环氧铝粉涂层在3.5%NaCl介质中的失效机理研究

采用电化学阻抗谱技术（EIS）研究了环氧铝粉涂层/Q235钢基体在3.5 %NaCl介质中的电化学腐蚀行为.利用扫描电镜（SEM）分析了涂层表面形貌,对涂层断面进行了能谱（EDX）线扫描和界面处腐蚀产物成分分析,探讨了环氧铝粉涂层的腐蚀失效机理.结果表明,腐蚀介质能通过涂层迅速渗透到涂层/基体界面,引起涂层电阻值的降低及界面处电化学腐蚀的开始.失效前涂层致密、连续,失效后涂层表面出现鼓泡、孔洞等现象.鼓泡是由腐蚀产物的体积膨胀和腐蚀介质渗入产生的压力推动共同产生的.界面处腐蚀产物主要是Fe和Al的氧化物及氯化物.涂层的失效机理为腐蚀介质渗入,涂层鼓泡、剥离.     

铝合金建筑型材腐蚀白斑的产生原因

经氟碳漆喷涂表面处理的铝合金建筑型材在建筑楼房安装放置一段时间后,在铝型材推拉门附近出现大量的腐蚀白斑和鼓泡现象。采用宏观检验、化学成分分析、金相组织检验、电镜微观分析以及涂层性能检测等方法对腐蚀的铝型材产品进行分析,探讨了铝型材的腐蚀机理。结果表明:铝型材腐蚀白斑主要成分除氧化铝外,含有大量氯的腐蚀物,由于铝型材表面存在大量氯元素,氯离子不断腐蚀渗透,形成腐蚀孔洞,从而造成铝型材表面腐蚀,引起铝型材的腐蚀失效。     

双相不锈钢空蚀表面TEM研究

对双相不锈钢空泡腐蚀试样进行单侧电解减薄,用透射电镜研究了表面组织。结果表明,双相不锈铜表面存在非晶层、铁素体纳米晶、面心立方和渗碳体纳米晶;非晶层内存在大量球形泡,泡内部主要为非晶态,泡壁主要为铁素体晶体。此外．空泡溃灭产生的瞬时温唐高达750K以上。     

电火花沉积工艺对汽车用镁合金涂层结构及腐蚀性影响

应用电火花沉积设备在AZ91镁合金表面进行表面处理,研究了沉积工艺参数对沉积层性能及组织结构的影响,并利用扫描电镜、NaCl浸泡试验等研究手段对镁合金改性层的微观表面形貌、截面形貌、浸泡试样腐蚀产物进行分析;并对涂层改善基体腐蚀性的机理进行分析与讨论。结果表明:采用沉积频率200 Hz、空占比50%和35 V的沉积电压进行电火花沉积时,强化层的组织均匀、结构致密、涂层厚度适中、涂层内部孔洞、缺陷明显降低,与基材相比,表现出较好的耐腐蚀性能。     

冷轧带钢电镀后表面起泡原因的分析

冷轧带钢在氰化物碱性介质中电镀锌后,基材表面出现间断的呈直线排列小鼓泡,经扫描电子显微镜观察和能量色散谱检测,发现气泡内有一大小约10μm以Mg的氧化物为主的块状物.在电镀过程中,由于氢原子的渗入引起基材表层起泡.     

灰铸铁气体渗氮表面鼓泡和脆化爆裂成因探讨

对灰铸铁件经气体渗氮而出现的表面鼓泡及泡壳脆化爆裂的成因，作者观察分析表明：鼓泡壳下是原石墨，石墨尖端裂纹呈放射状，并与邻近石墨片相互贯穿呈网络状孔洞，这些缺陷主要由氢蚀和氢脆所致。     

