Search

Abstract: An enhancement of plasticity in high strength ultrafine eutectic Fe–Nb composites has been accomplished by introducing heterogeneities in length-scale of the microstructure. Addition of Al acting as a stabilizer for the α-Fe phase in the Fe–Nb composites results in the formation of a larger volume fraction of primary α-Fe phase and an ultrafine eutectic structure with reduced lamellar spacing. As a result, Fe–Nb–Al composites exhibit a good combination of fracture strength and plasticity. Due to the presence of the solution hardened α-Fe phase, the Fe–Nb–Al composites exhibit significantly enhanced work hardening behavior at room temperature. [Copyright &y& Elsevier]

Abstract: An ultra-fine eutectic structure has been obtained in the Ti70.5Fe29.5 binary alloy by slow cooling from the melt through arc melting and cold crucible rod casting. The addition of 3.85 at.% Sn to the binary Ti–Fe alloy induces a change of the morphology of the eutectic and increases the volume fraction of the FeTi (Pm3m) phase. A significant improvement of the plastic deformability of the ternary alloy has been observed under uniaxial compressive loading resulting in 16% strain to failure compared to 3.4% for binary Ti70.5Fe29.5. The morphology of the eutectic colonies, their refinement and supersaturation of the β-Ti phase are crucial factors for improving the ductility of the ultra-fine eutectic alloys. [Copyright &y& Elsevier]

Abstract: A Ti67.79Fe28.36Sn3.85 (at.%) alloy has been prepared through arc-melting and solidification at a cooling rate of 40–10K/s. The as-prepared microstructure exhibits a two-phase ultrafine eutectic consisting of FeTi (B2) and β-Ti (A2) phases. The mechanical properties (maximum strength, σ max =1939MPa; strain to fracture, ɛ f =13.5%) are considerably improved if compared with the model Ti70.5Fe29.5 eutectic alloy (σ max =1733MPa, ɛ f =3.4%). The improvement of plastic deformability is assessed in terms of a detailed investigation of the microstructure and fractographic studies. The presence of Sn is believed to boost the ease of slip transfer across the interface between the A2/B2 phases due a higher lattice mismatch between the structures. [Copyright &y& Elsevier]

Abstract We investigate the influence of the ratio between carbon and boron on glass-forming ability, thermal stability and mechanical properties of the Co 65 Cr 13 Mo 22 ternary eutectic alloy modified by carbon and boron addition. Besides, the correlation between the extension of the supercooled liquid region (SCLR) and three bonding parameters, i.e. electronegativity, atomic size, and valence electron is investigated. The results reveal that carbon is more effective than boron to form a glassy phase in this system, and fully glassy alloys or metallic glass composites can be obtained when the metalloid contents are in the range of 20–25 at.%. Fully glassy alloys are only obtained when the carbon-to-boron ratio is 2:1. The glassy alloys and the glass composites exhibit high strength and extraordinarily wide SCLRs of >120 K. The width of the SCLR of the Co-based BMGs can be articulated as a function of three bonding parameters, which is different to the relationship previously observed for Fe-, Mg- and Pd-based BMGs. Based on these findings we propose the optimum C/B ratio for glass phase formation and the new criterion for predicting the width of the SCLR of Co-based BMGs by the three bonding parameters. Graphical abstract Unlabelled Image Highlights • Alloy design via adjusting ratio of carbon and boron based on the pseudo-ternary phase diagram • Unprecedentedly wide supercooled liquid regions of Co-based BMGs up to 122 K • Relationship between ΔT x and three bonding parameters • A new equation to express the ΔT x of Co-based BMGs [ABSTRACT FROM AUTHOR]

Highlights: [•] The colony of ultrafine structure was encapsulated by immiscible Bi upon solidification. [•] This chemical heterogeneity has a strong effect to dissipate the localization of the stress. [•] The ultrafine eutectic alloy with the chemical heterogeneity presented plasticity up to 8.5%. [ABSTRACT FROM AUTHOR]

