真空热循环作用下LF6合金焊接接头的拉伸性能和微观组织

采用精密多功能低温静载材料实验机、热循环试验装置、透射电镜和扫描电镜，系统研究了真空热循环条件下LF6合金焊接接头的拉伸性能和微观组织，分析讨论了真空热循环对LF6合金焊接接头的影响规律。研究结果表明，在循环300周次范围内，真空热循环可改善LF6合金焊接接头的拉伸性能，使其强度和塑性均得到提高。热循环对焊接接头拉伸性能具有影响，并同循环次数有关。初始循环时，由于位错不断增殖，使得LF6合金焊接接头的强度和塑性增加较快；经热循环70周次后，接头的强度和塑性均达到最高值；循环次数继续增加，强度和塑性开始下降，这可能与晶内位错密度降低、晶界处形成位错墙有关。     

纳米填料对环氧树脂胶粘剂强度的影响

通过在环氧胶粘剂中加入纳米填料,研究了纳米填料对环氧胶粘剂强度的影响规律。试验结果表明,在胶粘剂中加入纳米SiO2和一维纳米SiC晶须,获得的环氧树脂(E44、E51)胶粘剂的抗拉强度可以达到69·09MPa,剪切强度达到35·86MPa,改性环氧树脂中填料的最佳加入量为7%的纳米SiO2和10%的一维纳米SiC晶须纤维。     

硅烷偶联剂的界面性能研究

采用红外光谱表征了硅烷偶联剂及硅橡胶胶粘剂的结构;并用硅烷偶联剂预处理金属(马口铁)、塑料表面,然后用硅橡胶胶粘剂分别粘接金属与金属、塑料与塑料的界面,测定其粘接剪切强度及拉伸强度;用硅烷偶联剂预处理玻璃纤维表面,测定玻璃纤维增强不饱和树脂试样的拉伸强度.试验结果表明:红外光谱可以较准确地表征硅烷偶联剂及硅橡胶胶粘剂的结构:经过硅烷偶联剂预处理后,不论是金属界面、塑料界面间粘接剪切强度,还是玻璃纤维增强不饱和树脂的拉伸强度均有明显提高.     

添加泡沫镍中间层Al_2O_3/1Cr18Ni9Ti钎焊接头性能研究

连接温度850℃,保温时间20 min,用泡沫镍金属作为中间层真空钎焊Al2O3陶瓷与1Cr18Ni9Ti不锈钢;采用SEM、EDS分析了钎焊接头的微观组织,利用剪切试验和热循环检测了接头的力学性能。结果表明,不添加中间层时,接头平均剪切强度只有8.6 MPa,热循环寿命为5次,断裂位置发生在陶瓷侧,Ti元素主要分布在连接界面处;添加泡沫镍中间层时,接头平均剪切强度达到80.9 MPa,热循环寿命为60次,断裂位置发生在陶瓷与泡沫镍金属连接界面处,Ti元素主要分布在泡沫镍中间层。     

表面粗糙度对Q235钢粘合镀层力学性能的影响

采用胶粘剂把不同表面粗糙度的Q235钢粘合到一起,对粘合镀层的拉伸强度和剪切强度进行研究。结果表明,拉剪强度随Q235钢表面粗糙度的变化不断地发生变化,出现了波谷和波峰。     

CuAgNi钎料钎焊钨基粉末合金接头高温行为的研究

采用OM、SEM和XRD观察了CuAgNi钎料及其钎焊钨基粉末合金接头的微观组织,对比研究了CuAg和CuAgNi钎料钎焊钨基粉末合金接头的高温剪切强度,进一步分析了CuAgNi钎料钎焊接头的热疲劳性能。研究表明：Ni对钎焊接头室温和高温下的剪切强度均有促进作用;接近室温(50℃)时,钎焊接头剪切强度为214.7MPa,比不添加Ni时增加了32.37%;400℃时,剪切强度为121.9MPa,比未添加Ni时增加了91.67%;且当温度超过300℃时,结合界面的氧化使接头的结合强度急剧下降。热疲劳试验中,随着热循环次数的增加,裂纹在α-Ag和β-Cu结合处萌生后逐步扩展,使接头剪切强度逐步降低。     

TC4合金800℃热循环组织和力学性能变化

研究TC4合金经过800℃热循环后的组织和力学性能。结果表明:循环次数对合金的性能影响显著,随着循环次数的增加,合金的强度和塑性均开始下降;其中,合金热循环5次后强度下降迅速,随着循环次数的增加合金强度和塑性下降速度有所减缓。分析认为:在0～5次循环区间内,引起强度迅速下降的主要原因是由于组织中β相减少,5～100循环区间内强度下降主要是由于组织变化和合金表面氧化共同引起,而100～200次热循环区间强度下降主要由表面氧化所致。     

环氧胶接接头在碱介质中的老化行为研究

研究了环氧胶接接头在碱性介质中的老化行为,并用傅立叶红外光谱仪(FTIR)和扫描电镜(SEM)分析了其失效的机理.结果表明,环氧胶接接头在碱性介质中老化后,其剪切强度明显降低;提高温度会缩短环氧胶接接头在NaOH溶液中的老化寿命;胶粘剂分子链的降解是环氧胶接接头胶接性能降低的主要原因.     

