微量元素对Cu-Zr-Al块体金属玻璃形成能力及力学性能的影响

研究微量元素Ag、Ti、Ga、Ni和Sn对Cu55Zr38Al7铜基块体金属玻璃形成能力及力学性能的影响。结果表明:添加2%(摩尔分数)的Ag、Ti或Ga均可以提高Cu55Zr38Al7合金的玻璃形成能力;用6%的Ag替代Cu,玻璃棒的临界直径可从2 mm增加到4 mm;因此,替代化学性质相似的元素或者扩大合金系的原子尺寸范围对提高玻璃形成能力具有显著的效果;然而,添加微量元素均不同程度地降低Cu-Zr-Al金属玻璃的硬度。断口表面形貌显示;微量相似元素替代影响基体在压缩过程中剪切带的繁殖;在微量元素替代的伪四元铜基块体金属玻璃中,2%Ti和2%Ag替代可分别获得最大压缩强度2 163 MPa和最大压缩应变8.7%。因此,通过添加微量元素可以调谐金属玻璃的玻璃形成能力和力学性能。     

Effect of metalloid elements on magnetic properties of Fe-based bulk metallic glasses

In this work, we successfully prepare Fe₈₀(P, C, B)₂₀ bulk metallic glasses (BMGs) with the different content of P, C, B by combining fluxing treatment and J-quenching technique, and the effects of the metalloid elements (P, C, B) on the thermal stability and magnetic properties of the present Fe₈₀(P, C, B)₂₀ BMGs are investigated systematically. It is found that the replacements of P or B by C and P by B enhance the thermal stability of Fe₈₀(P, C, B)₂₀ BMGs. The substitutions of B for C or P and C for P result in the increase of both the saturation magnetization and the Curie temperature of Fe₈₀(P, C, B)₂₀ BMGs.     

Glass formation,thermal and mechanical properties of ZrCuAlNi bulk metallic glasses

The glass forming ability, thermal and mechanical properties of some ZrCuAlNi bulk metallic glasses were analyzed. The compositions of the alloys were theoretically determined with the dense packing and kinetic fragility index models. Cylindrical and conical ingots were produced by copper mould suction-casting under Ar atmosphere. The conical ingots were characterized by means of X-ray diffraction in order to determine the glassy structure. It was found that both alloys have a critical glassy diameter, D_c, of 3 mm. Thermal behaviours were investigated by differential scanning calorimetry at heating rates of 0.5, 0.67 and 0.83 K/s. The gamma parameter γ, supercooled liquid region ΔT_x, and reduced glass transition temperature T_rg, of the experimentally obtained glasses indicated high glass forming ability. The glassy compositions showed a fragility index of ～40 GPa. The compression test of the investigated alloys was carried out at a strain rate of 0.016 s^?1, obtaining a elastic modulus of ～83 GPa, total deformation of ～5%, yield strength of 1.6 GPa and hardness of 4 GPa. It was concluded that the use of the dense packing and kinetic fragility index models helped to predict glass-forming compositions in the family alloy investigated.     

Glass formation and magnetic properties of Fe-based metallic glasses fabricated by low-purity industrial materials

Fe-based metallic glasses of (Fe₇₄Nb₆B₂₀)_100-xCr_x (x=1, 3, 5) with high glass forming ability (GFA) and good magnetic properties were prepared using low-purity raw materials. Increasing Cr content does not significantly change glass transition temperature and onset crystallization temperature, while it enhances liquidus temperature. The addition of Cr improves the GFA of the (Fe₇₄Nb₆B₂₀)_100-xCr_x glassy alloys compared to that in Cr-free Fe-Nb-B alloys, in which the supercooled liquid region (ΔT_x), T_rg and γ are found to be 50–54 K, 0.526–0.538, and 0.367–0.371, respectively. The (Fe₇₄Nb₆B₂₀)_100–xCr_x glassy alloys exhibit excellent soft magnetic properties with high saturation magnetization of 139–161 A·m²/kg and low coercivity of 30.24–58.9 A/m. Present Fe-Nb-B-Cr glassy alloys exhibiting high GFA as well as excellent magnetic properties and low manufacturing cost make them suitable for magnetic components for engineering application.     

