Study of mechanical deformation of Zr55Cu30Al10Ni5 bulk metallic glass through instrumented indentation

Instrumented sharp indentation experiments using both conical and Vickers diamond pyramidal indenters were carried out to study deformation characteristics of Zr₅₅Cu₃₀Al₁₀Ni₅ bulk metallic glass. Finite element simulations of instrumented indentation were also performed to formulate an overall constitutive response. Comparing the experimentally obtained results with the finite element predictions, it can be stated that mechanical deformation of the bulk metallic glass can be described well by both Mohr-Coulomb and Drucker-Prager constitutive criteria. Using these criteria, the extent of material pile-up observed around the indenter was also estimated very well.     

Wettability and reactivity between B4C and molten Zr55Cu30Al10Ni5 metallic glass alloy

The isothermal wetting and spreading behaviors of molten Zr₅₅Cu₃₀Al₁₀Ni₅ metallic glass alloy on B₄C substrates were studied using a modified sessile drop method at 1133–1253 K in a high vacuum. A distinct reaction layer consisting of ZrB₂ and ZrC_x was produced at the interface and displayed good wettability with the molten alloy. The entire spreading kinetics could be characterized by four representative stages: (i) an initial rapid spreading presumably driven by adsorption of the active Zr atoms at the solid–liquid interface, (ii) a quasi-linear and (iii) a linear spreading stage controlled by the chemical reaction between Zr and B₄C in both cases, and (iv) an approach-to-equilibrium stage with precipitation of crystals in the liquid. An increase in temperature promotes the wetting and reaction. In view of the reasonable wettability and reactivity, there is a potential for preparing Zr-base bulk metallic glass matrix composites reinforced by in situ ZrC–ZrB₂ hybrid ceramic particulates using B₄C as a reaction agent by way of an infiltration synthesis technique.     

Precipitation of icosahedral quasicrystalline phase in metallic Zr65Al7.5Ni5Cu17.5Re5 glass

Recently, the precipitation of an icosahedral quasicrystalline phase (I-phase) in metallic Zr₆₅Al_7.5Ni₁₀Cu_12.5M₅ (M=Pd, Pt, Au and Ag) glasses, which were obtained by adding noble metals to the well-known metallic Zr₆₅Al_7.5Ni₁₀Cu_17.5 glass, was reported. In the present work, the crystallization process of a metallic Zr₆₅Al_7.5Ni₅Cu_17.5Re₅ glass, which was obtained by adding non-noble metal Re to Zr₆₅Al_7.5Ni₁₀Cu_17.5, was studied. Two exothermic peaks were observed in the differential scanning calorimetry curve of the metallic glass, of which the low temperature one corresponds to the precipitation of an I-phase. The present result demonstrates that the addition of Re is effective in promoting the precipitation of I-phase, in addition to the previously reported noble metals (Pd, Pt, Au and Ag). The atomic radii of these elements are limited to the range of 0.137 to 0.144 nm, implying that atomic size is a significant factor.     

Cooling rate effects on the microstructure and phase formation in Zr51Cu20.7Ni12Al16.3 bulk metallic glass

A detailed transmission electron microscope (TEM) study has been conducted to investigate the microstructures of the Zr₅₁Cu_20.7Ni₁₂Al_16.3 metallic glass formed at different cooling rates. It has been found that the most competitive crystalline phase to the amorphous structure is an oxygen-stabilized FCC NiZr₂-type phase, which in turn acts as the leading phase to trigger the formation of other crystalline phases in the slow-cooled alloy.     

Laser cladding of Zr65Al7.5Ni10Cu17.5 amorphous alloy on magnesium

Laser cladding of amorphous alloy Zr₆₅Al_7.5Ni₁₀Cu_17.5 on magnesium substrate was conducted using the blown powder method. The thickness of the coating was about 1.5 mm. The resulting microstructure, wear resistance and corrosion resistance of the coating were studied. The results of the XRD and TEM analyses showed that up to a depth of 1.1 mm, the coating had an amorphous structure, and no apparent crystalline structures were found. The coated specimen exhibited wear and corrosion resistance superior to that of the uncoated specimen: the wear loss was significantly reduced, some thirteen-fold; and the corrosion current was lowered by three orders of magnitude.     

Nanoscale amorphous “band-like” structure induced by friction stir processing in Zr55Cu30Al10Ni5 bulk metallic glass

Friction stir processing (FSP) is successfully applied in Zr-based bulk metallic glass in this study. In the FSP specimen obtained, large defects and cracks are not present in the FSP region. The microstructure in the friction zone (FZ) exhibited an amorphous “band-like” structure with widths of 10-45 nm and a small number of nanoscale crystalline particles were observed along the “band-like” structure. We concluded that the nanoscale amorphous “band-like” structure obtained in this study is nanoscale shear bands. From this result, FSP is expected to be a useful method of processing bulk metallic glass with nanoscale shear bands to investigate the influence of shear bands on the deformation behavior of bulk metallic glass.     

