Zr-based Bulk Glassy Alloys Research Articles

The effects of normal load on the dry-sliding, micro-scratch and nanoindentation behaviors of the Zr-based bulk glassy alloys

In this work, the macro-sliding, micro-scratch and nanoindentation behaviors of the Zr55Cu30Al10Ni5 bulk glassy alloy (BGA) were investigated. It was found that the frictional coefficient and wear rate of the BGA in the dry-sliding test increase with the increasing normal load, and the wear mechanism includes abrasive and oxidative wear. The micro-scratch test results show that the plastic deformation of the alloy and the density of shear bands at the edge of scratch scar increase with the increase in normal load. The friction mechanism between the indenter and the BGA shifts from stick-slip friction to ploughing friction and to micro-cutting as the applied normal load elevates. The nanoindentation result reveals that increasing the normal load leads to the plastic deformation accumulation, and the decreasing elastic modulus and hardness, which are related to the increase in the free volume and shear bands during the deformation process.

Nanocrystallization of Cu-Based Bulk Glassy Alloys upon Annealing

Cu-based bulk glassy alloy is a new amorphous system developed recently, which has large glass forming ability and relatively low cost (Dai et al., 2006; Fu et al., 2008; Kim et al., 2006; Malekana et al., 2010; Zhang & Zhang, 2008). The tensile fracture strength is much higher than crystals, reaching up to 2,000 to 2,400 MPa, with certain ductility. And compared to Zr-based and Pd-based bulk glassy alloys, the strength of Cu-based bulk glassy alloy is also on the top, which can be used as ultra-high strength structural materials in the future. Until now, many researchers in the world have done a lot of deep studies on Cu-based bulk glassy alloy. But as structural materials, the plastic property of prepared Cubased bulk glassy alloy which has lowers plastic property than steel materials also need to be improved. Therefore, it’s an urgent problem to improve the plasticity and toughness of amorphous alloys. Based on the research of bulk glassy alloy, in recent years, the research on the composite material of bulk glassy and nanocrystalline alloy has been carried out (Barekara et al., 2010; Liu et al., 2009; Xie et al., 2008; Yang et al., 2009; Zhang et al., 2013). Because when the nanocrystalline evenly distributed in the bulk glassy alloy matrix, the properties of bulk glassy alloy can be further optimized, while maintaining high strength and improving the lower plastic. So the application field of high strength structural material can be expanded. In this paper, Cu-based bulk glassy alloy was prepared through copper mold casting method. The nanocrystallization of bulk glassy alloy was obtained by annealing. The annealing process, microstructure and properties of the nanocrystallization were investigated. The preparation of Cu-based bulk glassy-nanocrystalline alloy composite materials on the basis of the theory and technology pISSN 2287-5123·eISSN 2287-4445 http://dx.doi.org/10.9729/AM.2016.46.1.32

Solidification Atmosphere and Glass-Forming Ability of Engineering Important Fe- and Zr-Based Bulk Glassy Alloys

It is important to clarify the best solidification condition for the formation of bulk glassy alloys in Fe- and Zr-based alloy systems with engineering values. The effectiveness of atmosphere during injection casting changes in the order of O2 > Air > N2 > Ar > He for Fe76Si9B10P5 bulk glassy alloy and 105 Pa He > 105 Pa Ar > 103 Pa Ar > vacuum for Zr65Al7.5Ni10Cu17.5−xPdx (x = 0–17.5 %) bulk glassy alloys. The effectiveness of oxygen atmosphere is due to the suppression of crystal nucleation rate caused by the increase in surface tension of liquid by the dissolution of oxygen in case of Fe-based alloy. In case of Zr-based bulk glassy alloys, the He atmosphere is effective due to the maintenance of cleanness of alloy liquid as well as the increase in the cooling rate. The opposite tendency of the effectiveness for helium atmosphere in the same injection casting is important for further development of the production techniques for large-scale Fe- and Zr-based bulk glassy alloys.

