共查询到17条相似文献,搜索用时 655 毫秒
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研究了Ti-50AI和Ti-45Al-8Nb合金在锌液中的腐蚀行为,并测量Ti-50Al和Ti-45Al-8Nb合金的正电子寿命谱,利用正电子寿命参数分别计算了合金基体和缺陷态的自由电子密度。TiAl合金自由电子密度比金属Ti和金属Al基体的低,当Ti和Al组成TiAl合金时,Ti原子和A1原子的部分价电子被局域化,TiAl合金中金属键和其价键共存。TiAl合金晶界缺陷的开空间较大,晶界缺陷处的自由电子密度较低,金属键结合力较弱。在TiAl合金中加入Nb元素,Ti-45A1-8Nb合金基体和晶界的自由电子密度增大,明显减慢了锌液对钛铝基合金的溶解速度。 相似文献
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掺V和Ag的TiAl合金中缺陷和电子密度的正电子湮没研究 总被引:2,自引:1,他引:2
测量了Ti50Al50,Ti50Al48V2,Ti50Al48Ag2合金和充分退火的Ti,Al,Ag,V金属的正电子寿命谱,利用正电子寿命参数分别计算了合金基体和缺陷态的自由电子密度。TiAl合金的脆性与其基体和晶界缺陷处的自由电子密度较低有关。在富Ti的TiAl合金中加入V,V原子比Al和Ti原子能提供较多的自由电子参与形成金属键,因而提高了合金基体和晶界缺陷处的自由电子密度;在TiAl合金中加入Ag也有类似的效应。在TiAl合金中加入V和Ag,有利于提高合金的韧性。 相似文献
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用正电子湮没技术研究Zr对Ni3Al缺陷态的影响 总被引:1,自引:0,他引:1
本文用正电子湮没技术(PTA)研究了含不同Zr量多晶Ni3Al的e^+寿命谱,结果表明:在Ni3Al中加入Zr,一部分Zr原子进行原子替位,晶格发生畸变,导致基体中正电子寿命(τ1)增长;另一部分在晶界偏聚的Zr调整了晶界结构,使平均寿命(τ)下降,当Zr量为1.2at-5时,缺陷态的寿命τ2显著增长,表明有自由体积较大的缺陷组态生成。 相似文献
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用正电子寿命谱测量方法研究了5种不同化学成分的近等原子比NiTi合金中的微观缺陷和自由电子密度。结果表明,当Ni原子和Ti原子形成NiTi合金时部分3d电子被局域化而形成共价键,导致合金中参与形成金属键的自由电子减少。近等原子比的NiTi合金中的基体和缺陷处的自由电子浓度均随Ni含量的增加而改变,并且当Ni含量为51 at%时达到最大值。研究还发现Ni51Ti49合金含有最少的缺陷,从而有助于马氏体相变的发生,这可能成为Ni51Ti49合金具有最好的形状记忆效应的一个原因。 相似文献
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测量Al,Si,Ti,Cr,Nb等纯元素以及Ti50Al50,Ti50l48Cr2,Ti50Al48Nb2合金的符合正电子湮没辐射多普勒展宽谱和寿命谱,获得金属及合金中d电子和缺陷的信息.结果表明,二元TiAl合金的电子密度和3d电子的信号较低,晶界缺陷的开空间较大.在TiAl合金中加入Cr或Nb,合金中的d-d电子作用增强,基体和晶界处的电子密度均增加.Ti50Al48Cr2合金的多普勒展宽谱的d电子信号高于Ti50Al48Nb2合金.讨论了Cr和Nb对TiAl合金中缺陷和d-d电子相互作用的影响. 相似文献
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Fe-Al系金属间化合物中的微观缺陷和电子密度 总被引:5,自引:1,他引:5
对二元Fe-Al合金,含Cr和Si的Fe3Al合金的正电子寿命谱测量表明:随着二元Fe-Al合金中Al含量的增加,空位浓度增加,微孔洞的开空间增大。在Al含量高于40%原子分数)的B2-FeAl合金中存在着较高的空位浓度和开空间相当于Fe中的10-15个空位聚集体的微空洞。在B2-FeAl和D03-Fe3Al合金中,晶格中最邻近的Fe-Al原子对之间发生Fe-d-Alp杂化使用。Al的3p电子与Fe的3d电子被局域化并形成共价键。导致合金中的自由电子密度降低。二元Fe-Al合金中的平均电子密度随着Al含量的增加而下降。用Cr元素对Fe3Al进行合金化。合金基体和晶界处的自由电子密度均增加;而加入Si元素,合金基体和晶界处的自由电子密度均减小。讨论了Fe-Al合金的微结构对其力学性能的影响。 相似文献
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Influence of chemical composition and alloying elements on microdefects and electron density in Ni—Al alloys 总被引:3,自引:0,他引:3
1 INTRODUCTIONLl2 Ni3AlandB2 NiAlareimportantintermetal liccompoundsinNiAlalloys .ANi3Alalloyhasrela tivelyhighstrengthandpresentsre 相似文献
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用正电子寿命谱测量方法研究了5种不同化学成分的近等原子比NiTi合金中的微观缺陷和自由电子密度.结果表明,当Ni原子和Ti原子形成NiTi合金时部分3d电子被局域化而形成共价键,导致合金中参与形成金属键的自由电子减少.近等原子比的NiTi合金中的基体和缺陷处的自由电子浓度均随Ni含量的增加而改变,并且当Ni含量为51 at%时达到最大值.研究还发现Ni51Ti49合金含有最少的缺陷,从而有助于马氏体相变的发生,这可能成为Ni51Ti49合金具有最好的形状记忆效应的一个原因. 相似文献
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《中国有色金属学会会刊》2020,30(5):1315-1324
In order to improve mechanical properties and optimize composition of TiAl−Nb alloys, Ti46Al5Nb0.1B alloys with different contents of Fe (0, 0.3, 0.5, 0.7, 0.9, and 1.1 at.