Critical Diameter For Glass Formation Research Articles

Advancing Bulk Metallic Glass Formation: Utilizing Rare-Earth Elements in Zr-Based Alloys

Zr-based bulk metallic glasses (BMGs) are characterized by excellent glass-forming ability, combined with superior mechanical properties. However, oxygen impurities degrade both these aspects as oxides serve as heterogeneous nucleation sites during solidification. Rare-earth elements (REEs) are known to be good oxygen scavengers, binding oxygen to less harmful forms. The most stable rare-earth oxide (REO) is M2O3, which occurs in three polymorphic forms, depending on the radius of metal cation: cubic, hexagonal, and monoclinic. Here, we show the effect of Sc, Y, Lu, Nd, and Gd additions in relation to the oxygen content on the glass-forming ability of the Zr52.5Cu17.9Ni14.6Al10Ti5 alloy. Microscopic observations (SEM) supported by chemical analysis (EDS, WDS), structure identification (XRD), and thermal analysis (DTA) were carried out. The critical diameter for glass formation (Dc) in the high oxygen alloy doped with cubic oxide-forming elements (Sc, Y, and Lu) can be even higher (Dc = 9 mm) compared to the undoped alloy synthesized from low oxygen components. Therefore, we have demonstrated that it is feasible to produce BMG using low-purity constituents with REE-based oxygen scavengers. This bridges the gap between laboratory development and cost-effective commercial applications.Graphical

Preparation of CoMoPC bulk metallic glasses using fluxing treatment and J-quenching technique

ABSTRACT A new series of Co80-x Mo x P14C6 (x = 8, 9 and 10 at.%) bulky glassy rods have been prepared by combining fluxing treatment and J-quenching technique. The glass-forming ability, thermal stability, magnetic and mechanical properties of the present CoMoPC bulk metallic glasses (BMGs) have been investigated. For the present Co80-x Mo x P14C6 (x = 8, 9 and 10 at.%) BMGs, the critical diameter for glass formation reaches the maximum value of 1.5 mm when x = 9, and the saturation magnetisation gradually decreases from 0.35 T (39 emu/g) to 0.17 T (19 emu/g) as increasing Mo content from x = 8 to x = 10. The present CoMoPC BMGs exhibit a fracture strength of 2.13–2.32 GPa and nearly zero plasticity.

Effects of Ag substitution for Fe on glass-forming ability, crystallization kinetics, and mechanical properties of Ni-free Zr–Cu–Al–Fe bulk metallic glasses

In present study, the effects of the substitution of Ag for Fe on the glass-forming ability (GFA), crystallization kinetics, and mechanical properties of Zr60Cu25Al10Fe5-xAgx (x = 0, 1, 2, 3, 4, and 5 at%) bulk metallic glasses (BMGs) were investigated. Under the same experimental conditions, the critical diameter for glass formation increased significantly by appropriately substituting Ag for Fe. The activation energies, including Eg, Ex, and Ep, all increased significantly, which indicated that Ag addition reduced the sensitivity of the amorphous alloys to temperature, as well as increased the energy barriers of atom rearrangements, nucleation and growth, i.e., the stability of the BMG enhanced. In addition, the plasticity of the alloys was enhanced thanks to the substitution. The plastic strain reached 3.7% when the content of Ag was 4 at%, which is nearly 10 times higher than the original composition (0.4%).

Enhancement of glass-forming ability and mechanical property of Zr-based Zr-Al-Ni bulk metallic glasses with addition of Pd

The effects of partial substitution of Ni by Pd in the high-Zr-based Zr65Al10Ni25-xPdx (at.%, x = 0, 5 and 10) alloys on their glass-forming ability (GFA), crystallization kinetics and mechanical property were investigated. The critical diameter for glass formation is increased from 3 mm for Zr65Al10Ni25 alloy to 5 mm for Zr65Al10Ni15Pd10. An icosahedral quasicrystal phase precipitates in the amorphous matrix in the first crystallization step of Zr-Al-Ni-Pd BMGs, implying that strong icosahedral short/medium-range order (IS/MRO) may exist in the Pd-containing alloys. In additional, Pd-bearing Zr-based BMGs present a lower Avrami exponent n indicating the higher stabilization of the supercooled liquid. Moreover, the Zr-Al-Ni-Pd BMGs exhibit larger compressive plasticity, higher notch toughness and Poisson's ratio than those of Zr65Al10Ni25 alloy, which can be correlated with the existence of strong IS/MRO clusters in amorphous phase.

