钛合金与不锈钢钎焊接头残余应力有限元分析

通过有限元分析的方法对TC4钛合金与1Cr18Ni9Ti不锈钢钎焊接头残余应力场进行分析,计算工艺参数对接头应力分布的影响.结果表明,在TC4、不锈钢母材与钎料接头两侧的界面区附近形成应力集中,并且在距离钛合金母材0.45mm处等效应力达到最大值.钎焊间隙在50μm时应力值最小,钎料的线膨胀系数在12×10-6℃-1时接头内应力达到最小值,连接温度对这些残余应力的集中与分布影响很小.     

置氢Ti-6Al-4V钛合金的热压缩变形行为研究

通过热模拟压缩实验,研究了氢对Ti-6Al-4V钛合金热变形行为的影响。结果表明,置氢可以显著降低Ti-6Al-4V钛合金高温压缩时的流动应力,提高Ti-6Al-4V钛合金的热加工变形速率一个数量级以上,并且明显降低了Ti-6Al-4V钛合金的变形温度。在变形温度760℃~800℃范围内,置氢量为0.4wt%的Ti-6Al-4V钛合金的流动应力最小;在变形温度840℃~920℃范围内,置氢量0.2wt%的Ti-6Al-4V钛合金的流动应力最小。同时,置氢前后Ti-6Al-4V钛合金的变形激活能计算结果表明,置氢量为0.4wt%的Ti-6Al-4V钛合金在α+β两相区的变形激活能为208.3kJ/mol,与未置氢Ti-6Al-4V钛合金相比降低了316kJ/mol。     

TA17/0Cr18Ni10Ti螺纹管钎焊接头的残余应力有限元分析

采用有限元模拟软件Msc.Marc,对使用高银基钎料钎焊的TA17钛合金和0Cr18Ni10Ti不锈钢螺纹管接头的残余应力分布进行了分析。结果表明,螺纹管钎焊接头钎料层中心区域为等应力分布区,该区域应力值达到钎料的屈服强度值。整个螺纹管接头的高应力区域位于钎料层两侧。外套管内螺纹段的高应力区域位于靠近内螺纹的牙顶和牙底区域,且牙底区域的应力比牙顶的应力稍大;内套管的外螺纹牙底区域的残余应力值最大。0Cr18Ni10Ti外套管的高应力区域应力值小于TA17内套管高应力区域的应力值。     

钛/不锈钢的爆炸焊接及其界面的影响

土尔其学者研究了使用不同炸药量爆炸焊接的钛/不锈钢板的接合界面的冶金性能。实验选用Ti-6Al-4V钛合金和SUS304不锈钢分     

中间层金属对Al_2O_3/1Cr18Ni9Ti钎焊接头组织及剪切强度的影响

采用Ag-Cu-Ti活性钎料连接Al2O3陶瓷与1Cr18Ni9Ti不锈钢,研究了Cu,Ni和表面镀Ni的Cu 3种中间层金属对钎焊接头组织和剪切强度的影响.结果表明,Cu作为中间层时,陶瓷与钎料能形成良好的界面反应;Ni作为中间层时,焊缝中形成大量的Ni3Ti金属间化合物,导致陶瓷/钎料不能形成良好的反应层,降低了接头的剪切强度;表面镀Ni的Cu片作为中间层金属时,少量Ni的存在不影响钎料中活性元素Ti的含量,钎料与陶瓷能形成良好的界面反应,同时Ni层的存在降低了钎料对Cu的溶蚀作用,该种中间层更能有效地缓解钎焊接头的残余应力.当Ni层的厚度为30 mm,Cu片的厚度为0.2 mm时,接头剪切强度可达到109 MPa.     

