非晶态合金与氢相互作用的研究进展

非晶态合金在力学性能、耐磨耐蚀性、磁性等方面比传统晶态合金具有显著优势,是一类有优良应用前景的新型结构与功能材料.非晶态合金与氢相互作用可以产生很多有趣的物理化学现象和应用.本文从物理基础和材料应用两个方面评述非晶态合金和氢相互作用的研究进展,在物理基础研究方面,从氢在非晶态合金中的存在状态出发,讨论氢在非晶态合金中的溶解、分布、占位和扩散等相关物理问题,进而分析氢对非晶态合金的热稳定性、磁性、内耗、氢脆等的影响.在材料应用研究方面,对非晶态储氢合金、非晶态合金氢功能膜、吸氢改善非晶态合金的塑性和玻璃形成能力、氢致非晶化、利用非晶态合金制备纳米储氢材料等方面的研究进展进行评述.最后总结并展望有关非晶态合金与氢相互作用的研究和应用.     

铀基非晶合金的发展现状

铀基非晶合金是非晶家族中的特殊成员,受限于铀元素的高活性与放射性特点,目前这类非晶材料的研究极不充分.本文结合非晶合金的最新发展动态简要介绍了铀基非晶发展历史,较系统地总结了本团队的最新铀基非晶研究工作:首先较详细地介绍了新型铀基非晶的制备技术、成分体系、形成规律与晶化行为,澄清了其形成机制与热稳定性;结合高分辨电镜分析展示了其微观结构特点;采用纳米压痕技术揭示了这类非晶的微纳力学性能;利用电化学测试方法评估了其耐腐蚀性能.这些结果丰富了非晶材料的内涵,有助于深化对非晶物理基础科学问题的理解,并推动新型铀合金材料的发展,为这种材料的潜在工程应用奠定了基础.     

Stability of amorphous alloys

The thermal stability of a number of Ti-base and Zr-base amorphous alloys was studied by means of differential scanning calorimetry. The crystallization temperatures of these amorphous alloys and those reported in the literature for a variety of other amorphous alloys (actinide-base alloys an refractory metal-base alloys) were analysed in terms of the corresponding formation enthalpies. It is shown that there is no correlation between the crystallization temperatures and the formation enthalpies. On the other hand the crystallization temperatures were found to scale more or less linearly to the corresponding formation enthalpies of a hole the size of the smaller type of atom in the binary amorphous alloys.     

铁基软磁非晶/纳米晶合金研究进展及应用前景

非晶合金通常是将熔融的金属快速冷却、通过抑制结晶而获得的原子呈长程无序排列的金属材料.由于具有这种特殊结构,铁基软磁非晶合金具有各向同性特征、很小的结构关联尺寸和磁各向异性常数,因而具有很小的矫顽力H_c,但可和晶态材料一样具有高的饱和磁感强度B_s.优异的软磁性能促进了铁基软磁非晶合金的应用研究.目前,铁基软磁非晶/纳米晶合金带材已实现大规模工业化生产和应用,成为重要的高性能软磁材料.本文回顾了软磁非晶合金的发现和发展历程,结合成分、结构、工艺对铁基非晶/纳米晶合金软磁性能的影响,介绍了相关基础研究成果和工艺技术进步对铁基软磁非晶/纳米晶合金研发和工业化应用的重要贡献.并根据结构、性能特征将铁基软磁非晶合金研发与应用分为三个阶段,指出了目前铁基软磁非晶合金研发与应用中面临的挑战和发展方向.     