Formation and mechanical properties of Zr-Nb-Cu-Ni-Al-Lu bulk glassy alloys with superior glass-forming ability

Glass-forming ability (GFA) and mechanical properties of (Zr0.58Nb0.03Cu0.16Ni0.13Al0.10)100-x Lu x (x = 0-3 at%) alloys have been investigated. The GFA of Zr58Nb3Cu16Ni13Al10 alloy is dramatically enhanced by adding Lu. The (Zr0.58Nb0.03Cu0.16Ni0.13Al0.10)98Lu2 alloy possesses the highest GFA in the studied Zr-Nb-Cu-Ni-Al-Lu alloys, with its critical diameter for glass formation reaching 20 mm by copper-mould casting method, while that of the Lu-free Zr58Nb3Cu16Ni13Al10 alloy is 7 mm. The critical diameters of (Zr0.58Nb0.03Cu0.16Ni0.13Al0.10)100-xLux (x = 1 at% and 3 at%) alloys are 15 mm and 12 mm, respectively. The Lu addition to Zr58Nb3Cu16Ni13Al10 alloy induces the change of initial crystallization phases from face-centred-cubic Zr2Ni and tetragonal Zr2Ni phases for the Lu-free Zr58Nb3Cu16Ni13Al10 alloy to an icosahedral quasi-crystalline phase for the Lu-doped alloys, which may be the origin for the enhanced GFA of the Lu-doped alloys. The compressive fracture strength and plastic strain of the bulk glassy (Zr0.58Nb0.03Cu0.16Ni0.13Al0.10)98Lu2 alloy are 1 610 MPa and 1.5%, respectively.

P55] 700°C Isothermal Section of the Al-Si-Ti Ternary Phase Diagram

The glass formation in the Ti–Cu system is revisited by means of the predictive γ* and λ + Δh1/2 amorphization criteria. Rapidly solidified ribbons of six selected compositions were investigated and in order to improve the glass-forming ability (GFA) minor amounts of Si were added to the best glass former predicted, Cu54Ti46. A series of (Cu0.54Ti0.46)100−xSix (x = 0.5, 1, 2) ribbons and rods with a diameter of 1 mm were prepared and analysed regarding their phase formation and thermal stability. For the alloy with the maximum GFA, (Cu0.54Ti0.46)99Si1, the critical diameter for glass formation is below 1 mm. Nevertheless, a good correlation was found between the experimentally determined GFA of the alloys and the prediction given by the λ+(Δh)1/2 and γ* criteria. The addition of Si decreases the liquidus temperature and promotes the precipitation of the Cu4Ti3 phase instead of γ-TiCu.

Effects of Metalloid B Addition on the Glass Formation, Magnetic and Mechanical Properties of FePCB Bulk Metallic Glasses

Low-cost Fe80P12−xC8Bx (x = 0, 1, 2, 3 and 4 at.%) bulk metallic glasses (BMGs) with good soft magnetic and mechanical properties were prepared, and effects of metalloid B addition on the glass-forming ability (GFA) as well as thermal, magnetic, and mechanical properties of the BMGs were investigated. It was found that the proper B substitution for P improves the GFA of the Fe–P–C BMGs. The alloy with 2 at.% B addition manifests the highest GFA with critical diameter for glass formation of 2 mm. Besides, these BMGs exhibit good soft magnetic properties featured by high saturation magnetization of 1.35–1.57 T and low coercivity of 2.2–7.7 A/m as well as unique mechanical properties of high fracture strength of ∼3.3 GPa and visible plastic strain of 0.4%–2.5%. The combination of high GFA, good soft magnetic and mechanical properties as well as low cost makes the present Fe–P–C–B BMGs promising as soft magnetic materials for industrial applications.