Effect of high-order multicomponent on formation and properties of Zr-based bulk glassy alloys

We examined the formation, thermal stability, mechanical properties and corrosion behavior of a multicomponent Zr55Al10Fe6Co6Ni6Cu6Pd6Ag5 bulk glassy alloy, with the aim of clarifying the effect of high-order multiplication of the number of components on their properties. The bulk glassy alloy rods of 2 and 6mm in diameter were formed by suction casting even at the low total content of typical glass-forming 3-d late transition metals like Co, Ni and Cu. The Vickers hardness is different in the center region and in the outer surface region. The difference seems to reflect the relaxation level of glassy structure. The Young’s modulus and the compressive fracture strength are nearly the same for the base Zr55Al10Ni5Cu30 alloy in spite of the existence of immiscible atomic pairs. Moreover, the multicomponent alloy exhibits better corrosion resistance than that for the base alloy. The glassy phase changes to a supercooled liquid state at 720K and then starts to crystallize at 754K with a single exothermic peak, in contrast to the appearance of a wide supercooled liquid region for the base alloy. The primary crystalline phase precipitates with very short incubation time and very low growth rate, which are different from those for the base alloy. The extremely low growth rate of the crystallites is presumably due to the reduction of diffusivity of late transition metal elements resulting from multiplication. Thus, the high-order multiplication has the features of (1) the maintenance of high glass-forming ability even at the lower Co, Ni and Cu content and in the absence of wide supercooled liquid region, (2) the suppression of the decrease in mechanical strength even in the dissolution of immiscible elements, (3) better corrosion resistance, and (4) low growth rate of the primary precipitates.

Recent Development and Applications of Bulk Glassy Alloys

This paper reviews past developments and the present understanding of the physical and mechanical properties of glass alloys, with an emphasis on recent results obtained since around 1990, together with applications of bulk glassy alloys achieved mainly in Tohoku University. After introducing the fundamental concepts around glassy alloys in the first section, the second section describes the relationships between structural relaxation and the discoveries of glassy alloys with a large supercooled liquid region. The third section reviews the history of bulk glassy alloy development, followed by the bulk glassy alloy systems and their features in the fourth section and the features of a glassy structure in the fifth section. The sixth, seventh, and eighth sections summarize the engineering and standardization of Zr‐based bulk glassy alloys. Section nine and the 10th focus on the glass‐forming ability of Zr‐based hypoeutectic glassy alloys and Cu–Zr–Al–Ag bulk glassy alloys. The mechanical properties of Ni‐based bulk glass alloys at low temperatures are shown in the 11th section, whereas the 12th section describes the formation and properties of Ni‐free Ti‐based bulk glassy alloys. The 13th and 14th sections deal with porous Zr‐based bulk glassy alloys including spherical pores and commercialized Fe‐based glassy alloys, respectively, whereas the 15th section reviews supercoold liquid forming. Finally, applications for Zr‐, Ti‐, and Fe‐based glassy alloys are described in the 16th section. In conclusion, the 17th section attempts to assess the present knowledge of the structure and physical properties and identify some outstanding problems for future work.

Relaxation Behavior of Zr-Cu-Al Ternary Bulk Glassy Alloy Studied by Using Positron Annihilation Techniques

Zr-based bulk glassy (BG) alloys show high tensile strength and a high Charpy impact value. In this study, the free volume changes for the hypoeutectic Zr60Cu30Al10 BG alloy during isothermal annealing below glass transition temperature (Tg) have been investigated by positron annihilation lifetime and coincidence Doppler broadening (CDB) measurements. The positron lifetime of hypoeutectic and eutectic BG alloys is almost the same, although the atomic volume ratio, estimated by the density for the eutectic BG alloy is different from that for the hypoeutectic BG alloy. The CDB spectra show a marked difference between eutectic and hypoeutectic BG alloys; that is, the spectrum of the hypoeutectic BG alloy is closes to that of Zr metal than that of the eutectic BG alloy. This result exhibits that the elemental fraction of Zr atoms around free volume in hypoeutectic BG alloy is greater than that in eutectic BG alloy. The CDB ratio profiles for the hypoeutectic BG alloy during annealing shows no appreciable change. The same trend was observed in the eutectic BG alloy.

