Elastic Properties and Microstructure of Metallic Glasses Pd 39 Ni 10 Cu 30 P 21 Studied by Microacoustical Technique
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Elastic Properties and Microstructure of Metallic Glasses Pd39Ni10Cu30P21 Studied by Microacoustical Technique Vadim M. Levin 1, Julia S. Petronyuk 1, Limin Wang 2, Jiankai Hu 3, Qianlin Zhang 4 1 Lab. of Acoustic Microscopy, Institute of Biochemical Physics, Russian Academy of Sciences, 4 Kosygin st., 119991, Moscow, Russia; 2 Institute of Physics & Center for Condensed Matter Physics, Chinese Academy of Sciences, P.O.Box 603, 100080, Beijing, People’s Republic of China; 3 Lab. of Ultrasonic NDT, Dept. of Electr. Engineering, Univ. of Science & Technology of China, 230026, Hefei, Anhui, China; 4 Dept. of Electronic Engineering, Graduate School, Chinese Academy of Sciences, 100039, Beijing, China;
ABSTRACT The elastic properties of Pd39Ni10Cu10P21 bulk metallic glass (BMG) have been analysed using measurements of sound velocities. Different states of the Pd39Ni10Cu10P21 system (glassy state, supercooled liquid (SCL) and polycrystalline state) were obtained by annealing the samples near the glass transition and crystallization onset temperature. The microacoustical technique has been applied to measure local values of longitudinal and transverse elastic wave velocities and their distribution over a specimen. Finally sound velocities VL and VT, density ρ, bulk K and shear G elastic moduli were measured for different states. The values of ρ, VL and K decrease as temperature increases and the transition from glass to SCL takes place. In the crystalline state ultrasonic measurements were performed by the standard pulse ultrasonic technique with low-frequency flat transducer because of high ultrasonic attenuation in this state. Acoustic images (C-scans) demonstrate coarse-grained microstructure in this state. This is assumed to be characteristic of the microstructure obtained by crystallizing BMG.
INTRODUCTION Multicomponent glass-forming alloys of the Pd-Ni-Cu-P and Zr-Ti-Cu-Ni-Be systems are intensively studied due to their extraordinary glass forming ability. Elastic characteristics of bulk metallic glasses (BMG) are sensitive to changes of the matter microstructure. Ultrasonic techniques are widely applied to measure elastic wave velocities, to evaluate BMG elastic properties in diverse states and to study transitions between these states [1-2]. The temperature dependence of elastic wave velocities and elastic moduli provides the important information on the microstructural features of BMG. Two variants of ultrasonic measurements are can be applied for these purposes. Standard ultrasonic methods are founded on using plane waves; the techniques give information on integral elastic and acoustic properties of the BMG sample as a whole. Application of focused ultrasound makes it possible to study local physical and structural characteristics of a matter. The microacoustical technique is based on employment of short probe pulses of focused ultrasound. It provides measuring elastic moduli in thin objects, in small-sized specimens or inclusions. Mechanical scanning of the probe focused ultrasonic beam (acoustic
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