Devitrification and phase transformation of (Ti0.5Cu0.25Ni0.15Sn0.05Zr0.05)100 − xMox metallic glasses

The thermal stability and the crystallization behavior of the melt-spun ribbons of (Ti_0.5Cu_0.25Ni_0.15Sn_0.05Zr_0.05)_100 − xMo_x metallic glasses were investigated in terms of the thermal analysis. The crystallization during the glass devitrification and the solidification of the liquid for the alloys exhibit a strong similarity.     

Composition dependence of the microstructure and mechanical behavior of Ti–Zr–Cu–Pd–Sn–Nb bulk metallic glass composites

Ti-based bulk metallic glass composite alloys Ti₅₆Zr₆Cu_19.8Pd_8.4Sn_1.8Nb₈, Ti₆₄Zr₄Cu_13.2Pd_5.6Sn_1.2Nb₁₂ and Ti₆₈Cu_13.2Pd_5.6Sn_1.2Nb₁₂ were designed to obtain the microstructure composing of β-Ti dendrites and glassy matrix. The compressive and three-point bending properties were investigated. It was found that the actual microstructure of the Nb-added alloys consisted of primarily precipitated β-Ti dendrites, network-like glassy matrix, and extra island-like Ti₂Cu intermetallic phase with different volume fractions. Under compressive loading, all the Nb-added alloys presented higher yield strength combined with remarkably increased plasticity. Under bending condition, however, the alloys Ti₅₆Zr₆Cu_19.8Pd_8.4Sn_1.8Nb₈ and Ti₆₄Zr₄Cu_13.2Pd_5.6Sn_1.2Nb₁₂ with higher Ti₂Cu volume fractions became completely brittle. The alloy Ti₆₈Cu_13.2Pd_5.6Sn_1.2Nb₁₂ could keep its plastic deformability due to the decreased Ti₂Cu volume fraction. Compressive deforming behavior of the Nb-added alloys was determined by the ductile β-Ti phase and glassy matrix, nevertheless, bending deforming behavior of the alloys was determined by the volume fraction and distribution of the brittle intermetallics.     

Effect of Ni on glass-forming ability of Cu-Ti-based amorphous alloys

1 Introduction Recently, a number of bulk metallic glassy alloys have been reported, such as La-Al-Ni[1], Cu-Ti-Zr-Ni [2, 3], Cu-Ti-Zr-Ni-Be[4, 5], Cu-Ti-Zr-Ni-Si[6?8] and Cu-Ti-Zr-Ni-Sn[9]. Because of the exceptional good glass-forming ability, these mu…     

Investigation of the mechanical properties of Ti-Fe-Sn ultrafine eutectic composites by dendrite phase selection

Microstructural investigation of Ti-Fe-Sn ultrafine eutectic composites reveals that β-Ti primary dendrite in eutectic matrix consists of TiFe and β-Ti for Ti₇₂Fe₂₂Sn₆ alloy. Similarly, the Ti₆₄Fe₃₂Sn₄ alloy and Ti₆₈Fe₂₃Sn₉ alloy consists of TiFe and Ti₃Sn micron-scale primary dendrites uniformly embedded in the TiFe and β-Ti eutectic structure. The β-Ti dendrite was formed in Ti₇₂Fe₂₂Sn₆ alloy, the large number of shear bands propagation and makes multiple steps on the fracture surface. The Ti₃Sn dendrite in Ti₆₈Fe₂₃Sn₉ ultrafine eutectic alloy leads slip bands which induce the work hardening that have important role in plasticity during deformation. On the other hand, TiFe dendrite in Ti₆₄Fe₃₂Sn₄ alloy was presented shear bands bypass and extinction while the propagation of shear bands. These microstructural changes lead to different deformation behavior in primary dendrite. Therefore, it is believed that the mechanical properties of Ti-Fe-Sn alloys could improve due to a different deformation behavior through the minute compositional tuning of Ti-Fe-Sn alloys.     

