多组元替换Zr-Al-Ni-Cu-Ag金属玻璃的热稳定性和晶化行为

为提高金属玻璃的热稳定性并获得大过冷液相区,研究了成分为Zr_65-x(Al_0.21Ni_0.29Cu_0.04Ag_0.46)_35+x（x=0,7.5,15.0,22.5）的金属玻璃,重点分析了组分浓度对合金热稳定性、热诱导沉淀相以及力学性能的影响。结果表明,随着合金组分浓度的增加,非晶漫散射峰的峰位向更高角度偏移,出现了玻璃转变现象。随着玻璃转变温度（T_g）和晶化温度（T_x）增加,液相线温度（T_l）降低,导致T_x和T_g之间的温度差（ΔT_x）减小,约化玻璃转变温度（T_rg）增大。此外,形核激活能（E_x）和长大激活能（E_p1）随着溶质浓度的增加而增加。初晶从四方Zr₂Ni、Zr₂(Cu, Ag)、ZrAg和六方Zr₅Al₃相的组合转变为单一四方ZrAg相,维氏硬度呈现出增加的趋势。通过研究,发现了具有141 K过冷液相区（ΔT_x）和高热稳定性的新型金属玻璃Zr_65-x(Al_0.21Ni_0.29Cu_0.04Ag_0.46)_35+x（x=7.5）,且具有较强的抵抗晶化的特性。本研究采用的多组元替换策略对提高金属玻璃的热稳定性具有重要意义。     

Tm对锆基块体非晶合金力学性能和腐蚀性能的影响

采用铜模负压吸铸工艺制备了(Zr_0.6336Cu_0.1452Ni_0.1012Al_0.12)_100-xTm_x（x=0~5,原子分数）块体金属玻璃（BMG）合金,研究了Tm对合金力学性能和抗腐蚀性能的影响。结果表明,当Tm含量增加到3%时,其玻璃形成能力（GFA）和压缩塑性显著提高,但过量Tm会降低GFA。x=3时合金的最大过冷液相区宽度为100 K,抗压强度为1669 MPa,塑性应变为21.01%,远高于Zr_0.6336Cu_0.1452Ni_0.1012Al_0.12 BMG的各项性能（67 K、1439 MPa和5.90%）。然而,电化学测试结果表明,x=3时的合金在3.5%（质量分数）NaCl溶液中的耐腐蚀性不佳,且其耐腐蚀性和力学性能随Tm含量的变化趋势与预期不同。可能是由于过量添加稀土元素Tm,容易形成更多的氧化物,导致点蚀加剧。进一步添加Tm可以提高Zr基BMG钝化膜的完整性和耐点蚀性能,但力学性能不理想。     

内生型(Ti0.474Zr0.34Cu0.06Be0.126)100 - x Fe x (x=0, 2)金属玻璃基复合材料的动态力学行为

为了解内生β-Ti相的Zr/Ti基金属玻璃复合材料的动态力学性能和热力学稳定性,采用力学弛豫谱研究了(Ti_0.474Zr_0.34- Cu_0.06Be_0.126)_100-xFe_x（x=0,2）金属玻璃复合材料。通过引入Fe元素,提高了β-Ti相的稳定性。此外,还发现了一个异常的内耗峰,这是由于在亚稳的β-Ti相中析出ω-Ti所引起的。在玻璃化转变温度T_g以下,由于相变和非晶基体部分结晶的耦合效应,2种金属玻璃复合材料的储能模量均表现出异常过冲行为。所得结果为更好地理解内生亚稳β-Ti型金属玻璃复合材料的复杂动态力学弛豫行为提供了借鉴。     

FRICTION WELDING OF Zr55Al10Ni5Cu30 BULK METALLIC GLASS

采用摩擦焊对Zr₅₅Al₁₀Ni₅Cu₃₀块体金属玻璃进行了焊接, 当焊机主轴转速为4.0×10³---5.0×10³ r/min, 摩擦压力为80---100 MPa, 摩擦时间为0.2---0.4 s, 顶锻压力和保压时间分别为200 MPa和2 s时, 能够成功实施Zr₅₅Al₁₀Ni₅Cu₃₀金属玻璃的焊接. 用SEM, XRD和TEM观察分析未检测到晶化相, 焊缝处金属仍保持非晶状态. 金属玻璃的塑性在玻璃转变点T_g附近随温度变化很大, 在T_g以上具有良好的塑性变形能力, 这是实施摩擦焊焊接的重要基础.     

