Ti40Zr25Ni15Cu20非晶钎料钎焊Si3N4陶瓷的界面结构及强度

采用Ti40Zr25Ni15Cu20非晶钎料进行了Si3N4陶瓷真空钎焊连接,利用SEM、EDX等微观分析手段,研究了钎焊界面的微观结构,得出界面反应层有两部分组成,接头界面微观结构为Si3N4/TiN/Ti-Si,Zr-Si化合物/钎缝中心;在相同钎焊工艺条件下,研究对比了晶态和非晶态钎料钎焊接头的强度,发现非晶态钎料钎焊的接头强度大大超过用晶态钎料钎焊的接头.     

Si/SiC复相陶瓷与殷钢钎焊接头组织结构研究

以Ti、Cu混合金属粉末为钎料真空钎焊Si/SiC复相陶瓷与殷钢,通过扫描电镜、能谱仪、X射线衍射对接头组织结构进行分析.结果表明:Ti-Cu钎料对陶瓷和殷钢都具有良好的润湿性;在980℃保温10 min条件下形成良好的连接接头.连接层主要由Ti-Cu化合物和Ti5Si3相组成,在连接层与陶瓷界面生成TiSi2、Ti3SiC2和TiC反应层:在980℃保温15 min条件下,连接层中生成的化合物种类没有变化,但在近缝区的陶瓷中产生了横向裂纹,导致接头强度急剧下降.接头室温剪切强度在980℃保温10 min时最高达到90 MPa.     

Ag-Cu+WC复合钎料钎焊ZrO2陶瓷和TC4合金

采用新型Ag-Cu+WC复合钎料进行ZrO₂陶瓷和TC4合金钎焊连接,探究了接头界面组织及形成机制,分析了钎焊温度对接头界面结构和力学性能的影响. 结果表明,接头界面典型结构为ZrO₂/TiO+Cu₃Ti₃O/TiCu+TiC+W+Ag_(s,s)+Cu_(s,s)/TiCu₂/TiCu/Ti₂Cu/TC4. 钎焊过程中,WC颗粒与Ti发生反应,原位生成TiC和W增强相,为Ti-Cu金属间化合物、Ag基和Cu基固溶体提供了形核质点,同时抑制了脆性Ti-Cu金属间化合物的生长,优化了接头的微观组织和力学性能. 随钎焊温度的升高,接头反应层的厚度逐渐增加,WC颗粒与Ti的反应程度增强. 当钎焊温度890 ℃、保温10 min时,复合钎料所得接头抗剪强度达到最高值82.1 MPa,对比Ag-Cu钎料所得接头抗剪强度提高了57.3%.     

Cu-Ni-Ti非晶钎料钎焊Si3N4陶瓷的界面结构及连接强度

采用Cu-Ni-Ti非晶钎料钎焊Si3N4陶瓷,利用SEM、EDS等分析手段研究了其钎焊界面的微观结构.结果表明:反应层由两部分组成,其中紧靠Si3N4陶瓷的反应层Ⅰ由TiN化合物组成,Ti-Si化合物构成了反应层Ⅱ.在1100℃×10 min下钎焊时,其接头强度有最大值284.6 MPa.在相同的钎焊工艺条件下,非晶钎料接头强度高于同成分晶态钎料.     

采用复合钎料钎焊Si3N4陶瓷

采用TiN／Ag—Cu—Ti复合钎料连接Si3N4陶瓷材料，采用扫描电镜观察了接头组织。TiN颗粒与Ag—cu组织结合紧密，并未与钎料基体进行反应，在钎缝中分布比较均匀，形成了局部金属基复合材料组织。由于颗粒与液态钎料之间能够形成较强的毛细作用，提高了活性元素Ti扩散的能力，Ti元素能够充分扩散到钎料与母材的界面上进行反应，生成一层致密的反应层。接头抗剪强度表明，在一定范围内，采用复合钎料可以明显提高接头强度。     