钛及钛合金电弧钎焊及接头强度

用Ti—Cu—Ni，Ti-Cr-Zr钎料在TIG电弧加热条件对TA2和Ti—6Al—4V钛合金进行钎焊。结果表明：用Ti—Cu—Ni钎料钎焊TA2和Ti—6Al—4V钛合金的搭接接头强度分别是418．3MPa和439．6MPa；用Ti—Cr—Zr钎料钎焊TA2和Ti—6Al—4V钛合金的搭接接头强度分别是575．2MPa和656．1MPa。对Ti-Cu-Ni钎料／母材界面分析认为固液异分化合物η相((Cu，Ni)Ti2)生成时呈笋状生长，嵌入钎缝对钎缝的强度提高有利。对Ti-Cr-Zr钎料／母材界面分析，认为主要是固溶体β-Ti(Cr)存在提高了钎缝强度。     

Ti811和TC4合金的热盐应力腐蚀行为研究

研究了Ti811(Ti-8Al-1Mo-1V)和TC4(Ti-6Al-4V)两种钛合金对热盐应力腐蚀(HSSC)的敏感性.结果表明:Ti811合金对HSSC非常敏感,在相同条件下其热盐应力腐蚀临界应力(σHSSC)明显低于TC4合金,且低于同温度的蠕变强度,而TC4合金的σHSSC高于同温度的蠕变强度;两种合金在HSSC暴露过程中,明显遭受到盐腐蚀,腐蚀产生的氢扩散到基体中,致使合金发生脆化,从而降低合金的室温塑性.     

钛基钎料高温钎焊TZM界面行为及热稳定性研究（英文）

采用Ti-8.5Si、Ti-33Cr和Ti-30V-3Mo钎料实现了钛锆钼(TZM)合金的高温真空钎焊连接,借助SEM、EDS及润湿性试验和抗剪试验等分析方法,研究了钛基钎料高温钎焊TZM及钎焊接头经高温热循环后的热稳定性。结果表明,Ti-8.5Si、Ti-33Cr在1520oC/6min的工艺条件下良好润湿TZM,润湿角分别为10o和9o,Ti-8.5Si钎料的铺展面积大于Ti-33Cr钎料的铺展面积,Ti-30V-3Mo钎料在1680oC/8 min的条件下在TZM板上的润湿角为5°。Ti-8.5Si/TZM接头界面形成(Ti, Mo)固溶体,钎缝中心由(Ti, Mo)固溶体和Ti5Si3相组成。Ti-33Cr/TZM接头界面形成(Ti,Mo)固溶体,钎缝中心由(βTi,Cr)固溶体和αTi+(αTi+αTi Cr2)共晶组成。Ti-30V-3Mo/TZM接头,钎缝区主要由(βTi, V)固溶体和αTi组成,界面区由Ti与Mo形成(Ti,Mo)固溶体。3种钎料钎焊TZM,均形成固溶体钎焊接头而实现钎料与TZM的冶金结合,钎焊接头强度分别为135.8 MPa(Ti-8.5Si)、132 MPa(Ti-33Cr)和131 MPa(Ti-30V-3Mo)。Ti-8.5Si/TZM、Ti-33Cr/TZM接头经过1200oC/60min没有观察到明显的晶间渗入和母材溶蚀,界面固溶体结合形式无变化。Ti-30V-3Mo/TZM接头经过1550oC/60 min热循环后,观察到1个晶粒深度的晶间腐蚀,没有明显的母材溶蚀现象,且界面依然保持固溶体结合形式。3种钛基钎料可实现TZM的高温钎焊,依靠界面固溶体实现冶金结合,经高温长时间热循环后钎焊接头组织性能稳定,发生晶间渗入敏感性低,为TZM的高温应用连接提供理论与试验指导。     

应力应变、疲劳与脆断、断裂力学

不同异种钢管道焊接接头残余应力的数值模拟 利用有限元软件ABAQUS,开发了一个顺次耦合的热应力有限元计算程序,对0Cr18Ni9／20和1Cr5Mo/20异种钢焊接接头残余应力进行了有限元模拟分析。结果表明,无论是采用A302奥氏体不锈钢焊条还是Incone182镍基焊条,0Cr18Ni9／20钢和1Cr5Mo/20钢焊接接头中最大的轴向残余应力和环向残余应力产生在20钢侧的热影响区,0Cr18Ni9侧有最小的焊接残余应力。     

TI-6Al-4V钛合金电子束焊接有限元分析

采用有限元方法模拟分析了厚6 mm的Ti-6Al-4V钛合金电子束焊接过程,计算研究了瞬态温度场的分布特点、规律及特征点的温度变化历程,在准确计算焊接温度场的基础上通过热-应力顺序耦合,模拟计算了Ti-6Al-4V钛合金电子束焊接头的应力场的分布特征.结果表明:模拟计算的焊缝形貌与实际焊接试验所得基本吻合,焊接温度场整...     