High Glass-Forming Ability and Unusual Deformation Behavior of New Zr-Cu-Fe-Al Bulk Metallic Glasses

A new series of bulk metallic glasses were developed by addition of Fe into the ternary Zr60Cu30Al10 alloy. Although Fe-Cu element pair shows distinct immiscibility with a large positive heat of mixing, substitution of Fe for Cu significantly improves the glass-forming ability of the ternary Zr60Cu30Al10 alloy. The critical diameter for glass-formation increases from 8 mm for Zr60Cu30Al10 alloy to 20 mm for Zr60Cu25Fe5Al10 and Zr62.5Cu22.5Fe5Al10 alloys. As compared with the ternary Zr60Cu30Al10 alloy, the new quaternary Zr-Cu-Fe-Al alloys show lower liquidus temperatures. The Zr60Cu25Fe5Al10 and Zr62.5Cu22.5Fe5Al10 alloys, the best BMG-formers in this alloy system, are found to locate very near a Zr-Cu-Fe-Al eutectic point. The new Zr-Fe-Cu-Al bulk metallic glasses exhibit high strength of about 1700 MPa. The plastic strain increases from 7.8% to 11.3% with increasing the content of Fe from 0 to 12.5%. The finding of a Ni-free Zr-based bulk glassy alloy with the extremely high glass-forming ability is expected to extend the future application of bulk metallic glasses.

Zr-based bulk glassy alloy with improved resistance to stress corrosion cracking in sodium chloride solutions

In order to evaluate stress corrosion cracking (SCC) susceptibility of Zr-based bulk glassy alloys and develop the BGAs with low susceptibility to SCC, the SCC behaviour of Zr 50Cu 40Al 10, Zr 50Cu 30Al 10Ni 10 and hypoeutectic Zr 70Cu 6Al 8Ni 16 BGAs in various environments including sodium chloride solution has been investigated using a slow strain rate technique at an initial strain rate of 5 × 10 −6 s −1. It is found, for the first time, that the Zr 70Cu 6Al 8Ni 16 BGA has no susceptibility to SCC in a 0.5 M NaCl solution. On the other hand, Zr 50Cu 40Al 10 and Zr 50Cu 30Al 10Ni 10 BGAs are highly susceptible to SCC in the NaCl solution, although they are not susceptible to SCC in de-ionized water, phosphate buffer, 0.5 M Na 2SO 4 and 0.5 M NaNO 3 solutions. The possible cause of the high susceptibility to SCC in the NaCl solution for the Zr 50Cu 40Al 10 and Zr 50Cu 30Al 10Ni 10 BGAs is discussed.

Free volume in Zr-based bulk glassy alloys studied by positron annihilation techniques

The eutectic Zr50Cu40Al10 bulk glassy (BG) alloys, which have a good glass forming ability, have been investigated for various properties, such as toughness, electronic resistivity and so on. Recently, the hypoeutectic Zr60Cu30Al10 BG alloys have been paid attention, because they exhibit no degradation of ductility and toughness after the isothermal annealing below the glass transition temperature (Tg). Although the toughness correlates with the free volume to be considered, the free volume of the hypoeutectic BG alloy has not been assessed in detail so far. In order to study the free volume in each BG alloy, therefore, positron annihilation lifetime and coincidence Doppler broadening (CDB) measurements have been performed for Zr60Cu30Al10 (hypoeutectic) and Zr55Cu35Al10 (middle-composition) and Zr50Cu40Al10 (eutectic) BG alloys. The value of the positron lifetime for hypoeutectic BG alloy is virtually the same. Additionally, the CDB ratio curve for hypoeutectic alloy dose not match that for eutectic alloy in an electron momentum region around 0.015 m0c, indicating that the fraction of Zr atoms around the free volume in hypoeutectic BG alloy is greater than that in eutectic BG alloy. Moreover, the CDB results show that the local structure around free volume for hypoeutectic BG alloy is different from that for eutectic BG alloy.

