Anomalous behavior of aluminum near the melting temperature: transition in the rate controlling mechanism of yielding and realization of superheated solid states under tension.

G.I. Kanel1, S.V. Razorenov2, K. Baumung3, and H. Bluhm3

1Institute for High Energy Densities, IVTAN, Izhorskaya 13/19, Moscow, 127412 Russia

2 Institute for Chemical Physics Research Chernogolovka, 142432 Russia,

3 Forschungszentrum Karlsruhe, P.O. Box 3640, 76021 Karlsruhe, Germany.

Abstract. Results of measurements of the spall strength and the Hugoniot elastic limit of aluminum, magnesium, and zinc over a wide temperature range are analyzed. A comparison of calculated temperatures in the stretched material with the extrapolated melting curve shows high resistance to spall fracture of single crystals is maintained when melting should start. The superheating of aluminum crystals reached 60 65 K. This anomaly was not recorded for polycrystalline metals where melting starts earlier at grain boundaries. The anomalous growth of the dynamic yield strength is interpreted as an evidence of a transition in the rate-controlling mechanism from the dislocation motion aided by thermal fluctuations to the phonon drag mechanism of over-barrier motion.

 

Als Vortrag:

12th APS Conference on Shock Compression of Condensed Matter, Atlanta, Georgia,

June 24-29, 2001