Effect of Nb addition on microstructure evolution and nanomechanical properties of a glass-forming Ti–Zr–Si alloy

The glass-forming Ti₇₅Zr₁₀Si₁₅ alloy is regarded as a potential material for implant applications due to its composition of non-toxic, biocompatible elements and some interesting mechanical properties. The effects of partial substitution of 15 at.% Ti by Nb on the microstructure and the mechanical behaviour have been investigated by X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray analysis, transmission electron microscopy and nanoindentation techniques. Copper mold casting and melt-spinning methods have been applied to study the influence of the cooling rate on the properties of both alloys, Ti₇₅Zr₁₀Si₁₅ and Ti₆₀Zr₁₀Nb₁₅Si₁₅. As a result of different cooling rates, significant microstructural variations from multiphase crystalline states in cast rods to nanocomposite structures in ribbons were observed. The limited glass-forming ability (GFA) of the Ti₇₅Zr₁₀Si₁₅ alloy results for melt-spun ribbons mainly in nanocomposite structures with β-type nanocrystals being embedded in a glassy matrix. Addition of Nb increases the glass-forming ability. Raising the overheating temperature of the melt prior to melt-spinning from 1923 K to 2053 K yields for both alloys a higher amorphous phase fraction. The mechanical properties were investigated using compression tests (bulk samples) and the nano-indentation technique. A decrease of hardness (H), ultimate stress and reduced Young's modulus (E_r) is observed for Ti₆₀Zr₁₀Nb₁₅Si₁₅ rods as compared to Ti₇₅Zr₁₀Si₁₅ ones. This is attributed to an increase of the fraction of the β-type phase. The melt-spun ribbons show an interesting combination of very high hardness values (H) and moderate reduced elastic modulus values (E_r). This results in comparatively very high H/E_r ratios of >0.075 which suggests these new materials for applications demanding high wear resistance.     

Effect of carbon on formation of mixed solid solutions during mechanochemical synthesis of Ni-Al-Mo-C mixtures and ordering of solutions during heating

Solid solutions Ni(Al, Mo, C) are formed via milling the Ni_2.8Al₁Mo_0.2 and Ni₃Al_0.8Mo_0.2 and graphite-containing Ni_2.8Al₁Mo_0.2C_{(0.25, 0.5)} and Ni₃Al_0.8Mo_0.2C_{(0.25, 0.5)} mixtures. In this case, some amount of Mo remains beyond the solid solution. Graphite added to a starting mixture decreases the Mo solubility and favors the amorphization of solid solutions. The complete amorphization was found for the mixture with the 5 at % C and 5 at % Mo, which was added instead of Ni. The heating of mechanically synthesized (MS) powder alloys leads to the ordering of carbon-free and carbon-containing solid solutions with the formation of the L1₂ and E2₁ structure, respectively. In the course of the ordering of the Ni(Al, Mo, C) solid solutions, Mo and carbon precipitate in the form of the molybdenum carbide (Mo₂C) second phase. The hardness of the MS three-phase Ni-Al-Mo-C solid solutions subjected to hot isostatic pressing is determined by the mass fraction of the formed Mo₂C carbide. It is shown that the carbon content in the multicomponent antiperovskite can be estimated by analyzing the ratio of integral intensities of superlattice reflections I ₍₁₀₀₎/I ₍₁₁₀₎.     

Glass-forming ability and stability of ternary Ni-early transition metal (Ti/Zr/Hf) alloys

Four Ni-bearing Ti, Zr and Hf ternary alloys of nominal composition Zr_41.5Ti_41.5Ni₁₇, Zr₂₅Ti₂₅Ni₅₀, Zr_41.5Hf_41.5Ni₁₇ and Ti_41.5Hf_41.5Ni₁₇ were rapidly solidified in order to produce ribbons. The Zr–Ti–Ni and Ti–Hf–Ni alloys become amorphous, whereas the Zr–Hf–Ni alloy shows precipitation of a cubic phase. The devitrification of all three alloys was followed and the relative tendency to form nanoquasicrystals and cF96 phases analysed. The relative glass-forming ability of the alloys can be explained by taking into account their atomic size difference. Addition of Ni often leads to quasicrystallisation or quasicrystal-related phases. This can be explained by the atomic radius and heat of mixing of the constituent elements. The phases precipitated at the initial stages of crystallisation indicate the possible presence of Frank–Kasper polyhedral structure in the amorphous alloys. Structural analysis reveals that the Laves and the anti-Laves phases have the same polyhedral structural unit, which is similar to the structural characteristics of glass.     

