退火处理对合金化Mo-3Nb单晶力学性能的影响

介绍了退火处理对合金化Mo 3Nb单晶室温力学性能的影响。试样材料采用俄罗斯提供和国内研制的两种合金化Mo 3Nb单晶材料。实验中采用退火处理条件为:温度范围900~1 800 ℃,时间2 h,退火炉真空度保持在4×10-4 Pa。用微型试样力学性能测试法测试力学性能。结果表明,随着退火温度升高,两种材料的室温屈服强度σy 和抗拉强度σb 都呈下降趋势,而均匀伸长率δu 呈上升趋势,其中经1 600 ℃和1 800 ℃退火试样的屈服强度和抗拉强度比原始试样下降近20%,实验还发现俄罗斯提供的单晶力学性能随退火温度的变化比国内研制单晶更加敏感。分析了退火处理对合金化Mo 3Nb单晶室温力学性能的影响因素。     

Mo-3Nb单晶定向焊接技术研究

采用X射线劳厄照相法对单晶接头进行定向装配,开展了Mo-3Nb单晶的定向焊接实验。结果显示,定向焊接可以消除单晶焊缝中的大角晶界,显著改善焊缝的微观组织;虽然在试样焊缝中心仍然存在着少量的亚结构,但是这些亚结构并不会对焊缝性能产生较大影响。     

Mo-3Nb合金单晶的蠕变性能

研究了电子束悬浮区域熔炼法制备的晶向为〈111〉的Mo-3Nb（质量百分数，下同）合金单晶在高温／低应力环境中的蠕变性能及其蠕变机理。结果表明，Mo-Nb合金单晶中，溶质原子Nb的添加增大了原子间扩散阻力，使材料高温稳态蠕变率减小，大大提高了材料的高温抗蠕变性能；在1500℃，10MPa时，Mo-3Nb合金单晶的稳态蠕变率较纯Mo单晶降低了3个数量级，且其蠕变机理为扩散蠕变。     

Mo-3Nb合金化单晶微型试样强度测试

介绍了微型试样的测试方法及机理,对所研制的Mo-3Nb合金化单晶材料分别采用微型试样测试和常规室温拉伸测试,并对2种方法所得结果进行比较,微型试样检测的抗拉强度、屈服强度值均低于常规拉伸试样,延伸率偏差较大,但作为Mo-3Nb合金单晶拉伸性能一种定性判据是有效的.     

钼和钨的合金化单晶

美国研究人员用电子束浮区法制取了Mo 2Nb、Mo 11Nb、Mo 0 2H、Mo 1Hf等合金单晶。Mo Nb的单晶生长较容易 ,以 5 5mm /h熔炼速度可生产Mo 11Nb单晶。Mo Hf合金因随Hf的增加 ,其熔炼速度减小 ,故Mo Hf、Mo 2 75Hf和Mo 3 75Hf的最大熔炼速度分别为 5 5mm/h、 2 2mm/h和 11mm /h ,当Hf大于 5 %时生长不出单晶。俄罗斯人用电子束区域熔炼法制取Mo Nb、Mo W、W Nb、Mo Re、W Re等固溶型合金单晶。Mo 0 11Nb在 15 2 0K～ 2 0 70K温度范围内的蠕变是依靠合金化原子在高应力状态的位错滑移机制进行的 ,蠕变速率与应力的关系服从…     

反复镦拔对Ni-20Cr-11Co-8Mo-4W合金组织和性能的影响

研究了反复镦拔工艺对Ni-20Cr-11Co-8Mo-4W合金组织和力学性能的影响。对Ni-20Cr-11Co-8Mo-4W合金反复镦拔前后的径向微观组织进行了金相、扫描电镜观察和分析,并对试验合金反复镦拔前后的室温冲击断口形貌进行了观察和分析。研究结果表明,反复镦拔工艺可以明显改善Ni-20Cr-11Co-8Mo-4W合金的微观组织,从而提高合金的力学性能。     

Ti-25Al-14Nb-2Mo-1Fe合金高温力学性能研究

通过加入第四组元β相稳定元素Fe和Mo来替代部分Nb元素制备Ti-25Al-14Nb-2Mo-1Fe合金.结果表明,较参比材料Ti-22Al-27Nb合金,Ti-25Al-14Nb-2Mo-1Fe合金的瞬时蠕变应变、1％蠕变时间和稳态蠕变速率均得到较大改善,并且自扩散激活能也得到提高;该合金在650℃高温条件下,具有较好的力学性能.     