Fe-based bulk metallic glass composites without any metalloid elements

Glass-formation of Fe-based bulk metallic glasses (BMGs) and their composites is strongly dependent on their metalloid content. A good Fe-based glass former usually needs a metalloid content of ～20 at.% or above; however, the high content of the metalloids usually has side-effects on the performance of the alloys. In this paper, we developed a series of metalloid-free Fe-based BMG matrix composites with a diameter of more than 10 mm in the Fe–Co–La–Ce–Al–Cu system. During cooling, phase separation took place, i.e. Fe-rich and Fe-depleted liquids formed. Upon subsequent cooling, the body-centered cubic (bcc)-Fe(Co, Al) solid solution and Ce(Fe, Co)₂ intermetallic phase precipitated out of the Fe-rich liquid and the remaining Co–La–Ce–Al–Cu liquid was eventually vitrified to form the amorphous matrix. Due to elemental partitioning, it was found that, for a given Fe content, there exists an optimum compositional range for Co and Ce so that a large fraction of the glassy matrix can form. In addition, the final microstructure of the current composites was strongly dependent on the cooling rates applied: excessively fast cooling rates restricted the diffusion and precipitation of the Fe atoms, which reduced formation of the glassy matrix.     

Saturated magnetization and glass forming ability of soft magnetic Fe-based metallic glasses

Saturated magnetization (B_s) and glass forming ability (GFA) are two important attributes of soft magnetic metallic glasses (MGs), both of which are affected by the local short-range order in amorphous structures. Based on the notion of free electron transfer, we propose a set of simple rules for the calculation of B_s from the chemical composition of soft magnetic Fe-based alloys. Through the comparison of the experimentally measured B_s and theoretically calculated B_s, we show that the soft magnetic Fe-based MGs can be generally categorized into two types: one has its GFA correlated positively with the ferromagnetic weakness and the other has its GFA correlated negatively with the ferromagnetic weakness. Finally, the structural mechanisms behind these correlations are discussed.     

Phase formation and mechanical properties of Cu-Zr-Ti bulk metallic glass composites

The effect of the type of the crystalline phase and its volume fraction on the mechanical property of Cu₅₀Zr_50-xTi_x alloys (x = 0-10) bulk metallic glass composites has been investigated in this study. Up to 6 at% of Ti, B19’ phase particles distributed in the glassy matrix, while at 8 and 10% of Ti, B2 phase particles are retained in the glass matrix due to suppression of the eutectoid transformation of B2 phase and by avoidance of martensitic transformation of B2 into B19’. The volume fraction of crystalline phase is strongly dependent on the cooling rate. The larger volume fraction of the crystalline phases results in the lower yield stress, the higher plastic strain, and the more pronounced work hardening behavior. At the crystalline volume fraction below ~30%, the variation of the yield strength can be described by the rule of mixture model (ROM), while at the crystalline volume fraction higher than ~50% by the load-bearing model (LBM). At the crystal fractions between 30 and 50%, there is a yield strength drop and a transition from the ROM to the LBM. This transition is due to the formation of the crystalline structural framework at higher crystal fraction.     

Microstructure and mechanical properties of metallic glass/metallic glass composites

We report microstructure and mechanical properties of bulk metallic glass (BMG)/metallic glass composites fabricated by mechanical alloying with subsequent consolidation process. The microstructural investigations of a bulk composite reveal that a submicron-scale layered structure with irregular interfaces consists of three amorphous phases in tornado-like morphology. Based on these results, poor plasticity of the metallic glass composite can be understood possibly due to the irregular interfacial morphology of the submicron-scale heterogeneous amorphous phases throughout the materials.     

合金元素对Cu-Ag合金组织、力学性能和电学性能的影响

采用冷变形及中间热处理方法制备了具有双相纤维复合组织的Cu-Ag合金，研究了成分与组织，性能的关系，随着变形程度的增加，合金强度上升而电导率下降，合金中Ag含量由6％增加至24％时，铸态组织中第二相数量明显增多，变形后能够形成更多的Ag纤维复合相，因而合金强度明显上升，在Cu-6%Ag中添加1％Cr元素可以使合金基体得到进一步强化并在一定程度上细化了Ag纤维相，也可使合金度得到显著改善，在Cu－6%Ag-1%Cr合金中添加微量稀土元素可使Ag纤维分布更为弥散，因而使合金在不降低导电性的同时增加强度，尤其在高强度范围内这种作用更为显著。     

