Large Supercooled Liquid Region Research Articles

Fabrication of Zr-Ti-Si glassy metallic overlay on 3D printed Ti-6Al4V implant prototypes for enhanced biocompatibility

Implantable materials with enhanced corrosion resistance and bioactivity are highly desired for biomedical application. A 3D metal printed prototype surface was coated with amorphous alloy components of elements Zr, Ti and Si (Zr54Ti35 Si11) as a novel biomedical grade ternary system for the implants. A DC magnetron sputtering technique was used to sputter the films on Ti-6Al-4 V implant prototypes, exhibiting a smooth and denser coating with root means square surface roughness of 1.4 nm. Surface morphology and structural integrity of the thin film metallic glass (TFMG) was studied from electron microscopic techniques and X-ray diffraction analysis. The TFMG is thermally stable with a large supercooled liquid region (∆Tx) of 81.2 °C. Mechanical characteristics of the coatings were studied using the nanoindentation method to correlate the hardness and modulus of the implant materials. Under the simulated body fluid condition, Ti-6Al-4 V implant with 500 nm thickness coatings (Zr54Ti35Si11) exhibited the superior corrosion resistance rate 1 × 10−6 mpy with a charge transfer resistance of 34 kΩ promising for practical application. Electrochemical impedance spectra and Tafel analysis revealed that the corrosion resistance was prominent in the 500 nm thickness TFMG system than the 250 nm and uncoated bare counterparts. The in-vitro biocompatibility and cytotoxicity studies of the as-coated 3D printed implants were studied using the human osteoblast and L929 fibroblast cell lines, respectively. A hemocompatibility study on the implant materials revealed that erythrocytes remain biconcave without aggregation, platelet activation and thrombogenesis, supporting the biocompatibility of the implants. The integration of such unique properties makes these TFMG system ideal candidates for biomedical implants.

Role of Fe substitution for Co on thermal stability and glass-forming ability of soft magnetic Co-based Co-Fe-B-P-C metallic glasses

Soft magnetic Co-based bulk metallic glasses (BMGs) with large supercooled liquid region (ΔTx) of 47 K and high saturation magnetic flux density (Bs) up to 1.21 T have been developed in a new Co-Fe-B-P-C alloy system without early transition metal and rare earth elements. Substitution of Co by 10–35 at.% Fe in a Co75B10P7.5C7.5 alloy promotes the occurrence of glass transition and enhances the stability of supercooled liquid and glass-forming ability (GFA). The ΔTx of 37–47 K and a critical sample diameter up to 1.2 mm can be achieved for Co40–55Fe20–35B10P7.5C7.5 BMGs. The improved thermal stability and GFA are attributed to complicated primary crystallization phases and stabilized alloy melts, respectively. The addition of Fe enhances the Bs of the Co-based BMGs from 0.79 to 1.21 T, and increases coercivity from 1.1 to 7.2 A/m. The Co-based BMGs also exhibit high yield strength of 3243–3665 MPa with plastic strain up to 2.3% and low viscosity of around 3.0 × 109 Pa·s in the supercooled liquid state.

Local structure order around Ni in Hf‒Cu‒Ni glassy ribbons: XANES and EXAFS study at Ni K‒edge

This work has investigated the formation of the local structure order around Ni in Hf‒Cu‒Ni glassy ribbons by employing X‒ray absorption near edge structure (XANES) and extended X‒ray absorption fine structure (EXAFS) spectroscopy at Ni K‒edge. XANES probed 1s to 4p transition at the shoulder of the spectra. The main peak of the spectra corresponds to the 1s to 4p dipole selection rule. The magnitude of the first peak of the EXAFS signal, belonging to the first coordination shell of Ni, decreased with an increase in Ni concentration. The coordination number (CN) of Ni/Cu atoms increases, whereas that of Hf atoms decreases with increasing Ni concentration. The first peak of Hf57Cu11Ni32 (Hf57), Hf59Cu18Ni23 (Hf59), and Hf60Cu21Ni19 (Hf60) is dominated by Ni–Ni and Ni–Cu pair. A nearly linear decrease in atomic distances of Ni‒Hf pair is observed with an increase in CN of Ni/Cu, thereby indicating atomic re‒arrangement around the central absorbing atom. Hf57 with large CN of Ni/Cu atoms has shown the most negative PHS (product of enthalpy of chemical mixing and normalized mismatch entropy) and large supercooled liquid region. This work reflects that the CN of an element strongly influences the glass formation ability of an alloy.