镁合金电火花沉积改性层性能及组织结构的研究

应用电火花沉积设备在AZ91D镁合金表面沉积纯铝涂层进行表面改性处理,研究了电火花沉积工艺参数以及前处理对沉积改性层性能和组织结构的影响;并结合扫描电镜、中性盐雾试验等研究手段对镁合金改性涂层的微观表面形貌、截面形貌、腐蚀情况以及显微硬度进行了分析和对比;同时,也对镁合金表面沉积纯铝涂层的沉积机理和沉积层改善基体耐腐蚀性、硬度进行分析与讨论。研究结果表明:电火花沉积工艺参数及预处理对AZ91D镁合金表面沉积纯铝涂层的组织结构、微观形貌特点有重要影响;电火花沉积工艺参数的降低以及沉积前对母材和电极的预热处理,涂层表面显微硬度较基材有了较大程度的提高;同时,强化层组织结构均匀致密、涂层厚度适中、涂层内部裂纹孔洞等缺陷明显降低,与镁合金基材相比,表现出较好的耐腐蚀性能。     

铜/钨异种金属A-TIG电 弧点焊工艺及性能研究

针对钨板轧制过程中,铜/钨接头处的连接问题,本文采用TIG对铜/钨异种金属进行焊接,分别对涂覆SiO2和未涂覆SiO2活性剂的试件进行搭接点焊,并对焊点形貌、接头截面及微观形貌和抗拉强度进行分析。结果表明,未涂覆SiO2的焊点呈凸起状,且不规则,界面结合处存在较多的孔洞缺陷,涂覆SiO2的焊点中心出现圆形凹坑,界面处孔洞等缺陷减少;接头界面处均发生了铜/钨的互扩散,涂覆SiO2的试件比未涂覆的界面更加致密;相同电流下,涂覆SiO2的接头强度比未涂覆SiO2的高,并且接头断裂位置明显不同     

化学镀Ni-P电镀Ni-Co-Mn复合层力学及耐热腐蚀性能研究

通过先化学镀后电镀的方法制得“基材-化学镀Ni-P层-电镀Ni-Co-Mn层”的复合层,采用金相观测、纳米压痕、纳米划痕、SEM、EDS等方法研究了镀层的力学性能及耐热腐蚀性能。结果表明,复合层的弹性模量与纳米硬度与电镀层相近,比单一化学镀层略低;复合层与基材结合得较好,复合层中两种镀层亦结合得较好,结合力超出纳米划痕的最大测量值28N,比单一电镀层与基材的结合力大;化学镀层与电镀层的组织致密度较高,耐热腐蚀性及抗氧化性较好,且化学镀层稍优于电镀层;先化学镀后电镀的工艺比单一电镀的结合牢固,比单一化学镀的镀层生长速率要快,且热腐蚀后与基材的结合力提升很多。     

C掺杂对Al中He行为的影响

用离子注入技术实现了Al表面C元素的掺杂,并利用XPS,XRD,TEM和SEM研究了C掺杂对Al中离子注入He行为的影响.结果表明,掺杂的C在Al表面形成了Al_4C_3,随着C掺杂量的增加,Al表面组织的择优取向和晶胞体积发生改变,从而影响了Al中的He离子注入行为.预先掺杂的C对He离子注入Al表面的鼓泡行为有重要影响,其影响程度与掺杂剂量有关.小剂量C掺杂后,能有效抑制鼓泡的长大,并使Al表面鼓泡均匀分布;更高剂量C掺杂后,C对表面鼓泡的抑制作用减弱,甚至加剧He离子的辐照损伤,Al表面出现孔洞和剥落现象.掺杂的C对Al基体的微观结构也有很大影响.     

W–Cu composites with homogenous Cu–network structure prepared by spark plasma sintering using core–shell powders

W–Cu composites with homogenous Cu–network structure were fabricated by spark plasma sintering using core–shell powders. The core-shell powders were obtained by intermittently electroplating method which can deposit shell composed of nano–copper on the core of micron tungsten particles. These nano–copper shells provide a large amount of grain boundaries, which are benefit for removing pores and improving the densification during sintering. Thus, the W–Cu composites can be obtained at low sintering temperature. The thermal conductivity, hardness and bending strength of the sintered W–Cu composites were investigated. The W–Cu composites show homogeneous microstructure and high thermal conductivity due to the formed fine Cu–network structure, low W–W contiguity and nearly full density.     

