The effects of high pressure and superheating on the planar growth of Al3Ni phase in hypo-peritectic Al-30wt%Ni alloy

Abstract

The constitutional undercooling criterion of the Al3Ni intermetallic compound with nil solubility was established, which reveals that there is no constitutional undercooling when the initial Al-Ni alloy concentration is lower than 43 wt%. Meanwhile, the interface stability growth criterion for the Al3Ni was also established by considering the effects of pressure and superheating on diffusion coefficient, interface growth rate, interface energy, and kinetic coefficient. The results demonstrate that when the pressure is greater than 4.2 GPa, the Al3Ni phase will move forward with a planar interface without superheating. Under the combined effects of high pressure and superheating the transition point of Al3Ni planar growth decreases. For example, with a superheat of 600 K, the pressure for stable planar growth decreases to 2.7 GPa. In addition, the microstructure of hypo-peritectic Al-30 wt%Ni alloy solidified at different conditions was investigated. It shows that the Al3Ni phase growth interface is unstable at 2 and 4 GPa with no superheating. The microstructure of the sample synthesized at 2 GPa with the superheat degree 600 K is typically hypereutectic microstructure. While the whole sample can be divided into there regions (high pressure solid solution region, mushy zone, and fully melted region which consists of planar growth single phase Al3Ni area and hypoeutectic zone) at 3 GPa/600 K.