Ti-3Zr-2Sn-3Mo-25Nb合金表面活性微弧氧化膜的制备及其骨诱导性(英文)

通过微弧氧化法在新型医用近β钛合金Ti-3Zr-2Sn-3Mo-25Nb表面制备一层含Ca、P多孔薄膜,再将其在胺基化溶液中活化处理以在薄膜表面引入NH-2。借助XRD、SEM和EDS研究该多孔复合薄膜的组成和表面形貌,并通过模拟体液浸泡实验、体外细胞培养实验和动物体内植入实验研究经上述表面改性处理后的Ti-3Zr-2Sn-3Mo-25Nb合金的骨诱导活性。结果表明:该薄膜主要由金红石型TiO2和锐钛矿型TiO2组成,是一种含有Ca、P的陶瓷混合物;薄膜在模拟体液中具有很好的生物活性,成骨细胞能够很好地在薄膜上分化、生长;表面覆膜处理的Ti-3Zr-2Sn-3Mo-25Nb合金的体内骨诱导活性优于未处理的Ti-3Zr-2Sn-3Mo-25Nb合金的。     

Mo-3Nb单晶管定向电子束焊接的组织及性能

对外径为20 mm,壁厚为4 mm的Mo-3Nb单晶管进行电子束定向焊接。利用光学显微镜背散射衍射(EBSD)等手段分析焊缝区域的断口形貌及显微组织,利用拉伸试验机和维氏硬度仪检测焊缝抗拉强度和硬度。结果表明,采用定向焊接获得的焊缝基本呈单晶状态,存在少量小角晶界。显微特点为无热影响区,熔池线清晰连续。焊缝区为薄弱区,抗拉强度略低于母材。焊接接头各区域硬度基本无差异,焊缝区与母材硬度基本相同。1 600℃热处理后显微结构与硬度均没有变化。     

Mo-3Nb单晶管定向电子束焊接的组织及性能北大核心

对外径为20 mm,壁厚为4 mm的Mo-3Nb单晶管进行电子束定向焊接。利用光学显微镜背散射衍射(EBSD)等手段分析焊缝区域的断口形貌及显微组织,利用拉伸试验机和维氏硬度仪检测焊缝抗拉强度和硬度。结果表明,采用定向焊接获得的焊缝基本呈单晶状态,存在少量小角晶界。显微特点为无热影响区,熔池线清晰连续。焊缝区为薄弱区,抗拉强度略低于母材。焊接接头各区域硬度基本无差异,焊缝区与母材硬度基本相同。1 600℃热处理后显微结构与硬度均没有变化。     

Design for Ti-Al-V-Mo-Nb alloys for laser additive manufacturing based on a cluster model and on their microstructure and properties

In this study, α+β Ti-Al-V-Mo-Nb alloys with the addition of multiple elements that are suitable for laser additive manufacturing (LAM) were designed according to a Ti-6Al-4V cluster formula. This formula can be expressed as 12[Al-Ti₁₂](AlTi₂)+5[Al-Ti₁₄]((Mo, V, Nb)₂Ti), in which Mo and Nb were added into the alloys partially instead of V to give alloys with nominal compositions of Ti-6.01Al-3.13V-1.43Nb, Ti-5.97Al-2.33V-2.93Mo, and Ti-5.97Al-2.33V-2.20Mo-0.71Nb (wt.%). The microstructures and mechanical properties of the as-deposited and heat-treated samples prepared via LAM were examined. The sizes of the β columnar grains and α laths in the Nb-containing samples are found to be larger than those of the Ti-6Al-4V alloy, whereas Mo- or Mo/Nb-added alloys contain finer grains. It indicates that Nb gives rise to coarsened β columnar grains and α laths, while Mo significantly refines them. Furthermore, the single addition of Nb improves the elongation, whereas the single addition of Mo enhances the strength of the alloys. The simultaneous addition of Mo/Nb significantly improves the comprehensive mechanical properties of the alloys, leading to the best properties with an ultimate tensile strength of 1,070 MPa, a yield strength of 1,004 MPa, an elongation of 9%, and micro-hardness of 355 HV. The fracture modes of all the alloys are ductile-brittle mixed fracture.     

