Structural Characterization Of Phase Separated Fe-Cu-Zr-B Amorphous Alloy

In the Fe-Cu binary and multi-elements system,because of the positive mixing enthalpy between Fe and Cu?13 KJ/mol?,the homogeneous liquid would separate into two liquid phases with distinct chemical compositions and achieve phase-separated composite structure at solid state.Although many efforts has been made to understand the formation of the composite structure,the distribution of second phase particles and the formation of the corresponding atomic structure are still unknown.In the present study,the distribution of the second phase particles and the atomic structure of Fe-Zr-B matrix have been systematically investigated through high resolution transmission electron microscopy?HR-TEM?and synchrotron radiation high energy X-ray diffraction?HE-XRD?method along with the Reverse Monte Carlo simulation.Main conclusions are as follows:1.According to the HR-TEM and SAED results,the Fe₇₅Zr₁₀B₁₅5 turns out a typical amorphous feature while the Fe₆₅Cu₁₀Zr₁₀B₁₅ and Fe₇₀Cu₅Zr₁₀B₁₅show typical phase-separated feature with composite structure with the coexist of fcc-Cu and Fe-Zr-B amorphous phase.The scattering factors of the first diffraction ring are with the same value(2.95?^-1)among three compositions which could roughly reflect the invariant of the amorphous structure at this scale.2.The distribution of the second phase particles is further investigated based on the TEM results.Due to the different degrees of supercooling,the mean particle size and number density are quite different between Fe₆₅Cu₁₀Zr₁₀B₁₅ and Fe₇₀Cu₅Zr₁₀B₁₅.For Fe₆₅Cu₁₀Zr₁₀B₁₅,the values of mean particle size and number density are 37.3 nm and 6.4×10^-6 1/nm³;In contrast,for Fe₇₀Cu₅Zr₁₀B₁₅,the values of mean particle size and number density are 14.8 nm and 3.6×10⁵ 1/nm^-3.3.The volume ratio of particles between Fe₆₅Cu₁₀Zr₁₀B₁₅ and Fe₇₀Cu₅Zr₁₀B₁₅ is 2.8 which denotes the insufficient transformation from Cu liquid globules to fcc-Cu in the solid state.Namely,there are few amount of Cu atoms dissolved in Fe-Zr-B amorphous matrix in Fe₆₅Cu₁₀Zr₁₀B₁₅ and Fe₇₀Cu₅Zr₁₀B₁₅.4.The first peak position of the pair distribution function shifted from2.541?to 2.551?with the increasing number of Cu.Meanwhile,the values for the maximum range of the first coordination layer moved from3.41?to 3.43?correspondingly;However,the values for coordination number of the first layer are identical among three compositions.5.Voronoi tessellation on clusters of the amorphous matrices of Fe₇₅Zr₁₀B₁₅,Fe₇₀Cu₅Zr₁₀B₁₅5 and Fe₆₅Cu₁₀Zr₁₀B₁₅ are investigated through the Reverse Monte Carlo simulation,correlating with the obtained pair distribution functions.The distribution of main clusters keeps almost the same with different Cu contents.Moreover,the mean crystallization parameters,which reflect the structural order,are 0.5853,0.5992,0.5976for Fe₇₅Zr₁₀B₁₅,Fe₇₀Cu₅Zr₁₀B₁₅5 and Fe₆₅Cu₁₀Zr₁₀B₁₅ respectively.According to the simulation results,the atomic structure of Fe-Zr-B amorphous phase keeps invariant among three compositions and the shift of the first peak positions of pair distribution function could be further ascribed to the increasing contents of fcc-Cu.