Devitrification of Zr-Ni-Al-Cu-Ti(Nb,Ta) glassy alloys

The devitrification behavior and phase formation in Zr_65-55Ni₁₀Al_7.5Cu_7.5Ti_5-10(Nb,Ta)_5-10 metallic glass have been studied by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. It has been found that mutual addition of Ti and Ta/Nb benefits the formation of nanoscale icosahedral phase in the glassy phase on heating and the oxygen content in the alloy makes significant influence on the devitrification behavior of these alloys. At the same time in Nb-bearing alloys and alloys containing 5 at.% Ta icosahedral phase was found to coexist with crystalline one.     

Bulk Glassy Alloys: Historical Development and Current Research

This paper reviews the development of current research in bulk glassy alloys by focusing on the trigger point for the synthesis of the first bulk glassy alloys by the conventional mold casting method. This review covers the background, discovery, characteristics, and applications of bulk glassy alloys, as well as recent topics regarding them. Applications of bulk glassy alloys have been expanding, particularly for Fe-based bulk glassy alloys, due to their unique properties, high glass-forming ability, and low cost. In the near future, the engineering importance of bulk glassy alloys is expected to increase steadily, and continuous interest in these novel metallic materials for basic science research is anticipated.     

金属间化合物与大块玻璃合金的形成

综述了大块玻璃合金液态结构,结晶动力学行为,玻璃态形成机制以及其与金属间化合的关系,应用二元合金液态结构的理论模型,分析与推测,分析与推测大块玻璃合金的液相结构,解释了大块玻璃合金的特殊热力学性质和大块玻璃态形成机制,介绍了Ｚｒ基大块玻璃合金的一些研究结果。     

Kinetics of thermal devitrification (crystallization) of FexCryBz glassy alloys

Devitrification process of four glassy Fe _x Cr _y B _z alloys of different composition was investigated by both methods, differential-scanning-calorimetry and X-ray diffraction. It is shown that the crystallization process proceeds via one or two stages depending on the alloy composition. Kinetic parameters for the crystallization process (activation energy, rate constant, frequency factor) as well as the crystallization enthalpy are determined for all four alloys that are used. It is shown that exothermal maxima on DSC thermograms correspond to the crystallization process when polycrystalline Fe₂B and FeB phases are formed.     

Synthesis of amorphous niobium-nickel alloys by vapor quenching

Thin film samples (10–15 μm thick) of niobium-nickel alloys in the composition range Nb-5 to 95 at. % Ni were vapor quenched bu r.f. sputtering onto fused quartz substrates held at a temperature of 180°C. It was found that fully glassy alloys were synthesized in the composition range Nb-30 to 85 at. % Ni, which is 2.5 times larger than that reported for splat-quenched alloys. Crystallization temperatures exhibited a maximum near the deepest eutectic in this alloys system and are comparable with those of splat-quenched materials. Nearest neighbor distances are in agreement with results for splat-quenched materials while “effective particle sizes” are consistently smaller. These results are discussed relative to the mechanism by which glassy alloys are synthesized during vapor quenching and the structure of the glassy state.     

Nano-devitrification of glassy alloys

This overview paper summarizes a large number of data connected with nano-devitrification of metallic glassy and amorphous alloys on heating which form nanoscale crystalline or quasicrystalline particles. In some alloys this effect leads to formation of the nanocomposites with enhanced mechanical properties compared to fully glassy and crystalline alloys.     

Crystallization and Corrosion Resistance of (Fe0.78Si0.09B0.13)100-xNix （x=0,2 and 5） Glassy Alloys

The crystallization of the (Fe0.78Si_0.09B0.13)100-xNix glassy alloys （x=0, 2 and 5） has been investigated by X-ray diffraction （XRD） and differential scanning calorimeter （DSC）. Corrosion resistance analyses have been carried out using electrochemical measurements and corrosion products have been analyzed by scanning electron microscopy （SEM）. The experimental results show that the addition of Ni can promote the nucleation of α-Fe, retard the decomposition of the metastable borides, and alter the crystallization mode of the present Fe-based glassy alloys. The lattice constant （a0Fe） of α-Fe in the annealed samples shows a decreasing trend with increasing annealing time. The Ni addition can improve the corrosion resistance of the as-quenched Fe-based glassy alloys in H2SO4, NaCl and NaOH solutions. The results indicate that Ni can promote the diffusion of Si atoms during quenching and annealing processes.     