具有高非晶形成能力的高熵合金Cu29Zr32Ti15Al5Ni19

用铜模吸铸法成功地合成了由两个固溶体相构成的高熵合金(HEA) Cu₂₉Zr₃₂Ti₁₅Al₅Ni₁₉和相同成分的非晶态合金(HE-BMG)。实验结果表明该成分的高熵合金具有高的非晶形成能力。铸态高熵合金Cu₂₉Zr₃₂Ti₁₅Al₅Ni₁₉的抗压强度为1127MPa。在750℃保温2小时后的Cu₂₉Zr₃₂Ti₁₅Al₅Ni₁₉高熵合金的硬度仍高达826HV。     

(Zr55All0Ni5Cu30)0.97Ce0.03非晶合金在含Cl-介质中的腐蚀电化学行为研究

  用电化学技术方法研究了Zr₅₅Al_l0Ni₅Cu₃₀和(Zr₅₅Al_l0Ni₅Cu₃₀)_0.97Ce_0.03非晶合金在含Cl^-介质中的腐蚀电化学行为及添加稀土Ce的影响.结果表明：随Cl^-浓度增加,两种非晶合金的腐蚀速度加快;添加稀土Ce后提高合金耐蚀性;随极化电位的提高,两种非晶合金在0.05 mol/L Na₂SO₄及含Cl^-介质中均出现钝化特征,维钝电流密度随Cl^-浓度增加而减小;Zr₅₅Al_l0Ni₅Cu₃₀非晶合金的电化学阻抗谱由单容抗弧组成(Zr₅₅Al_l0Ni₅Cu₃₀)_0.97Ce_0.03非晶合金的交流阻抗谱在Cl^-浓度较低时呈单容抗弧特征,而随Cl^-浓度的增加,单容抗弧变为双容抗弧.     

Ti-Cu基合金玻璃形成能力与力学性能

本文基于“二元共晶混合”法设计Ti-Cu-Ni-Zr合金成分,通过水冷铜模铸造法制备出不同直径Ti-Cu-Ni-Zr合金棒。利用X射线衍射仪(XRD)、差示扫描量热仪(DSC)、万能试验机和扫描电镜(SEM)研究了Ti-Cu-Ni-Zr合金玻璃形成能力和力学性能。结果表明,Ti-Cu-Ni-Zr合金具有较高的玻璃形成能力,其临界直径可达4 mm;Ti-Cu-Ni-Zr合金玻璃形成能力近似相等,而表征玻璃形成能力的热力学参数过冷液相区ΔT_x,参数γ,约化玻璃转变温度T_rg也近似相等。通过对合金力学性能进行研究,结果表明,Ti_32.3Cu_47.6Ni_7.9Zr_12.2和Ti_31.6Cu_48.2Ni_7.7Zr_12.5大块非晶合金分别具有0.7%和0.2%的塑性,而Ti₃₀Cu_49.5Ni_7.2Zr_13.3和Ti_28.55Cu_50.7Ni_6.75Zr₁₄大块非晶合金断裂机制近似为脆性断裂。Ti-Cu-Ni-Zr大块非晶合金塑性越大,其剪切带数量越多且扩展深度越大,反之亦然。另外,对于塑性材料,当锯齿流变振幅越大时,对应样品表面剪切带扩展深度越明显,当锯齿流变振幅越小时,对应样品表面剪切带扩展深度较浅;近似脆性断裂的锯齿流变对应次剪切带萌生,而对于完全脆性大块非晶合金,在应力-应变曲线上并未发现锯齿流变现象,相应的在样品外表面也并未发现次剪切带。     

