TORQUE-RELATED LAMELLAR CARBIDE GROWTH-ASSOCIATED WITH ANNEALING TWINS IN 304-STAINLESS-STEEL

A configurational, equilibrium theory for relative interfacial torques has been invoked to qualitatively explain growth-specific lamellar precipitation of M(23)C(6) carbides in 304 stainless steel where the lamellar growth is always in the [112] directions coincident with traces of {111} planes at 90 degrees to (110) grain surface orientations. For (112) grain surface orientations, M(23)C(6) lamellar growth is always in the [1(1) over bar0$] direction which is also coincident with traces of(11(1) over bar) planes at 90 degrees to the grain surface plane. These {111} trace directions for lamellar growth are denoted T90 directions and are shown to coincide with high, relative interfacial torques (or torque configurations) resolved in coherent {111} annealing twin boundaries. For grain surface orientations containing annealing twins or twin/grain boundary geometries whose coherent {111} boundaries are not coincident with T90 directions, such as (100), there are no high-torque configurations and no significant lamellar M(23)C(6) growth coincident with {111} trace directions.