Formation and mechanical properties of bulk Cu-Ti-Zr-Ni metallic glasses with high glass forming ability

Bulk amorphous Cu52.5Ti30Zr11.5Ni6 and Cu53.1Ti31.4Zr9.5Ni6 alloys with a high glass forming ability can be quenched into single amorphous rods with a diameter of 5 mm, and exhibit a high fracture strength of 2 212 MPa and 2 184 MPa under compressive condition, respectively. The stress—strain curves show nearly 2% elastic strain limit, yet display no appreciable macroscopic plastic deformation prior to the catastrophic fracture due to highly localized shear bands. The present work shows clearly evidence of molten droplets besides well-developed vein patterns typical of bulk metallic glasses on the fracture surface, suggesting that localized melting induced by adiabatic heating may occur during the final failure event.     

Structure and magnetic properties of Fe-based powders prepared by mechanical alloying

FeSiAlCr alloy powders were prepared by mechanical alloying, the milling time were 20 h, 40 h, 60 h and 80~h, respectively. Powders morphology was studied by SEM. Microstructure of powders milled for various times were analyzed by XRD. The complex permittivity and complex permeability of four powders were tested in the frequency range from 0.5 to 18 GHz, and their microwave absorption properties were analyzed. It was found that the particle size of powders milled for 80~h was less than 2μm. Silicon and aluminum atoms were dissolved into the crystal lattice of iron, and chromium atoms can form alloy with iron atoms. The minimum peak value of reflectivity can reach to -11.3 dB at the frequency of 4.3 GHz for 80 h milling powders, and the other one was -6 dB at 16.5 GHz.     

Effect of elements with positive enthalpy of mixing on mechanical properties of bulk metallic glasses

Samples of (Cu₄₆Zr₄₆Al₈)_100?xZ_x metallic glass forming alloys with diameters 2–6 mm were prepared by injection casting. The effect of minor amounts of elements Z = Gd, Co and Re with positive enthalpy of mixing within the Gd–Zr, Cu–Co and Cu–Re terminal systems was compared. The addition of Gd up to x = 2 slightly enhances the glass forming ability, Co reduces the critical diameter of bulk metallic glass formation, whereas even for small fractions of Re bulk samples were crystalline, but only amorphous splats can be prepared. Both Gd and Co diminish the crystallization temperature T_x with respect to the Cu₄₆Zr₄₆Al₈ master alloy, but in Re-bearing splats T_x is increased. Alloying with optimum amounts of Gd and Co up to x = 2 leads to plastic deformability of rods, 2 and 3 mm in diameter, in comparison with the brittle Cu₄₆Zr₄₆Al₈ bulk metallic glass.     

Effect of Al addition on formation and mechanical properties of Mg-Cu-Gd bulk metallic glass

The effect of partial substitution of Al for Cu on the glass forming ability（GFA） and mechanical properties of Mg65Cu25-xAlxGd10 （x=0, 1, 3 and 5, molar fraction, %） alloys were studied by X-ray diffi-actometry（XRD）, differential scanning calorimetry（DSC） and uniaxial compression test. The result reveals that GFA of the alloys changes slightly with increasing x from 0 to 3, and then abruptly decreases with x increasing up to 5. The plasticity can be greatly improved with appropriate substitution of Cu by A1 （3%, molar fraction） in Mg65Cu25Gd10 bulk metallic glass, and the resultant fracture strength, total strain to failure, and plastic strain are 898 MPa, 2.19% and 0.2%, respectively.     

Microstructure and mechanical properties of Zr-Cu-Al bulk metallic glasses

Zr49Cu46Al5 and Zr48.5Cu46.5Al5 bulk metallic glasses（BMGs） with diameter of 5 mm were prepared through water-cooled copper mold casting. The phase structures of the two alloys were identified by X-ray diffractometry（XRD）. The thermal stability was examined by differential scanning calorimetry（DSC）. Zr49Cu46Al5 alloy shows a glass transition temperature, Tg, of about 689 K, an crystallization temperature, Tx, of about 736 K. The Zr48.5Cu46.5Al5 alloy shows no obvious exothermic peak. The microstructure of the as-cast alloys was analyzed by transmission electron microscopy（TEM）. The aggregations of CuZr and CuZr2 nanocrystals with grain size of about 20 nm are observed in Zr49Cu46Al5 nanocrystalline composite, while the Zr48.5Cu46,5Al5 alloy containing many CuZr martensite plates is crystallized seriously. Mechanical properties of bulk Zr49Cu46Al5 nanocrystalline composite and Zr48.5Cu46.5Al5 alloy measured by compression tests at room temperature show that the work hardening ability of Zr48.5Cu46.5A15 alloy is larger than that of Zr49Cu46Al5 alloy.     