Zr基大块非晶中添加元素对非晶形成能力及耐蚀性的影响

运用实空间递归方法研究了添加元素Nb,Ta,Y,La对Zr基非晶合金的非晶形成能力和耐腐蚀性能的影响.用计算机编程构造了Zr基非晶中初始晶化相Zr₂Ni的原子结构模型,用Zr₂Ni中的二十面体原子团簇模拟非晶中的二十面体团簇.计算了替代二十面体中心或顶角位置原子前后Ni,Zr及合金元素的局域态密度、团簇中心Ni与近邻Zr原子及Ni与替代元素Nb,Ta,Y,La间的键级积分,还计算了合金元素替代前后团簇的费米能级.局域态密度计算结果表明：合金元素Cu占据二十面体团 关键词： 电子结构 Zr基大块非晶 非晶形成能力 耐蚀性     

Inherent submicroporosity and crystallization of amorphous alloys

The effect of inherent submicroporosity (regions with an excess free volume) in amorphous alloys on the regularities of their crystallization is investigated. Inherent submicroporosity arises in amorphous alloys prepared by quenching under different conditions. It is proved that this effect should be taken into account in the first stage of crystallization of amorphous alloys.     

铁基纳米晶合金的热膨胀研究

研究了铁基纳米晶合金Ｆｅ_１３．５Ｃｕ_１Ｎｂ_３Ｓｉ_１３．５Ｂ_９和Ｆｅ_９１Ｚｒ_７Ｂ_２的热膨胀特性，并与相应成分的非晶合金做了比较。结果表明，在居里温度以下，纳米晶合金的热膨胀系数比非晶合金大得多，而在居里温度以上，两者几乎相等。认为上述的热膨胀的差别可能与铁基非晶态合金中存在的因瓦效应有关。 关键词：     

Nanocrystalline iron-based alloys investigated by Mössbauer spectrometry

Nanocrystalline alloys exhibit great fundamental and technological interests because of their microstructural properties, and their excellent soft magnetic properties. ⁵⁷Fe Mössbauer spectrometry is a well suitable technique to investigate Fe-based nanocrystalline alloys: its local probe behaviour permits to elucidate the nature of hyperfine interactions at different resonating iron nuclei and to distinguish their immediate atomic surroundings. We review on the recent Mössbauer developments performed on first FeCuMBSi and then FeCuBSi nanocrystalline alloys. From Mössbauer studies, one can estimate the crystalline (i.e., amorphous) fraction, the Si-content in Fe--Si nanocrystalline grains emerging from amorphous alloys of the first series, the temperature dependence of magnetic behaviours of both crystalline and amorphous phases; finally, we present a novel fitting procedure applied to FeCuBSi nanocrystalline alloys which result from bcc-Fe crystalline grains embedded in an amorphous matrix. In this case, the hyperfine structure is able to model the intergranular phase.     

Metallic magnetism in amorphous TM-Y (TM = Mn,Fe, Co,Ni) alloys

Systematic variations of magnetic properties in amorphous TM-Y (TM = Mn, Fe, Co, Ni) alloys are investigated on the basis of a finite temperature theory of amorphous metallic magnetism which takes into account both thermal spin fluctuations and the fluctuations due to structural and configurations disorder. It is shown that the magnetic phase diagrams calculated in the most random atomic configuration explain qualitatively the spinglass (SG) in Mn-Y, the SG ferromagnetism (F) transition in Fe-Y, and the F-paramagnetism transition in Co-Y and Ni-Y alloys. Magnetization vs concentration curves and susceptibility vs concentration curves as well as the effective Bohr magneton numbers are also shown to be explained qualitatively or semi-quantitatively by the theory. Their miscroscopic mechanisms are elucidated by means of their electronic structures, magnetic couplings, and atomic short range order. It is found that the magnetism in Fe-Y and Mn-Y amorphous alloys is strongly influenced by the atomic short range order. The result explains different magnetic phase diagrams in amorphous Fe-Y alloys and experimental SG transition temperatures in amorphous Mn-Y alloys.     