EFFECT OF Gd ADDITION ON THE GLASS FORMING ABILITY AND MECHANICAL PROPERTIES IN A Zr–BASED BULK AMORPHOUS ALLOY

适量的Gd掺杂可提高Zr_50.7Cu₂₈Ni₉Al_12.3块体非晶合金的玻璃形成能力, 当Gd元素掺杂量 (原子分数) 为1%时, 即(Zr_50.7Cu₂₈Ni₉Al_12.3)₉₉Gd₁, 柱状非晶合金直径可达16 mm (不掺杂时为14 mm). 稀土Gd掺杂降低了锆基块体非晶合金的断裂强度与塑性 变形能力. 随着Gd含量的增加, 其断裂方式由单一的剪切断裂转变为剪切断裂与破碎断裂的复合形式, 且含Gd元素掺杂的非晶合金断口呈现了脉状纹络与纳米周期性条纹共存的特征.     

过冷液态Zr48Cu36Ag8Al8块体非晶合金的相分离及组织演变

本文通过x射线衍射(XRD)、差示扫描量热法(DSC)和透射电子显微镜(TEM)研究了退火温度对Zr₄₈Cu₃₆Ag₈Al₈金属玻璃微观结构演化的影响。结果表明,快速凝固获得的样品为典型的非晶态结构。当样品在703K保温20分钟时,均一的非晶基体相分离成两种非晶合金,即,发生相分离。由于相分离结构与非晶基体在等温退火过程是竞争的关系,这个结构很容易向晶化态进行转变,形成AlZr₂ AlAg₃相。Zr₄₈Cu₃₆Ag₈Al₈金属玻璃的微观结构在过冷液相区等温退火过程中经历了的局部结构转变,相分离以及纳米晶转变,这个过程意味着Zr₄₈Cu₃₆Ag₈Al₈金属玻璃的微观结构对退火温度十分敏感。此外,相分离的形成可以加速纳米晶的形成。     

玻璃形成能力及稳定性三角形判定准则

根据降温过程的玻璃形成能力（GFA）和升温过程的玻璃稳定性（GS）,构建了以伪四特征参数组合为顶点的判定玻璃形成能力和稳定性的三角形（Tri-FAS）,从而推导出判定GFA&GS的准则：G-FAS=T_g/T_l+T_x/T_l+T_x/T_g（T_x为起始结晶温度;T_l为液体温度;T_g为玻璃化转变温度）,并从降温过程非晶化与晶化之间的竞争关系和准则各组成项对准则的均衡贡献两个方面进行了修订：G-FAS_m=T_g/(1.5T_x)+T_x/T_l+T_x/T_g和G-FAS_m′=T_g/T_l+T_x/T_l+(T_x/T_g)^a (a≈1.5±0.2)。讨论了G-FAS与临界冷却速率R_c、G-FAS与T_xg（T_xg反映了玻璃的过冷液区,T_xg=T_x/T_g）的相关性,分别能够反映GFA和GS。通过大量金属玻璃和其他玻璃形成体从GFA和GS两方面对判定准则的有效性进行了评估,结果显示：该判定准则无论是GFA方面还是GS方面,在不同玻璃形成体系中均可靠有效,具有广泛应用性。提出的Tri-FAS和G-FAS判定准则在玻璃的生产和实际应用过程中具有指导作用。     

High-strength Cu-based bulk glassy alloys in Cu–Zr–Ti and Cu–Hf–Ti ternary systems