Glass formation, corrosion behavior, and mechanical properties of novel Cr-rich Cr–Fe–Mo–C–B–Y bulk metallic glasses

The glass formation, corrosion behavior, and mechanical properties of novel Cr-rich CrxFe58.8−xMo14.7C14.7B9.8Y2 (x=29.4, 36.75, and 44.1at.%) bulk metallic glasses (BMGs) were evaluated. It is found that the critical diameter for glass formation and supercooled liquid region remarkably decrease from 3mm to 1mm and 68K to 79K, respectively, with the increase in Cr content. Compared with SUS316 stainless steel, those BMGs exhibit more excellent corrosion resistance in 1M HCl solution. However, the corrosion resistance is not significantly improved with increasing Cr content, which may imply that the threshold value of Cr content to efficiently achieve high corrosion resistance for the present alloy system is around 29.4at.%. In addition, the fracture strength, Vickers microhardness, Young’s modulus, shear modulus, and the ratio of hardness to elastic modulus for the present BMGs are up to 4.31GPa, 14.15GPa, 249GPa, 95GPa, and 0.057, respectively.

Glass formation in the Ti–Cu system with and without Si additions

The glass formation in the Ti–Cu system is revisited by means of the predictive γ* and λ+Δh1/2 amorphization criteria. Rapidly solidified ribbons of six selected compositions were investigated and in order to improve the glass-forming ability (GFA) minor amounts of Si were added to the best glass former predicted, Cu54Ti46. A series of (Cu0.54Ti0.46)100−xSix (x=0.5, 1, 2) ribbons and rods with a diameter of 1mm were prepared and analysed regarding their phase formation and thermal stability. For the alloy with the maximum GFA, (Cu0.54Ti0.46)99Si1, the critical diameter for glass formation is below 1mm. Nevertheless, a good correlation was found between the experimentally determined GFA of the alloys and the prediction given by the λ+(Δh)1/2 and γ* criteria. The addition of Si decreases the liquidus temperature and promotes the precipitation of the Cu4Ti3 phase instead of γ-TiCu.

Glass-forming ability, crystallization kinetics, mechanical property, and corrosion behavior of Zr–Al–Ni–Ag glassy alloys

The effects of partial substitution of Ni by Ag in Zr56Al16(Ni1−xAgx)28 (at.%, x=0, 0.1, 0.2, 0.3, and 0.4) alloys on their glass-forming ability (GFA), crystallization kinetics, mechanical property, and corrosion behavior were investigated. The critical diameter for glass formation of Zr56Al16Ni28 alloy is significantly enhanced by partially substituting Ag for Ni. The Zr56Al16(Ni0.7Ag0.3)28 BMG exhibits the best GFAand its critical diameter for glass formation is 20mm. Ag-bearing Zr-based BMG presents a lower Avrami exponent n than that of Ag-free Zr–Al–Ni BMG, indicating the nucleation rate is reduced by the addition of Ag. The corrosion resistance of Zr–Al–Ni BMG is improved by Ag alloying, and the Zr–Al–Ni–Ag BMG exhibits higher corrosion resistance than that of other known Zr-based BMGs with high GFA. Moreover, the BMGs possess high compressive yield strength of 1830–2000MPa, large plastic strain of 2.7–3.1%, and high specific strength of 274–312MPacm3/g.

Glass-forming ability, fragility parameter, and mechanical properties of Co–Ir–Ta–B amorphous alloys

The effect of partial substitution of Co by Ir in Co57−x IrxTa8B35 (at.%, x = 0, 5, 10, and 15) alloys on glass-forming ability (GFA), fragility parameter m, and mechanical properties was investigated. It was found that the glass-forming ability reflected by critical diameter for glass formation is in good agreement with the width of supercooled region (ΔTx). The Co47Ir10Ta8B35 BMG exhibits the best GFA yielding the formation of an amorphous rod with a diameter of 5 mm, along with the largest ΔTx value of 64 K. The Ir-bearing Co47Ir10Ta8B35 BMG presents a lower fragility parameter m than Co57Ta8B35 BMG, which indicates better thermal stability and GFA. In addition, the Co47Ir10Ta8B35 BMG shows super-high yield strength of ∼5200 MPa and ultimate compressive strength of ∼5600 MPa as well as significant plasticity of ∼1.2%. The combination of good GFA, large ΔTx and excellent mechanical properties for the new Co–Ir–Ta–B BMG is significant for scientific research and industrial application.

