Papers by Keyword: Glass Forming Ability

Abstract: Metallic Glasses (MGs) have unique mechanical and physical properties making them highly desirable for applications across various fields. However, some MGs have poor Glass-Forming Ability (GFA) and conventional methods to improve it are time-consuming, resource-demanding, and costly. In this study, advanced machine learning (ML) techniques are leveraged to develop robust and data-driven models capable of predicting the critical diameter (Dmax) of MGs from the concentrations of their constituent elements. Dmax is an essential indicator for GFA, whereby higher Dmax values indicate better GFA. A comprehensive dataset encompassing 8,734 MG alloys and their associated Dmax was compiled, cleaned, and analyzed from various sources. The Gradient Boosting model was the best-performing predictive model achieving a R² of 0.86 and a RMSE of 1.66 mm for estimating Dmax, outperforming other models such as Random Forest and XGBoost. Furthermore, the SHAP (SHapley Additive exPlanations) analysis was utilized to rank the importance of individual elements of the alloys, identifying Zirconium (Zr) as the most influential feature in predicting Dmax. Additionally, pseudo-ternary diagrams were generated based on the Gradient Boosting model to identify potential novel BMGs with enhanced GFA. The model's robustness and utility were validated by comparing the Dmax values predicted by the ML model to experimentally obtained values for the Ni_76-xFe_xP₁₄B₆Ta₄ alloy across varying Fe concentrations (x). The results of the study enhance the accuracy of GFA predictions and establish a robust data-driven framework for expediting and automating the discovery of novel BMGs.

Abstract: The elastic properties of the Zr₅₀Cu₄₀Ag₁₀ metallic alloy, such as the bulk modulus B, the shear modulus G, the Young’s modulus E and the Poisson’s ratio σ, are investigated by molecular dynamics simulation in the temperature range T=250–2000 K and at an external pressure of p=1.0 bar. It is shown that the liquid–glass transition is accompanied by a considerable increase in the shear modulus G and the Young’s modulus E (by more than 50%). The temperature dependence of the Poisson’s ratio exhibits a sharp fall from typical values for metals of approximately 0.32–0.33 to low values (close to zero), which are characteristic for brittle bulk metallic glasses. Non-monotonic temperature dependence of the longitudinal and transverse sound velocity near the liquid-glass transition is also observed. The glass forming ability of the alloy is evaluated in terms of the fragility index m. Its value is m≈64 for the Zr₅₀Cu₄₀Ag₁₀ metallic glass, which is in a good agreement with the experimental data for the Zr-based metallic glasses.

Abstract: The alloys Al₈₈Co₄Y₈, Al₈₈Ni₄Y₈, Al₈₇Ni₁₀Ce₃ and Al₈₅Ni₁₀Ce₅ were heated and mixed by using intermediate frequency furnace. By controlling different melt superheat tempratures, a series of thin strip alloy samples were prepared by single roller spinning quenching method. The X-ray diffraction (XRD) results show that melt temperatures have different effects on the amorphous structure formation of Al-(Co,Ni)-(Y,Ce) alloy. In addition The glass forming ability of Al-based amorphous alloy prepared by thermal analysis was analyzed. Experiments results indicate that the higher the melt temperature of Al₈₈Co₄Y₈ alloy, the easier the formation of the crystallization phase.

Abstract: In this paper, a centimeter-size Zr-Cu-Al-Nb bulk metallic glass (BMG) with high notch toughness of 107±13 MPa∙m^0.5 was designed and fabricated by copper mold casting. With 1% Nb substitution for Zr in Zr₄₈Cu₄₅Al₇ glass forming alloy, the glass forming ability (GFA) and toughness of the BMG were enhanced significantly. The coexistence of nano-crystallization and phase separation in the glassy matrix was observed in Zr₄₇Cu₄₅Al₇Nb₁, which would possibly lead to the high toughness of this alloy due to the easy and populous nucleation of shear bands and the increasing resistance of shear band propagation. The influences of nano-crystallization and phase separation on the toughness of BMGs are discussed in detail. The strategy utilized in this study provides a novel approach in search for new BMGs with high toughness and good GFA.

Abstract: For the bulk amorphous Fe_24+xCo_24-xCr₁₅Mo₁₄C₁₅B₆Y₂(X=0, 2, 4, 6 and 17) alloy, the corresponding corrosion properties associated with glass forming ability (GFA) have been carried out. Neutral salt spray corrosion test results show that the Fe₂₈Co₂₀Cr₁₅Mo₁₄C₁₅B₆Y₂ alloy has the minimum corrosion rate, followed by Fe₂₆Co₂₂Cr₁₅Mo₁₄C₁₅B₆Y₂, Fe₂₄Co₂₄Cr₁₅Mo₁₄C₁₅B₆Y₂, Fe₃₀Co₁₈Cr₁₅Mo₁₄C₁₅B₆Y₂, Fe₄₁Co₇Cr₁₅Mo₁₄C₁₅B₆Y₂ and Ti6Al4V alloys. Specifically, the Fe₂₈Co₂₀Cr₁₅Mo₁₄C₁₅B₆Y₂ alloy with the highest GFA also has the best corrosion resistance. With the increasing of Co addition, the corrosion resistance of the FeCo-based bulk metallic glasses is first increases and then decreases, which has the same trend of GFA with the change of Co elements. Furthermore, corrosion morphology are different for FeCo-based BMGs with different Co content.