Vickers indentation tests in a Zr62.55Cu17.55Ni9.9Al10 bulk amorphous alloy

Vickers indentation tests were conducted on a Zr_62.55Cu_17.55Ni_9.9Al₁₀ bulk amorphous alloy to investigate the evolution of shear bands and its plastic deformation dimension via a bonded interface technique. Under all indentation loads, the plastic deformation is accommodated through semi-circular and radial shear bands. The plastic deformation dimension increases with increasing the indentation loads. A simplified λ = C(P)^0.5 model was put forward to predict and estimate the plastic deformation dimension characterized by shear bands in the subsurface. For the Zr_62.55Cu_17.55Ni_9.9Al₁₀ amorphous alloy, C is about 15.314 µm/N^0.5. The normalized shear band zone is independent to the indentation load.     

First investigations on twin-rolled Zr59Cu20Al10Ni8Ti3 bulk amorphous alloy by mechanical spectroscopy

Zr₅₉Cu₂₀Al₁₀Ni₈Ti₃ is one among compositions of ZrCu-based alloys giving bulk amorphous material by cooling from the melt. Twin-roll casting enabling samples suitable for our inverted torsion pendulum has been processed in strips of about 0.60 mm thick.

Low temperature IF measurements have been conducted on a specimen from room temperature to −120 °C at different heating and cooling rates. IF spectra exhibit peaks at around −40 °C (cooling) and −10 °C (heating) which are sensitive to heating rates and to the number of cycle (heating and cooling). DSC measurements have also been performed to help interpret the phenomena linked to the IF peaks.     

Compressive fracture of Zr55Al10Ni5Cu30 bulk amorphous alloy at high temperatures

The fracture behavior of the Zr₅₅Al₁₀Ni₅Cu₃₀ bulk amorphous alloy under uniaxial compression at high temperatures has been investigated. At room temperature, the fracture occurred along the maximum shear plane which declined by 45° to the direction of the applied load, and a crack with serrated edge appeared on the ridge of the veins at the fracture surface for the Zr₅₅Al₁₀Ni₅Cu₃₀ bulk amorphous alloy. At high temperatures, the compressive fracture surface of the Zr₅₅Al₁₀Ni₅Cu₃₀ bulk amorphous alloy became much rougher than that at room temperature and steps appeared on the fracture surface. With increasing temperature, a different pattern from the vein-like morphology appeared on the fracture surface, which is very similar to the lava-flow. This type of fracture pattern is most likely due to the adiabatic heating created by plastic flow.     

Corrosion behavior of Zr41.2Ti13.8Ni10Cu12.5Be22.5 bulk metallic glass in various aqueous solutions

In this study electrochemical corrosion behavior of Zr_41.2Ti_13.8Ni₁₀Cu_12.5Be_22.5 bulk metallic glass (BMG) in various aqueous solutions (3.5% NaCl, 1 N HNO₃, H₂SO₄ and HCl) in order to compare with 316L stainless steel were thoroughly investigated. Scanning electron microscopy (SEM) was used to evaluate the influence of corrosion on the surface topography in immersion specimens to examine where the corrosion pits initiated. Corrosion rate of Zr_41.2Ti_13.8Ni₁₀Cu_12.5Be_22.5 BMG in 3.5% NaCl solution was ∼0.6 mpy and its excellent corrosion resistance can be concluded. Polarization and SEM results also vouched a remarkable corrosion resistance of Zr_41.2Ti_13.8Ni₁₀Cu_12.5Be_22.5 BMG in 3.5% NaCl aqueous solution in comparison with 316L stainless steel.     