Glass formation in Fe-Cr-Zr-B-Mo alloys by tuning Nb addition

Fe-based bulk metallic glasses (BMGs) with high boron content have potential application as a coating material used in the framework for storing spent nuclear fuels to support their safe long-term disposal. The high glass forming ability (GFA) and large supercooled liquid region are therefore required for such Fe-based BMGs in either the glassy powder fabrication or the subsequent coating spraying. In order to meet these requirements, the influence of Nb content on the GFA of Fe57Cr10Zr8B18Mo7−xNbx (x=1–5, at.%) alloys was investigated, as Nb has positive roles in GFA and thermal stability of BMGs. The results indicate that a fully amorphous phase in the as-cast samples with 3 mm in diameter is obtained for both the Fe57Cr10Zr8B18Mo5Nb2 and Fe57Cr10Zr8B18Mo4Nb3 alloys. The corresponding supercooled liquid regions of the two BMGs are 78 K and 71 K, respectively. The mechanism for improving their GFA was analyzed based on the principle of metal solidification, the parameters for glass formation and thermal properties of the alloys. The compression strength and Vicker’s hardness of the two BMGs are 1,950 MPa and 1,310 HV, 2,062 MPa and 1,180 HV, respectively. The developed BMGs with high B content, good GFA, and very high hardness can be used as coating materials to the framework for spent nuclear fuels.

Roles of Y and Fe contents on glass-forming ability, thermal stability, and magnetic properties of Co-based Co–Fe–Y–B bulk metallic glasses

Soft magnetic Co-based bulk metallic glasses (BMGs) with large supercooled liquid region (ΔTx) and high saturation magnetic flux density (Bs) have been developed in a new Co–Fe–Y–B alloy system. Addition of appropriate contents of Y and Fe into a Co75B25 alloy enlarges the ΔTx and improves the glass-forming ability (GFA). ΔTx of 50–64 K and a critical diameter of up to 2.0 mm have been achieved for the (Co0.5–0.7Fe0.3–0.5)71.5Y3.5B25 BMGs. The coercivity (Hc) of Co75-xYxB25 and (Co0.7Fe0.3)75-xYxB25 (x = 0–5) alloy series shows a similar V-shape change with Y content, and gets the minimum at x = 3.5, while that of (Co1-yFey)71.5Y3.5B25 (y = 0–0.5) alloys keeps rising with the increase of Fe content. The Bs of the alloys monotonically decreases with more Y addition and increases with enriching of Fe. The (Co0.5–0.7Fe0.3–0.5)71.5Y3.5B25 BMGs exhibit high Bs of 1.00–1.17 T and low Hc of 5.4–6.4 A/m. The BMGs possess high yield strength of 3978–4152 MPa with distinct plastic strain of up to 0.9% and Vickers hardness of 1218–1233 as well. The possible mechanisms of Y and Fe affecting the GFA, thermal stability, and magnetic properties of the Co-based Co–Fe–Y–B metallic glasses have been discussed.

Enhancement of glass-forming ability and thermal stability of a soft magnetic Co75B25 metallic glass by micro-alloying Y and Nb

Soft magnetic Co-based Co–Y–Nb–B bulk metallic glasses (BMGs) without Fe have been developed by micro-alloying Y and Nb into a Co75B25 alloy. First, addition of 3–4 at.% Y promotes the occurrence of glass transition and increases the supercooled liquid stability and magnetic softness. Co71.5Y3.5B25 metallic glass possesses a large supercooled liquid region (ΔTx) of 33 K and low coercivity (Hc) of 1.5 A/m. Subsequent alloying 2–4 at.% Nb into Co71.5Y3.5B25 alloy further enlarges ΔTx to 50 K, lowers Hc to 0.9 A/m, and enables the formation of BMGs with a critical sample diameter up to 2.0 mm. The alloying Nb causes the formation of complex (Co, Nb, Y)23B6 competing phase during crystallization and widens the melt undercooling during solidification, which improves the supercooled liquid stability and glass-forming ability, respectively. Co–Y–Nb–B BMGs also exhibit good soft magnetic and mechanical properties, i.e., low Hc of 0.9–1.2 A/m, relatively high saturation magnetic flux density of 0.36–0.57 T, high yielding strength of 3877–3930 MPa with plastic strain of 0.2%–0.3%, and high Vickers hardness of 1156–1201. The developed soft magnetic Co-based BMGs are promising for applications as structural and functional materials.

