Study on the Effect of Applied Pressure on Directional Dendritic Growth by In-Situ Observation

A custom experimental apparatus was designed to realize the in-situ observation of dendritic growth under pressure in directional solidification of model material, succinonitrile. The evolution of dendritic growth under ambient pressure \((P_{0} )\) and pressure of 3.0 MPa (P) was captured by a high-speed microscope and compared by analyzing qualitative distinctions in morphology and the quantitative ones in tip velocity and SDAS. Qualitatively, increased pressure promotes dendrite growth in directional solidification, elevating growth velocity and facilitating the burgeoning and growth of secondary arms, resulting in longer and more developed dendrites and much smaller SDAS. Quantitatively, the average tip velocities under \(P_{0}\) and P are 14.5 μm/s and 29.8 μm/s, respectively, with 100% rise when growing under pressure P. Moreover, the SDAS is 50.3 μm and 30.2 μm, respectively, declining by 40% when solidified under pressure P. This phenomenon can be attributed to the effect of pressure on melting point and its destabilizing effect on S/L interface.