NiAl基金属间化合物的研究进展

介绍和评述了NiAl基金属间化合物的研究进辰。由于NiAl基金属闻化合物的一些优异性能,长期以来作为高温结构的候选材料而得到了广泛的关注,但是NiAl在室温下塑性差和高温时强度低限制了它的使用。着重介绍了对NiAl的晶体结构和缺陷、力学性能、化学性能等方面的研究,利用控制显微结构、合金化和改进加工技术等方法改善了NiAl的室温塑性和高温强度。     

Ni-Al基金属间化合物的高温腐蚀与防护

本文讨论了Ｎｉ３Ａｌ、ＮｉＡｌ基金属间化合物的高温氧化、热腐蚀行为及各种防护涂层对其氧化、热腐蚀性能的影响。     

NiAl金属间化合物的快速凝固组织

用单辊快速凝固法制备了Ｎｉ原子分数为０．５３－０．６０的Ｎｉ－Ａｌ金属间化合物薄带,研究了成分与微观组织的关系,发现试样均为Ｂ２型单相ＮｉＡｌ,Ｎｉ０．５３Ａｌ０．４７的快速凝固组织为１０μｍ左右的等轴晶,Ｎｉ０．５６Ａｌ０．４４－Ｎｉ０．６Ａｌ０．４的组织分别为５μｍ左右的不规则和规则柱状晶,发现近理想配比的ＮｉＡｌ在快速凝固时形成针状晶亚结构。     

NiAl金属间化合物热爆合成动力学的试验研究

通过粉坯密度，加热速率，颗粒尺寸及合金元素等对ＮｉＡｌ热爆的点燃温度及最高反应放热温度的影响，研究了热爆合成的动力学规律，结果表明，热爆合成的点燃温度随颗粒尺寸的增大，加热速率的加快，粉坯密度的地加而升高。其反应最高温度随镍颗粒尺寸的增大，加热速率的加快和粉坯密度的增加而升高。     

TiAl基金属间化合物的研究现状与发展趋势

系统地总结了TiAl基金属间化合物结构材料的研究现状、存在的问题以及在航空航天等领域的应用情况。对TiAl基金属间化合物的组织控制与性能研究、冶金熔炼、成形加工等进行了归纳,结合TiAl基金属间化合物材料与应用研究取得的新进展,预测了TiAl基金属间化合物轻质结构材料在今后一段时期的发展趋势。     

内生TiC颗粒增强NiAl基复合材料的初步研究

用ＨＰＥＳ工艺合成了２０ｖ．％ＴｉＣ颗粒增强的ＮｉＡｌ基复合材料,其维氏硬度、压缩屈服强度都比单相ＮｉＡｌ有大幅度提高。特别是室温和１０００℃以上,屈服强度比基体提高近二倍,室温塑性也优于单相ＮｉＡｌ。     

持续电流作用下金属间化合物NiAl薄板热弯成形

目的 为了解决和克服现有耐高温金属间化合物成形难、传统等温热成形效率和能源利用率低的问题,开发持续电流作用下金属间化合物薄板热弯成形新技术。方法 首先,对NiAl板材进行系统的升温实验,确定热弯成形的电流密度。然后对NiAl板材进行三点弯曲实验,确定凸模下压速度。最后,在自行设计并制作的可实现电与载荷持续复合作用的热弯成形装置和陶瓷绝缘模具上对板材进行热弯成形实验。结果 在电流密度为8.5 A/mm²、加热温度为1 300 ℃、凸模下压速度为0.5 mm/min的实验条件下,成形后的热弯件尺寸精度良好、厚度均匀,无开裂和回弹产生。结论 该方法主要针对热弯曲成形工艺,解决了金属间化合物难变形及传统脉冲电流辅助热成形难以在变形过程中持续通电的问题,改善了金属间化合物成形时产生的开裂和回弹。     

Ni-Al系金属间化合物的应用开发

本项目的研究开发工作是“863”计划在“七五”期间资助的“铸造Ni_3Al基高温合金研究”(863-715-16-02-03)和“八五”期间资助的“Ni_3Al基铸造高温合金及其应用研究”(863-715-16-01-03)的继续。立项研究13年来研制成功了一种在1050～1150℃范围内适用的燃气涡轮发动机导向叶片材料,命名为IC6合金。IC6合金的特点是:成分简单,资源立足国内,不含稀贵元素Hf、Ta、Re、Co等,成本低,合金料易于回收。从室温到1200℃,它都具有较高的屈服强度和较好的塑性,在760～1100℃范围具有     

The dynamic tensile behavior of tough,ultrahigh-strength steels at strain-rates from 0.0002 s to 200 s

The present study examines the strain-rate sensitivity of four high-strength, high-toughness steels at strain-rates ranging from 0.0002 s⁻¹ to 200 s⁻¹: AerMet 100, modified 4340, modified HP9-4-20, and a recently developed Eglin AFB steel alloy, ES-1c. A newly developed dynamic servohydraulic method was employed to perform tensile tests over this entire range from quasi-static to near split-Hopkinson or Kolsky bar strain-rates. Each of these alloys exhibits only modest strain-rate sensitivity. Specifically, the semi-logarithmic strain-rate sensitivity factor β was found to be in the range of 14–20 MPa depending on the alloy. This corresponds to a ∼10% increase in the yield strength over the 6-orders of magnitude change in strain-rate. Interestingly, while three of the alloys showed a concomitant ∼3–10% drop in their ductility with increasing strain-rate, the ES-1c alloy actually exhibited a 25% increase in ductility with increasing strain-rate. Fractography suggests the possibility that at higher strain-rates ES-1c evolves towards a more ductile dimple fracture mode associated with microvoid coalescence.     