用非晶钎料加铜层连接Si3N4的界面结构与强度

采用TiZrCuB非晶钎料和铜箔中间层连接Si3N4陶瓷,研究了钎料成分和铜箔厚度对接头界面结构和抗弯强度的影响.结果表明,采用Ti40Zr25CuB0.2非晶钎料和70!m铜箔中间层,在1 323 K×30 min和0.027 MPa压力下连接Si3N4陶瓷,其接头抗弯强度最高为241 MPa;Si3N4陶瓷连接接头界面反应层为TiN,界面微观结构为Si3N4/TiN/Ti-Si+α-Cu+Ti-Zr+Cu-Zr;改变中间层厚度可以调整反应层的结构和厚度;随铜箔厚度增加,Ti-Si化合物层逐渐脱离TiN层被推向钎缝中心并细化呈颗粒状.     

钎料中Ti元素含量对Si3N4/Si3N4接头界面结构及性能的影响

在900℃保温10 min的工艺条件下采用Ti含量不同的AgCu+Ti+nano-Si₃N₄复合钎料（AgCu_C）实现了Si₃N₄陶瓷自身的钎焊连接,并对不同Ti元素含量的接头界面组织及性能进行了分析.结果表明,接头典型界面结构为Si₃N₄/TiN+Ti₅Si₃/Ag_（s,s）+Cu_（s,s）+TiN_P+Ti₅Si_3P/TiN+Ti₅Si₃/Si₃N₄.随着复合钎料中Ti元素含量的增加,钎缝中团聚的纳米Si₃N₄颗粒逐渐减少,母材侧的反应层厚度逐渐增加后趋于稳定.当Ti元素含量高于4%时,钎缝中形成了类似于颗粒增强金属基复合材料的界面组织;当Ti元素含量达到10%时,有少量Ti-Cu金属间化合物在钎缝中形成;钎焊接头的抗剪强度随着Ti元素含量的增加而呈现先增加后降低的变化趋势,当Ti元素含量为6%时接头的抗剪强度达到最高值,即75 MPa.     

采用Cu-Ti钎料高温连接Si3N4陶瓷

采用Cu80Ti20钎料在1413~1493 K的温度,保温时间5~15 min的工艺条件下分别进行了Si₃N₄陶瓷的高温活性钎焊,在所选工艺条件下均成功得到了无明显缺陷和裂纹的钎焊接头,通过对接头组织和成分的分析,接头的组成为Si₃N₄陶瓷/TiN界面反应层/Cu-Ti化合物+Ti5Si3/TiN界面反应层/Si₃N₄陶瓷.在1413 K保温10min条件下,固溶体中的Ti元素扩散至钎缝与母材的界面并发生反应,形成了致密连续的厚度约为1 μm的反应层.获得了钎焊温度、保温时间、钎缝宽度及界面层厚度等对接头强度的影响规律,在试验中所采用的工艺参数条件下,接头抗剪强度达到了105 MPa.     

Cf/SiC复合材料与钛合金(Ti-Zr-Cu-Ni)+W复合钎焊分析

在适当的工艺参数下,用(Ti-Zr-Cu-Ni)+W复合钎料真空钎焊Cf/SiC复合材料与钛合金,采用SEM,EDS和XRD分析接头组织结构,利用剪切试验检测接头的力学性能.结果表明,钎焊时复合钎料中的钛、锆与Cf/SiC复合材料反应,在Cf/SiC复合材料与连接层界面生成Ti3SiC2,Ti5Si3和少量TiC(ZrC)化合物的混合反应层,在连接层与钛合金界面形成Ti-Cu化合物扩散层.增强相钨粉能有效缓解接头的残余热应力,提高接头力学性能,在连接温度930℃,保温时间20 min的工艺条件下,增强相钨粉含量为15%(体积分数)时,接头抗剪强度最高为166 MPa.     