Microstructure and properties of the in situ formed amorphous-crystalline composites in the Fe-Cu-based immiscible alloys

The paper presents microstructures and mechanical properties of the melt-spun Fe₃₀Cu₃₂Si₁₃B₉Al₈Ni₆Y₂ and Fe₄₄Cu₁₈Si₁₃B₉Al₈Ni₆Y₂ alloys. It was found that liquid phase separation of the initially homogeneous melt occurred due to a positive heat of mixing between two major elements. The microstructures of the melt-spun ribbons were composed of the Fe-rich amorphous and the Cu-rich crystalline phases. A significant effect of the melt ejection temperature and the chemical composition (Fe and Cu content) on microstructures of rapidly solidified alloys was revealed. The microstructures of ribbons melt-spun from the miscibility gap region were non-uniform. On the other hand the microstructures of ribbons melt-spun from homogeneous melt temperature region were composed of the spherical precipitates distributed within the matrix. Superior hardness values of the examined ribbons melt-spun from the same temperature were found for the alloy with higher iron content. An increase of the melt-ejection temperature in the homogeneous melt region resulted in hardness decrease in case of the Fe₃₀Cu₃₂Si₁₃B₉Al₈Ni₆Y₂ alloy and its increase for the Fe₄₄Cu₁₈Si₁₃B₉Al₈Ni₆Y₂ ribbons.     

Structure and phase transformations in copper-alloyed rapidly melt-quenched Ni<Subscript>50</Subscript>Ti<Subscript>32</Subscript>Hf<Subscript>18</Subscript>-based alloys with high-temperature shape memory effect

Methods of transmission and scanning electron microscopy, chemical microanalysis, electron diffraction, and X-ray diffraction have been used to carry out the comparative study of the structure and chemical and phase composition of thin ribbons of four quasi-binary alloys (Ni₅₀Ti₃₂Hf₁₈, Ni₄₅Ti₃₂Hf₁₈Cu₅, Ni₃₅Ti₃₂Hf₁₈Cu₁₅, and Ni25Ti32Hf18Cu25) obtained in the amorphous state by rapid quenching from the melt by jet spinning. The critical temperatures of the devitrification and B2 ? B19′ martensitic transformation of the alloys have been determined based on the data of temperature dependences of the electrical resistivity. The specific features of the formation of the ultrafine-grained structure upon the devitrification and of the phase transformations have been studied depending on the heat-treatment regimes and chemical composition of the alloys (concentration of copper atoms).     

Solid State Interaction in Ni-Mo-B System During Mechanical Alloying and Annealing

This work presents the results of a study of Ni_87?x Mo _x B₁₃ alloys (x?=?7, 10 and 14?at.%), which were obtained by mechanical alloying (MA) of elemental powder mixtures in a MAPF-2M high-energy planetary ball mill. The x-ray diffraction analysis and differential scanning calorimetry measurements were used. The single-phase fcc solid solutions of Mo and B in Ni were formed by MA of Ni-Mo-B mixtures of various compositions for 6-8?h. The coherent domain sizes of solid solutions calculated from the x-ray peak widths were 12-14?nm. The exothermic effects on the DSC curves, which corresponded to the phase transformations of supersaturated Ni(Mo,B) solid solutions, were observed during heating of the synthesized alloys. After heating to 700?°C, the alloys contained a fcc Ni(Mo) phase and a metastable hexagonal MoB₄ phase. Thermodynamically stable phase composition of Ni₈₀Mo₇B₁₃ and Ni₇₇Mo₁₀B₁₃ alloys, containing three phases: fcc Ni (Mo), Ni₂₁Mo₂B₆ with cubic lattice and Ni₃B with orthorhombic lattice, was reached after the isothermal annealing at 1000?°C. The ratio between the amounts of these phases in the alloys corresponds to their location in a three-phase area of the Ni-Mo-B equilibrium phase diagram.     