BN与LPSO相混杂增强的镁基复合材料制备及性能

研究了六方氮化硼(h-BN)颗粒增强镁基复合材料的制备工艺及其性能。通过化学镀法在h-BN颗粒表面包覆一层纯镍,镀镍处理能显著改善h-BN与镁合金熔体的润湿性,改善其与基体的界面结合。通过向基体合金中加入Y元素,利用镀镍层熔入熔体中的Ni获得了由Mg-Ni-Y组成的LPSO结构(长周期堆垛有序结构),制得了h-BN+LPSO混杂增强的镁基复合材料。超声处理后,hBN增强相体积分数为3%的镁基复合材料热导率为99.92W/(m·K),室温(RT)至100℃的平均热膨胀系数为18.36×10^-6K^-1,抗拉强度为171MPa,伸长率为3.9%,获得了兼具较高力学性能和优异热物性能的镁合金材料。     

Gra./Cu和CNTs/Cu复合材料的截流值与阴极斑点研究

采用粉末冶金方法制备石墨铜复合材料(Gra./Cu)和碳纳米管铜复合材料(CNTs/Cu),研究2种铜基复合材料的真空电弧截流现象和阴极斑点特性。结果表明,与Gra./Cu相比,CNTs/Cu在真空放电过程中电弧更加稳定,且分散性好,截流值小;在正对阳极处CNTs/Cu的真空电弧烧蚀坑明显比Gra./Cu的细小,灼痕直径约为0.1～5μm,分布面积也较小,而Gra./Cu的灼痕直径为10～100μm;两者的相同之处在于,在电击穿过程中阴极斑点的运动呈一种随机的、突变式的跳跃,而且选择性发生在Cu相上,Cu相被消耗。总之,CNTs/Cu比Gra./Cu具有更高的耐电弧烧蚀能力,CNTs的加入可以有效地增加铜基复合材料的电弧稳定性和降低截流值。     

Characterization and Tribological Properties of Graphene/Copper Composites Fabricated by Electroless Plating and Powder Metallurgy

Self-lubricating copper matrix composites reinforced with graphene were prepared by electroless plating and powder metallurgy.The morphology and structure of graphene,Cu@graphene powder,and Cu@graphene/Cu composites were characterized and the tribological properties of Cu@graphene/Cu composites were investigated.The X-ray diffraction pattern of Cu@graphene confirms the coexistence of characteristic peaks of both copper and graphene,with a weakened characteristic peak of carbon impurity.The obtained morphology of Cu@graphene reveals that the surface of the graphene is completely covered with a uniform and compact copper layer with lots of copper nanoparticles.Raman and Fourier transform infrared spectroscopy analyses show that the oxygen functional groups and defects on the surface of the redox graphene can be reduced through the electroless plating process.The tribological results indicate that the coefficient of friction of Cu@graphene/Cu composites initially decreases and then increases with an increase in Cu@graphene content.The lowest coefficient of friction,which is about 29.47% lower than that of pure Cu,is achieved in the Cu@graphene/Cu composites with 3.0 wt%Cu@graphene.The chemical composition and topography of the wear tracks for Cu@graphene/Cu composites infer that the formation of a well-consolidated graphene-rich lubricious tribolayer at the contact surface and a higher microhardness work together to enhance the tribological performance of Cu@graphene/Cu composites.     

Solid state interfacial reactions in electrodeposited Cu/Sn couples

Cu/Sn couples, prepared by sequentially electroplating Cu and Sn layers on metallized Si wafers, were employed to study the microstructures, phases and the growth kinetics of Cu-Sn intermediate phases, when electroplated Cu/Sn couples were aged at room temperature or annealed at temperatures from 373 K to 498 K for various time. Only Cu6Sn5 formed in aged couples or couples annealed at temperature below 398 K. The Cu6Sn5 layer was continuous, but not uniform, with protrusions extending into the Sn matrix. W...     