Factors influencing the tensile strength, hardness, and ductility of hydrogen-cycled palladium

A systematic study of the tensile strength, hardness, and ductility of palladium has been performed on foil specimens that have undergone hydrogen absorption and desorption under a variety of conditions. The experimental parameters under control in the various hydrogen treatments were: (i) the amount of hydrogen absorbed, (ii) the isotope of hydrogen (protium versus deuterium) absorbed, (iii) the number of hydrogen absorption/desorption cycles, and (iv) the hydrogen absorption/desorption temperature. In all instances hydrogen absorption/desorption cycling significantly alters the tensile strength, hardness, and ductility of well-annealed palladium. The results show that, in general, the strength and hardness of palladium increases as a result of hydrogen cycling while the ductility decreases. The extent of the respective increases and decreases has been found to differ depending on the parameter being varied. The most sensitive parameter was found to be the amount of hydrogen absorbed during cycling.     

Balancing the strength and ductility of Mg-6Zn-0.2Ca alloy via sub-rapid solidification combined with hard-plate rolling

In this study,we successfully prepared a Mg-6Zn-0.2Ca alloy by utilizing sub-rapid solidification (SRS)combined with hard-plate rolling (HPR),whose elongation-to-failure increases from ～17 ％ to ～23 ％without sacrificing tensile strength (～290 MPa) compared with its counterpart processed via conven-tional solidification (CS) followed by HPR.Notably,both samples feature a similar refined grain structure with an average grain size of ～2.1 and ～2.5 μm,respectively.However,the high cooling rate of ～ 150 K/s introduced by SRS modified both the size and morphology of Ca2Mg6Zn3 eutectic phase in comparison to those coarse ones under CS condition.By subsequent HPR,the Ca2Mg6Zn3 phase was further refined and dispersed uniformly by severe fragmentation.Specially,the achieved supersaturation containing exces-sive Ca solute atoms due to high cooling rate was maintained in the SRS-HPR condition.The mechanisms that govern the high ductility of the SRS-HPR sample could be ascribed to following reasons.First,refined Ca2Mg6Zn3 eutectic phase could effectively alleviate or avoid the crack initiation.Furthermore,excessive Ca solute atoms in α-Mg matrix result in the yield point phenomenon and enhanced strain-hardening ability during tension.The findings proposed a short-processed strategy towards superior performance of Mg-6Zn-0.2Ca alloy for industrial applications.     

Exceptionally strong and ductile bulk metallic glass composite with bioinspired architecture mimicking porcupine fish spine

Introducing soft crystalline phases into the glassy matrix to produce bulk metallic glass composites(BMGCs)is an effective way to enhance the ductility of bulk metallic glasses(BMGs).However,the in-troduction of soft crystalline phases severely sacrifices the strength,resulting in the strength-ductility trade-off.To defeat this dilemma,here,we successfully fabricate a bioinspired BMGC with architecture mimicking a porcupine fish spine.The bioinspired BMGC shows a pronounced yield strength of～800 MPa with an excellent fracture strain of～35％.The fabrication of the bioinspired BMGC is achieved through infiltration and vitrification of molten Zr50Ti5Cu27Ni10Al8(Zr50)melt into the crystalline Nb skeleton fab-ricated by laser additive manufacturing(LAM).Such enhanced strength-ductility synergy is attributed to the asynchronous deformation associated with the delicate bioinspired heterogeneous architecture.The bioinspired structural design motif,enabled by the combination of LAM and infiltration casting technolo-gies,opens a new window to develop high-performance BMGCs on a large scale for structural applica-tions.     

Fast and simultaneous growth of graphene,intermetallic compounds,and silicate on Cu–Ni alloy foils

A graphene bilayer was grown on copper–nickel alloy foils (30 at-% Ni: 70 at-% Cu designated as a 30Ni–70Cu) via an inductively coupled plasma–chemical vapor deposition chamber, and was characterized. The first layer fully covered the foil, while there was partial coverage of the second layer. At the same time, the alloy catalyst produced a compound of magnesium silicate in some regions and of copper sulfide in other regions on which a graphene monolayer simultaneously grew without any discontinuity or boundaries of the 1st graphene monolayer between simultaneous growth and graphene-only growth regions. Compared with Cu foils, the alloy foils led to faster growth of the graphene film in graphene-only growth regions, while maintaining the same quality, homogeneity, and thickness uniformity as a monolayer graphene grown on Cu. Raman spectroscopy and scattering demonstrated that the 2D and D bands of the Raman spectra were in the same position for the monolayer graphene on 30Ni–70Cu regardless of the grown regions and for the graphene on the Cu with a full width at half maximum of ∼38 cm⁻¹ ranging from 30 to 55 cm⁻¹ of 2D, and without a D band in the spectra of the graphene monolayer and bilayer. Thus the resulting graphene growth is affected primarily by the Cu catalyst, partly by the compounds grown simultaneously with the graphene monolayer on the foil surface via thermal reactions of the impurities dissolved in the alloy matrix, and partly by the Ni. The quality of the graphene is dependent on the major composition of Cu catalyst in the alloy foils. On the other hands, the alloying element of Ni governs the growth kinetics unless the alloy foils is covered with the intermetallic compounds and silicate.     

Stress-dependent deformation behaviour in bulk nanocrystalline titanium–nickel alloys

In this study, the deformation mechanisms operating with stress in bulk nanocrystalline (NC) titanium–nickel with an average grain size below a critical size of 10–20?nm have been investigated. We demonstrate a sequential variation of the deformation mechanism from grain boundary (GB) sliding and grain rotation to grain growth and dislocation activity with the increase of the deformation stress. These deformation mechanisms are different from the previous understanding that below a critical grain size of 10–20?nm, GB sliding and grain rotation govern plastic deformation of NC materials.