%) were prepared by melting. Macro/microstructure and compression properties of the alloys were systematically investigated. Results show that Fe element can decrease the grain size, aggravate the Al-segregation and also form the Fe-rich B2 phase in the interdendritic area. Compressive testing results indicate that the Ti46Al5Nb0.1B0.3Fe alloy shows the highest ultimate compressive strength and fracture strain, which are 1869.5 MPa and 33.53%, respectively. The improved ultimate compression strength is ascribed to the grain refinement and solid solution strengthening of Fe, and the improved fracture strain is due to the reduced lattice tetragonality of γ phase and grain refinement of the alloys. However, excessive Fe addition decreases compressive strength and fracture strain, which is caused by the severe Al-segregation. 相似文献
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《中国铸造》2015,(5)
Five equiatomic alloys(Ti Zr Hf VNb, Ti Zr Hf VTa, Ti Zr Nb Mo V, Ti Zr Hf Mo V and Zr Nb Mo Hf V) composed of five elements with high melting temperature, respectively were prepared by arc-melting to develop a novel high temperature alloy. The five alloys exhibit different dendritic and interdendritic morphologies. The Ti Zr Hf VNb, Ti Zr Hf VTa and Ti Zr Nb Mo V alloys formed disordered solid solution phases with body-centered cubic structure, and exhibited high compressive strength and good plasticity. The Ti Zr Hf Mo V and Zr Nb Mo Hf V alloys are composed with Laves phase(Hf Mo2) and disordered solid solution phases with body-centered cubic structure. The Ti Zr Hf Mo V and Zr Nb Mo Hf V alloys are harder and more brittle than the other three alloys due to the existence of hard and brittle Laves phases. At high temperatures, the strength decreases to below 300 MPa for the Ti Zr Hf VNb and Ti Zr Hf Mo V alloys. Solution strengthening is the primary strengthening mechanism of the Ti Zr Hf VNb, Ti Zr Hf VTa and Ti Zr Nb Mo V alloys, and brittle Laves phase is the main cause for the low ductility of the Ti Zr Hf Mo V and Zr Nb Mo Hf V alloys. 相似文献
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《Acta Materialia》1999,47(4):1129-1139
The site occupancies of V, Cr, Mn, Fe, Ni, Zr, Nb, Mo, Ta, Ga and Sn (1–5 at.%) in TiAl alloys with different compositions, and in Ti3Al with the compositions of Ti–26 at.%Al–(1–2 at.%)X, were measured by the atom location channelling enhanced microanalysis (ALCHEMI) method. For TiAl alloys, the results show that Zr, Nb and Ta atoms invariably occupy Ti sites, while Fe, Ni, Ga and Sn atoms occupy Al sites, the alloy composition having no significant influence on their site preference. By contrast, the site preference of V, Cr, and Mn changes considerably with alloy composition (the Ti/Al ratio in particular), the probability of these elements substituting for Ti decreasing in the above order. For quaternary Ti–Al–V–Cr alloys, the site occupancies of V and Cr do not show much mutual influence. In general, with increasing atomic number, elements in the same period show increasing tendency to substitute for Al, as is the tendency to substitute for Ti for elements in the same group of the periodic table. For Ti3Al alloys, Ga and Sn atoms occupy Al sites, while V, Cr, Mn, Zr, Nb, Mo and Ta atoms occupy Ti sites, the site preference of V, Cr, Mn and Mo in TiAl alloys being different from that in Ti3Al. The experimental results are interpreted in terms of a Bragg–Williams-type model and bond-order data obtained from electronic structure calculation. Qualitative agreement between the model and measurements is reached. 相似文献