Formation, Thermal Stability, and Mechanical Properties of Glassy Zr<SUB>60</SUB>Al<SUB>10</SUB>Ni<SUB>10</SUB>Cu<SUB>20</SUB> Alloy Rods with Diameters of 18 and 20 mm

Bulk glassy alloy rods of diameters 18 and 20mm were formed during the tiltcasting of Zr 60 Al 10 Ni 10 Cu 20 . A further increase in the rod diameter to 22 mm resulted in the formation of a mixed structure with approximately 60 vol% glassy phase and 40 vol% crystalline phase, which comprised the central region of the transverse cross-section of the alloy rod. The glass transition temperature (Tg), onset temperature of crystallization (T x ), and liquidus temperature (T 1 ) were measured to be 666 K, 768 K, and 1153K, respectively, and the resultant ΔT x (= T x - Tg), Tg/T 1 , and γ (= T x /(Tg + T 1 )) values were 102 K, 0.578, and 0.422, respectively. The high glass-forming ability of supercooled liquids is attributed to the high resistance of the liquids against crystallization due to the large ΔT x . and high Tg/T 1 and γ values. For the alloy rod of diameter 20 mm, the Young's modulus, yield strength, elastic strain, and plastic strain under a uniaxial compressive load are 80 GPa, 1820 MPa, 0.022, and 0.060, respectively; the plastic strain of the rod with diameter 20 mm is greater than that (0.04) of the glassy alloy rod of diameter 2 mm, although there exist no appreciable differences between their strength levels and fracture behaviors. The success of formation of the large-sized Zr-based bulk glassy alloy rod, which exhibits large plastic strains in conjunction with high strength levels, is promising with regard to further extension of the applications of such highly functional materials.

Formation, Thermal Stability and Mechanical Properties of Bulk Glassy Alloys with a Diameter of 20 mm in Zr-(Ti,Nb)-Al-Ni-Cu System

Bulk glassy alloy rods with a diameter of 20 mm were produced for Zr61Ti2Nb2Al7:5Ni10Cu17:5 and Zr60Ti2Nb2Al7:5Ni10Cu18:5 by a tilt casting method. The replacement of Zr by a small amount of Ti and Nb caused a distinct increase in the maximum diameter from 16 mm for Zr65Al7:5Ni10Cu17:5 to 20 mm, accompanying the decrease in liquidus temperature and the increase in reduced glass transition temperature. The primary precipitation phase from supercooled liquid also shows a distinct change, i.e., from coexistent Zr2Cu, Zr2Ni and Zr6NiAl2 phases for the 65%Zr alloy to an icosahedral phase for the 61%Zr and 60%Zr alloys. These results allow us to presume that the enhancement of the glassforming ability is due to an increase in the stability of supercooled liquid against crystallization caused by the development of icosahedral shortrange ordered atomic configurations. The 60%Zr specimens taken from the central and near-surface regions in the transverse cross section at the site which is 15 mm away from the bottom surface of the cast glassy rod with a diameter of 20 mm exhibit good mechanical properties under a compressive deformation mode, i.e., Young’s modulus of 81 GPa, large elastic strain of 0.02, high yield strength of 1610 MPa and distinct plastic strain of 0.012. Besides, a number of shear bands are observed along the maximum shear stress plane on the peripheral surface near the final fracture site. The finding of producing the large scale Zr-based bulk glassy alloys exhibiting reliable mechanical properties is encouraging for future advancement of bulk glassy alloys as a new type of functional material. [doi:10.2320/matertrans.MER2008179]

Preparation of a Zr-based bulk glassy alloy foam

A Zr 48 Cu 36 Al 8 Ag 8 bulk metallic glass (BMG) containing spherical pores with 3.9% porosity was prepared by melting a Zr 48 Cu 36 Al 8 Ag 8 powder under 1.0 MPa pressurized helium. Annealing treatment of the porous alloy in a supercooled liquid region causes expansion of the pores. Highly porous BMG with a cellular structure was prepared by sudden reduction of the helium pressure in the crucible before quenching. The porous alloys exhibited significant plasticity due to a high density of shear bands initiated from pores.