New Cu-based bulk glassy alloys were formed in Cu–Zr–Ti and Cu–Hf–Ti systems by the copper mold casting method. The critical diameter is 4 mm for the Cu₆₀Zr₃₀Ti₁₀ and Cu₆₀Hf₂₅Ti₁₅ alloys which are larger than 1 mm for the Cu₆₀Zr₄₀ and Cu₆₀Hf₄₀ glassy alloys. The substitution of Zr or Hf for Ti causes an increase in the glass-forming ability (GFA). As the Ti content increases, the glass transition temperature (T_g), crystallization temperature (T_x), and the supercooled liquid region ΔT_x(=T_x−T_g) decrease for both Cu₆₀Zr_40−xTi_x and Cu₆₀Hf_40−xTi_x alloys. In contrast, the liquid temperature (T_l) has a minimum value of 1127 K for the Cu₆₀Zr₂₀Ti₂₀ alloy and 1175 K for the Cu₆₀Hf₂₀Ti₂₀ alloy, resulting in a maximum T_g/T_l of 0.63 and 0.62, respectively. The alloys with the highest T_g/T_l value showed the highest GFA for these Cu-based alloys. The bulk glassy alloys exhibit high tensile fracture strength of 2000–2160 MPa, compressive fracture strength of 2060–2150 MPa and compressive plastic elongations of 0.8–1.7%. The finding of the new Cu-based bulk glassy alloys with high GFA, high fracture strength above 2000 MPa and distinct plastic elongation is encouraging for the future development of a new type of bulk glassy alloy which can be used for structural materials.     

Local atomic arrangements and their topology in Ni–Zr and Cu–Zr glassy and crystalline alloys

Different experimental techniques (X-ray diffraction, neutron diffraction with isotopic substitution, extended X-ray absorption spectroscopy) and theoretical methods (reverse Monte-Carlo simulation, molecular dynamics modelling, Voronoi analysis) were applied to elucidate the atomic structure of Ni–Zr and Cu–Zr alloys in glassy and crystalline states and to explain differences in the glass-forming abilities of the Ni₆₄Zr₃₆ and Cu₆₅Zr₃₅ compositions. Both glasses show similar strong topological ordering, but it is established that the degree of chemical ordering is much more pronounced in Ni₆₄Zr₃₆ glass than in Cu₆₅Zr₃₅ glass. The short-range atomic order and topology in the glassy and crystalline structures are remarkably different, and these differences are presumed to hinder crystal nucleation and growth, hence promoting glass formation upon fast cooling of the Ni₆₄Zr₃₆ and Cu₆₅Zr₃₅ liquid alloys. The larger differences observed for the Cu₆₅Zr₃₅ alloy in glassy and crystalline states are suggested to play a decisive role in increasing its bulk-glass-forming ability.     

Enthalpy relaxation in Cu46Zr45Al7Y2 and Zr55Cu30Ni5Al10 bulk metallic glasses by differential scanning calorimetry (DSC)

Structural relaxation process in Cu₄₆Zr₄₅Al₇Y₂ and Zr₅₅Cu₃₀Ni₅Al₁₀ bulk metallic glasses during annealing below the glass transition temperature T_g was investigated by differential scanning calorimetry (DSC). The features of enthalpy relaxation are sensitive to both annealing temperature and annealing time. For a given annealing time t_a, the results indicated that the relaxation time t_a decreases with increasing the annealing temperature T_a, in good agreement with results relative to other bulk metallic glasses. Additionally, the enthalpy relaxation behaviour of the bulk metallic glasses appears independent on the cooling rate used before the physical aging experiments, i.e. on the initial as-cast state. The recovered enthalpy evolution of the bulk metallic glasses is well described by the Kohlrausch–Williams–Watts (KWW) exponential relaxation function as ΔH(T_a) = ΔH_eq{1 ? exp[?(t_a/τ)^β]}. Kohlrausch exponent β and enthalpy relaxation time τ are sensitive to the composition of the bulk metallic glasses. Finally, the influence of different heating treatment processes on the enthalpy relaxation in the bulk metallic glasses is presented and shows that this phenomenon is mainly reversible. The structural relaxation behaviour is interpreted by free volume model and quasi-point defects model. Kinetic fragility parameters m in Cu₄₆Zr₄₅Al₇Y₂ and Zr₅₅Cu₃₀Ni₅Al₁₀ bulk metallic glasses are 72 and 69, respectively, indicating therefore that these alloys are intermediate glasses.Crystallization process was also investigated by DSC experiments. According to the Kissinger model, corresponding activation energy is 3.18 eV in Cu₄₆Zr₄₅Al₇Y₂, and 3.19 eV in Zr₅₅Cu₃₀Ni₅Al₁₀, respectively.     