Abstract: A composition design method from thermodynamic and structural rules for metallic glasses is proposed in this paper. Using the above composition design method, BMG compositions could be determined quickly and it could guide the development of new amorphous alloys. Several new amorphous alloys were fabricated with this new method in Cu-Zr-Ti and Cu-Zr-Al alloying systems. Since this composition design provides a method of determination from both thermodynamic and atomic structure factors, this method increases the accuracy of the amorphous alloy composition design and reduces the development of new amorphous alloy error rate.

Abstract: The Cu₅₀Zr₄₂Al₈ dumbbell-shaped alloy with original scale distance of 25 mm and diameters of 4.5 mm was prepared by the suspend melting-copper mould suction casting. The structure tensile performance testing and the fracture morphology observation of Cu₅₀Z_r42Al₈ BMG as-quenched and 400k/1h isothermal annealing were investigated, respectively. The deformation and fracture behavior of samples had been studied. The results showed that the structure of all samples were composed of amorphous phase and possess good glass formation abilitysample as-quenched is always in the elastic deformation stage during elongation and the tensile strength is 629MPa; however ,for specimen after 400k/1h isothermal annealing ,the yield phenomenon occurs before breaking and the maximum tensile strength is 755Mpa, and the same time, the maximum failure extensibility increases from 0.56% for sample as-quenched to 0.80% for 400k/1h isothermal annealing. The fracture pattern of test sample at annealing assumes venation pattern, which is similar to fractography of Cu₅₀Zr₄₂Al₈ BMG as-quenched, in addition, which appeared apparent viscous flow behavior and melting characteristics.

Abstract: The melt-spun method, X-ray diffractometer (XRD), differential scanning calorimeter (DSC),vickers microhardness measurement and bend test were adopted to study the effects of Cr substitution of Mo on the glass forming ability (GFA), thermal stabilities and mechanical properties of (Fe_0.58Co_0.42)₇₃Mo_17-xCr_xZr₁₀(x=0,3,6,9,12,17at%) ribbons. The results show that when x ranges from 9~17, the ribbons are in an amorphous state. With increasing the Cr content, all the characteristic temperatures including T_gT_xT_p move towards to the lower temperature regions, but the supercooled regionsΔT_x increases, the GFA of sample is rising. In the bend test, all the amorphous ribbons can be classified asductile.

Abstract: In this work, the critical cooling rate R_c for glass formation of a series of Fe_80-xCo_xP₁₃C₇ (x = 0, 5, 10, 15, 20 at.%) alloys was determined by means of constructing CCT curves using Uhlmanns method. The calculated critical cooling rates for x = 0, 5, 10, 15, 20 at.% are 621, 441, 548, 894, 922 K/s, respectively. These results well coincide with the maximum diameters of Fe_80-xCo_xP₁₃C₇ amorphous alloys determined by experiments varying with the content of Co. The calculated R_c was also on the reasonable order of magnitudes. In addition, the values of three common GFA criterions of T_rg, ΔT_x and γ were calculated according to the thermodynamic data determined from DSC and DTA curves of Fe_80-xCo_xP₁₃C₇ (x = 0, 5, 10, 15, 20 at.%) bulk amorphous alloy. The validity of these GFA criterions in the series of Fe_80-xCo_xP₁₃C₇ (x = 0, 5, 10, 15, 20 at.%) alloys were investigated and it was pointed out that these three GFA criterions were not able to explain the experimental results of the maximum diameters of Fe_80-xCo_xP₁₃C₇ amorphous alloys varying with the content x of Co.

Abstract: A series of wedge shape Fe24+XCo24-XCr15Mo14C15B6Y2 (x=0,2,4,6,8) samples were prepared by copper mold suction casting method. The effects of high Co contents on glass forming ability (GFA) and mechanical properties of Fe24+XCo24-X Cr15Mo14C15B6Y2 bulk metallic glasses (BMG) were investigated, respectively. The glass forming ability of bulk amorphous Fe24+XCo24-XCr15Mo14C15B6Y2 (x=0,2,4,6,8) and Fe41Co7Cr15Mo14C15B6Y2 alloys have been researched. Simultaneously, the thermal conductivity parameters of those alloys were tested. The maximum thickness of amorphous region of wedge-shaped samples are dm =7.80 mm for Fe28Co20Cr15Mo14C15B6Y2, dm =7.10 mm for Fe41Co7Cr15Mo14C15B6Y2 and the thermal conductivity are λ=7.11 w.m-1.k-1 and 7.19 w.m-1.k-1, the thermal diffusivity are α=1.875 mm2/s and 1.905 mm2/s for Fe28Co20Cr15Mo14C15B6Y2 and Fe41Co7Cr15Mo14C15B6Y2 BMGs, respectively. The glass forming ability of Fe28Co20Cr15Mo14C15B6Y2 alloy is bigger than that of well known Fe41Co7Cr15Mo14C15B6Y2 alloy. With the change of Co content, the Vickers hardness of Fe24+XCo24-XCr15Mo14C15B6Y2 (x=0,2,4,6,8) change from 1292 to 1322Hv.