Abstract: A series of binary Ag80−x Cu20+x ultrafine eutectic composites with x =0, 10, 20, 30 and 40 is prepared by copper mold casting in order to systematically investigate an influence of asymmetrical solubility between Ag and Cu solid solutions on the strengthening of ultrafine eutectic composites. The asymmetrical solubility of the ultrafine eutectic composites determined by the effective solubility index derived from rule of mixtures plays an important role to maintain the strength even with increasing the volume fraction of the micron-scale dendrites. Based on the results, the control of the strengthening of the ultrafine eutectic composites is governed by not only well-known volume fraction of the micron-scale dendrites but also the solubility in the micron-scale dendrites. [Copyright &y& Elsevier]

Abstract: Addition of Si into a Fe70Ni15B15 ultrafine eutectic composite has a significant influence to modulate the microstructure to bimodal eutectic structure comprising lamellar- and irregular-type eutectic by suppressing the formation of the micron-scale dendrites upon solidification. The (Fe70Ni15B15)94Si4 bimodal eutectic composite presents considerably enhanced plasticity of ∼13% with high strength of ∼1520 MPa. The rotational motion of the spherical eutectic colony is considered to be a crucial factor to effectively dissipate shear localization thus improving the plastic deformability. [ABSTRACT FROM AUTHOR]

Abstract: A series of novel Mg90Cu10−x Zn x alloys with x =4, 5, 6 and 7 ultrafine eutectic composites consisting of micron-scale α-Mg dendrites and ultrafine eutectic matrix have been successfully fabricated into a plate sample. By comparing to commercial AZ91 alloy, the ultrafine eutectic composites in the present investigations reveal higher yield strength of ∼230–320MPa at room temperature with gradual enhancement of plasticity up to 8.4% with increasing Zn content. [Copyright &y& Elsevier]

Abstract: Microstructural investigations on ultrafine eutectic (Ti65Fe35)100−x Sn x alloys with x =0, 1 and 3at.% reveal that additional Sn is effective to control formation of the micron-scale dendrites and to decrease the length-scale of lamellar spacing with enhancing macroscopic plasticity at room temperature compression. Hence, it is possible to understand the influence of the microstructural change on the plasticity of the ultrafine eutectic Ti–Fe–Sn alloys. [Copyright &y& Elsevier]

Microstructural investigations of a Fe 81 Nb 9 B 10 ultrafine-eutectic composite reveal that spherical eutectic colonies are composed of the radial lamellar structure together with NbFeB pro-eutectic phases which are central area on radial structure. The spherical eutectic colonies are proposed to be effectual in high yield strength as well as large plasticity by a rotational motion of those along the colony boundary during deformation. Formation of the wavy and dense shear bands is related with strong interaction between specific microstructure and localized shear deformation. Accordingly, the control of microstructural and mechanical factors in hierarchical ultrafine composite is crucial for enhancement of macroscopic mechanical properties. [ABSTRACT FROM AUTHOR]

Abstract: Microstructural investigation on Ti63.5Fe30.5Sn6 and Mg72Cu5Zn23 alloys reveals that bimodal eutectic structure containing the synchronization of structural and spatial heterogeneities in the spherical lamellar entity homogeneously forms upon solidification. Furthermore, the bimodal eutectic Ti63.5Fe30.5Sn6 and Mg72Cu5Zn23 alloys present the enhancement of both strength and plasticity at room temperature compared to the recently developed high strength Ti- and Mg-based alloys. This implies that the bimodal eutectic structure can be one of the effective ways to improve the plasticity of the high strength alloys. [Copyright &y& Elsevier]

Abstract: Microstructural investigation on a series of (Fe65.8Ni14.1B14.1Si6)100−x Nb x alloys with x =0, 2, 4, 6 and 8 reveals that Nb addition leads to modify the constitutive phase and morphology of ultrafine eutectic structure. The microstructural change from bimodal to irregular eutectic structures by addition of Nb has a strong influence to deteriorate the macroscopic plasticity. The bimodal structure and eutectic colony morphology is considered to be an important factor for enhancing both strength and plasticity. [ABSTRACT FROM AUTHOR]