Effects of a small amount of Si or Ge addition on stability and hydrogen-induced internal friction of Ti34Zr11Cu47Ni8 glassy alloys

Effects of a small amount of Si or Ge addition on stability and hydrogen-induced internal friction behavior of Ti₃₄Zr₁₁Cu₄₇Ni₈ glassy alloys have been investigated by X-ray diffraction, thermal analysis and temperature dependence of internal friction. It is found that the addition of 1 at.% Si, 2 at.% Si or 1 at.% Ge is effective to stabilize the glassy state and that Si is more effective than Ge. The peak internal friction of the single glassy phase alloy increases with increasing hydrogen content below about 20 at.% H. It is found that (Ti₃₄Zr₁₁Cu₄₇Ni₈)₉₉Si₁ glassy alloys have lower peak internal friction than the Ti₃₄Zr₁₁Cu₄₇Ni₈ glassy alloys, while (Ti₃₄Zr₁₁Cu₄₇Ni₈)₉₈Si₂ and (Ti₃₄Zr₁₁Cu₄₇Ni₈)₉₉Ge₁ glassy alloys have much higher peak internal friction. It should be noted that a (Ti₃₄Zr₁₁Cu₄₇Ni₈)₉₈Si₂ glassy alloy containing 14.4 at.% H shows high internal friction, Q⁻¹ of about 4 × 10⁻². The peak temperature of the single glassy phase alloys decreases with increasing hydrogen content below about 20 at.%. It should be noted that the addition of an extremely small amount of Si is effective to increase the peak temperature of the single glassy phase alloys. The relationship between the tensile strength and specific damping capacity indicates that the hydrogenated (Ti₃₄Zr₁₁Cu₄₇Ni₈)₉₈Si₂ glassy alloys have almost the same potential for a damping material as crystalline Mn–Cu–Al and Cu–Al–Ni alloys and hydrogenated Zr–Cu–Al glassy alloys.     

The crystal structure of HfZrP

The crystal structure of HfZrP has been determined using single crystal X-ray diffraction data. This compound crystallizes in the orthorhombic space group Cmmm (No.65), with a=19.004(3), b=29.372(4), c=3.565(1) Å and the Zr₂P structure type. The Hf and Zr atoms are disordered on one site with total occupancy of 1.0. X-ray powder patterns indicate that (Hf_xZr_1−x)₂P alloys consist of single phase (Zr₂P-type),two phases and single phase (Hf₂P-type) corresponding to 0≤x≤0.5, 0.5<x<0.8 and 0.8≤x≤1.0, respectively.     

Study of serrated flow and plastic deformation in metallic glasses through instrumented indentation

The plastic deformation behavior and serrated flow in seven bulk metallic glass (BMG) systems were investigated through instrumented indentation. These materials include Ce₆₅Al₁₀Ni₁₀Cu₁₀Nb₅, Mg₆₅Cu₂₅Gd₁₀, Pd₄₃Ni₁₀Cu₂₇P₂₀, Cu₆₀Zr₂₀Hf₁₀Ti₁₀, Pt_57.5Cu_14.7Ni_5.3P_22.5, Ni₆₀Nb₃₇Sn₃ and Fe₄₃Cr₁₆Mo₁₆C₁₅B₁₀ BMGs, which show a glass transition temperature (T_g) ranging from 360 to 908 K at a heating rate of 0.33 K/s. Remarkable difference in deformation behavior was found among these BMGs in the load–depth curves during nanoindentation. Prominent serrations are observed in Mg-, Pt- and Pd-based BMGs with medium T_g during the loading process, whereas no distinct serrated flow was found in Ce-, Ni- and Fe-based BMGs with quite low or high T_g. The subsurface plastic deformation regions after indentation were investigated using depth-sensing microindentation to characterize the shear band feature developed in various BMG systems. The size of the shear band upset is found to be larger in the alloys with lower T_g. The effect of T_g on the operation of shear bands and the serrated flow behavior in various BMG systems were discussed.     