Structural, mechanical and corrosion properties of TiOxNy/ZrOxNy multilayer coatings

Results on the deposition and characterization of TiO_xN_y/ZrO_xN_y multilayers, with bilayer periods of 20 and 400 nm, are presented. The coatings were deposited on TiNiNb alloy substrates by the pulsed magnetron sputtering method. The elemental composition, hardness, adhesion and corrosion resistance of the coatings were analyzed.As resulted from the XPS analysis, the individual layers consisted of a mixture of titanium or zirconium oxynitrides and corresponding oxides. X-ray analysis revealed that the coatings were amorphous. Only slight differences between the microhardness and adhesion values of the coatings with small and large bilayer period Λ were found. The experiments also showed that the multilayered coatings improved the corrosion resistance of the uncoated alloy and reduced the amount of ion release in artificial body fluids.     

生物医用NiTi形状记忆合金腐蚀研究进展

镍钛形状记忆合金(NiTi-SMA)具有较好的耐腐蚀和机械性能,在口腔和临床医学中有着大量而广泛的应用。NiTi-SMA腐蚀后释放Ni²⁺会引发细胞毒性和过敏反应,进一步提高NiTi-SMA的耐蚀性是目前生物医学材料领域发展的核心之一。本文对近年来国内外有关口腔医学和临床医学中常用NiTi-SMA的腐蚀研究现状进行了总结,同时也对NiTi-SMA增材制造及表面改性技术进行了评述,以期为开发高性能抗腐蚀生物医用NiTi-SMA提供一定的指导意义。     

Li掺杂Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li(1/7-x))O3高熵陶瓷的制备及介电性能研究

近年来,在高熵合金基础上发展起来的高熵陶瓷逐渐引起了研究者的广泛关注,其出现为开发高性能的无机非金属材料提供了新的设计思路。本文采用固相法制备了BaMO3基钙钛矿型高熵陶瓷Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li(1/7-x))O3 (x = 0, 2.3%, 5.3%, 8.3%, 11.3%),并研究了Li含量对高熵陶瓷物相结构、微观形貌及介电性能的影响。结果表明,Li含量对陶瓷结构的影响不大,陶瓷均保持立方钙钛矿结构,且无杂相产生;陶瓷的晶粒尺寸相对较均匀。当x = 0时,即B位七元等摩尔比Ba(Ti1/7Sn1/7Zr1/7Hf1/7Nb1/7Ga1/7Li1/7)O3高熵陶瓷,其介电常数达到了最大值2920 (@100 Hz),相较于已报道的不掺Li的六元高熵钙钛矿陶瓷Ba(Ti1/6Sn1/6Zr1/6Hf1/6Nb1/6Ga1/6)O3提升了近50倍。     

MOCVD growth and characterizations of BxAl1−xAs and BxAl1−x−yInyAs alloys

Zinc-blende B_xAl_1−xAs and B_xAl_1−x−yIn_yAs alloys have been grown on exactly oriented (0 0 1)GaAs substrates by low pressure metalorganic chemical vapor deposition (LP-MOCVD). The influence of susceptor coating, growth temperature and gas-phase boron mole fraction on boron incorporation into AlAs has been comprehensively investigated. It has been found that boron incorporation into AlAs could be enhanced and the optimal growth temperature range of B_xAl_1−xAs alloys changed from 580 °C to 610 °C when SiC-coated graphite susceptors were replaced by the non-coated ones. In this study, the maximum boron composition x of 2.8% was achieved for the pseudomorphically strained B_xAl_1−xAs alloys. AFM measurements show that RMS roughness of B_xAl_1−xAs alloys increased sharply with the increase of gas-phase boron mole fraction. Raman spectra of B_xAl_1−xAs alloys show a linear increase of the BAs shift with boron composition x. Based on BAlAs deposition, bulk B_xAl_1−x−yIn_yAs (x = 1.9%) quaternary alloy was grown lattice-matched to GaAs successfully. Moreover, 10-period BAlAs/GaAs and BAlInAs/GaAs MQW heterostructures were also demonstrated.     

