Self-diffusion in Zr 55 Al 10 Ni 10 Cu 25 and Pd 40 Cu 30 Ni 10 P 20 Bulk Metallic Glass
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Self-diffusion in Zr55Al10Ni10Cu25 and Pd40Cu30Ni10P20 Bulk Metallic Glass H.Nakajima1, T.Kojima1, K.Nonaka2, T.Zhang3, A.Inoue3 and N.Nishiyama4 1 The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047,Japan 2 Department of Materials Science and Technology, Iwate University, Morioka 020-8551, Japan 3 Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan 4 ERATO,Japan Science and Technology Corporation, Sendai982-0807, Japan ABSTRACT Self-diffusion coefficients of Ni in Zr55Al10Ni10Cu25 and of Ni and Pd in Pd40Cu30Ni10P20 bulk metallic glass below and above the glass transition temperature Tg have been measured with an ion-beam sputter-sectioning technique using the radioactive isotope 63Ni and 103Pd. The diffusion coefficients in the supercooled liquid region are much higher than those extrapolated from low temperature data in the amorphous region. The temperature dependence of the diffusion coefficients exhibits non-Arrhenius behaviour in the supercooled liquid phase. Such a deviation from the Arrhenius plots is interpreted by a cooperation of moving tracer atom with the surrounding atoms. The difference of the diffusion behaviour in between Zr-Al-Ni-Cu and Pd-Cu-Ni-P glasses is attributed to the different structural stability of both glasses.
INTRODUCTION Bulk amorphous alloys produced with much lower critical cooling rates than the rapidly quenched amorphous alloys have been found in multicomponent alloys such as Mg-TM-Ln [1], Ln-Al-TM [2], Zr-Al-TM [3], Zr-Ti-TM-Be [4] etc., where the transition metal TM is Fe, Co, Ni and Cu, and the lanthanide metal Ln is Y, La, Nd, etc. These metallic glasses show an extremely wide supercooled liquid region ΔTx, which is defined by the difference between the crystallization temperature (Tx) and the glass transition temperature (Tg). It has been suggested that there is a close relationship between their extremely good thermal stability and the width of a supercooled liquid region. Various thermal properties such as structural relaxation, glass transition and crystallization are known to be controlled by atomic diffusion processes. Therefore, the knowledge of diffusion is very important for understanding of various processes occurring in the materials. Moreover, diffusion studies in metallic glasses are also of great interest from a technological point of view. However, only limited number of investigations on self- and impurity diffusion were carried out (Geyer et al.[5], Nakajima et al.[6], Nonaka et al.[7], Budke et al.[8], Fielitz et al.[9], Geyer et al.[10], Ehmler et al.[11], Knorr et al. [12]). The accumulation of reliable experimental data is necessary to understand the mechanism of diffusion in metallic glasses. As mentioned above, large sized specimens can be produced at present to measure the diffusion concentration profiles precisely in either a single amorphous phase or the supercooled liquid phase. This paper reports the measurements of self-diffusion coefficients of Ni in Zr55Al10Ni10Cu25 and of Ni an
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