Solidification microstructure evolution modeling in Nb-Si based intermetallics-strengthened-metal-matrix composites

For higher fuel efficiency and greater thrust to weight ratios, there is a continuous drive for higher performance turbine engine components. Nb-silicide intermetallics, owing to their high melting point and high-temperature strength, are potential candidates for high temperature applications. These intermetallics when precipitated in the metal matrix of a (Nb) solid solution, result in intermetallic-strengthened metal matrix composites that have a good combination of room temperature toughness and high temperature strength. The microstructures of these in-situ composites can be complex and vary significantly with the addition of elements such as Ti and Hf. Hence an improved understanding of phase stability and the microstructural evolution of these alloys is essential for alloy optimization. In the present paper we describe binary alloy microstructural evolution modeling of dendritic and eutectic solidification obtained using phase-field simulations. The effect of parameters such as heat extraction rate, the ratio of the diffusivity of the solute in liquid to solid, and the liquid-solid interfacial energy, on microstructural evolution during solidification is discussed in detail.