DI52A-07
The effects of pressure and alloying Ni and C on sound velocity of liquid Fe-alloys

Friday, 18 December 2015: 11:50
303 (Moscone South)
Hidenori G Terasaki1, Soma Kuwabara1, Keisuke Nishida2, Yuta Shimoyama1, Yusaka Takubo1, Yuji Higo3, Yuki Shibazaki4, Satoru Urakawa5 and Tadashi Kondo1, (1)Osaka University, Osaka, Japan, (2)The University of Tokyo, Tokyo, Japan, (3)Japan Synchrotron Radiation Institute, Hyogo, Japan, (4)Tohoku University, Sendai, Japan, (5)Okayama University, Okayama, Japan
Abstract:
Liquid outer cores of terrestrial planets and satellites are considered to be composed of Fe–Ni with some amount of light elements. It is important to study the effect of Ni together with light elements on the elastic properties, such as sound velocity, of liquid Fe to give a constraint on the core composition. In this study, we have measured the compressional wave velocity (VP) of liquid Fe–Ni and Fe–Ni–C up to 6.6 GPa and estimated the effect of pressure on the and alloying elements (Ni and C) on the VP of liquid Fe-alloys.

High-pressure experiments were carried out using 1500 ton Kawai-type multi-anvil press at BL04B1 beamline, SPring-8 synchrotron facility. VP was measured using pulse-echo overlap method. Used sample compositions were Fe-10wt%Ni and Fe-10wt%-4wt%C.

The obtained VP of liquid Fe–Ni was approximately 2%–3% smaller than that of liquid Fe. Thus, alloying with 10 wt% of Ni slightly reduces the VP of liquid Fe, whereas alloying with C is likely to increase the VP. The compressibility and density of liquid Fe–Ni and Fe–Ni–C were estimated from the measured VP data combined with the equation of state. In the relation between the density (r) and sound velocity (VP), it was found that the effect of C on the VP and r values was opposite to that of Ni at the lunar core condition (~ 5 GPa). This result gives an important constraint for estimating the light element in the lunar core by comparing with lunar seismic data.

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