Evolution of the amorphous structure in melt-spun Ti50Ni25Cu25 alloy subjected to high pressure torsion deformation

Peculiarities of structure and mechanical behaviour of amorphous Ti₅₀Ni₂₅Cu₂₅ alloy were the focus of this research. The melt-spun ribbons of amorphous Ti₅₀Ni₂₅Cu₂₅ were subjected to high pressure torsion (HPT) at temperatures of 20–150 °C in order to modify their structure and mechanical behaviour. Some features of obtained HPT-processed samples were compared with initial state with the help of x-ray diffraction (XRD), transmission electron microscopy (TEM) and nanohardness testing. Analysis of structural data and mechanical behaviour allowed us to assume that severe plastic deformation (SPD) processing of melt-spun Ti₅₀Ni₂₅Cu₂₅ alloy might lead to the formation of the structure similar to the new kind of noncrystalline state – “nanoglass” state.     

Experimental Investigation of Phase Equilibria in the Cu–Mo–Ti Ternary System

Phase equilibria of the Cu–Mo–Ti ternary system at 800 and 900 °C have been experimentally investigated using electron probe microanalysis and x-ray diffraction analysis. A ternary intermetallic compound (τ phase) was newly found, exhibiting a homogeneity range at both 800 and 900 °C. Furthermore, the nominal as-cast alloys Cu₅₀Mo₁₀Ti₄₀, Cu₃₀Mo₃₀Ti₄₀, Cu₁₅Mo₅₀Ti₃₅, Cu₄₀Mo₃₀Ti₃₀, Cu₁₅Mo₂₀Ti₆₅, Cu₁₅Mo₃₀Ti₅₅, Cu₁₅Mo₂₅Ti₆₀, Cu₄₀Mo₁₀Ti₅₀, and Cu₆₀Mo₅Ti₃₅ presented a common separated microscopic morphology because of the ternary extent of the Cu–Mo binary liquid phase separation. The newly determined phase equilibria may provide essential information to support thermodynamic assessment and development of Cu–Mo-based alloys.     

Martensitic transformation behavior in Ni–Al and Ni–Al–Re melt-spun ribbons

The martensitic transformation behavior was investigated in rapidly solidified (melt-spun) Ni–(34–37)at%Al and Ni–(32–34)at%Al–2at%Re ribbons. The addition of Re increased the temperature for the formation of Ni₅Al₃, hence the martensitic transformations were observed at higher temperatures than those of binary Ni–Al alloys.     

Microstructure,martensitic transformation and mechanical properties of Ni–Mn–Sn alloys by substituting Fe for Ni

The effects of partial substitution of Fe element for Ni element on the structure, martensitic transformation and mechanical properties of Ni_50–xFe_xMn₃₈Sn₁₂ (x=0 and 3%, molar fraction) ferromagnetic shape memory alloys were investigated. Experimental results indicate that by substitution of Fe for Ni, the microstructure and crystal structure of the alloys change at room temperature. Compared with Ni₅₀Mn₃₈Sn₁₂ alloy, the martensitic transformation starting temperature of Ni₄₇Fe₃Mn₃₈Sn₁₂ alloy is decreased by 32.5 K. It is also found that martensitic transformation occurs over a broad temperature window from 288.9 to 352.2 K. It is found that the mechanical properties of Ni–Mn–Sn alloy can be significantly improved by Fe addition. The Ni₄₇Fe₃Mn₃₈Sn₁₂ alloy achieves a maximum compressive strength of 855 MPa with a fracture strain of 11%. Moreover, the mechanism of the mechanical property improvement is clarified. Fe doping changes the fracture type from intergranular fracture of Ni₅₀Mn₃₈Sn₁₂ alloy to transgranular cleavage fracture of Ni₄₇Fe₃Mn₃₈Sn₁₂ alloys.     

Magnetic and magnetocaloric properties in melt-spun and annealed Ni42.7Mn40.8Co5.2Sn11.3 ribbons

The Ni_42.7Mn_40.8Co_5.2Sn_11.3 ribbons were prepared by melt spinning. After heat treatment, the martensitic transformation temperature and Curie temperature of austenite of the annealed ribbons increased remarkably. Inverse and direct magnetocaloric properties were investigated in the melt-spun and annealed ribbons. The effective refrigerant capacities for these ribbons were discussed in this paper.     

