AbstractUndercooled melts are metastable with respect to the lower Gibb's free energy of the corresponding solid state and due to the activation barrier against nucleation. This gives access to direct solidification into metastable solid phases. Nucleation of metastable bcc phase in FeNi alloys has been demonstrated if undercoolings below its melting temperature are achieved and if the nucleation barrier is decreased by offering nucleation seeds of proper catalytic potency. Moreover, measurements of rapid dendrite growth velocities on containerlessly undercooled Ni-base alloys reveal deviations from local equilibrium at the solid-liquid interface. These are generated by a kinetic undercooling of the solidification front and solute trapping effects at high crystallisation velocities. The microgravity environment of space gives access to an extended degree of undercooling and thus to an enhanced range of metastable materials.
Non-equilibrium solidification of undercooled metallic melts
Advances in Space Research ; 11 , 7 ; 255-262
1991-01-01
8 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
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