Nanocrystallization of Al₉₂Sm₈studied by electrical resistivity—formation of monatomic Sm spherical layer

Abstract

We present a model describing the temperature dependence of the resistivity of the Al92Sm8 system during formation of fcc-Al nanocrystals. We take into consideration changes in resistivity of the amorphous phase due to the changing content of Al, the varying density of the crystallization nuclei, the creation of the Sm layer on the grain surface and decomposition appearing during annealing of the amorphous phase. Our calculations exhibit a better agreement with experimental electrical resistivity data for the nanocrystallization model considering previous decomposition of amorphous structure and formation of a monatomic Sm layer on grain boundaries than for a model of nanocrystallization on quenched-in nuclei with growth controlled by diffusion with a diffusion field impingement.

Electron transport properties of Al–Sm and Al–Sm–Ni amorphous and nanocrystalline alloys

“…The (2) mechanism involves a nucleation on quenched-in nuclei followed by a nanocrystals growth controlled by diffusion with diffusion field impingement of diffusion fields. Our recent analysis [4] shows that applying this model to electrical resistivity one obtains unacceptable discrepancies with experimental results. The satisfactory conformity with experimental data is easily achieved in a framework of (3) model based on spinodal decomposition.…”

“…1 demonstrate that a raising crystalline fraction X (with raising T m ) renders a monotonic reduction of electrical resistivity at room temperature accompanied by the TCR enhancement. The values of X are determined from DSC measurements, as described in [4].…”

“…Crystalline fraction X obtained from DSC measurements [4] for alloy annealed to T m = 470 K equals to 0.14.…”

Thermal variation of electrical resistance of an Al85Ni5Y8Co2 metallic glass free of quenched-in nuclei

“…Co-existence of quenched-in nuclei, glass transition on a DSC curve and nucleation of Al crystals were observed in an Al 85 Ni 5 Y 8 Co 2 metallic glass [9], which apparently contradict to Perepezko's quenched-in nuclei growth model [7]. On the other hand, spinodal decomposition prior to nanocrystallization has been found for Al 92 Sm 8 amorphous alloy, which was previously attributed to a typical growth of quenched-in nuclei on the basis of absence of glass transition on a DSC profile [7,[10][11][12]. The formation mechanism of high density of nano-meter sized Al crystals remains still an open question and deserves some more careful study.…”

Thermoelectric and electrical resistivity study of Hitperm alloys

“…These changes in the transport properties are caused by the electron mobility raising in the more structurally ordered nanocrystalline phase [22]. The more advanced analysis proves that a complete description of transport parameters in the nanocrystallizing alloys, requires to account for the additional factors, like the electrical resistivity of emerging nanocrystalline phase, grain sizes and electron scattering on grain boundaries [23]. The somewhat specific behavior of the Nb containing alloys Table 1 Parameters obtained by fitting Eqs.…”