Unique Microstructure Evolution of HPT-Processed (α+γ) Two-Phase Stainless Steel

A high-pressure torsion (HPT) processed Fe-21Cr-5Ni-2Mo (mass%) two-phase stainless steel was used to study the morphology and crystallographic features of austenite (γ) precipitated from ferrite (α) during aging in (α + γ) region. The starting material a gas-atomized powder with completely ferritic structure. HPT process carried out produce fully dense compact under 6 GPa for 5 revolutions. given an equivalent strain about 130. After process, matrix formed pancake–like nanograined structure strong texture, i.e. ND (Normal Direction) // {110} α. By annealing at 1173 K 3.6 k, ultrafine microduplex high-angle grain boundaries formed. In addition, texture formation α / {111} γ plane duplex phases had average sizes 2.1 μm 1.6 μm, respectively. area fraction phase 37.2%, which exceeded that cold-pressed compact, 6.7%. Both refinement precipitation were accelerated by process. other words, application alloys enables Kurdjumov-Sachs (K-S) orientation relationship between is usually observed alloy, however, K-S not dominant except close packing parallel relationship, γ, HPT-processed material.