Investigation on supercooling directional solidification process

Supercooling directional solidification(SDS) is introduced by combining melt supercooling and conventional directional solidification by applying supercoolng inheritance. Then SDS of Cu-5.0%Ni alloy was achieved successfully on the self designed SDS equipment. The results are as follows: (1) The microstructure of supercooling solidification is made up by four characteristic regions, from the sample bottom to top are: fine equiaxial dendrites, transition from fine equiaxial dendrites to columnar dendrites, columnar dendrites and coarse equiaxial dendrites. Columnar dendrites occupies about more than 60% of the whole sample length. Its primary arm spacing is about 30 μm, the growth of secondary arms are strongly suppressed. The primary arm spacing is nearly the same as LMC method(G L =250 K/cm, v=500 μm/s), the primary stems are straight, fine and completed, with an inclination angle of about 5.8°; (2) A semi quantitative T-T model is brought forward to describe the dendrite growth rate v vs. Undercooling Δ T. Predictions of T-T model agrees well with experimental results. The formation of fine equipped dendrites, transition region and dendrite region can be explained successfully by ΔT-v-xrelation of T-T model.