TiNi-V共晶钎料钎焊Si3N4陶瓷接头界面结构及性能

采用真空电弧熔炼技术制备了TiNi-V高温共晶钎料合金,研究了该钎料在Si3N4陶瓷表面的铺展行为．随后采用TiNi—V钎料实现了Si3N4陶瓷的钎焊连接,利用SEM,EDS以及XRD等分析方法,确定了接头的典型界面结构为：Si3N4／TiN＋Ti-si化合物／NiV．重点研究了钎焊温度对接头界面结构及力学性能的影响．结果表明,随着钎焊温度的升高,熔融钎料与Si3N4陶瓷反应程度增加,导致钎缝中TiN＋Ti-Si化合物层厚度不断增加,且在接头残余应力的作用下形成了大量显微裂纹,降低了接头性能．当钎焊温度为1200℃,钎焊时间为10min时,接头室温抗剪强度达到最大为28MPa．断口分析显示接头断裂于TiN＋Ti-Si化合物层为脆性断裂．     

采用Ti/Ag-Cu/Cu中间层钎焊连接Si3N4陶瓷和TiAl合金的界面结构及性能

采用Ti/Ag-Cu/Cu中间层实现了Si₃N₄陶瓷与TiAl合金的钎焊连接,获得了良好的接头.利用SEM,EDS等微观手段,分析了接头界面结构和元素分布情况.结果表明,Si₃N₄陶瓷/Ti/Ag-Cu/Cu/TiAl典型界面微观结构可能为:Si₃N₄/TiN/Ti-Si/Cu-Ti+Ag（s,s）+Cu（s,s）/AlCuTi/TiAl.在连接温度1 133 K、保温时间30 min、接头压力0.040 MPa时,接头四点弯曲强度达到最大值170 MPa.     

Preparation and properties of sintered molybdenum doped with La2O3/MoSi2

Sintered Mo with the addition of La₂O₃/MoSi₂ was prepared via the process of solid–solid doping + powder metallurgy. X-ray diffraction experiment, hardness test, three-point bending test and high-temperature tensile test were carried out to characterize the samples. The XRD pattern of a typical sample shows that the sintered Mo was mainly composed of Mo, La₂O₃ and Mo₅Si₃. Mo₅Si₃ was probably formed through the reaction between MoSi₂ and the Mo matrix. Densities and fracture toughnesses of both doped Mo and pure Mo were measured and contrasted. Sintered Mo with the addition of 0.2 wt% La₂O₃/MoSi₂ has the highest toughness, while more addition of La₂O₃/MoSi₂ has smaller effect on improving toughness or even embrittles Mo. The results of three-point bending test and high-temperature tensile test show that the bending strength and high-temperature tensile strength of doped Mo are both higher than those of pure Mo. The formation of Mo₅Si₃ improves the high-temperature strength. The La₂O₃/Mo₅Si₃ dispersed in the Mo matrix refined the grains, and thus strengthened the Mo matrix by dispersion strengthening and grain refinement.     

C_f/SiC复合材料与钛合金Ag-Cu-Ti-C_f复合钎焊

采用Ag-Cu-Ti-Cf(Cf:碳纤维)复合钎料作中间层,在适当的工艺参数下真空钎焊Cf/SiC复合材料与钛合金,利用SEM,EDS和XRD分析接头微观组织结构,利用剪切试验检测接头力学性能.结果表明,钎焊时复合钎料中的钛与Cf/SiC复合材料反应,在Cf/SiC复合材料与连接层界面形成Ti3SiC2,Ti5Si3和少量TiC化合物的混合反应层.复合钎料中的铜与钛合金中的钛发生互扩散,在连接层与钛合金界面形成不同成分的Cu-Ti化合物过渡层.钎焊后,形成碳纤维强化的致密复合连接层.碳纤维的加入缓解了接头的残余热应力,Cf/SiC/Ag-Cu-Ti-Cf/TC4接头抗剪强度明显高于Cf/SiC/Ag-Cu-Ti/TC4接头.     

Thermal shock behavior of Si3N4-TiN nano-composites

Si₃N₄-TiN nano-composites were fabricated by hot press sintering nano-sized Si₃N₄ and TiN powders. The microstructure, mechanical properties and thermal shock behavior of Si₃N₄-TiN nano-composites were investigated. The addition of proper amount TiN particles can significantly increase the flexural strength and the fracture toughness. Si₃N₄-TiN nano-composites showed both higher critical temperature difference and higher residual strength compared with those of monolithic silicon nitride nano-ceramic when the amount of TiN is less than 15 wt.%. But a further increase in the amount of TiN leaded to a decrease in the thermal shock resistance.     