Enhancing strength and plasticity of Zr-based bulk metallic glasses by Zr partially substituted Fe and isothermal annealing

Zr-based bulk metallic glasses (BMG) Zr65+xCu17.5Fe10-xAl7.5 (x = 0, 2.5, 5, 7.5) with high zirconium content were prepared by an injection copper-mold casting method. The influence of Zr partially substituted Fe and isothermal annealing on the microstructure and mechanical properties of the Zr65+xCu17.5Fe10-xAl7.5 BMGs has been systematically studied. The as-prepared BMG with a Zr content of 70 at.% achieves superior glass forming ability with a large supercooled liquid region width of 82 K and compressive performance. An optimized isothermal annealing (0.5 h) below the glass transition temperature of the as-cast Zr70Cu17.5Fe5Al7.5 BMG contributes significant enhancement in compressive fracture strength and plasticity, from 1845 MPa and 7.4% (as-cast) to 2096 MPa and 12.7% (annealed), respectively. The result of the present study provides a new strategy for designing high-performance BMG-based alloys.

Soft magnetic Co-based Co–Fe–B–Si–P bulk metallic glasses with high saturation magnetic flux density of over 1.2 T

Co-based (Co, Fe)75B15Si7P3 bulk metallic glasses (BMGs) without any early transition metal or rare-earth elements have been successfully developed, which possess outstanding soft magnetic properties with high saturation magnetic flux density (Bs) and good mechanical properties. Addition of an appropriate amount of P into a Co75B15Si10 alloy promotes the occurrence of glass transition and increases the stability of the supercooled liquid, and a Co75B15Si7P3 metallic glass exhibits a large supercooled liquid region of 33 K. Subsequent replacement of Co by 15–35 at.% Fe enhances the glass-forming ability (GFA) of the Co75B15Si7P3 alloy, and the BMG rods with diameters up to 2.0 mm are obtained. The improved GFA might be originated from the high thermal stability of the alloy melts as indicated from the large undercoolings. The Co-based (Co, Fe)75B15Si7P3 BMGs possess low coercivity of 0.8–4.6 A/m, high Bs of 1.02–1.24 T, effective permeability of 12700–18500 at 1 kHz, and Curie temperature of 739–789 K, indicating superior soft magnetic properties compared to other reported Co-based BMGs. The BMGs also exhibit high compressive yield strength of 3343–3590 MPa with distinct plastic strain up to 2.7% and high Vickers hardness of 1150–1175. The combination of high GFA and excellent soft magnetic and mechanical properties makes the Co-based BMGs a good prospect of functional materials.

Understanding the role of Er on glass-forming ability parameters and critical cooling rate in Fe‒based multicomponent bulk metallic glasses

In this paper, the role of a lanthanide element, Erbium (Er) on the glass-forming ability (GFA) parameters such as Trg, ΔTx, α, γm, ε, γ∗ and critical cooling rate (RC) of previously reported Fe‒based multicomponent (Fe0.9Co0.1)65−xMo14C15B6Erx (x = 0.125,0.25,0.50,0.75,1,2) BMGs has been studied. With varying Er from x = 0.125 to 0.75, it is observed that the critical diameter (ZC) of the alloy was increased from 2.0 mm to 4.0 mm whereas ZC decreased to 1.5 mm at x = 2.0. Our study also shows that the width of the supercooled liquid region (SLR) reduced from 61 K to 42 K as x varies from 0.125 to 2.0. For x = 0.125 and 0.50, SLR was found to be maximum as 61 K. From x = 0.125 to 0.50, it was observed that Tg, Tx, and Trg were found to increased and attains maximum value. Moreover, for x = 0.75 to 2.0, these parameters were decreased linearly. Similarly, α, γm and ε were found to decrease linearly whereas γ∗ and PHSS were increased linearly from 0.125 to 2.0. Moreover, with the increase in Er content, the RC of the alloy was increased linearly. Alloys Fe57.05Co6.45Mo14C15B6Er0.5 and Fe57.825Co6.425Mo14C15B6Er0.75 were found to have maximum ZC of 4.0 mm and large SLR of 55 K and 57 K, respectively. These alloys were found to have a low cooling rate among others. Finally, it was found that the presence of Er in the range of x = 0.50 to x = 0.75 has a positive effect on ZC and SLR along with low RC.

