Internal Friction and Elastic Modulus Change Associated with Structural Relaxation and Crystallization in Amorphous Mg-N
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Internal friction and elastic modulus change associated with structural relaxation and crystallization in amorphous Mg-Ni-Y alloys. Y. M. Soifer, N. P. Kobelev*, E. Korin, L. Soifer, D .Mogilyanskii, A. Bettelheim** * Institute of Solid State Physics, RAC, Chernogolovka 142432, Moscow region, Russia **Department of Chemical Engineering, Ben-Gurion University of the Negev, P.O. Box 653 84105, Israel
ABSTRACT Mechanical spectroscopy technique has been applied to investigation of structural relaxation and crystallization of Mg-Ni-Y amorphous alloys of different composition. The composition of the alloys was varied due to change of yttrium concentration from 0 to 7 at.%. The internal friction (IF) and Young’s modulus have been measured by a vibrating reed method at frequency of ~200 Hz at heating and cooling runs in the temperature range from 300K to 650K. Crystallization kinetic studies of the alloys by DSC and XRD showed that the transition from amorphous to crystalline state in the Mg-Ni-Y alloys has gone through several stages with origination of intermediate phase. IF spectra and Young’s modulus of the alloys have been analyzed and the effect of yttrium content on the stability of intermediate phase was investigated. INTRODUCTION Magnesium based amorphous alloys have attracted great interest as they combine enough high strength with very low density and therefore can be considered as potential candidates for many applications in the aerospace and ground transportation industries. In the first turn the saying above refers to the alloys containing nonequilibrium phases such as amorphous, quasicrystalline and nanocrystalline phases [1,2,3]. The particular properties and variation of the relationship between these phases can essentially influence the mechanical and other physical properties of the alloys. Since the internal friction (IF) and Young’s modulus measurements are very sensitive methods for investigation of structural rearrangements in solids, mobility of atoms which are responsible for the thermodynamic behavior and mechanical properties of metallic glasses, they used widely for studies of structural relaxation and crystallization of amorphous alloys. Our recent studies [4,5] of the crystallization process of amorphous Mg84Ni12.5Y3.5 alloy showed that this process was multistage and one of the intermediate phases, we called it " MgxNiyYz" phase, exhibited the highest elastic modulus among the all structural phases known for this alloy. The present study is undertaken with the objective to evaluating the influence of alloy composition and heat treatment conditions on the alloy phase structure and their role in formation of elastic, dissipative and mechanical properties of the Mg-Ni-Y alloys. EXPERIMENTAL Rapidly quenched amorphous Mg-Ni-Y alloys have been produced by melt-spinning on the copper drum surface in vacuum. The composition of the alloys was varied due to change of yttrium concentration from 0 to 7 at.%. There were 4 types of specimens of different content of L11.3.1
yttrium: alloy 1 (Y=0 at %),
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