Abstract
The undercooling dependence of the solidification mechanism was systematically explored by the elec-trostatic levitation(ESL)facility.During the experiments,the maximum undercooling reached up to 406 K(0.26 TL)and the growth velocity of the primary TiNi phase was in-situ determined at various undercool-ings.At the initial increase of alloy undercooling,the value of growth velocity sluggishly rose followed by a power function.In this case,the primary TiNi phase preferentially developed as the equiaxed dendrite,then the remnant liquid participated as Ti2Ni and α-Ti phases on the grain boundary.Once the under-cooling exceeded the critical value of 350 K,the growth velocity of the primary phase displayed a sharply increase tendency.Meanwhile,the TEM results demonstrated that the precipitation of the intermetallic Ti2Ni compound was gradually restrained during the rapid solidification and the R-phase existing in the TiNi matrix at large undercooling implied that the martensitic transformation was incomplete.
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