Metastable Austenite Phase in Rapidly Quenched Fe-Cr-C Alloys

Abstract

By rapid quenching technique, metastable austenitic alloys with high strength and hardness have been found in Fe-Cr-C ternary system. This formation range is limited to about 1.0-2.2wt%C and 7-30wt%Cr. The austenite phase has ultra-fine grains of about 0.2μm in diameter. Their Vickers hardness, 0.2% proof stress and tensile fracture strength increase with the amounts of carbon and chromium, and the maximum values reach about 630DPN, 1500 and 1550MPa, respectively. These alloys are so ductile that no crack is observed even after closely contacted bending test. In addition, the changes in microstructure and mechanical properties of the tempered austenitic alloys have been investigated and it has been observed that a large secondary hardening occurs at about 870K due to phase transformation from austenite to equilibrium structure of ferrite and M₇C₃ pearlite. Thus the present alloys may be attractive as a fine gauge high-strength wire or plate.