Precipitation in as-solidified undercooled Ni–Si hypoeutectic alloy: Effect of non-equilibrium solidification

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 528; no. 22; pp. 6844 - 6854
• Main Authors: Fan, Kai, Liu, Feng, Yang, Gencang, Zhou, Yaohe
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 25.08.2011; Elsevier
• Subjects: Cross-disciplinary physics: materials science; rheology; Diffusion; Exact sciences and technology; Kinetics; Materials science; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Precipitation; Solid-state reactions; Solidification; Precipitation; Kinetics; Diffusion; Solid-state reactions; Nickel base alloys; Particle size; Annealing; Cooling; Superheating; Real time; Solidification; Supercooled liquids; Silicon alloys; Aging; Supercooling; Dendrites; Nucleation density; Transition element alloys
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2011.05.004

► The solid solubility of Si atom in α-Ni matrix increased with undercooling in the as-solidified sample. ► The effect of non-equilibrium solidification on precipitation has been theoretically described. ► The nucleation density, the real-time particle size and the precipitation rate are all increased upon annealing. ► The precipitate process can be artificially controlled by modifying the initial melt undercooling and the annealing time. Applying glass fluxing and cyclic superheating, high undercooling up to ∼350 K was achieved for Ni–Si hypoeutectic alloy melt. By isothermally annealing the as-solidified alloy subjected to different undercoolings, precipitation behavior of Ni 3Si particle, at 973 K, was systematically studied. It was found that, the nucleation density and the real-time particle size, as well as the precipitation rate, were all increased, provided the sample was solidified subjected to higher undercooling. This was ascribed mainly to the increased solid solubility of Si atom in α-Ni matrix upon non-equilibrium solidification. On this basis, the non-equilibrium dendrite growth upon solidification and the soft impingement prevailing upon solid-state precipitation have been quantitatively connected. As such, the effect of liquid/solid transformation on subsequent precipitation was described.