Zr55Al10Ni5Cu30非晶合金晶化相转变的价电子结构分析

基于EET理论,计算了F-Zr₂(Ni,Cu)和tI-Zr₂Cu及tI-Zr₂(Cu,Ni)相的价电子结构,用最强键键合力n₁、结构单元总成键能力F和单位成键能力F_v分析了F-Zr₂Ni亚稳相向tI-Zr₂Cu型稳定相的转变过程。研究发现:F-Zr₂Ni的n^{F-Zr₂Ni₁值比tI-Zr₂Cu的ntI-Zr₂Cu₁值大115.36%,FF-Zr₂Ni_v值比tI-Zr₂Cu的FtI-Zr₂Cu_v值大34.03%;F-Zr₂(Ni0.3,Cu0.7)的nF-Zr₂(Ni0.3,Cu0.7)₁值比tI-Zr₂Cu的ntI-Zr₂Cu₁值大0.36%,FF-Zr₂(Ni0.3,Cu0.7)_v值比tI-Zr₂Cu的FF-Zr₂Ni}_v值大1.25%; tI-Zr₂(Cu0.6,Ni0.4)的n^{tI-Zr₂(Cu0.6,Ni0.4)₁值比F-Zr₂(Ni0.3,Cu0.7)的nF-Zr₂(Ni0.3,Cu0.7)}₁值大12.95%, F^{tI-Zr₂(Cu0.6,Ni0.4)_v值比F-Zr₂(Ni0.3,Cu0.7)的FF-Zr₂(Ni0.3,Cu0.7)}_v值大14.41%; 从价电子结构角度看,F-Zr₂Ni不能直接转变为tI-Zr₂Cu,F-Zr₂(Ni,Cu)不易分解重构为tI-Zr₂Cu;F-Zr₂(Ni0.3,Cu0.7)可分解并转变为tI-Zr₂(Cu0.6,Ni0.4)。     

Microstructure Evolution of Zr50Cu18Ni17Al10Ti5 Bulk Metallic Glass during Cold-rolling

Zr50Cu18Ni17Al10Ti5 bulk metallic glass has been rolled at room temperature up to 95% in thickness reduction, and the dependence of microstructure on the strain was investigated. With increasing thickness reduction, the full width at half maximum (FWHM) and crystallization enthalpy decrease gradually till 80%, and then increase evidently at 95%. It is revealed that the reversible transition between the ordered and disordered atomic configurations was found in the metallic glass as the deformation proceeds, which is further verified by the high-resolution transmission electron microscopy images. The final microstructure in metallic glass during cold-rolling is the net result of two competing processes between shear-induced disordering and diffusion controlled reordering.     

Influence of quenching rate on the crystallization behaviors of Mg63Ni22Pr15 metallic glass

The influence of the quenching rate (from 5 m/s to 40 m/s) on the crystallization behaviors of melt-spun Mg₆₃Ni₂₂Pr₁₅ metallic glasses has been studied. The isochronal differential scanning calorimeter (DSC) measurement at 20 K/min shows that the transition temperatures increase with the quenching rate, while the parameters of the glass-forming ability keep constant. The kinetics of isothermal crystallization performed at 481 K within the supercooled liquid region is discussed with some nucleation and growth models. The fittings show that with decreasing quenching rate, the quenched-in nucleation becomes more important and even dominant in the crystallization process.     

Zr46Cu46Al7Gd1块体非晶合金氧化过程的光学表征

相比于晶态合金,非晶合金表现出显著不同的氧化行为,其氧化过程受无序原子结构和非平衡状态的影响.为揭示非晶合金的早期氧化过程,需要对其氧化行为进行快速表征.本文以Zr₄₆Cu₄₆Al₇Gd₁块体非晶合金为对象,通过测量光学常数的变化对氧化行为进行表征.与X射线衍射、扫描电子显微镜和热重分析测得的结果相比,光学常数不仅可以反映非晶合金发生明显氧化的起始温度,还可以反映难以用传统方法表征的早期氧化过程.本研究结果说明光学常数是反映氧化行为的灵敏参数,将有助于认识非晶合金氧化过程随温度、时间和组分变化的演化过程.     

Structural evolution of the Ti70Ni15Al15 powders prepared by mechanical alloying

Amorphization and crystallization behaviors of Ti₇₀Ni₁₅Al₁₅ powders during mechanical alloying (MA) and subsequent heat treatments are studied. Amorphous phase that cannot be obtained in the rapidly quenched ribbon is formed in the powders after MA for 60 h. Upon continuous heating of the amorphous powders in DSC, two exothermic events are observed. The first exothermic event corresponds to the crystallization of the amorphous matrix into a supersaturated α-Ti phase of hexagonal close-packed structure. The growth kinetic of the α-Ti phase is sluggish, resulting in the formation of nanostructured α-Ti matrix. The second exothermic event corresponds to the solid state transformation of the meta-stable α-Ti into the equilibrium phases, Ti₂Ni and Ti₃Al. Using the amorphous powders, Ti-based bulk materials with novel microstructures can be developed for structural applications.     

Preparation and crystallization of Ti53Cu27Ni12Zr3Al7Si3B1 bulk metallic glass with wide supercooled liquid region

Ti-based bulk metallic glass (BMG) alloy with the composition of Ti₅₃Cu₂₇Ni₁₂Zr₃Al₇Si₃B₁ was prepared by copper molder casting method and ribbon sample was prepared by melt spinning to compare. The thermal instability of this glass phase was examined by using differential scanning calorimetry (DSC) and differential thermal analysis (DTA). The results revealed that the supercooled liquid region (ΔT_x), glass transition temperature (T_g) and reduced glass transition temperature (T_g/T_m) of the glassy alloy are detected to be 69, 685 and 0.62 K, respectively. The crystallization behavior of the Ti-based glass phase was also investigated by annealing the glass phase at series temperatures above T_g. The annealed microstructures were examined by means of X-ray diffraction experiments. The crystallization process of the BMG can be characterized by metastable crystalline phases at the first crystallization step and further transition to stable crystalline phases at high temperature through metastable crystalline phase.     

