose their mechanical properties when they are welded by fusion welding techniques.Friction stir welding(FSW) is a reliable technique to retain the properties of the alloy as the joining takes place in the solid state.The welds are susceptible to corrosion due to the microstructural changes in the weld nugget during FSW.In this work,the effect of post weld treatments,viz.,peak aging(T6) and retrogression reaging(RRA),on the microstructure,mechanical properties and pitting corrosion has been studied.Friction stir welding of 8 mm-thick AA7075 alloy was carried out.The microstructural changes of base metal and nugget zone of friction stir welds were studied using optical microscopy,scanning electron microscopy and transmission electron microscopy.Tensile and hardness test of base metal and welds has been carried out.Pitting corrosion resistance was determined through dynamic polarization test.It was observed that the hardness and strength of weld were observed to be comparatively high in peak aged(T6) condition but the welds showed poor corrosion resistance.The resistance to pitting corrosion was improved and the mechanical properties were maintained by RRA treatment.The resistance to pitting corrosion was improved in RRA condition with the minimum loss of weld strength.     

Enhancement of wear and ballistic resistance of armour grade AA7075 aluminium alloy using friction stir processing

Industrial applications of aluminium and its alloys are restricted because of their poor tribological properties. Thermal spraying, laser surfacing, electron beam welding are the most widely used techniques to alter the surface morphology of base metal. Preliminary studies reveal that the coating and layering of aluminium alloys with ceramic particles enhance the ballistic resistance. Furthermore, among aluminium alloys,7075 aluminium alloy exhibits high strength which can be compared to that of steels and has profound applications in the designing of lightweight fortification structures and integrated protection systems. Having limitations such as poor bond integrity, formation of detrimental phases and interfacial reaction between reinforcement and substrate using fusion route to deposit hard particles paves the way to adopt friction stir processing for fabricating surface composites using different sizes of boron carbide particles as reinforcement on armour grade 7075 aluminium alloy as matrix in the present investigation. Wear and ballistic tests were carried out to assess the performance of friction stir processed AA7075 alloy. Significant improvement in wear resistance of friction stir processed surface composites is attributed to the change in wear mechanism from abrasion to adhesion. It has also been observed that the surface metal matrix composites have shown better ballistic resistance compared to the substrate AA7075 alloy. Addition of solid lubricant Mo S2 has reduced the depth of penetration of the projectile to half that of base metal AA7075 alloy. For the first time, the friction stir processing technique was successfully used to improve the wear and ballistic resistances of armour grade high strength AA7075 alloy.     

Pitting corrosion resistance and bond strength of stainless steel overlay by friction surfacing on high strength low alloy steel

Surface modification is essential for improving the service properties of components. Cladding is one of the most widely employed methods of surface modification. Friction surfacing is a candidate process for depositing the corrosion resistant coatings. Being a solid state process, it offers several advantages over conventional fusion based surfacing process. The aim of this work is to identify the relationship between the input variables and the process response and develop the predictive models that can be used in the design of new friction surfacing applications. In the current work, austenitic stainless steel AISI 304 was friction surfaced on high strength low alloy steel substrate. Friction surfacing parameters,such as mechtrode rotational speed, feed rate of substrate and axial force on mechtrode, play a major role in determining the pitting corrosion resistance and bond strength of friction surfaced coatings. Friction surfaced coating and base metal were tested for pitting corrosion by potentiodynamic polarization technique. Coating microstructure was characterized using optical microscopy, scanning electron microscopy and X-ray diffraction. Coatings in the as deposited condition exhibited strain-induced martensite in austenitic matrix. Pitting resistance of surfaced coatings was found to be much lower than that of mechtrode material and superior to that of substrate. A central composite design with three factors(mechtrode rotational speed, substrate traverse speed, axial load on mechtrode) and five levels was chosen to minimize the number of experimental conditions. Response surface methodology was used to develop the model. In the present work, an attempt has been made to develop a mathematical model to predict the pitting corrosion resistance and bond strength by incorporating the friction surfacing process parameters.     

Effect of post weld heat treatment on tensile properties and microstructure characteristics of friction stir welded armour grade AA7075-T651 aluminium alloy

This paper reports the effects of post weld heat treatments, namely artificial ageing and solution treatment followed by artificial ageing, on microstructure and mechanical properties of 12 mm thick friction stir welded joints of precipitation hardenable high strength armour grade AA7075-T651 aluminium alloy. The tensile properties, such as yield strength, tensile strength, elongation and notch tensile strength, are evaluated and correlated with the microhardness and microstructural features. The scanning electron microscope is used to characterie the fracture surfaces. The solution treatment followed by ageing heat treatment cycle is found to be marginally beneficial in improving the tensile properties of friction stir welds of AA7075-T651 aluminium alloy.     

低合金船体钢点蚀敏感性的研究

通过极化试验比较了4种含有不同合金元素的低合金钢的点蚀诱发敏感性,并用电子探针对钢中的主要夹杂物及点蚀诱发后的腐蚀形态作了鉴定.结果表明:镍-铬系钢比锰系钢具有更好的耐点蚀性能;点蚀总是从夹杂物与周围钢基体毗邻的界面处开始诱发;含有硫化物的复相夹杂对点蚀的敏感性更强.     

羧酸盐对锡和铝在中性溶液中的缓蚀作用研究

分别采用交流阻抗、线性极化、动电位扫描等电化学方法初步研究了羧酸盐缓蚀剂在中性介质中对锡和铝的缓蚀作用.实验结果表明,锡和铝在中性介质中的腐蚀以点蚀为主,而该羧酸盐结构中含有羧基,对锡和铝有良好的缓蚀效果,尤其是处于最佳缓蚀浓度时.     

Effect of fusion welding processes on tensile properties of armor grade,high thickness,non-heat treatable aluminium alloy joints

AA5059 is one of the high strength armor grade aluminium alloy that finds its applications in the military vehicles due to the higher resistance against the armor piercing (AP) threats. This study aimed at finding the best suitable process among the fusion welding processes such as gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) by evaluating the tensile properties of AA5059 aluminium alloy joints. The fracture path was identified by mapping the low hardness distribution profile (LHDP) across the weld cross section under tensile loading. Optical and scanning electron microscopies were used to characterize the microstructural features of the welded joints at various zones. It is evident from the results that GTAW joints showed superior tensile properties compared to GMAW joints and this is primarily owing to the presence of finer grains in the weld metal zone (WMZ) and narrow heat-affected zone (HAZ). The lower heat input associated with the GTAW process effectively reduced the size of the WMZ and HAZ compared to GMAW process. Lower heat input of GTAW process results in faster cooling rate which hinders the grain growth and reduces the evaporation of magnesium in weld metal compared to GMAW joints. The fracture surface of GTAW joint consists of more dimples than GMAW joints which is an indication that the GTAW joint possess improved ductility than GMAW joint.