Experimental Verification of a Critical Condition for the Formation of As-Cast Coarse Columnar Austenite Grain Structure in a Hyperperitectic Carbon Steel

Abstract

Experimental verification of a critical condition for the formation of coarse columnar γ grain (CCG) structure in as-cast hyperperitectic carbon steels, which was put forward based on theories of grain growth and phase-field simulations in early studies, is carried out by means of a Bridgman-type directional solidification experiment. The occurrence of the discontinuous and continuous grain growth processes and the resulting formation of CCG and equiaxed γ grain structures, respectively, are demonstrated. Importantly, these changes of the as-cast microstructures and the grain growth modes are in excellent agreement with the previously proposed critical condition of the CCG formation.