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

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Abstract
By rapid quenching technique, nonequilibrium austenitic alloys with high strength and hardness have been found in Fe-Cr-C ternary system. This formation region is limited to about 1.02.2 wt%C and 730 wt%Cr. The austenite phase has ultra-fine grains of about 0.2 μm in diameter. Their Vickers hardness, 0.2% proof stress and tensile fracture strength increase with increase in the amounts of C and Cr, and the maximum values attain about 630 DPN, 1 500 MPa and 1 550 MPa, 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 high-strength wire or plate.