Overheating effects on thermal stability and mechanical properties of Cu36Zr48Ag8Al8 bulk metallic glass

A pronounced effect of overheating is observed on the thermal stability and mechanical properties of Cu₃₆Zr₄₈Ag₈Al₈ bulk metallic glass. Higher overheated temperature enhances the thermal stability of bulk amorphous alloys, corresponding to higher specific-heat capacity and the smaller initial defect concentration. And a threshold overheating temperature is found for the fully amorphous structure. Bulk amorphous alloys exhibit good compressive plasticity at small overheat levels, whereas the compressive fracture strength and micro-hardness exhibit a significant increase first and then a slightly decrease. Mechanical properties of BMGs can be tailored in certain extent by controlling the overheated level, which is correlated with free volume and residual stresses.     

Observation of glass transition upon cooling in Pd40Ni10Cu30P20 alloy by DSC

Two-stage cooling experiments were carried out in a differential scanning calorimeter for an untreated bulk amorphous alloy Pd₄₀Ni₁₀Cu₃₀P₂₀. The results showed that the critical cooling rate for glass formation for the alloy was about 50 K/min. The continuous cooling transformation (CCT) curve was constructed based on the cooling experimental results and the critical cooling rate for glass formation subsequently calculated is in excellent agreement. The present results are compared with previous reported results and effects on the critical cooling rate for glass formation are discussed.     

Effect of heating process on fracture behaviors of Wf/Cu82Al10Fe4Ni4 composites

W_f/Cu₈₂Al₁₀Fe₄Ni₄(30) composites and W_f/Cu₈₂Al₁₀Fe₄Ni₄(60) composites were prepared by penetrating casting method. Three-point bending test and dynamic compression test showed that W_f/Cu₈₂Al₁₀Fe₄Ni₄(30) composites possessed higher mechanical properties than W_f/Cu₈₂Al₁₀Fe₄Ni₄(60) composites. Microstructure observation of W_f/Cu₈₂Al₁₀Fe₄Ni₄(30) composites revealed that a small amount of tungsten diffused into the Fe–Ni solid solution precipitated on the surface of tungsten fibers. The damage occurred mainly within the tungsten fibers after three-point bending test and dynamic compression test in W_f/Cu₈₂Al₁₀Fe₄Ni₄(30) composites, indicating that the composites possessed high interface strength. Dislocation density was high and stacking faults emerged in W_f/Cu₈₂Al₁₀Fe₄Ni₄(30) composites after dynamic compression. Microstructure observation of W_f/Cu₈₂Al₁₀Fe₄Ni₄(60) composites revealed that long strip of tungsten grains occurred at the edge of tungsten fibers, within which damage mainly emerged after three-point bending test, indicating that strength of the edge of tungsten fibers was low in W_f/Cu₈₂Al₁₀Fe₄Ni₄(60) composites. The fibrous structure of tungsten fiber was coarse or even disappeared in some areas, and dislocation density was low in W_f/Cu₈₂Al₁₀Fe₄Ni₄(60) composites after dynamic compression.     

On the room-temperature deformation mechanisms of lamellar-structured Fe30Ni20Mn35Al15

A eutectic alloy Fe₃₀Ni₂₀Mn₃₅Al₁₅ (in at.%), consisting of B2 (ordered b.c.c.) and f.c.c. phases, was prepared by directional solidification, drop-casting or quenching from 1623 K in order to obtain different lamellar sizes and morphologies. The hardness of the individual phases, measured using nanoindentation, was 4.38 ± 0.20 GPa for the B2 phase and 2.72 ± 0.14 GPa for the f.c.c. phase. The roles of these phases in mechanical deformation were investigated. In both the drop-cast and the quenched alloy, which contained refined discontinuous lamellae, the B2 lamellae showed little sign of plastic deformation and simply behaved as obstacles to moving dislocations. The yield strength increased with refinement of the lamellae, whereas the ductility decreased. In contrast, tensile tests performed along the growth direction of the directionally solidified alloy, which contained lamellae several microns wide aligned with the growth direction, showed that the f.c.c. lamellae experienced plastic deformation by glide of 〈1 1 0〉 dislocations, whereas the B2 lamellae fractured elastically into ∼30 μm long segments. Tearing at interfaces occurred for B2 lamellae inclined to the tensile axis.