Structure, Thermal Stability and Mechanical Properties of Zr<SUB>65</SUB>Al<SUB>7.5</SUB>Ni<SUB>10</SUB>Cu<SUB>17.5</SUB> Glassy Alloy Rod with a Diameter of 16 mm Produced by Tilt Casting

Bulk glassy alloy rods with a diameter of 16 mm and a length of 40 to 45 mm were produced for Zr65Al7:5Ni10Cu17:5 alloy by a tilt casting method. The alloy specimens taken from the different sites which are away by about 10 mm, 15 mm and 30 mm from the bottom surface of the cast rod consist of a glassy phase and their thermal stability, mechanical properties and fracture mode are almost independent of the specimen sites. The glass transition temperature, temperature interval of supercooled liquid region before crystallization and heat of crystallization are about 643 K, 102 K and 55 J/g, respectively, for the specimens taken from the three different sites. Besides, Young’s modulus, yield strength, fracture strength, yield strain and plastic strain of the specimens are about 87 GPa, 1540 MPa, 1580 MPa, 0.018 and 0.005, respectively. The fracture mode consisting of shear plastic deformation along the maximum shear stress plane, followed by an instantaneous final rupture is also independent of the specimen sites. These data indicate that the cast glassy alloy rod with a diameter of 16 mm has nearly the same characteristics, though the cooling rate is significantly dependent on sample sites. The knowledge of producing the Zr-based bulk glassy alloy rod with nearly the same characteristics in the large diameter range up to 16 mm is encouraging for future applications of bulk glassy alloys as a new type of engineering material. [doi:10.2320/matertrans.MER2008127]

Preparation of Open-Cell Porous Zr-Based Bulk Glassy Alloy

A Zr-Nb-Al-Ni-Cu porous bulk glassy alloy was prepared by a melt infiltration technique using La 2 O 3 compact. The alloy has open-cell structure with a pore size of about 50 micrometer and roughened cell wall structure. The yield strength and Young's modulus of the porous alloy are 180 MPa and 17 GPa, respectively, which are coincident with those for human cortical bone. The porous alloy exhibited good corrosion resistance in a simulated human body fluid, indicating the possibility of application as biomaterials.

Effects of loading rates, notch root radius and specimen thickness on fracture toughness in bulk metallic glasses

The fracture toughness ( K Q) tests were carried out in order to study the effect of loading rate ( K ˙ ), notch root radius ( R) and specimen thickness ( B) on the K Q in Zr-based bulk glassy alloys (BGAs). The plane strain fracture toughness K IC of the BMG of Zr 50Cu 40Ni 10 at.% prepared by an arc tilt casting method showed a large value of 53 MPa m 1/2 under the conditions satisfying ASTM E399. With K ˙ of about 0.1 MPa m 1/2 s −1, there were cases that the K Q exhibited more than 100 MPa m 1/2. The K Q increased with increasing R even for smaller R of 30 μm, and K Q exhibited more than 120 MPa m 1/2 with R of more than 90 μm. K Q decreases a little with decreasing the B from 2.3 to 0.12 mm was shown. In these cases, the estimated plane stress plastic zone sizes agreed well with the length of shear bands near the fatigue crack tips or notch roots on specimen surfaces.

New Cu–Zr-based bulk metallic glasses with large diameters of up to 1.5 cm

Cu–Zr-based bulk glassy alloys are synthesized with high glass-forming ability in a Cu42−xZr42+xAg8Al8 system by copper mold casting. Bulk glassy alloys with a diameter of 10 mm can be easily obtained in this alloy system. Also, 15-mm glassy alloy rods are formed for the Cu40Zr44Ag8Al8, Cu38Zr46Ag8Al8 and Cu36Zr48Ag8Al8 alloys by copper mold casting. These glassy alloys exhibit high fracture strengths of over 1850 MPa with Young’s moduli of about 115 GPa.

