A new Cu–Hf–Al ternary bulk metallic glass with high glass forming ability and ductility

We have discovered a new Cu-based bulk metallic glass (BMG). Although of a simple Cu₄₉Hf₄₂Al₉ ternary composition, the as-cast alloy is a monolithic, uniform BMG with a critical diameter as large as 10 mm. The width of the supercooled liquid region ΔT_x and the reduced glass transition temperature T_rg for this glass are 85 K and 0.62, respectively. In addition to its high glass-forming ability and high density of 11 g/cc, this BMG exhibits high ductility with a compressive plastic strain of 11–13%, making it a good candidate for applications as well as for studies of deformation behavior of Cu-based BMGs.     

Fe-Co-Ni-Zr-Mo-W-B块体非晶合金的玻璃形成能力与热稳定性

采用铜模铸造法,可以制备出直径为3 mm的非晶圆柱棒.结合差热分析、X射线衍射和透射电镜分析测试结果,从动力学和结构学等方面阐述了Ni元素对Fe58Co10-xNixZr10Mo5W2B15(x=0,3,4,5,6,摩尔分数,%)合金系玻璃形成能力和热稳定性的影响.结果表明:Ni元素含量的微量变化可以明显改善Fe58Co10-xNixZr10Mo5W2B15(x=0,3,4,5,6)合金系的玻璃形成能力;当Ni含量达到4%时,Fe58Co6Ni4Zr10Mo5W2B15具有最佳的玻璃形成能力,晶化温度(Tx)、玻璃转变温度(Tg)、过冷液相区宽度(△Tx)、玻璃形成能力判据Trg和y分别为887 K、957 K、70 K、0.590 2和0.400 4.     

Fe-based soft magnetic amorphous alloys with high saturation magnetization above 1.5 T and high corrosion resistance

Fe-rich amorphous alloys with minor-addition of Cr and/or Nb were examined with the aim of developing Fe-based amorphous alloys exhibiting simultaneously high saturation magnetization above 1.5 T and good corrosion properties. Fe₈₂Cr₂B₈P₄Si₃C and Fe₈₂NbB₉P₄Si₃C amorphous alloys were found to exhibit high saturation magnetizations of 1.49 T and 1.57 T, respectively, and rather good corrosion resistance in 3.5 mass% NaCl solution at 298 K. The minor-addition of Cr or Nb enables the formation of amorphous alloy particles without harmful oxide layer by water atomization process which makes these alloys suitable for applications as soft magnetic core materials. The addition of 1 at% Nb improved the corrosion resistance through the increase in E_corr value, which makes easy to reach passive state, and the suppression of pitting corrosion. Besides, it has been proved that the simultaneous addition of Nb and Cr has an effect on forming protective passive film.     

Development of FeNiNbSiBP bulk metallic glassy alloys with excellent magnetic properties and high glass forming ability evaluated by different criterions

Fe₃₈Ni₃₈Nb_2.5B_21.5−x−yP_xSi_y (x, y = 1–8) bulk metallic glassy alloys with high glass forming ability and excellent magnetic properties were developed. Bulk samples with maximum diameters of 3 mm are fabricated by copper mold casting method. The glassy alloys have large ΔT_x of 40–70 K. The alloys exhibit excellent magnetic properties like extremely low H_c of 0.5–0.8 A/m, high μ_e of 1.6–2.85 × 10⁴ and comparatively high B_s of 0.6–0.8 T which changes regularly with the content variations of P, B and Si. By ascertaining applicability of the empirical GFA criterions, T_rg, α, β and γ can be used in evaluating the GFA of FeNiBSiPNb system alloys.     

Cu47Ti34Zr11Ni8块体非晶合金的热稳定性和力学性能

采用差压铸造法成功制备了Cu47Ti34Zr11Ni8块体非晶合金,研究了其热稳定性和力学性能.结果表明:该块体非晶合金的玻璃转变温度Tg=672 K,晶化温度Tx1=735 K,过冷液相区△Tx=63 K,约化玻璃温度Trg=0.575,弯曲断裂强度高达2 350 MPa,断裂前弹性变形量为2.1%,弯曲模量为102 GPa;淬态微米级结晶相的出现使合金的三点弯曲断裂强度下降至1 100 MPa.     

