Anomalous dendrite growth in undercooled melts of Al-Ni alloys

Abstract

We have measured dendrite growth velocities as a function of undercooling on liquid Al-Ni alloys using electromagnetic levitation on Earth and in reduced gravity. In total, six differently concentrated alloys are investigated, one of them for comparative investigations during the sounding rocket mission TEXUS 44. While on the Ni-rich side of Al-Ni alloys growth velocity is increasing with increasing undercooling, Al-rich Al-Ni alloys show an unusual decrease of the growth velocity with increasing undercooling in the terrestrial investigations. The comparison of the results of complementary terrestrial and microgravity experiments suggests that the anomalous growth behavior of Al-rich Al–Ni alloys may be caused by fluid-flow related processes during non-equilibrium solidification of undercooled melts. Support by ESA within contract number 15236/02/NL/SH (NEQUISOL) and by the European Commission EC under contract FP6-500635-2 (IMPRESS) is gratefully acknowledged.