大块非晶形成合金液体的热物理性能与玻璃形成能力

大块非晶合金由于其优异的性能而成的具有很大潜力的新材料，而合金的玻璃形成能力（GFA）的大小是能否获得大块非晶合金的根本所在。因此研究合金的玻璃形成能力成为材料科学领域重要的研究课题。本文从液体热物理性能出发，结合在这些方面所做的研究工作对大块非晶形成合金液体的玻璃形成能力做了一些探讨，希望对大块非晶合的研究有所裨益。     

Superconductivity of Ni-Nb-Zr-H glassy alloys with nanoclusters

We investigated the hydrogen effect on superconductivity in the (Ni0.36Nb0.24Zr0.40)(100-x)H(x)(0 < or = x < or = 6.4) glassy alloys with nanoclusters, as a function of temperature. The resistivity of these alloys started to drop from onset temperature of around 9.5 K. The (Ni0.36Nb0.24Zr0.40)98.6H1.6 showed zero resistance at 2.1 K. However, the application of a magnetic field > 4.6 T arrested the drop of resistivity, showing the existence of superconductivity of type II. The maximum onset temperature of 11.3 K was observed at 4.4 at% H. The superconducting behavior of the glassy alloys would be associated with electron pair transport along zigzag paths, which link the shortened atomic -Ni-Ni-Ni- array in the Zr5Ni5Nb3 clusters, and tunneling among the clusters.     

THE EFFECT OF VACUUM ANNEALING ON THE ABILITY OF ANTIOXIDATION OF GLASSY Cu-Zr ALLOYS

用电阻测量、X 光衍射和DTA、DSC 技术,研究了在低于玻璃化温度Tg 的真空退火对Cu_(50)Zr_(50)、Cu_(55)Zr_(45)、Cu_(60)Zr_(40)非晶合金抗氧化性能的影响。研究表明,真空退火中形成的极薄的优质的ZrO_2覆盖膜能有效阻挡氧化,大大提高上述非晶合金在晶化前和晶化后的抗氧化能力;在更高温度,由于ZrO_2膜的破裂和脱落,使其抗氧化能力丧失,但是破碎的ZrO_2膜仍然对这时的氧化有重要作用。     

具有大过冷液相温度区间的Cu基大块非晶合金的制备和机械性能

利用铜模铸造方法制备了具有大过冷液相温度区间的Cu-Zr-Ti-Ni系高强度Cu基大块非晶合金,对于Cu55Zr55Ti15Ni5合金,最大直径达5mm.过冷液相区温度范围ΔTx达45.48～70.98 K.Cu基玻璃合金棒表现出非常高的机械性能和明显的塑性,对于Cu50Zr25Ti15Ni10、Cu55Zr25Ti15Ni5和Cu54Zr22Ti18Ni6合金,压缩断裂强度分别达2155MPa、2026MPa和1904MPa,维氏硬度分别达674、678和685.加入Co元素扩大了CuZr-Ti-Ni系合金的ΔTx,Cu50Zr22Ti18Ni6Co4合金的ΔTx高达74.5K.     

Investigation of mechanical properties and devitrification of Cu-based bulk glass formers alloyed with noble metals

