Phase stability in austenitic stainless steel weld deposits

Abstract

Recent theories of precipitation, nucleation, and growth are discussed in relation to the phase stability of two steel weld deposit materials. The materials consist of regions of δ-ferrite surrounding austenite grains. Copious precipitation occurs in the δ-ferrite. Nucleation and growth intragranular precipitation models are shown to represent the real situation for M₂₃C₆, σ, and spherical Laves phase, whereas needle-shaped Laves phase appears to be governed by a boundary assisted growth mechanism. Needle-shapes are produced by small microcompositional changes occurring in the Laves phase. These changes cause low energy facets to form, with the resulting deviation from spherical shape and change in growth mechanism.

MST/614