Laser cladding of eutectic-based Ti-Ni-Al alloy coating on magnesium surface

A Ti_70.3Ni_22.2Al_7.5 alloy, optimized from a basic binary eutectic Ti₇₆Ni₂₄ alloyed with different amounts of Al, was laser-clad on AZ91HP magnesium alloy. The coating mainly consists of β-Ti solid solution and Ti₂Ni intermetallic compound resulting in high hardness, good wear resistance and corrosion resistance. The interface between the clad layer and the substrate has a good metallurgical bonding.     

Annealing effects on the crystallization and shape memory effect of Ti50Ni25Cu25 melt-spun ribbons

As-spun Ti₅₀Ni₂₅Cu₂₅ ribbon is fully amorphous with a lower wavenumber Q_p than the amorphous Ti–Ni alloys owing to its high Cu content. Both crystallization activation energy E_a and onset temperature T_x for Ti₅₀Ni₂₅Cu₂₅ ribbon are lower than those for Ti₅₀Ni₅₀ ribbon, indicating that the former has lower thermal stability. When Ti₅₀Ni₂₅Cu₂₅ ribbon is annealed at 500 °C for 3 min, the initial as-crystallized grains contain a low Cu content and perform a prominent shape memory effect. Through prolonging the annealing time, more grains are crystallized in the ribbon but it becomes more fragile and its recoverable strain decreases. This is due to the increasing Cu content in the crystallized grains. Crystallized Ti₅₀Ni₂₅Cu₂₅ ribbon can exhibit a good shape memory effect only under appropriate annealing conditions.     

Measurement of phase equilibria in Ti-Ni-Sn system

Phase relations of the Ti-Ni-Sn ternary system were investigated via alloy sampling assisted with X-ray diffractometry (XRD) and electron probe micro-analysis (EPMA). A new binary phase with composition of TiSn₄ (molar fraction, %) was detected at 508 K. In addition, a supplementary phase (Ti_1–x–yNi_xSn_y)Ni₃ (τ, AuCu₃-type) was observed at 873 and 973 K. According to the characterised microscopic structure in various annealed alloys, four ternary phases were detected in Ti-Ni-Sn ternary system: TiNiSn, TiNi₂Sn, Ti₂Ni₂Sn and (Ti_1–x–yNi_xSn_y)Ni₃. Additionally, isothermal sections of Ti-Ni-Sn ternary system at 508, 873 and 973 K were constructed. By comparing three isothermal sections, a peri-eutectic reaction, L+TiNi₂Sn→Ni₃Sn₄+TiNiSn, was deduced, which occurs at a temperature between 873 and 973 K. Furthermore, the solubility of Sn in TiNi and Ni in Ti₅Sn₃ was detected.     

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.     

Surface analyses and biocompatibility study of 500 °C oxidized Ni50Ti50 and Ni40Ti50Cu10 shape memory alloys

Ni₅₀Ti₅₀ and Ni₄₀Ti₅₀Cu₁₀ shape memory alloys (SMAs) are oxidized at 500 °C. Considering the surface roughness, the thicknesses of oxide layer and Ni-free layer, the surface Ni concentration, the proper oxidation times for oxidized specimens are found to be 60 min for Ni₅₀Ti₅₀ and 30 min for Ni₄₀Ti₅₀Cu₁₀. Experimental results reveal that the oxidation is diffusion-controlled with its oxide layer containing titanium oxide and that the surface Ni concentration is much lower than the nominal composition. When Ni₅₀Ti₅₀ and Ni₄₀Ti₅₀Cu₁₀ SMAs are oxidized at these times, the latter has better corrosion resistance than the former in Hanks' solution at 27 °C. However, the results of cytotoxicity and cell proliferation assays indicate that the biocompatibility of unoxidized Ni₄₀Ti₅₀Cu₁₀ is worse than that of unoxidized Ni₅₀Ti₅₀, but that of oxidized Ni₄₀Ti₅₀Cu₁₀ ranks as good as that of oxidized Ni₅₀Ti₅₀.