The mechanical properties, glass-forming ability, supercooled liquid region and devitrification behaviour of the Cu–Zr–Ti–(Pd, Ag, Pt and Au) bulk glass formers were studied by using a mechanical testing machine, X-ray diffraction, transmission electron microscopy, differential scanning calorimetry and isothermal calorimetry. The bulk glassy alloys of diameter 2 mm were formed in the Cu₅₅Zr₃₀Ti₁₀Pd₅ and Cu₅₅Zr₃₀Ti₁₀Ag₅ alloys while Cu₅₅Zr₃₀Ti₁₀Au₅ bulk alloy showed mixed glassy and crystalline structure. No glassy phase was formed in the Cu₅₅Zr₃₀Ti₁₀Pt₅ bulk alloy whereas the glassy phase was formed in all of the ribbon samples prepared by rapid solidification. The studied alloys except for the Pt-bearing one have slightly increased compressive fracture or yield strength values compared to ternary Cu₆₀Zr₃₀Ti₁₀ glassy alloy. At the same time Pd and Au addition significantly expand the supercooled liquid region of Cu–Zr–Ti glassy alloy and increase Young’s modulus. A nanoicosahedral phase is primarily formed in the Cu₅₅Zr₃₀Ti₁₀(Pd,Au)₅ glassy alloys in the initial stage of the devitrification process by nucleation and three-dimensional diffusion-controlled growth. Nearly the same quasilattice constant obtained in the Cu₅₅Zr₃₀Ti₁₀(Pd,Au)₅ alloys illustrates the same type of the icosahedral phase in these alloys. However, no icosahedral phase was found in the Cu₅₅Zr₃₀Ti₁₀(Ag,Pt)₅ alloys.     

Investigation of mechanical properties and devitrification of Cu-based bulk glass formers alloyed with noble metals

The mechanical properties, glass-forming ability, supercooled liquid region and devitrification behaviour of the Cu–Zr–Ti–(Pd, Ag, Pt and Au) bulk glass formers were studied by using a mechanical testing machine, X-ray diffraction, transmission electron microscopy, differential scanning calorimetry and isothermal calorimetry. The bulk glassy alloys of diameter 2 mm were formed in the Cu₅₅Zr₃₀Ti₁₀Pd₅ and Cu₅₅Zr₃₀Ti₁₀Ag₅ alloys while Cu₅₅Zr₃₀Ti₁₀Au₅ bulk alloy showed mixed glassy and crystalline structure. No glassy phase was formed in the Cu₅₅Zr₃₀Ti₁₀Pt₅ bulk alloy whereas the glassy phase was formed in all of the ribbon samples prepared by rapid solidification. The studied alloys except for the Pt-bearing one have slightly increased compressive fracture or yield strength values compared to ternary Cu₆₀Zr₃₀Ti₁₀ glassy alloy. At the same time Pd and Au addition significantly expand the supercooled liquid region of Cu–Zr–Ti glassy alloy and increase Young's modulus. A nanoicosahedral phase is primarily formed in the Cu₅₅Zr₃₀Ti₁₀(Pd,Au)₅ glassy alloys in the initial stage of the devitrification process by nucleation and three-dimensional diffusion-controlled growth. Nearly the same quasilattice constant obtained in the Cu₅₅Zr₃₀Ti₁₀(Pd,Au)₅ alloys illustrates the same type of the icosahedral phase in these alloys. However, no icosahedral phase was found in the Cu₅₅Zr₃₀Ti₁₀(Ag,Pt)₅ alloys.     

Estimation on Magnetic Refrigeration Material （Gd1-xREx）5Si4 （RE=Dy, Ho）

A systematic (Gd1-xREx)5Si4 (RE=Dy, Ho) alloys are investigated to estimate their magnetocaloric effect.The Curie points of (Gd1-xREx)Si4 alloys can tunable from 266 K to 336 K when RE=Dy, Ho; x=0～0.35 and 0～0.15, respectively, and decrease nearly linearly with increasing x. These alloys keep orthorhombic structures Ge5Sm4 and exhibit second order transition when they experience in a change magnetic field at about Curie when magnetic field changes 0～2 T. The adiabatic temperatures changes (△Tad) of these alloys at Curie points are larger than 1 K in a field change 0～1.4 T, the curve of △Tad is wide as that of Gd. The relative cooling power is about 0.8～0.9 J/cm3 when field changes 0～2 T, 55% of that of Gd. Comparing with Gd5(Si1-xGex)4, these alloys do not contain expensive element Ge, so that their cost are lower than the former. Because they could work at temperature region 260～340 K due to their Curie points can be tuned, which is an advantage comparing with Gd, these alloys are potential magnetic refrigerants working in a magnetic refrigerator with a low magnetic field at room temperatures.     