基于d-电子合金设计理论和JMatPro软件新型生物医用钛合金的设计

基于d-电子合金设计理论和JMatPro软件,运用正交试验,设计了具有较低弹性模量和较高强度且含有无毒元素Nb、Mo、Zr和Sn的新型生物医用∥钛合金Ti-35Nb-4Sn-6Mo-9Zr,并对该合金的显微组织和力学性能进行分析。结果表明,Ti-35Nb-4Sn-6Mo-9Zr合金在800。C下固溶处理后,由单一的β等轴晶构成。与Ti-6Al-4V相比,该合金具有较优越的力学性能：E=65GPa,σb=834MPa,σ0.2=802MPa,6=11％,有望成为新型种植材料。该方法可以有效地降低实验次数,并得到理想的实验结果。     

生物医用β型Ti-15Mo-xNb合金的显微组织、力学性能和干态耐磨性(英文)

为了研究元素Nb含量对β型Ti-Mo基合金显微组织和性能的影响,制备了4种Ti-15Mo-xNb(x=5%,10%,15%和20%)合金,并研究其显微组织和性能。采用CJS111A型球-盘式摩擦磨损试验机评价了Ti-15Mo-xNb合金与Gr15对磨时的干摩擦磨损性能。结果表明:Nb含量对Ti-15Mo-xNb合金显微组织结构形态的影响较大,4种合金主要由β相组成,其硬度值均高于HV200;Ti-15Mo-5Nb合金的压缩屈服强度最低,Ti-15Mo-10Nb合金的压缩屈服强度最高;在干磨状态下Ti-15Mo-xNb合金的摩擦因数不稳定但其值较高;在不同的加载条件下,磨损表面均出现了较深的平行磨痕,在加载载荷为1N时Ti-15Mo-5Nb合金的摩擦因数最低;Ti-15Mo-xNb合金的磨损机制为粘着磨损。     

粉末冶金Nb-35Ti-6Al-5Cr-8V合金组织演变及其力学行为

采用粉末冶金法对不同球磨时间的Nb-35Ti-6Al-5Cr-8V合金机械合金化粉末塑变行为,热压烧结材料的微观组织结构和力学行为进行了研究。研究结果表明：塑性良好的Nb-35Ti-6Al-5Cr-8V粉末随着球磨时间增加首先变形为大尺寸的片状、后经持续的加工硬化破碎成絮状;热压烧结能够制备微观组织可控晶粒细化的Nb-35Ti-6Al-5Cr-8V合金,合金由单一的Nbss相构成,Ti、Al、Cr、V元素固溶引起Nb晶格尺寸减小0.0685 ?;随着球磨时间增加合金晶粒明显细化进而显著提高了合金的维氏硬度和室温压缩强度,其变化符合材料硬度和强度的Hall-Petch规律。粉末冶金制备Nb-35Ti-6Al-5Cr-8V合金的各项力学性能明显优于熔铸法制备合金。     

Formation of low angle boundaries and stray grains in welds of single-crystal Mo-3Nb alloys

ABSTRACT

Mo-3Nb single-crystal alloy is an ideal material for emitters of thermionic fuel elements. In this experiment, heat-affected zone of electron beam welding of Mo-3Nb single-crystal tubes was investigated, and it was discovered that heat-affected zone basically inherited the orientation of parent metal while there were still plenty of low angle boundaries and a few stray grains (SGs). Those low angle boundaries (LABs) stemmed from the fusion line and converged toward the centreline. Besides, the distribution of LABs was asymmetrical about the centreline of welding pool, and Laue diffraction pattern showed that the side with more LABs had higher dislocation density than the other. Furthermore, SGs existed merely at the bottom of welding pool and were discontinuously distributed along the circumferential direction of single-crystal tube.     