Microstructure,phase transformation and mechanical properties of NiMnGa particles/Cu composites fabricated by SPS

Microstructure, phase transformation and mechanical properties of NiMnGa particles/Cu composites prepared by spark plasma sintering method were investigated by SEM, EDS, XRD, susceptibility measurements and mechanical tests. The NiMnGa particles were found to react with Cu matrix and the composites exhibited a similar crystal structure to the Cu matrix. The martensitic transformation and Curie transition of the composites were weakened due to the composition change of NiMnGa particles caused by reactions. With increasing NiMnGa particles content, the martensitic transformation and Curie transition of the composites were enhanced to some extent. However, the martensitic transformation temperature and Curie transition temperature were decreased by ~50 K as compared to those of the original NiMnGa particles. The compressive strength of the composites increased with the increase of NiMnGa particles content, whereas the compressive strain was decreased gradually.     

MgO/Cu基复合材料耐电弧侵蚀行为研究

采用放电等离子烧结法(SPS)制备了纳米级MgO陶瓷颗粒增强铜基复合材料(MgO/Cu复合材料),重点研究了MgO颗粒含量对其耐电弧侵蚀性能的影响,阐述了MgO颗粒在电接触过程中的耐电弧侵蚀机理。结果表明,随着MgO颗粒体积分数增加,MgO/Cu复合材料的耐电弧侵蚀性能逐渐提高,当MgO颗粒体积分数为5%时,MgO/Cu复合材料的总体质量损耗和燃弧能量均达到最低值。研究分析表明,高熔点的MgO颗粒有助于改善MgO/Cu复合材料的力学性能和耐电弧侵蚀性能。电弧侵蚀过程中,高熔点MgO颗粒的存在提高了液相铜基体的熔池粘度,减少了电弧喷溅,从而提高了MgO/Cu复合材料的耐电弧侵蚀性能。     

Deformation behavior and crack propagation on interface of Al/Cu laminated composites in uniaxial tensile test

The microstructural characterization and uniaxial tensile tests of Al/Cu laminated composites were taken to investigate the interface effect and fracture process of the composites.The electron microscopic graphs before and after tensile test were used to evaluate the fracture behavior.Experimental results show that the fracture surfaces of laminated composites mainly present brittle failure characteristics,accompanied with several dimples on the matrixes and a few tearing on the interface.Cracks...     

钨丝／Zr基金属玻璃复合材料的界面反应与扩散

采用渗流铸造工艺制备了钨丝增强不同Nb含量的Zr基金属玻璃复合材料，利用X-Ray衍射、扫描电镜以及电子探针考察了复合材料界面反应和界面扩散情况，研究了基体合金中的Nb含量对复合材料界面反应和界面扩散的影响。结果表明：对Zr55Al10Ni5Cu30基复合材料，渗流时，钨丝与液相中的Zr发生界面包晶反应，生成W5Zr3界面相，并使界面位置向液相方向移动。在Zr55Al10Ni5Cu30合金的基础上添加Nb，发现Nb优先在钨丝界面偏聚，降低了Zr在钨丝界面的偏聚和活度，抑制钨丝与液相中的Zr包晶反应的发生，没有生成W5Zr3界面相，界面处只存在简单的扩散层。同时发现Zr元素在钨丝中的扩散系数降低，此时界面位置向钨丝方向移动。     

TiC颗粒增强钨基复合材料的烧蚀性能

用自制的氧乙炔烧蚀装置对ＴｉＣ颗粒增强钨基复合材料的烧蚀性能进行了测试,同时用多波长比色高温计对烧蚀试样表面温度和用热电偶对试样背面温度进行了在线监测。复合材料的质量烧蚀率和和线烧蚀率由低到高的排列顺序为：Ｗ〈３０％ＴｉＣｐ／Ｗ〈４０％ＴｉＣｐ＝Ｗ。ＴｉＣ颗粒加入到Ｗ中可明显提高材料的抗烧蚀性能,而且ＴｉＣ颗粒含量越高,材料的抗烧性能越好。ＴｉＣｐ／Ｗ复合材料的烧机理是Ｗ和ＴｉＣ的氧化烧和燃气流的