Deposition and characterization of CrN/Si3N4 and CrAlN/Si3N4 nanocomposite coatings prepared using reactive DC unbalanced magnetron sputtering

Nanocomposite coatings of CrN/Si₃N₄ and CrAlN/Si₃N₄ with varying silicon contents were synthesized using a reactive direct current (DC) unbalanced magnetron sputtering system. The Cr and CrAl targets were sputtered using a DC power supply and the Si target was sputtered using an asymmetric bipolar-pulsed DC power supply, in Ar + N₂ plasma. The coatings were approximately 1.5 μm thick and were characterized using X-ray diffraction (XRD), nanoindentation, X-ray photoelectron spectroscopy and atomic force microscopy. Both the CrN/Si₃N₄ and CrAlN/Si₃N₄ nanocomposite coatings exhibited cubic B1 NaCl structure in the XRD data, at low silicon contents (< 9 at.%). A maximum hardness and elastic modulus of 29 and 305 GPa, respectively were obtained from the nanoindentation data for CrN/Si₃N₄ nanocomposite coatings, at a silicon content of 7.5 at.%. (cf., 24 and 285 GPa, respectively for CrN). The hardness and elastic modulus decreased significantly with further increase in silicon content. CrAlN/Si₃N₄ nanocomposite coatings exhibited a hardness and elastic modulus of 32 and 305 GPa, respectively at a silicon content of 7.5 at.% (cf., 31 and 298 GPa, respectively for CrAlN). The thermal stability of the coatings was studied by heating the coatings in air for 30 min in the temperature range of 400-900 °C. The microstructural changes as a result of heating were studied using micro-Raman spectroscopy. The Raman data of the heat-treated coatings in air indicated that CrN/Si₃N₄ and CrAlN/Si₃N₄ nanocomposite coatings, with a silicon content of approximately 7.5 at.% were thermally stable up to 700 and 900 °C, respectively.     

Nb、Cu金属层厚度对Si3N4/Nb/Cu/Ni/Incone l600接头组织和性能的影响

采用Nb／Cu／Ni作中间层，在连接温度为1403K、连接时间为50min、连接压力为7．5MPa的条件下，采用不同尺寸的中间层进行了Si3N4陶瓷与Inconel 600高温合金的部分液相扩散连接。通过改变Nb层、Cu层厚度，研究了Cu层、Nb层厚度变化对Si3N4／Nb／Cu／Ni／Inconel 600接头的组织和性能的影响。研究发现，当Cu层厚度小于0．05mm时，随着Cu层厚度的增加，接头中的Cu—Ni合金层厚度增加，接头强度快速增加；当Cu层厚度超过0．05mm时，接头中的Cu—Ni合金层厚度由于压力的作用不明显增加，接头强度增加缓慢。随着Nb层厚度的增加，反应层厚度增加，接头的强度先增大后减小。     

Preparation, microstructure and properties of molybdenum alloys reinforced by in-situ Al2O3 particles

The conventional molybdenum alloys, lacking of hard particles enhancing wear property, have relative poor wear resistance though they are widely used in wear parts. To resolve the above question, Mo alloys reinforced by in-situ Al₂O₃ particles are developed using powder metallurgy method. The in-situ α-Al₂O₃ particles in molybdenum matrix are obtained by the decomposition of aluminum nitrate after liquid-solid incorporation of MoO₂ and Al(NO₃)₃ aqueous solution. The α-Al₂O₃ particles well bonded with molybdenum distribute evenly in matrix of Mo alloys, which refine grains of alloys and increase hardness of alloys. The absolute density of alloy increases firstly and then decreases with the increase of Al₂O₃ content, while the relative density rises continuously. The friction coefficient of alloy, fluctuating around 0.5, is slightly influenced by Al₂O₃. However, the wear resistance of alloy obviously affected by the Al₂O₃ particles rises remarkably with the increasing of Al₂O₃ content. The Al₂O₃ particles can efficiently resist micro-cutting to protect molybdenum matrix, and therefore enhances the wear resistance of Mo alloy.