Ti-6Al-2Zr-1Mo-3Nb合金微弧氧化陶瓷膜的结构与性能

利用微弧氧化技术,在Ti-6Al-2Zr-1Mo-3Nb合金表面制备陶瓷涂层。用扫描电镜和X射线衍射仪观察并分析陶瓷膜层的组织形貌和相结构,用电子万能材料试验机和数字万用表研究膜层的结合强度和绝缘性,并用MMS-1G高温高速销盘摩擦磨损试验机和YWX/Q-750盐雾试验机考察涂层的摩擦性能和耐腐蚀性能。结果表明:陶瓷层主要由金红石TiO2相和锐钛矿TiO2相构成,膜基结合强度达到30MPa以上,膜层绝缘性和耐腐蚀性良好,耐磨性得到明显改善,涂层的磨损机制表现为轻微的磨粒磨损与粘着磨损。     

Comparative studies on densification behavior,microstructure, mechanical properties and oxidation resistance of Mo-12Si-10B and Mo3Si-free Mo-26Nb-12Si-10B alloys

Two bulk Mo-Si-B based alloys (Mo-12Si-10B and Mo-26Nb-12Si-10B (at.%), abbreviated as 0Nb and 26Nb alloy respectively) were fabricated by mechanical alloying and then hot pressing. Comparative studies were carried out on the densification behavior, microstructure, room-temperature fracture toughness, elevated temperature compression and oxidation resistance of these two alloys. The results showed that alloy 0Nb was composed of (Mo), Mo₃Si and Mo₅SiB₂, while alloy 26Nb was free of Mo₃Si and had higher (Mo) content and a little γNb₅Si₃. Compared to the alloy 0Nb, alloy 26Nb presented better compactibility, higher room-temperature fracture toughness (8.84 ± 0.17 vs. 6.77 ± 0.20 MPa·m^1/2) and elevated temperature compression strength (851.7 ± 11.7 vs. 644.2 ± 10.2 MPa) but worse oxidation resistance.     

Role of crystal defects on brittleness of C15 Cr2Nb Laves phase

First-principles calculations, high-resolution transmission electron microscopy (HRTEM) investigations and geometrical phase analysis of lattice strain based on HRTEM images have been carried out on C15 Cr₂Nb Laves phase. Asymmetrical nanoscale regions with severe lattice distortion were observed in the vicinity of Shockley partial dislocation cores. These disturbed regions are the result of synchroshear inside the Nb–Cr–Nb triple layers. Reactions of dislocations with twin boundaries (TBs) also result in severe lattice distortion. The resulting local lattice distortion and perturbed strain field deleteriously impact dislocation-governed plasticity. First-principles calculations show that cleavage occurs preferentially between the single Cr layer and the Nb–Cr–Nb triple layer in these materials. TBs, which are on single Cr layers, nucleate and propagate cracks readily in Cr₂Nb, as evidenced by the lattice dilatation along a TB interacting with one 60° dislocation. The present study shows atomic level evidence on how crystal defects and their interactions influence the mechanical properties, especially the poor toughness at low temperatures, of C15 Cr₂Nb. This provides new insights into the origin of low temperature brittleness of Laves compounds with complex structures.     

Effects of high niobium addition on the mechanical properties and high-temperature deformability of gamma TiAl alloy

The effects of Nb on the mechanical properties, high-temperature deformability and some other basic properties of TiAl–Nb alloys were investigated over a wide compositional range, and an appropriate composition for high-temperature applications was investigated for both wrought and cast materials. The lattice parameter of Ti–50Al–xNb alloy, which is a γ single phase alloy, shows an anisotropic variation with Nb content. This lattice distortion is assumed to be responsible for the strengthening and embrittlement of high-Nb ternary alloys. In the case of wrought materials, no appropriate composition exists in the high-Nb content region since wrought materials require good forgeability and high-temperature strength which are properties of antithesis. In the case of cast materials, however, an appropriate composition exists in the vicinity of Ti–46Al–7.5Nb (at.%).