Magnetic properties of amorphous alloys

The magnetic properties of existing amorphous iron based materials, i.e., Fe--metalloid, Fe--early transition metals and Fe--rare earth alloys, are briefly discussed for some representative alloys. The spin orientation of amorphous Fe--metalloid alloys has been determined by the angular dependence of hyperfine interactions. It is shown that in iron--early transition metals ferromagnetic order is not long-ranged, but determined by magnetic clusters. The magnetic hyperfine field distributions of Fe-rich iron--early transition metals consist of a high and a low field tail. The magnetic structure has been investigated for two representative Fe--RE (RE = Er, Ce) amorphous alloys. For the first time, the magnetic coupling phenomenon in amorphous/crystalline multilayers has been discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

穆斯堡尔谱学研究非晶TM80M20合金的微观结构

在室温下和4.2K下测定了非晶Fe₈₀B_20-xM_x合金(M=P,C)的穆斯堡尔吸收谱。利用分布参数拟合程序得到了超精细内场H_i和同质异能移IS同类金属成份的变化关系。利用这些结果考察了非晶合金的微观结构,比较了两类结构模型:Bernal-Polk模型和微晶模型。对比非晶合金和它们的相应晶相的行为得知,这类非晶合金中不存在微晶近程序,Bernal-Polk模型对描述TM-M类非晶合金的微观结构优于微晶模型。 关键词：     

Magnetic relaxations in amorphous soft magnetic alloys

The paper reviews selected results of the extended experimental investigations of magnetic properties, time–temperature stability and workability of the soft magnetic amorphous alloys controlled by structural magnetic relaxation. Complex approach to the magnetic relaxations in multicomponent amorphous alloys is presented. The transition from magnetic after-effect to a new MAE spectrometry is illustrated on ternary amorphous CoSiB alloy.     

Medium-Range Order Structure and Fragility of Superheated Melts of Amorphous CuHf Alloys

The structural factors of amorphous CuHf alloys at different temperatures are determined by using a high temperature x-ray diffractometer. It is found that not only the short-range order structure but also the medium-range order structure exists in amorphous CuHf alloys. The dynamic viscosities of CuHf alloy melts are measured by a torsional oscillation viscometer. The fragility of superheated melts of CuHf alloys is calculated based on the viscosity data. The experimental results show that the glass-forming ability of the CuHf alloys is closely related to the fragility of their superheated melt. The relationship between the medium-range order structures and the fragility of superheated melts has also been established in amorphous CuHf alloys. In contrast to the fragility of supercooled liquids, the fragility of superheated liquids promises a better approach to reflecting the dynamics of glass forming liquids.     

Low temperature properties of Pr amorphous alloys

Starting from the Fert and Campbell Hamiltonian and assuming a suitable η-distribution, the magnetization and the specific heat for Pr amorphous alloys are evaluated in the molecular field approximation with ferromagnetic interaction.Recent low-temperature experimental data on the specific heat of Pr amorphous alloys are reasonably explained.     

Nanostructures, disordered ferromagnetism and spin glasses

Magnetic systems with a considerable amount of irregular interfaces were investigated by ⁵⁷Fe Mössbauer spectroscopy. Chemically homogeneous ferromagnets around the percolation threshold composition of disappearing magnetism and chemically heterogeneous alloys prepared by nanocrystallization of amorphous alloys belong to this class of materials. Low temperature and high field measurements were performed on nanocrystalline FeZrBCu alloys, on ball‐milled Fe with nano‐size grains and on melt‐quenched amorphous Fe–Zr and Fe–Y alloys in order to clarify the origin of large high‐field susceptibility and to investigate the common features of the approach to magnetic saturation. Curie point determination of the residual amorphous phase in the nanocrystalline FeZrBCu alloys, results on the structure of the nanocrystalline b.c.c. phase and of the interfacial region will be reported.     

铸锭凝固组织对相应非晶合金晶化过程中二十面体准晶相形成动力学的影响

通过在真空电弧熔炼炉内对合金铸锭进行反复熔炼处理，获得到了凝固组织不同的Zr₆₅Al_7.5Cu_12.5Ni₁₀Ag₅合金铸锭.在相同的制备条件下，由凝固组织不同的合金铸锭通过吸铸法制备得到了薄片非晶合金.利用差示扫描量热法(DSC)对非晶合金的晶化动力学进行了分析.x射线衍射谱表明，在Zr₆₅Al_7.5Cu_12.5Ni₁₀Ag₅非晶合金晶化过程中，二十面体准晶相(I相)作为初生相析出.Kissinger分析结果表明，合金铸锭的凝固组织细化，相对应的非晶合金发生晶化时，I相形成与分解的有效激活能都增大，说明非晶合金及析出的I相的热稳定性都提高.从结构的遗传性角度就合金铸锭凝固组织对相应非晶合金晶化过程中二十面体准晶相的形成动力学的影响进行了讨论. 关键词： 二十面体准晶相 晶化动力学 凝固组织     