The influence of Ag substitution for Cu on glass-forming ability and thermal properties of Mg-based bulk metallic glasses

A group of pseudo-ternary Mg–(Cu–Ag)–Dy bulk metallic glasses (BMGs) was developed by copper mold casting. The glass-forming ability (GFA) is significantly improved by the coexistence of similar elements of Ag and Cu. The critical diameter for glass formation increases from 10mm for ternary Mg56.5Cu32Dy11.5 alloy to 18mm for pseudo-ternary Mg56.5Cu27Ag5Dy11.5 alloy. Thermal stability, crystallization and melting behaviors of the Mg-based BMGs were evaluated. The decrease of Gibbs free energy difference between undercooled liquid and crystalline phases caused by similar element substitution with optimal amount can be responsible for the increase in GFA of the resulting alloys.

Enhancement of glass-forming ability of FeSiBP bulk glassy alloys with good soft-magnetic properties and high corrosion resistance

The effect of Nb micro-addition on the glass-forming ability, magnetic and corrosion properties of (Fe0.76Si0.09B0.1P0.05)100−xNbx (x=0–4) alloy system was investigated. It was found that micro-addition of 1% Nb is effective in increasing the critical diameter for glass formation from 2.5 for the base alloy to 3.5mm for (Fe0.76Si0.09B0.1P0.05)99Nb1 glassy alloy. Moreover, the 1% Nb-containing glassy alloy exhibits excellent soft-magnetic properties, i.e., high saturation magnetization (Is) of 1.45T and low coercive force (Hc) of 1A/m. A significant improvement in corrosion resistance of the glassy alloys with Nb micro-alloying in 1N H2SO4 solution is also observed. The good combination of high glass-forming ability (GFA), excellent soft-magnetic properties and enhanced corrosion resistance indicates the possibility of future development as new engineering and functional materials.

Effect of Si addition on glass-forming ability and mechanical properties of Cu–Zr–Al bulk metallic glass

The effect of Si addition on the glass-forming ability (GFA) and mechanical properties of (Cu 50Zr 43Al 7) 100− x Si x ( x = 0, 0.5, 1, 1.5 and 2 at.%) alloys were investigated. The GFA of Cu 50Zr 43Al 7 alloy is improved by addition of a small amount of Si, and the critical diameter for glass formation increases from 10 mm for the alloy with x = 0–12 mm for the alloy with x = 1 when prepared using copper mold casting. Different criteria are used to evaluate the influence of Si content on the GFA, and the possible mechanisms involved in the achievement of this GFA are also discussed. In the uniaxial compression, the bulk glassy alloys exhibit a limited plastic strain of less than 1%, but the compressive fracture strength and Young's modulus were obtained in high values of 1969–2129 MPa and 101–144 GPa, respectively. Fracture surface and shear bands of samples were studied by using scanning electron microscopy (SEM).

Enhanced glass-forming ability of a Sm-based alloy with the addition of La

The effects of La on the glass -forming ability (GFA) of a Sm-based alloy were investigated. By partial substitution of Sm with La in (Sm 0.62Al 0.14Ni 0.12Cu 0.12) 97Fe 3 (at.%) alloy, of which the critical diameter for glass formation is 3 mm, (Sm 0.32La 0.3Al 0.14Ni 0.12Cu 0.12) 97Fe 3 glassy rods with a diameter up to 10 mm can be fabricated by copper mold casting. The configuration entropy and critical cooling rate of the Sm–La–Al–Ni–Cu–Fe alloy were calculated. It is indicated that the configuration entropy is increased and the critical cooling rate is decreased with the addition of La, implying that the La-containing alloys exhibit higher GFA than that of the La-free Sm–Al–Ni–Cu–Fe alloy. Moreover, with the addition of La, the Sm-based alloys exhibit reduced Gibbs free energy between the liquid phase and the crystalline phase in the supercooled liquid region and stronger liquid behavior, which are also beneficial to the enhanced GFA of the Sm–La–Al–Ni–Cu–Fe alloys.

Synthesis of bulk glassy Fe–C–Si–B–P–Ga alloys with high glass-forming ability and good soft-magnetic properties

Effects of Ga additions on the glass-forming ability (GFA) and magnetic properties of the Fe 76C 7.0Si 3.3B 5.0P 8.7 alloy were investigated. It was found that addition of 1–2% Ga can increase the critical diameter for glass formation from 1 to 3 mm. Moreover, the as-cast alloy containing 1% Ga exhibit good soft-magnetic properties including a high saturation magnetization value of 1.55 T and a low coercive force of 4.9 A/m. The combination of high GFA and good soft-magnetic properties make the newly developed Fe-based bulk metallic glasses promising for electric applications.