Influence of alloying elements on mechanical properties of Al-Li plates

The effect of alloying elements such as Cu, Mn and Zr on the mechanical properties of the Al-Li plates was studied, and the grain structure, crystallographic texture and precipitates were also investigated. It is found that the element Zr has a two-fold effect on the anisotropy of mechanical properties; the addition of element Mn can reduce the crystalline texture and the anisotropy of Al-Li plates. However, the effect of Cu element appears less pronounced.     

Y元素添加对CuZrAl块体金属玻璃的结构和力学性能的影响(英文)

研究添加Y元素对CuZrAl块体金属玻璃的结构和力学性能的影响。结果表明,添加Y元素提高CuZrAl体系的玻璃形成能力,而且由于添加Y元素可以降低该体系的结合能,从而降低其断裂强度。Cu45Zr48Al7块体金属玻璃的断裂表面主要呈脉状,而Cu46Zr42Al7Y5块体金属玻璃的断裂表面则很平滑。TEM观察表明,Cu45Zr48Al7的微观结构为非晶基体中含有纳米相,然而Cu46Zr42Al7Y5块体金属玻璃为全非晶结构。     

Effects of electrolyte ph on the electrochemical behavior of Fe-based bulk metallic glass

The effects of electrolyte pH on the electrochemical behavior of Fe-based bulk metallic glass with a composition of Fe_68.8C_7.0Si_3.5B₅P_9.6Cr_2.1Mo_2.0Al_2.0 were investigated at an ambient temperature. The results indicate that corrosion behavior is strongly dependent on the pH values. The corrosion current densities and capacitance values decrease with an increase in pH values in acidic electrolytes, while the opposite tendencies are obtained in alkaline electrolytes. While the corrosion product of the outer layer in low pH conditions is an amorphous structure, crystalline ferric oxide is obtained in the electrolyte with pH=14. The electrochemical behavior is discussed on the basis of the results of electrochemical and microstructural analysis.     

Formation and mechanical properties of Ni-free Zr-based bulk metallic glasses

Glass formation and mechanical properties of Zr–Al–Co–Cu–Ag bulk metallic glasses (BMGs) were investigated. The glass-forming ability (GFA) of Zr₅₅Al₂₀Co₂₀Cu₅ alloy is significantly improved with minor addition of Ag, indicating by the impressive increase of the critical diameter of glass formation from 5 mm for Zr₅₅Al₂₀Co₂₀Cu₅ to 16 mm for (Zr_0.55Al_0.20Co_0.20Cu_0.05)₉₇Ag₃ and (Zr_0.55Al_0.20Co_0.20Cu_0.05)₉₅Ag₅ alloys. The Zr–Al–Co–Cu–Ag BMGs exhibit high compressive strength of 2160–2280 MPa and distinct plasticity of 0.6–2.5%. The Zr-based BMGs with outstanding GFA and mechanical properties as well as low-level cytotoxicity elements are expectative for industrial and biological applications.     

Role of yttrium in glass formation of Ti-based bulk metallic glasses

Starting with Zr of two different purities, Ti-based bulk metallic glasses (BMGs) with a nominal composition of Ti40Zr25Cu12Ni3Be20 were prepared. The effect of the addition of yttrium at levels of 0.2 at.%, 0.4 at.%, 0.5 at.%, 0.6 at.%, and 1 at.% on the glass forming ability (GFA) of the alloy has been investigated by means of metallography, X-ray diffraction, and differential scanning calorimetry. Experimental data in-dicates that high impurity content dramatically reduces the glass forming ability. Microalloying with 0.5 at.% Y is effective in suppressing the crystalline phase formation and alleviating the detrimental effect of oxygen in the low-purity alloy. On the contrary, in the alloy contain-ing high-purity element, the effective yttrium addition is less than 0.4 at.%. The results indicate that the beneficial effect of the optimum dopants is mainly due to scavenging the oxygen impurity via the formation of innocuous phase.