In-situ observation of unsteady peritectic growth modes

A transparent non-facetted/non-facetted peritectic system was used for in-situ studies of peritectic growth morphologies above and below the limit of constitutional undercooling. For a hypo-peritectic alloy with near peritectic composition an oscillatory growth mode was found for velocities in the cellular/dendritic regime. It is demonstrated that the co-existence of two distinct cellular/dendritic solid/liquid interfaces which try to reach stable growth conditions causes this oscillations. Additionally, it is shown that on reducing the withdrawal speed the two distinct interfaces arrange into an isothermal coupled peritectic growth mode.