Thermoplastic deformation behavior of a Fe-based bulk metallic glass within the supercooled liquid region

Fe41Cr15Co7Mo14C12B9Y2 (Fe-B9) bulk metallic glass (BMG) rods with high glass forming ability and large supercooled liquid (SCL) region were fabricated by arc melting and suction casting. The amorphous state of these Fe-B9 BMG rods was ascertained by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The thermoplastic deformation behavior of these BMG rods was studied by using the hot compression test at different temperatures (873K, 883K, 893K, and 903K in the SCL region) and strain rates (1×10−3–5×10−2s−1). The results of the hot compression test reveal that the flow stress of Fe-B9 BMG reduces systematically with increasing temperature and decreasing strain rate. Strain sensitivity exponent (m) values of the Fe-B9 BMG were calculated to be about 0.36–0.59 in the SCL region, indicating that Fe-B9 BMG possesses superplasticity. Overall, the optimum working conditions of thermoplastic forming for Fe-B9 BMG can be achieved by compressively deforming the sample with a constant strain rate of 2.5×10−3s−1 at a temperature from 873 to 883K.

Crystallization Behavior of Al70Fe12.5V12.5Nb₅ Amorphous Alloy Formed by Mechanical Alloying.

In this study, the formation and crystallization of the Al70Fe12.5V12.5Nb5 amorphous alloys has been investigated. The addition of Nb enhances the supercooled liquid region and glass forming ability of the Al-Fe-V amorphous alloys. The Al70Fe12.5V12.5Nb5 amorphous alloy exhibits two distinct crystallization steps and a large supercooled liquid region at more than 100 K. Kissinger and Ozawa analyses showed that the two activation energies for crystallization (Ex) were estimated to be 366.3 ± 23.9 and 380.5 ± 23.9 kJ/mol. Large supercooled liquid regions are expected to gain an application field of Al-based amorphous alloys.

Metallic glass ultrathin films with hierarchical structure and their dynamic and thermodynamic behavior.

Metallic glass (MG) ultrathin films with hierarchical structure were in situ grown and characterized by scanning tunneling microscopy. A reversible dynamic behavior is observed at 77 K indicating a high mobility within the Fe85Sc15 MG ultrathin films. The complete scheme of the phase transition from amorphous solid to supercooled liquid and further to the crystalline phase is depicted. We find Fe85Sc15 MG ultrathin films with a reduction of the glass transition temperature of ∼290 K and an expanded temperature window of the supercooled liquid region of 180 K, which is almost 6 times larger than that of the conventional bulk MG with identical composition.

Microstructure, magnetic properties and cryogenic magnetocaloric effect in Cu20Al20Er60 amorphous ribbons

The glass forming ability, microstructure as well as the cryogenic magnetic and magnetocaloric properties in melt-spun Cu20Al20Er60 ribbons were reported. The as-spun ribbons were confirmed to possess fully amorphous structure with a large supercooled liquid region of 54.3 K. A broad second-order paramagnetic to ferromagnetic (PM-FM) magnetic transition together with a large reversible cryogenic magnetocaloric effect (MCE) in Cu20Al20Er60 amorphous ribbon was found around TC of 13.3 K. The MCE parameters of the maximum magnetic entropy change (−ΔSMmax), relative cooling power (RCP) and refrigerant capacity (RC) for Cu20Al20Er60 amorphous ribbons were evaluated to be 15.3 J/kg K, 543 J/kg and 420 J/kg for a magnetic field change (ΔH) of 0–7 T, respectively.