铜基大块非晶合金添加微量元素对腐蚀行为的影响机理研究

通过分子动力学方法模拟了Cu-Al合金液相,然后模拟降温过程得到Cu-Al非晶合金.通过计算机编程建立了Cu-Al-M非晶基体、Cu-Al-M非晶表面及吸附O原子Cu-Al-M非晶表面原子结构模型.利用实空间连分数方法,研究了添加微量合金元素Zr,Nb,Ta,V,Y,Sc对Cu基大块非晶合金的腐蚀行为的影响机理.研究发现合金元素Zr,Nb,Ta,V,Sc不向清洁Cu基非晶表面偏聚,但除Y外向有氧吸附的表面偏聚,说明有氧吸附后Cu基非晶表面偏聚发生逆转.键级积分计算表明Zr,Nb,Ta,V,Y,Sc元素均增大与氧之间的结合力,易形成氧化膜,提高Cu基大块非晶的耐蚀性.稀土Y提高Cu基大块非晶的耐蚀性可能是由于它向合金与氧化膜界面偏聚并提高了合金与氧化膜的结合力.     

Simulation study for atomic size and alloying effects during forming processes of amorphous alloys

1 Introduction Since amorphous alloys were successfully prepared by Duwez et al.[1] in the 1960s by rapid cooling from the eutectic alloy of Ag-Cu system, the investigation about atomic size and alloying effects during the formation process of amorphous alloys has become such an important area that many people paid a good deal attention. From the experiments that AgxCu1-x alloys formed amorphous structures, Takayama[2] has determined the content range of amorphous alloys, being x = 35—65, …     

Effects of structure on exchange interactions in crystalline and amorphous alloys GdxY50−xAg50

Magnetic interactions and effects of dilution with nonmagnetic Y on the magnetic properties of crystalline and amorphous alloys Gd_xY_50−xAg₅₀ (10 ≤ x ≤ 50) have been investigated by measurements of bulk magnetization and susceptibility and by Mössbauer spectroscopy with ¹⁵⁵Gd. The crystalline alloys order antiferromagnetically for all Gd concentrations with a noncollinear arrangement of Gd moments induced by negative biquadratic exchange interactions. In amorphous alloys, ferromagnetic order is found for large Gd concentrations (x ≥ 40). Below the critical concentration x_cr, in the range 30<x_cr<40, properties typical for magnetic cluster glasses are observed. Magnetic hyperfine fields B_hf at ¹⁵⁵Gd nuclei vary with x in opposite directions in amorphous and in crystalline alloys. In crystalline alloys, the variation is due to a positive transferred hyperfine field. In amorphous alloys, a reduction of |B_hf| with decreasing Gd concentration is caused by a reduction of the frozen Gd moments in the cluster glass phase.     

ATOMIC SHORT-RANGE ORDER OF AMORPHOUS Ta-Cu ALLOYS PREPARED BY MECHANICAL ALLOYING

In the present work, the atomic short-range ordering structure of the amorphous Ta-Cu alloys formed by mechanical alloying was investigated through radial distribution function (RDF) analysis. The results suggest that the elemental powders of Ta and Cu were well mixed by mechanical alloying at atomic level. The regions of short-range order (r_s) increase with Cu concentration in Ta-Cu alloys, This means that the short-range ordering becomes stronger in those alloys with higher Cu content. The coordination number was estimated to be 12-13 from the area under the first maximum of the RDF (r) curves for all the Ta-Cu amorphous alloys. This result indicates that the amorphous alloys formed by mechanical alloying are also of topologically dense-packing structure.