J-15胶粘剂剪切强度试样制备工艺探讨

剪切强度是胶粘剂关键的性能指标,试样制备是影响胶粘剂剪切强度试验结果的重要过程。因标准对试样制备的过程描述不甚详细,导致J-15胶粘剂剪切强度试验多次出现数据偏差大、稳定性差等问题,给科研生产的顺利进行带来不便。为解决此问题,本文研究胶接表面粗糙度及固化压力2个关键因素对J-15胶粘剂剪切强度的影响,获得最优的试样制备工艺参数。结果表明：J-15胶粘剂剪切强度试样制备基材采用240#砂纸进行处理,升温至170℃,保温3 h后施加固化压力0.4 MPa时,剪切强度值最佳。将此作为胶粘剂剪切强度试样制备的推荐使用参数,有利于J-15胶粘剂剪切强度试验数据的准确和稳定。     

填料对环氧胶粘涂层耐蚀及耐磨性影响

在环氧肢粘涂层中加入不同填料，通过试验研究其对环氧肢粘涂层拉伸剪切强度、耐腐蚀及耐冲蚀磨损性能的影响，由此推荐粉煤灰作为冷敷环氧肢粘涂层填料的最佳含量。     

真空热处理对APS-NiCoCrAlY+APS-YSZ热障涂层热循环寿命的影响

通过大气等离子喷涂在HA188合金基材上制备NiCoCrAlY+YSZ热障涂层,然后分别对试样在高真空和低真空中进行1080 ℃的热处理。通过在1100 ℃对热处理前后的热障涂层进行热循环考核,并在具备EDS的扫描电镜下分析了热循环前后的显微组织和成分。结果表明,真空热处理显著提高了APS-NiCoCrAlY+APS-YSZ热障涂层的热循环寿命,一方面是由于真空热处理后在APS-NiCoCrAlY/APS-YSZ界面上形成连续的TGO层受到了抑制,降低了由TGO产生的应力开裂,另一方面真空热处理后的涂层热循环时在APS-NiCoCrAlY的内部产生了更多的氧化物,在一定程度上降低了APS-NiCoCrAlY的热膨胀系数,减少了由APS-NiCoCrAlY/APS-YSZ热膨胀系数不匹配造成的应力开裂。并且低真空热处理的涂层内部失效裂纹没有像高真空热处理的涂层那样均匀连续扩展。     

Study on static and fatigue strength of structural adhesive-bonded joints of steel sheets for automotive application

The static and fatigue strength of crush durable structural adhesive-bonded lap joints of steel sheets for automobiles was evaluated by tensile shear tests. The steel sheets used in this study were uncoated and galvannealed (GA) with tensile strength ranging from 270 MPa-grade to 980 MPa-grade and the thickness ranging from 0.7 to 1.8 mm. Also, the effects of the adhesive types were evaluated. The results are as follows: In the static tensile shear tests, when the steel sheets deformed during the tensile test, the tensile shear strength increased with the increase in the base metal properties, such as the yield strength and thickness; however, when the base metal properties were sufficiently high not to undergo plastic deformation, the tensile shear strength exhibited a constant value. On the other hand, the effect of base metal properties on the fatigue joint strength was relatively small. The static joint strength of the GA steel joints was slightly lower than that of the uncoated steel sheets; however, the fatigue strength of the GA steel joints was higher than that of the uncoated steel sheets. The coating failure of the GA was affected by the type of adhesive, base metal properties and type of test. Choosing the proper adhesive can reduce the failure of the GA coating, and the high strength steel showed fewer coating failures than the mild steel.     