Structure and magnetic characterization of amorphous and crystalline Nd–Fe–Al alloys

Glass formation has been studied in Nd₆₀Fe₃₀Al₁₀ alloy produced by melt-spinning, water quenching and copper mold chill casting. Partially amorphous alloys were obtained by melt-spinning at low wheel speeds of 5 to 15 m/s and by water quenching of a 1-mm diameter rod, while fully amorphous alloys were obtained by melt-spinning at higher wheel speeds of 20 and 30 m/s and chill casting of a 1-mm diameter rod. A high coercivity was observed in the partially amorphous ribbon melt-spun at 5 m/s and water quenched rod, and in the fully amorphous chill cast rod, while low values of coercivity were obtained in fully amorphous ribbons melt-spun at high speeds of 20 and 30 m/s. Crystallization of water quenched and chill cast samples after heat treatment at high temperature resulted in a substantial reduction of the high coercivity. Results of X-ray diffraction indicate that formation of Nd and a ternary Fe–Nd–Al phase with an unknown crystal structure were present after crystallization. TEM results and a magnetic study of the heat treated samples indicate that as long as there is an amorphous phase produced by low cooling rate, the high coercivity remains. The high coercivity of bulk amorphous samples is discussed. The unknown ternary Fe–Nd–Al phase is antiferromagnetic with a Neel temperature at about 260 K.     

Microstructure identification of devitrified Cu–Ti–Zr–Ni bulk amorphous alloy

The microstructures of devitrified Cu–Ti–Zr–Ni bulk amorphous alloy were identified by X-ray diffractometry (XRD) and transmission electron microscope (TEM). XRD and TEM examinations show that the deep eutectic structures of the tested alloy consist of CuTi₂–Cu₁₀Zr₇, Cu₃Ti–CuZr, Cu₃Ti–Cu₁₀Zr₇–CuZr low-order eutectics. Moreover, short-range ordering clusters in the melt with configuration similar to that of Cu₁₀Zr₇ compound may contribute to the glass forming ability of bulk amorphous Cu–Ti–Zr–Ni alloy.     

富铁Fe-Nd-Al系大块非晶合金的制备及其性能

利用普通的铜模铸造制备了一系列富Fe的Fe-Nd-Al块状非晶合金,采用X射线衍射仪、差示量热扫描仪、振动样品磁场仪和Instron万能材料试验机研究了Fe-Nd-Al块状非晶合金的热稳定性、室温磁性和力学性能。结果表明：Fe50Nd35Al15、Fe45Nd40Al15和Fe42.5Nd42.5Al15块状非晶合金的△Tm（△Tm=Tm-Tx）和晶化开始温度（Tx）与熔点（Tm）的比值分别为106、90和64K及0.88、0.90和0.93;其临界尺寸分别为1.5、3和4mm。此外,随Fe含量的减少,大块非晶的非晶形成能力和硬磁性能提高,但其力学性能有所下降。     

Synthesis and characterization of amorphous Zr-based alloys with Ta and W additions

A reference Zr₅₇Cu₂₀Al₁₀Ni₈Ti₅ bulk metallic glass as well as a number of alloys obtained by addition of refractory elements Ta or W (combined with Sn) to the main Zr–Cu–Al–Ni system were elaborated by mould casting, twin roll casting and planar flow casting. The chemical compositions were chosen according to empirical rules, and as combinations of the binary eutectics for strongly interacting elements, taking into account the corresponding enthalpies of mixing. Optical microscopy, X-ray diffractometry, differential thermal analysis, differential scanning calorimetry, scanning electron microscopy and tensile mechanical testing were used to characterize the fully and partially obtained amorphous materials. Correlation of glass forming ability, thermodynamic parameters, crystallization behaviour and mechanical properties with chemical composition and production technology is discussed.     

Surface modification of Zr-based bulk amorphous alloys by using ion irradiation

Surfaces of the [Zr_0.65Cu_0.18Ni_0.09Al_0.08]₉₈M₂ (M = Er and Gd) bulk amorphous alloys were modified by irradiation with energetic singly charged argon (Ar⁺) ions. Samples of both the alloys were irradiated with 2.17 × 10¹⁷ argon ions of 10 keV energy. As cast and ion irradiated samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Mechanical properties like Vicker's hardness, nanohardness, elastic modulus and elastic recovery were measured. Considerable increase in elastic modulus and hardness was observed because of ion irradiation in these alloys. The ion irradiated samples of the [Zr_0.65Cu_0.18Ni_0.09Al_0.08]₉₈Er₂ alloy showed better properties as compared to [Zr_0.65Cu_0.18Ni_0.09Al_0.08]₉₈Gd₂ alloy. CuZr₂ phase was detected in ion irradiated alloys by XRD and confirmed by EDS. The range of Ar⁺ ions was found to be approximately 9.3 ± 5.4 nm in both alloys.     

