Three-dimensional observation of ferrite plate in low carbon steel weld

Abstract

The early stages of the formation of acicular ferrite in a low carbon steel weld were studied by serial sectioning and computer-aided three dimensional (3D) visualization. The specimens were taken from the weld of low carbon steel, containing 0.08% C, 0.9% Si, 1.57% Mn and 0.032% O, and were austenitized and isothermally reacted at 600 and 570̈C for less than 10s. Very thin and long plates were formed initially and thickening occurred probably after lengthening was hampered due to impingement on prior austenite grain boundaries and/or pre-formed ferrite plates. Multi-variant ferrite plates were nucleated at inclusions and grew radially in the directions close to 〈110〉γ with habit planes near {111}γ, thus forming a characteristic "Widmanstätten star" noted earlier in a medium carbon steel on polished surfaces.