高压下Zr60Ni20Al20金属玻璃形成过程的研究

 本文报道用高压淬火的方法制备出了Zr₆₀Ni₂₀Al₂₀大块金属玻璃。以经典成核理论为依据，估计了压力对晶核成长速度的影响，在高压下过冷熔体的晶体生长速度比常压下的晶体生长速度低几个数量级，这说明高压淬火之所以有利于金属玻璃的形成，主要是因为压力抑制了过冷熔体内的晶体生长过程。     

Internal friction behavior of Zr_(59)Fe_(18)Al_(10)Ni_(10)Nb_3 metallic glass under different aging temperatures

We investigate the role of aging temperature on relaxation of internal friction in Zr₅₉Fe₁₈Al₁₀Ni₁₀Nb₃metallic glass.For this purpose,dynamic mechanical analysis with different annealing temperatures and frequency values is applied.The results indicate that the aging process leads to decrease in the dissipated energy in the temperature range of glass transition.It is also found that the increase in applied frequency weakens the loss factor intensity in the metallic glass.Moreover,the Kohlrausch-Williams-Watts(KWW)equation is used to evaluate the evolution of internal friction during the aging process.According to the results,higher annealing temperature will make the primary internal friction in the material increase;however,a sharp decline is observed with the time.The drop in characteristic time of internal friction is also closely correlated to the rate of atomic rearrangement under the dynamic excitation so that at higher annealing temperatures,the driving force for the collaborative movement of atoms is easily provided and the mean relaxation time significantly decreases.     

Influences of substrate temperature on microstructure and corrosion behavior of APS Ni_(50)Ti_(25)Al_(25) inter-metallic coating

In the present investigation, Ni_(50)Ti_(25)Al_(25)(at.%) mechanically alloyed powder is deposited on carbon steel substrate.Before the coating process, the substrate is heated to temperature ranging from room temperature to 400℃. The microstructure, porosity, microhardness, adhesion strength, and corrosion behavior of the coating are investigated at different substrate temperatures. Results show that coating porosity is lower on high temperature surface. Microhardness and adhesion strength of the deposition layer on the substrate without preheating have lower values than with preheating. The polarization test result shows that corrosion performance of the coating is dependent on micro cracks and porosities and the increasing of substrate temperature can improve the quality of coating and corrosion performance.     

Acid corrosion of amorphous and crystalline Cu-Zr alloys

Corrosion resistance of amorphous and crystalline Cu₄₅Zr₅₅, Cu₅₀Zr₅₀ and Cu₆₀Zr₄₀ alloys in strong acid (C_H⁺ = 1 M ℓ^-1) solutions was investigated with the use of potentiodynamic and gravimetric techniques. It was observed that the corrosion resistance of these alloys tested in H₂SO₄ and HNO₃ solutions was very high. However, amorphous Cu-Zr alloys exhibit a lack of resistance in HCl solutions where the corrosion rate increases with the rise of Cu content in the alloy (selective etching of Zr). Crystallization of alloys strongly improves their resistance to corrosion in HCl provided the Zr content in an alloy ⩾ 50 at%.     

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     

Dynamic mechanical relaxation and thermal creep of high-entropy La_(30)Ce_(30)Ni_(10)Al_(20)Co_(10) bulk metallic glass

Dynamic mechanical relaxation is a fundamental tool to understand the mechanical and physical properties of viscoelastic materials like glasses. Mechanical spectroscopy shows that the high-entropy bulk metallic glass(La_(30)Ce_(30)Ni_(10)Al_(20)Co_(10)) exhibits a distinct β-relaxation feature. In the present research, dynamic mechanical analysis and thermal creep were performed using this bulk metallic glass material at a temperature domain around the β relaxation. The components of total strain, including ideal elastic strain, anelastic strain, and viscous-plastic strain, were analyzed based on the model of shear transformation zones(STZs).The stochastic activation of STZ contributes to the anelastic strain. When the temperature or external stress is high enough or the timescale is long enough, the interaction between STZs induces viscous-plastic strain. When all the spectrum of STZs is activated, the quasi-steady-state creep is achieved.     

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.     