Chemical diffusion in bulk glass-forming Pd40Cu30Ni10P20 melts

Interdiffusion and self-diffusion of bulk metallic glass-forming Pd–Cu–Ni–P alloys have been investigated above the liquidus temperature at 993 K by the long-capillary method. Good agreement between the calculated partial mixing enthalpies and observed uphill-diffusion was found. The flow direction of uphill-diffusing elements is towards regions with the highest negative heat of mixing.     

Correlation between Poisson ratio and Mohr–Coulomb coefficient in metallic glasses

Yielding in metallic glasses is often described in terms of the Mohr–Coulomb criterion, τ + μσ ≥ τ₀. It suggests that a material yields when a combination of shear (τ) and normal stresses (σ), linked through the friction coefficient (μ), reaches the critical shear stress (τ₀). In this paper, an increase of the friction coefficient for increasing Poisson ratio is foreseen, if the elastic limit observed under uniaxial (tensile or compressive) and shear stresses remain constant. Experimental values of Young and shear moduli and Poisson ratio of metallic glasses have been collected from the literature. Compressive and tensile yield stresses have been also collected and elastic limits have been calculated. The elastic limit observed under compressive stress decreases with increasing Poisson ratio and it appears similar for metallic glasses based on the same metals. The values of the friction coefficient for metallic glasses have been obtained from the fracture angle observed under uniaxial stress (compressive or tensile) and from the ratio between compressive and tensile strength. Experimental data of the friction coefficient appear rather scattered and a clear trend as a function of Poisson ratio cannot be outlined. The increase of toughness of metallic glasses with increasing Poisson ratio has been ascribed to the corresponding reduction of the compressive elastic limit.     

The microstructure of liquid immiscible Fe–Cu-based in situ formed amorphous/crystalline composite

In the microstructures of slowly and rapidly cooled liquid of the immiscible alloy Fe₃₀Cu₃₂Ni₁₀Si₁₃Sn₄B₉Y₂ two distinct regions were observed following arc melting and slow cooling, confirming that liquid/liquid phase separation had occurred. Rapid cooling from a temperature within the liquid immiscibility gap, melt spinning, resulted in an amorphous/crystalline composite, formed from the previously melted Fe- and Cu-rich regions, respectively. Transmission electron microscopic studies of this melt-spun ribbon revealed the glassy nature of the Fe-rich matrix, as well as of the Fe-rich spheres formed within the previously existing Cu-rich liquid.     

Preparation and properties of quaternary CoMoPB bulk metallic glasses

A new series of Co_80−xMo_xP₁₄B₆ (x = 7, 9, and 11 at%) bulk glassy alloys were successfully prepared by a combination method of fluxing treatment and J-quenching technique. The glass-forming ability (GFA) of the obtained Co-based alloys is sensitive to the Mo content substituted for Co, and the maximum attainable diameter for a fully amorphous state can reach 4.5 mm at x = 9. The compressive tests show that the obtained Co-based BMGs exhibit a compressive strength of 3.3–3.9 GPa, but nearly zero compressive plasticity. The new Co-based BMGs possess good soft magnetic properties, and their saturated magnetization values decrease from 47 emu/g (0.45 T) to 14 emu/g (0.14 T) with increasing the content of the Co substitute from 7 at% to 11 at%, which may be attributed to the anti-ferromagnetic coupling between the Mo and Co atoms. Because of their good GFA, high Co content, few constituting elements, and relatively high strength, the obtained Co-based BMGs (especially Co₇₁Mo₉P₁₄B₆ BMG) can be considered promising as starting alloys to develop the new Co-based BMGs for the advanced structural and functional applications.     

Synthesis of copper-based bulk metallic glasses in the ternary Cu–Mg–Ca system

This paper reports the discovery of novel copper-based bulk metallic glasses free of group IV transition metals (Zr, Hf and Ti) in the Ca–Cu–Mg ternary system. Alloys of compositions ranging from Cu-33–55 at.%, Mg-18–36 at.% and Ca-18–36 at.%, located far from eutectic reactions, were found to exhibit high glass-forming ability (up to 8 mm using conventional copper mold casting), high hardness (up to 328H_V) and low densities (2.9–4.0 g/cm³).     