Glass-forming ability, thermal properties, and corrosion resistance of Fe-based (Fe, Ni, Mo, Cr)-P-C-B metallic glasses

Co-addition of appropriate Mo, Cr and Ni in the Fe80P12C4B4 alloy not only enhances the thermal stability of the supercooled liquid and glass-forming ability (GFA) but also reduces the glass transition temperature (Tg) of the Fe-based metallic glass. The Fe55Ni15Cr7Mo3P12C4B4 bulk metallic glass (BMG) exhibits a low Tg of 690K, large supercooled liquid region (ΔTx) of 60K, and high GFA with a critical diameter of 2.5mm. The co-addition of Mo, Cr and Ni remarkably improves the corrosion resistance of the BMGs in 1M HCl and 0.5M H2SO4 solutions, which is superior compared to the SUS316L stainless steel. The alloys also possess high compressive yield strength of ~3.01GPa with distinct plastic strain of ~1.2%. The good combination of low Tg, large ΔTx, high GFA, excellent corrosion resistance and mechanical properties makes the developed (Fe, Ni, Cr, Mo)80P12C4B4 BMGs show great promise as anti-corrosion materials suitable for thermoplastic processing.

Manipulation of thermal and mechanical stability by addition of multiple equiatomic rare-earth elements in Al-TM-RE metallic glasses

In the present study, we demonstrate that the addition of multiple equiatomic rare-earth elements (REs) in the order of electronegativity in Al84Ni10RE6 (RE = La, Ce, Nd, Gd, Y) metallic glasses (MGs) can result in stabilizing supercooled liquid region and destabilizing shear avalanches via controllably induced compositional complexity. In detail, the addition of multiple equiatomic REs leads to a relatively fragile glass, but interrupts easy crystallization behavior in Al84Ni10(LaCeNdGdY)6MG, which causes a larger supercooled liquid region and higher thermoplastic formability. Furthermore, the increased structural instability reduces cut-off size of self-organized shear avalanches and increases the number of chaotic shear avalanches, which can distribute the applied strain more homogeneously, resulting in enhanced intrinsic ductility. These results provide a guideline on how to design promising Al-based MGs with high thermal stability and improved mechanical stability, which is a key step to developing ductile Al-based bulk metallic glasses through thermoplastic forming process.

Materials properties of ion beam sputtered Ti-Cu-Pd-Zr thin film metallic glasses

Ti40Cu36Pd14Zr10 (at.%) thin film metallic glasses (TFMG) of 1μm thickness were ion beam sputtered on to glass, Si (100) wafer and commercially pure titanium (CP Ti). The Ti-based TFMG are thermally stable with a large super cooled liquid region (Tx) of 49.3°C. XPS and Auger electron spectroscopy (AES) analyses revealed the presence of titanium, copper, zirconium and palladium ions on surface of the films. Ion scattering spectroscopy (ISS) was used to characterize the chemical composition of surface monolayer which indicated a significant level of oxygen on the top surface of the film. X-ray diffraction and TEM indicated an amorphous microstructure of the film. The STEM mapping of the films was quite homogenous and no chemical segregation was discernible in the maps. EDAX showed a slight difference in the composition of the films with respect to sputtering target. Amorphous films with atomically smooth surfaces of roughness in the order of (Ra) 0.l6nm with the nanohardness of 7.7GPa and Young's modulus of 106GPa were observed. The sputtered specimen had superior corrosion resistance in simulated body fluid (SBF). The electro catalytic activity of Ti40Cu36Pd14Zr10 showed a sign of borohydride oxidation in 1M KOH. The MTT assay using L929 fibroblast cells revealed the non-cytotoxic nature of the coating.

Effect of substituting elements on thermal stability and glass-forming ability of an Al-based Al Ni Er metallic glass

Abstract Addition of a small amount of La and Co enhances the stabilization of supercooled liquid and glass-forming ability (GFA) of an Al85Ni7Er8 metallic glass. The Al85Ni5Co2Er6La2 alloy exhibits large supercooled liquid region of 40 K, high GFA with a critical thickness of 450 μm, and the viscosities on the order of 107−109 Pa s in the supercooled liquid state. The Al-based glassy nano-scale patterns were formed by imprinting, indicating its good thermoplastic formability. The possible mechanism for the improvement of the supercooled liquid stability of the Al Ni Er alloy by addition of La and Co elements was discussed in terms of the crystallization behavior.