超声辐照对碳纳米管增强环氧树脂黏度和力学性能的影响

采用超声辐照处理多壁碳纳米管增强环氧树脂复合材料,分析了超声辐照条件对复合材料的黏度、力学性能及拉伸断口显微形貌的影响。结果表明:温度一定时,多壁碳纳米管增强环氧树脂体系的黏度随超声辐照时间的延长而逐渐降低;超声辐照时间为5min时,环氧树脂的拉伸强度、弯曲强度、拉伸剪切强度达到最大值,较处理前分别提高了37%,167%和86%;经超声辐照后,拉伸断口形貌显示出更多的韧性断裂特征。     

聚四氟乙烯射频等离子体表面改性研究

采用氧等离子体对PTFE粘接件进行处理,测试了压剪粘接件和拉伸粘接件的粘接强度,分析了氧等离子体处理前后PTFE的接触角变化情况,同时,采用了AFM对PTFE进行了表面形貌的观察.     

Novel adhesion promotion of aluminium for aerospace environments

This study focuses on analysing the durability of adhesive bonds formed in samples of Aluminium 6063, Titanium Nitride deposited Al 6063 and Anodized Al 6063 using epoxy adhesive Weicon A. Two types of studies are performed, first, samples of Aluminium 6063, Titanium Nitride deposited Al 6063 and Anodized Al 6063, are bonded by an epoxy adhesive Weicon A. Second, the samples are bonded by the adhesive with reinforcement of Ca₂SiO₄ nanoparticles in different proportions. The samples are examined using the scanning electron microscopy to study the morphology of the coating. A lap shear test is performed to determine the strength of the adhesive after the specimens were subjected to harsh chemical environments. A thermogravimetric analysis is performed on the adhesive to understand the effect of nanoparticles in the thermal stability in the Weicon A. It is understood from the tests that the titanium nitride coated Al 6063 samples bonded with Weicon A exhibited greater bond strength and also retained the strength when exposed to harsh environments. The inclusion of calcium silicate nano-particles showcased a considerable reduction in the bond strength. The thermal stability of Weicon A seems to be unaffected by the inclusion of calcium silicate nanoparticles.     

Finite element analysis of thermal stress in magnetron sputtered Ti coating

The thermal, shear and radial stresses generated in the Ti coating deposited on glass and Si substrates were investigated by finite element analysis (ANSYS). The four-node structural and quadratic element PLANE 42 with axisymmetric option were used to model the Ti coating on glass and Si substrates. The influence of deposition temperature, substrate and coating properties on the generation of thermal stress in Ti is analyzed. It is found that the thermal stress of Ti coating exhibits a linear relationship with deposition temperature and Young's modulus of the coating, but it exhibit an inverse relationship with the coating thickness. The results of simulated thermal stress are in accordance with the analytical method. The radial stress and shear stress distribution of the coating–substrate combination are calculated. It is observed that high tensile shear stress of Ti coating on glass substrate reduces its adhesive strength but high-compressive shear stress of Ti on Si substrate improves its adhesive strength.     

热老化与热循环条件下Bi对Sn-1.0Ag-0.5Cu无铅焊点界面组织与性能的影响

研究了在热老化和热循环过程中Bi的添加对低银无铅钎料Sn-1.0Ag-0.5Cu (SAC105)的BGA焊点界面微观组织演变的影响,分析了Bi的添加对SAC105微焊点热老化与热循环剪切性能的影响. 结果表明,Bi元素添加量为2%(质量分数)时,对热循环过程中微焊点界面处金属间化合物(IMC)层整体厚度的增加起到抑制作用,同时阻碍了热循环过程中因焊点热失配导致的IMC层破碎. 但是Bi的添加促进了界面IMC层中Cu₃Sn层的生长,因此在经过20天以上热老化处理后SAC105-2Bi微焊点界面IMC层厚度与SAC105微焊点接近. 此外,Bi的添加可以显著提升热循环处理后SAC105微焊点的抗剪切能力. SAC105-2Bi微焊点的剪切力学性能受到热循环处理的影响较小. 与SAC105微焊点相比,SAC105-2Bi微焊点的断裂模式更早地从韧性断裂向脆性断裂转变,因此Bi的添加降低了SAC105微焊点的热循环可靠性.     

The Influence of Nano-Al2O3 Additive on the Adhesion between Epoxy Resin and Steel Substrate

The influence of nano-Al2O3 additive on the adhesion between epoxy resin and steel substrate has been investigated. The results of tensile testing indicated that the adhesion strength was increased dramatically by addition of Al2O3 nanoparticles in epoxy resin compared with that of the unmodified resin. The highest adhesion strength was obtained with 1 wt% nano-Al2O3 added in epoxy adhesive, more than two times higher than that of the unmodified. Scanning electronic microscope (SEM) revealed that a boundary layer exists between epoxy and steel substrate, energy spectrum analysis indicates there is enrichment of the nano-Al2O3 particle. Those results confirmed that the nano-Al2O3 additive was closely related to the change of interface morphology and the improvement of adhesion strength. The reason for adhesion improvement was also be discussed.