Abstract The effect of the processing parameters on the microstructure during laser solid forming (LSF) of Ti -20wt%Ni alloy was investigated. The microstructure consists of β-Ti dendrite and（β-Ti +Ti2Ni）rod and lamellar eutectic in the inter-dendrite. The characteristic dendritic size F decreased with the decreasing of laser energy density De, resulting from the decreasing of laser power and increasing of scanning velocity, in fact, the characteristic dendritic spacing was decided by. On the other hand, the eutectic spacing also decreased with the increase of scanning velocity. The variation of the characteristic dendritic size and eutectic spacing is roughly in accord with the KGT model and TMK model respectively.
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