Glass-forming ability and thermoplastic formability of ferromagnetic (Fe, Co, Ni) 75 P 10 C 10 B 5 metallic glasses

Abstract Substitution of Co and Ni for Fe in an Fe 75 P 10 C 10 B 5 metallic glass effectively increases the stability of supercooled liquid and glass-forming ability. The bulk metallic glasses with large supercooled liquid region (Δ T x ) exceeding 50 K and the critical sample diameter ( d c ) of over 1 mm were obtained in a wide composition range from 30 to 60 at.% Fe, 0 to 45 at.% Co and 0 to 40 at.% Ni in the (Fe, Co, Ni) 75 P 10 C 10 B 5 alloy system by copper mold casting. An Fe 40 Co 20 Ni 15 P 10 C 10 B 5 alloy shows maximum d c of 2.5 mm, largest Δ T x of 60 K, low glass transition temperature of 675 K, low viscosity on the order of 10 8 –10 9 Pa s in the supercooled liquid state, high compressive yield strength of 2860 MPa with a distinct plastic strain, and good soft magnetic properties, i.e., rather high saturation magnetization of 1.13 T and low coercive force of 3.8 A/m. The nano-scale Fe 40 Co 20 Ni 15 P 10 C 10 B 5 glassy patterns were precisely formed by imprinting, indicating its good thermoplastic formability.

New soft magnetic Fe25Co25Ni25(P, C, B)25 high entropy bulk metallic glasses with large supercooled liquid region

New Fe25Co25Ni25(P, C, B)25 high entropy bulk metallic glasses (HE-BMGs) with large supercooled liquid region (ΔTx) and excellent soft magnetic and mechanical properties were developed. Fully HE-BMG rods were successfully prepared by copper mold casting in the composition region of 7.5–12.5 at% P, 7.5–10 at% C, and 5–10 at% B, respectively. The HE-BMGs possess low glass transition temperature (Tg) of ∼672 K and large ΔTx of ∼56 K, which are comparable to those of Zr-based BMGs, whereas exhibit much higher yield strength of ∼3210 MPa with distinct plasticity. The alloys also show low coercivity of ∼1.2 A/m and high saturation magnetization of ∼0.86 T. The mechanism of good stability of the supercooled liquid and the correlation between strength and Tg for the HE-BMGs were discussed.

Stabilisation of Ce-Cu-Fe amorphous alloys by addition of Al

The present work describes the formation of amorphous alloys in the (Al1−xCex)62Cu25Fe13 quaternary system (0 ≤ x ≤ 1). When the amount of Ce falls in the range 0.67 ≤ x ≤ 0.83, the alloys obtained exhibit a completely amorphous structure confirmed by powder X-ray diffraction. Otherwise, at compositions x = 0.5, 0.58, 0.92 and 1, a primary crystalline phase forms together with an amorphous matrix. The crystallisation temperature (Tx) decreases with increasing Ce content, varying from 593 K for x = 0.5–383 K for x = 1. Composition x = 0.75 is considered as the best glass former, exhibiting a large supercooled liquid region of 40 K width that precedes crystallisation. In order to form bulk amorphous alloys, ribbons with this later composition were consolidated into few millimetre thick discs using pulsed electric current sintering at different temperatures, yet preserving the amorphous structure. Meanwhile, increasing temperature above 483 K triggers crystallisation of a primary phase isostructural to AlCe3. Further increase in the temperature up to 573 K yields a higher fraction of the crystalline phase. Testing mechanical properties, using nanoindentation, revealed that both elastic modulus (E) and hardness (H) depend on the Al content, ranging from E = 85.6 ± 3.7 GPa and H = 6.2 ± 0.7 GPa for x = 0.5 down to E = 39.8 ± 1.0 GPa and H = 3.1 ± 0.2 GPa for x = 0.92.