高压下Co在Zr46．75Ti8．25Cu7．5Ni10Be27．5大块金属玻璃过冷液相区中的扩散

通过离子注入结合二次离子质谱分析方法 ,研究了高压下Co在Zr4 6 .75Ti8.2 5Cu7.5Ni1 0 Be2 7.5大块金属玻璃过冷液相区中的扩散行为 .在 6 0 3K时 ,Co在Zr4 6 .75Ti8.2 5Cu7.5Ni1 0 Be2 7.5大块金属玻璃中的扩散系数随压力的增大而增大 ,其扩散激活体积ΔV =- 1.2 36Ω ,Ω是合金的平均原子体积 .结果表明 ,在热平衡状态下Co在Zr4 6 .75Ti8.2 5Cu7.5Ni1 0Be2 7.5大块金属玻璃中的扩散是通过间隙机理进行的     

Effect of Co substitution on the glass forming ability and magnetocaloric effect of Fe_(88)Zr_8B_4 amorphous alloys

<正>As greater attention is paid to energy consumption and global warming,magnetic refrigeration(MR)technologies based on the magneto-caloric effect(MCE)have been developed.Systems based on MR are expected to be more compact,energy     

Zr-Cu-Ni-Al-Nb大块非晶合金的晶化行为、力学性能及电化学腐蚀行为的研究

利用水冷铜模铸造法成功制备了Zr_65-xCu_17.5Al_7.5Ni ₁₀Nb_x (x=0，2，5)大块非晶合金. X射线衍射、热分析研究结果表 明，Nb的添加显著改变了非晶合金的晶化行为，促进了二十面体准晶相的形成. 各合金的准 静态压缩实验表明，Nb的适量添加有利于提高大块非晶合金的强度和塑性. 其中x=5的大块 非晶合金的抗压强度σ_b和塑性应变量ε_p 关键词： Zr基大块非晶合金 晶化行为 力学性能 耐腐蚀性能     

Ni_(50)Al_(50)合金的液固转变及晶体生长过程的分子动力学模拟

采用分子动力学模拟技术研究了液态Ni50 Al50 合金在不同冷速下的凝固特点 ,模拟采用EAM作用势 ,计算了不同温度 ,不同冷速下Ni50 Al50 的偶分布函数。结果表明EAM作用势能很好地描述液态Ni50 Al50 的无序结构 ,在快速凝固条件下 ,液态Ni50 Al50 形成非晶 ,当冷速较慢时 ,液态Ni50 Al50 形成晶体 ,分析了不同冷速下体系的相变热力学及相变动力学特点。最后采用液固两层构型法 ,清楚地观察到Ni50 Al50 晶体生长的全过程。     

Geometric structure of Bergman clusters related to bulk amorphous alloys and quasicrystals

The fcc Zr₂Ni- and MgCu₂-type phases, being primary crystalline products of certain amorphous alloys with high glass-forming ability, should provide local structural information about the related amorphous alloys. The present paper gives a detailed analysis of the common structural features of these two fcc phases. They are both built from a similar building block consisting of tetrahedrally packed icosahedra. They also have shelled local structures similar to the first two shells of the Bergman-type clusters found in many icosahedral quasicrystals. Therefore the Bergman-type clusters probably play an important role in amorphous phase formation. Because of topological close packing inside dual-intergrown icosahedra, characteristic of Bergman clusters, the atomic radius ratios of the first- and second-shell atoms with respect to the central atom are nearly equal and fall in the range 1.1–1.2.     

Surface and bulk crystallization of amorphous alloys Ni-Si-B probed by electrical resistivity

Electrical resistivity measurements are tested as a sensitive probe of the crystallization processes in amorphous metallic alloys of Ni₇₈Si₇B₁₅, rendering the determination of nucleation rates at the surface and in bulk. It is shown that the increase in the electrical resistivity just below the crystallization temperature is mainly due to nucleation phenomena. Moreover, the Avrami coefficient, calculated from resistivity data, provides information about types of crystallization mechanisms, dimensionality of the crystallite growth and the sequence of crystallization stages.     

Outstanding magnetocaloric effect of Fe_(88-x)Zr_8B_4Sm_x(x=0, 1, 2, 3) amorphous alloys

正Since the first investigation on the formation and magnetic properties of Fe-C-P amorphous phase by Duwez and Lin in1967[1,2],Fe-based amorphous alloys have attracted extensive interest because of their low cost,excellent soft magnetic properties,good corrosion resistance,and mechanical properties[2-7].Among the Fe-based amorphous alloys,Fe-Zr-B ternary amorphous alloys exhibit excellent magnetocaloric effect(MCE)near room temperature,and thus,act as a fertile ground for the exploration of novel working materials for magnetic refrigerators[6-14].     