Ag/LaNixCo1-xO3触点材料的制备及电接触性能研究

本文运用溶胶-凝胶燃烧法合成了双钙钛矿型LaNixCo1-xO3(LNCO)纳米材料,利用粉末冶金和热挤压技术制备了相应的Ag/LNCO触点材料及元件样品。重点考察了不同Ni、Co含量对Ag/LNCO触点材料微观结构、物相组成、物理性能、力学性能及电寿命服役能力的影响,对其电弧侵蚀失效行为进行了研究,并与SnO2粉体增强Ag基触点材料进行对比。结果表明:溶胶凝胶法合成的LNCO纳米颗粒粒径为20-30 nm,经粉末冶金工艺制备的Ag/LaNi0.5Co0.5O3触点材料电学性能和电寿命都优于Ag/SnO2触点材料,其电阻率低至2.10 μΩ?cm,电寿命性能达到51287次。表明Ag/LaNi0.5Co0.5O3触点材料性能较佳,是一种可以取代Ag/CdO的新型触点材料。     

Hydrothermal synthesis of superconductors Ba1−xKxBiO3 and double perovskites Ba1−xKxBi1−yNayO3

Superconductors Ba_1−xK_xBiO₃ and body-centered double perovskites Ba_1−xK_xBi_1−yNa_yO₃ have been selectively synthesized by a facile hydrothermal route. The appropriate ratio and adding sequence of initial reagents, alkalinity, reaction temperature and time are the critical factors that influence the crystal growth of the compounds. The purity and homogeneity of the crystals were detected by the ICP, SEM, EDX and TEM studies. Magnetic measurements show that the superconducting transition temperatures T_C of Ba_1−xK_xBiO₃ decrease from 22 K (for x = 0.35) to 8 K (for x = 0.55) with increasing the K doping level.     

Magnetic phase diagrams of the TbRh2−xPdxPdxSi2 and TbRu2−xPdxSi2 systems

The a.c. susceptibility and high field magnetization on TbRh_2−xPd_xPd_xSi₂ and TbRu_2−xPd_xSi₂ compounds were investigated up to 140 kOe. The (T,x) magnetic phase diagrams were determined. For both systems, an increase in the Pd content causes a decrease in the Néel temperature and changes the magnetization curves.     

High strength and good ductility of casting Al-Cu alloy modified by PrxOy and LaxOy

A modified Al-Cu alloy with high tensile strength and ductility of about 574.0 MPa and 10.4%, respectively, was obtained by adding multiple rare earth oxides (Pr_xO_y and La_xO_y) as modifier. Compared with the unmodified Al-Cu alloy, the tensile strength and ductility of the modified sample were increased by 24.3% and 42.5%, respectively. The improvement both in the strength and ductility may attribute to the finer crystal grains and dendrites, more homogeneously distributed θ′ phase precipitates and the intermetallic compounds formed at the crystal grain boundaries as well as in the space of the dendrites.     

Si3N4/Ti/Cu/Ni/Cu/Ti/Si3N4二次部分瞬间液相连接强度

采用Ti/Cu／Ni中间层对Si3N4陶瓷进行二次部分瞬间液相(PTLP)连接，研究连接工艺参数对Si3N4／Ti/Cu／Ni连接强度的影响，同时研究了连接强度随试验温度的变化规律。结果表明，在该试验条件下，室温连接强度随着二次连接温度的提高和二次保温时间的延长而提高，改变连接工艺参数对Si3N4／Ti/Cu／Ni二次PTLP连接界面反应层厚度无明显影响；连接强度在试验温度400℃时达到最大，随后随试验温度升高，连接强度降低，但在800℃前，其高温强度具有很好的稳定性。