The thermoelastic behaviour of semicrystalline and of glassy poly(ether-ether-ketone)

A thermoelastic evaluation, based on simultaneous measurements of the mechanical work and of the concomitant heat of deformation by a stretching micro calorimeter, was performed on semicrystalline and glassy PEEK. The objective of this study was to utilize the sensitive technique to detect differences that would account for observed effects of micro structure on mechanical performance. A clear difference was detected beyond a 0.6% strain, where the behaviour of glassy PEEK began to exhibit inelastic features such as yielding and plastic deformation. This difference between the glassy and the semicrystalline polymers was considered the reason for the superior mechanical fatigue and fracture properties produced by the latter micro structure.     

Thermal Stability of Amorphous Hydride Mg_(50)Ni_(50)H_(54) and Mg_(30)Ni_(70)H_(45)

The thermal stability of amorphous ternary hydrides Mg_(50)Ni_(50)H_(54) and Mg_(30)Ni_(70)H_(45) and their corre-sponding amorphous binary alloys Mg_(50)Ni_(50) and Mg_(30)Ni_(70) were studied with X-ray diffraction(XRD) and differential scanning calorimetry(DSC). Samples of the amorphous alloys were preparedby mechanical alloying and the amorphous hydrides were obtained by charging the alloys with gas-eous hydrogen at 3.0 MPa and 423 K. It was found that the amorphous hydrides released most oftheir hydrogen before the crystallization of the essentially hydrogen depleted amorphous alloy. Thecrystallization temperature of amorphous Mg_(50)Ni_(50)H_(54) elevated and that of amorphousMg_(30)Ni_(70)H_(45) did not change in relation to the original binary amorphous alloy. This is very excep-tional for amorphous hydrides. The reason for the effects of hydrogen absorption/desorption on thecrystallization of amorphous alloys was discussed.     

Correlation between the thermal change of resistance and the process of devitrification of glassy titanium based alloys

Investigations were carried out on the temperature dependence of electrical resistance of glassy alloys based on titanium: 52% Ti, 39% Cu, 8% Ni and 1 wt.% Si (A); 39% Ti, 51% Cu, 10 wt.% Ni (B); 60% Ti, 13% Cu and 27 wt.% Ni (C); 50% Ti, 45% Cu and 5 at.% Ni (D), from room temperature up to 30–40 K above the crystallization temperature. It was shown that the temperature coefficients of resistance in the glassy state region are negative for alloys A, C and D and positive for alloy B. After crystallization, with all alloys except C, coefficients are positive. A clear correlation exists between the stepwise process of crystallization of the glassy state and the change of electrical resistance. Each step of devitrification is followed by a discontinuous change (decrease) of the resistance which is caused by the increase of the mean free path of electrons because of the growth of the ordering of the alloy structure.     

Cu基块体非晶合金的研究进展

综述了国内外最近几年来Cu基大块非晶合金的研究现状,介绍了Cu基大块非晶合金在玻璃形成能力、机械性能、耐腐蚀性能、非晶-纳米晶合金方面的研究成果,最后探讨了Cu基大块非晶合金未来的研究重点.     

Dependence of Amorphous Formation Ability on Intrinsic Parameters in Dy-Gd-Co-Al Alloys

A series of Dy(Gd)-based bulk amorphous alloy rods were prepared by water-cooled copper mold method. Thermal stability and structure of Dy-Gd-Co-Al alloys were investigated by differential scanning calorimetry and X-ray di-raction,respectively.The results show that the Dy-Gd-Co-Al alloys have good glass-formation ability,and the Dy31Gd25Co20Al24 alloy can be readily cast into full glassy rods up to 5 mm in diameter.The glass-forming ability of multicomponent alloys was greatly dependent on their chemical in...     

Gd–Ni–Al bulk glasses with great glass-forming ability and better mechanical properties

A series of Gd–Ni–Al ternary glassy alloys with the maximum diameter of 4 mm were obtained by common copper mold casting. The maximum values of the reduce glass transformation temperature (T _g/T _m) and the distance of supercooling region ΔT _x of these alloys in this study were 0.648 and 50 K, respectively. The compressive fracture strength (σ _f) and Young’s modulus (E) of Gd–Ni–Al glassy alloys were 1,240–1,330 MPa and 63–67 GPa, respectively. The magnetic properties of these BMGs were investigated. The Gd–Ni–Al bulk glassy alloys with great glass forming ability and good mechanical properties are promising for the future development as a new type of function materials.