Electrochemical synthesis and corrosion behaviour of poly (pyrrole-co-o-anisidine-co-o-toluidine)

In this study, a ter-polymer film of pyrrole, o-anisidine and o-toluidine has been electrochemically synthesized on low carbon steel. The synthesis solution was aqueous oxalic acid containing 2:1:1 monomer feed ratio between pyrrole, o-anisidine and o-toluidine, respectively. The characterization of synthesized ter-polymer film was realized with help of UV–Vis absorption, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) techniques. The stability of this ter-polymer film as a coating material has also been investigated on steel, in 3.5% NaCl solution. Under such severe conditions, the ter-polymer film was found to exhibit low permeability against water ingress. It was able to exhibit protective coating behavior on steel, even after 72 h exposure time. The DSC results revealed that the ter-polymer film had better thermal stability with respect to single polypyrrole film. The synthesized ter-polymer film was completely different in aspect of morphology, stability and other structural properties when compared to single polypyrrole film. This highly stable and extremely thin (0.80 μm) film can find application for various purposes (anticorrosive, electrocatalytic, etc.), at where the stability of polypyrrole like films constitutes a drawback.     

Mössbauer study of amorphous Nd x Fe81B19-x (0≦x≦19) alloys

Amorphous Nd_xFe₈₁B_19-x (0≤x≤19) alloys have been studied by⁵⁷Fe Mössbauer spectroscopy. It is found that the average and peak hyperfine fields and the isomer shift decrease with increasing Nd content x. The magnetization for the samples containing Nd shows a strong tendency to lie in the direction perpendicular to the ribbon plane and its direction varies with Nd content.     

Crystallization and thermal fatigue of ZrTiCuNiBe bulk amorphous alloys heated by laser pulses

The crystallization and thermal fatigue behavior of Zr41Ti14Cu12.5Ni10Be22.5 bulk amorphous alloys heated by laser pulses was investigated. The results showed that crystallization occurred even below the crystallization temperature Tx in a low cycle time. Cracks appearred before or after crystallization of the heated area in the sample. The crystallization degree increased with the heating temperature and cycles. An increase in the fatigue cracks number was also observed. The plastic deformation in the heat...     

Low thermal expansion and broad band photoluminescence of Zr_(0.1)Al_(1.9)Mo_(2.9)V_(0.1)O_(12)

A new material of Zr0.1Al1.9Mo2.9V0.1O12 is synthesized by the traditional solid state synthesis method.The phase transition,coefficient of thermal expansion,and luminescence properties of Zr0.1Al1.9Mo2.9V0.1O12 are explored with Raman spectrometer,dilatometer,and x-ray diffraction(XRD)diffractometer.The results show that the Zr0.1Al1.9Mo2.9V0.1O12 possesses the strong broad-band luminescence characteristics almost in the whole visible region.The sample is crystallized in a monoclinic structure group of P21/a(No.14)crystallized at room temperature(RT).The crystal is changed from monoclinic to orthorhombic structure when the temperature increases to 463 K.The material has very low thermal expansion performance in a wide temperature range.Its excellent low thermal expansion and strong pale green light properties in a wide temperature range suggest its potential applications in light-emitting diode(LED)and other optoelectronic devices.     

Correlation between the optical properties of surface layers and bulk characteristics of amorphous alloys

Spectral ellipsometry was used to study surface layers of Fe₈₀ A ₅B₁₅ (A = Ti, V, Cr, Mn, Fe, Co, Ni) and Fe_78-x Ni_xSi₉B₁₃ (x = 0, 1, 4, 8, 16, 21 at. %) amorphous metal alloys obtained by melt spinning. The optical characteristics of the alloys were determined by solving the inverse problem of ellipsometry. A correlation between the optical properties of the surface layers of amorphous alloys and their thermal stability was found.     

Outstanding Magneto-Caloric Effect of a Gd_(60)Ni_(37)Co_3 Amorphous Alloy

Outstanding magneto-caloric properties of a Gd_(60)Ni_(37)Co_3 amorphous alloy are reported.The magnetic entropy change peak(—ΔS_m~(peak) near the Curie temperature(T_c = 135 K) of the amorphous alloy under 5T is about10.42 J·kg~(-1)K~(-1) and the refrigeration capacity(RC) under 5 T is about 860J·kg~(-1),both of which are almost the highest among the amorphous alloys with T_c above 100 K.The magneto-caloric behaviors and the mechanism for the rather high magneto-caloric effect of the Gd_(60)Ni_(37)Co_3 metallic glass are investigated.