Formation of Oriented and Graded Grain Structure in Fe-Cu-C Alloy by Liquid Phase Sintering and Carburization

Abstract

Quantitative microstructural measurements were made on the oriented and graded structures of the liquid-phase sintered and subsequently carburized Fe-Cu-C compacts. The possible mechanism of the formation of the microstructure has been proposed, in which a concurrent effect of chemically driven liquid film migration, and the decrease in the grain boundary energy, both originated from carbon dissolution, as well as of the surface flattening by capillarity, is the main cause for the formation of oriented and elongated grains. The energy minimization in the graded mirostructure was discussed in terms of the total interface energy in liquid phase sintered alloys. The constancy of the total interface energy throughout the graded compact, the linear relationship between the liquid volume fraction and dihedral angles, as well as the liquid flow towards carbon-diffusion front, strongly suggest that the graded compact is energetically in equilibrium.