Cast structure and mechanical properties of Zr–Cu–Ni–Al bulk glassy alloys

Homogeneous melting without any nuclei was performed using the cold copper nozzle arc casting furnace and ladle arc-melt type furnace. Casting of a bulk glassy alloy can be achieved by using a copper nozzle arc casting furnace, which eliminates nucleation site (cold spot) for crystallization. Besides, the pouring molten alloy was melted homogeneously by arc heating before casting into the mold, similar to a pseudo float melting state. To produce a bulk glassy alloy sheet, a combination of the ladle arc-melt type furnace and squeeze cast method was used. Using this method, we succeeded in producing Zr₅₀Cu₃₀Ni₁₀Al₁₀ bulk glassy alloys in a rod shape by the former method and in a sheet form by the later method. Tensile strength of the Zr₅₀Cu₃₀Ni₁₀Al₁₀ bulk glassy alloy sheet is about 1900 MPa and the plasticity of the alloy at room temperature is significantly improved by cold rolling.     

冷-热处理对Zr基块体非晶合金结构和性能的影响

传统晶态材料构件或装备在低温环境中会出现可动部分卡死、龟裂、特性改变甚至脆性断裂等现象。低温极端条件如温度突变、高应变速率冲击等对材料性能带来的不利影响严重制约了其在低温极端环境领域的应用。块体非晶合金在低温条件下具有强度更高塑性更好的特殊性能,在极地科考以及航空航天等极端条件下具有极大的应用优势。本文以(Zr_0.6336Cu_0.1452Ni_0.1012Al_0.12)₉₇Tm₃块体非晶合金为研究对象,研究冷-热处理时间对块体非晶合金的结构、力学性能和腐蚀性能的影响。结果表明,当处理时间由30 min延长到90 min时,试样的晶化体积分数从2.3%增加到4.0%,屈服强度由1701 MPa增加到1810 MPa。在3.5 wt.% NaCl溶液中,合金具有较小的自腐蚀电流密度与较大的电化学阻抗,这意味着经冷-热处理后的块体非晶合金具有优异的耐腐蚀性能。本研究为块体非晶合金在低温极端环境领域的应用提供了强有力的理论支撑。     

Electrochemical properties and surface analysis of Cu–Zr–Ag–Al–Nb bulk metallic glasses

The electrochemical properties and surface characteristics of Cu–Zr–Ag–Al–Nb bulk metallic glasses (BMGs) were investigated. The alloys exhibit excellent corrosion resistance after immersion in 1N H₂SO₄ and 1N NaOH. The corrosion rates of the alloys in chloride-ion-containing solutions significantly decrease by alloying with Nb element. The formation of Zr- and Nb-enriched surface films could be responsible for the high corrosion resistance.     

Corrosion resistance of Zr-Al-Ni-Cu（Nb） bulk amorphous alloys

The corrosion resistance of Zr-Al-Ni-Cu(Nb) bulk amorphous alloys was systematically investigated. The experimental results show that the corrosion resistance of Zr-based bulk amorphous alloys can not be considered to be excellent at any situation, whereas it is affected by many factors such as the kind of corrosive medium, solution concentration and the alloy composition. It is found that Zr-Al-Ni-Cu bulk amorphous alloys are seriously corrodedin HCl solution in comparison with their excellent corrosion resistance at other acid, alkali and salt circumstances for passivating. Its resistance ability against the chlorine ion induced pitting corrosion can be greatly improved by the addition of Nb element.     

Zr基大块非晶合金的超塑性成形性能

研究了Zr41.25Ti13.75Ni10Cu125Be22.5大块非晶合金的过冷温度区域范围、时间-温度-转变曲线及其在过冷温度区域的力学行为,并在此基础上,对精密凸轮零件进行了模锻成形实验,分析了不同温度和应变速率对成形结果的影响.结果表明:Zr41.25T13.75Ni10Cu12.5Be22.5大块非晶合金在635.6～710.4 K的过冷区域范围内,其应变速率敏感系数接近1,具有良好的超塑性性能;较理想的超塑性成形温度为653～668 K,应变速率为5.0×10-4～5.0×10-3s-1.在温度为668 K、应变速率为5.0×10-4s-1的工艺条件下,非晶合金的可成形时间大于1000 s,最大流动应力小于70 MPa.