Formation, thermal and mechanical properties of bulk glassy alloys in Zr–Al–Co and Zr–Al–Co–Cu systems

New Zr-based bulk glassy alloys in Zr–Al–Co and Zr–Al–Co–Cu systems were developed. The largest supercooled liquid region is upto 64 K for the Zr55Al20Co25 alloy and 80 K for the Zr55Al20Co20Cu5 alloy, respectively. Glassy rods with a diameter of 3 mm for the Zr55Al20Co25 alloy and 5 mm for the Zr55Al20Co20Cu5 alloy can be prepared by copper-mold casting. Glassy Zr55Al20Co20Cu5 sheet with a thickness of 2 mm was also formed by squeeze copper-mold casting. The bulk glassy Zr55Al20Co20Cu5 alloy exhibits Young’s modulus of 92 GPa, elastic limit of 2.1%, tensile strength of 1960 MPa, compressive fracture strength of 2200 MPa, and compressive plastic strain of 0.6%. The tensile strength value is considerably higher than those for the other Zr-based bulk glassy alloys reported upto date. The synthesis of the new Zr-based bulk glassy alloys with high glass-forming ability and high tensile strength approaching 2000 MPa is expected to result in a future extension of application fields as a high strength material.

Temperature dependence of heat capacity and electrical resistivity of Zr-based bulk glassy alloys

Abstract The specific heat at constant pressure ( C p ) and electrical resistivity ( ρ ) of Zr 55 Al 10 Cu 35 , Zr 55 Al 10 Cu 30 Ni 5 and Zr 55 Al 10 Cu 25 Ni 10 bulk glassy alloys were measured in the temperature range below 300 K. It was found that the measured C p of the Zr 55 Al 10 Cu (35− X ) Ni X ( X =0, 5 and 10 at.%) alloys are almost the same. The coefficient of electronic specific heat ( γ exp ) and the Debye temperature ( θ D ) of the Zr 55 Al 10 Cu 30 Ni 5 alloy were found to be 4.05 mJ mol −1 K −2 and 278 K, respectively. The ρ of the Zr 55 Al 10 Cu 35 Ni 5 alloy increased as the temperature decreased in the temperature range between approximately 2.8 and 300 K. The ρ of the alloy with the X =5 decreased abruptly below approximately 2.8 K. The ρ of the Zr 55 Al 10 Cu 35 and Zr 55 Al 10 Cu 25 Ni 10 alloys increased with decreasing temperature in the temperature range between 1.8 and 300 K.

Characterization of Crystalline Inclusions in Cast Bulk Zr-Cu-Ni-Al Glassy Alloy

In order to clarify intrinsic features of bulk glassy alloys, the structural control is the most significant factor. However, it is difficult to obtain a single glassy phase by conventional casting methods. Crystalline inclusions in Zr-based bulk glassy alloy are often seen on the fracture surface. Crystalline inclusions are easily formed in molten alloy state by inhomogeneous nucleation or impurities i.e. oxygen, magnesium dichloride and so on. In Zr 5 5 Cu 3 0 Ni 5 Al 1 0 bulk glassy alloy, most of the crystalline inclusions are probably considered as τ 3 type intermetallic compound with typical composition of Zr 5 1 Cu 2 8 Al 2 1 . The morphology of the crystalline inclusions is changed by the quantity of absorbed oxygen impurities in bulk glassy alloy.

Hydrogen-induced internal friction of Zr-based bulk glassy alloys in a rod shape above 90 K

Hydrogen-induced internal friction of Zr 65Al 7.5Ni 10Cu 17.5 bulk glassy alloys in a short rod shape (1.5 mm in diameter, 44 mm in length) have been investigated above 90 K using a vibrating reed technique. A quite broad and asymmetric peak is observed around 240 K ( H=2.21 at.%) in the temperature dependence of internal friction. Strain amplitude dependence of internal friction of Zr 63.57Al 7.32Ni 9.79Cu 17.11H 2.21 have been also measured at about the peak temperature and room temperature. It is found that the internal frictions at both temperatures are independent of the strain amplitude. Effects of hydrogen concentration ( H=0.24–2.21 at.%) on the temperature dependence of internal friction have been also clarified. The peak temperature decreases with increasing hydrogen concentration and the peak internal friction increases almost linearly. These results are compared with the reported results of Zr–Al–Ni–Cu–Pd bulk glassy alloys and discussed from the viewpoints of local structure of the Zr-based glassy alloys.