Glass-forming ability and I-phase formation in Y-doped Zr–Nb–Cu–Ni–Al glassy alloys

The effect of yttrium addition on the Glass-Forming Ability (GFA) and thermal stability of Zr58Nb3Cu16Ni13Al10 alloy has been investigated. (Zr0.58Nb0.03Cu0.16Ni0.13Al0.10)100− x Y x (x = 0–3 at.%) metallic glasses were formed by melt-spinning and copper-mould casting methods. By adding 1.5 at.% Y, the GFA of Zr58Nb3Cu16Ni13Al10 alloy is dramatically enhanced, and the critical diameter for glass formation increased from 7 mm to as large as 15 mm. The crystallization processes of the Y-free and Y-doped glassy alloys were studied by differential scanning calorimetry, X-ray diffraction and transmission electron microscopy. It was found that the initial precipitates are face-centred-cubic Zr2Ni and tetragonal Zr2Ni phases for the Y-free Zr58Nb3Cu16Ni13Al10 alloy, but a single icosahedral quasi-crystalline phase for the Y-doped (Zr0.58Nb0.03Cu0.16Ni0.13Al0.10)98.5Y1.5 alloy. This suggests that the yttrium greatly affects the local atomic configuration, which may be the origin for the enhanced GFA of the Y-doped alloys.

Precipitation of Icosahedral Phase in Zr-Ni-Nb-Cu-Al Metallic Glasses

The crystallization behaviors of Zr-Ni-Nb-Cu-Al metallic glasses are greatly influenced by the substitution of Ni for Zr. For the glassy Zr71� xNixNb3Cu16Al10 (x ¼ 7, 9, 11 at%) alloys, the onset temperature of crystallization Tx increases from 717 to 748 K with increasing Ni content from 7 at% to 11 at%. The primary crystallization reaction of the studied glassy alloys corresponds to the formation of icosahedral phase from amorphous matrix. The precipitation of quasicrystalline phase with a large volume fraction in the Zr64Ni7Nb3Cu16Al10 alloy indicates that the decrease of Ni content promotes the formation of icosahedral phase. Johnson-Mehl-Avrami analysis of isothermal transformation data suggests that the icosahedral phase precipitation proceeds by a diffusion-controlled growth mode with nearly constant nucleation rate. Furthermore, the Zr71� xNixNb3Cu16Al10 (x ¼ 7, 9, 11 at%) alloys possess high glass-forming ability, and the critical diameter for glass formation reaching 6 mm, 9 mm and 9 mm by copper-mould casting method, respectively. [doi:10.2320/matertrans.M2009072]

Ductile Fe–Mo–P–C–B–Si bulk metallic glasses with high saturation magnetization

Fe–Mo–P–C–B–Si bulk metallic glasses (BMGs) with high glass-forming ability (GFA), good mechanical properties and high saturation magnetization were synthesized by copper mold casting. The critical diameter for glass formation of the Fe–Mo–P–C–B–Si alloys was up to 5 mm. The Fe-based BMGs exhibited high compressive fracture strength of 3110–3280 MPa, plastic strain up to 5.7% prior to final failure and high saturation magnetization reaching 1.34 T. The ductile Fe–Mo–P–C–B–Si BMGs with high GFA and high saturation magnetization are promising for applications as structural and functional materials.

Effects of Addition of Al, Ti and Ag on Glass-Forming Ability of Cu<sub>50</sub>Zr<sub>50</sub> Alloy

The thermal stability and crystalline phases precipitated from the as-cast rods of the Cu50Zr50-based alloys with addition of Al or simultaneous addition of Al/Ti or Al/Ag elements were investigated using DSC, DTA and XRD. The value of Tx, Trg and γ as a function of alloy composition shows a same trend, in which the Cu46Zr46Al8 alloy exhibits the largest value of Tx, Trg and γ. However, this trend is different from the variation of the dc with alloy composition, in which the Cu42Zr42Al8Ag8 alloy has the largest dc for glass formation. Trg′ based on Tg/Tm has a good correlation with the critical diameter for glass formation in this alloy system. It was found that the alloy with higher GFA has more complex precipitated crystalline phases from the as-cast rod with a diameter larger than the critical diameter for glass formation.