Effect of Thermomechanical and Austenite Partitioning Processing on Microstructure and Mechanical Properties of 0.4 Carbon Steel Containing Aluminum

Abstract

Casting of steel with different aluminum content was carried out. Thermo-mechanical process was carried out at 1200°C. A cross-sectional area reduction of 95% was done using hot forging hammer. Two regimes of thermomechanical processes were adopted in this study. First regime was intercritical annealing (between AC1 and AC3 to obtain 50% austenite and 50% ferrite) followed by rapid quenching in salt bath to the martensite zone for 15minutes to produce ferrite, martensite and carbon saturated austenite and to prevent the whole transformation of austenite to martensite. The second regime was reheating 50oC above AC3, followed by rapid quenching in salt bath to the martensite zone (for 15 minutes) to get partially partitioned martensite and super saturated retained austenite. The initial tensile strength after hot forging is 1067MPa and 942MPa for alloys 1 and 2 respectively. The tensile strength after intercritical annealing is 1621MPa while after quenching from austenite to martensite zone with austenite partitioning is 2113MPa. Elongation after intercritical annealing and austenite partitioning is null due to bad shapes and distribution of ferrite with sharp corners.