Mechanical relaxations of a (Zr77.5Ti22.5)55(Ni48Cu52)21.25Be23.75 amorphous alloy studied using dynamic mechanical analysis

The dynamic mechanical properties of a (Zr_77.5Ti_22.5)₅₅(Ni₄₈Cu₅₂)_21.25Be_23.75 amorphous alloy were investigated by frequency-dependent elastic moduli and isothermal multi-frequency measurements. The frequency-dependent loss modulus showed a relaxation behavior resulting from a glass transition, and the variation of the peak frequency was related to the Arrhenius equation. Isothermal multi-frequency measurement data were used to construct the master curves of the elastic moduli and tan δ by applying the time-temperature superposition principle. The temperature dependence of the shift factor was found to follow the Arrhenius relationship, and the activation energies for the low temperature relaxation and glass transition were approximately 156.6kJ/mol and 554kJ/mol, respectively. The glass transition temperature (T _g) was manifested by the crossover region of the shift factor dependence, and from the relationship between the shift factors and the temperature aboveT _g), the fragility index of this alloy was estimated.     

Embrittlement of Zr-based bulk metallic glasses

Embrittlement of Zr_46.75Ti_8.25Cu_7.5Ni₁₀Be_27.5 and Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 bulk metallic glasses (BMGs) is studied after annealing at temperatures below and above the glass transition temperature T_g for time scales comparable with structural relaxation and crystallization. The effect of annealing on the bending ductility, the isoconfigurational elastic constants, the structure and the thermal stability is examined. The embrittlement during sub-T_g annealing originates from structural relaxation and can be reversed by subsequently annealing for a short duration above T_g. The embrittlement kinetics correlate with the structural relaxation. However, only a fraction of relaxation time at a given temperature (<T_g) is sufficient to embrittle the BMG significantly. Above T_g, plasticity is retained for annealing far beyond the relaxation time but, instead, embrittlement is caused by crystallization. The magnitude of the decrease in Poisson’s ratio is insufficient to explain the severe embrittlement within the framework of a critical value as previously suggested.     

Microstructure and properties of cold consolidated amorphous ribbons from (NiCu)ZrTiAlSi alloys

Amorphous ribbons of compositions (Ni₅₆Cu₂)Zr₁₈Ti₁₃Al₆Si₅ and (Ni₃₆Cu₂₃)Zr₁₈Ti₁₄Al₅Si₄ were consolidated by high pressure torsion (HPT) at room temperature. In the HPT experiments a 6 GPa pressure and two turns were applied. Samples in the form of discs, 6–7 times thicker than the ribbons and about 10 mm in diameter were achieved. The minimal deformation for the homogenous consolidation was estimated to be in the range of 400%. XRD showed that the microstructure was dependent on the composition. The sample with high Cu content remained amorphous while the sample with low Cu content revealed some crystallization. DSC experiments allowed a comparison of the glass transition temperature T_g and crystallization process of the amorphous ribbon and HPT sample which were different. The glass transition temperature T_g of the amorphous HPT sample of (Ni₃₆Cu₂₃)Zr₁₈Ti₁₄Al₅Si₄ composition decreased. For both alloys the nanohardness and the elastic modules showed decrease for cold consolidated samples in comparison to the ribbons.     

Enthalpy recovery and free volume relaxation in a Zr44Ti11Ni10Cu10Be25 bulk metallic glass

We report on the free volume of the Zr₄₄Ti₁₁Ni₁₀Cu₁₀Be₂₅ bulk metallic glass in terms of its enthalpy recovery and volumetric relaxation below the glass transition temperature, T_g. Glassy samples are isothermally annealed below T_g using differential scanning calorimetry and the resulting enthalpy recovery, ΔH_r, is measured upon re-heating into the supercooled liquid region. Volumetric changes below T_g are measured isothermally using Thermo-Mechanical Analysis. The total changes in the relative free volume, Δν_f/ν_m, between the initially glassy state and the equilibrium liquid are calculated from the volumetric relaxation. The measured values of ΔH_r and Δν_f/ν_m correlate well within the framework of free volume theory and a linear relationship is found between the two.