Study on dual-phase structure of AISI4140 steel

Heat treatment is a combination of heating and cooling operations, implemented to a metal or alloys in solid state that will produce desired properties. All basic heat treating processes for steel involve the complete or partial transformation or decomposition of austenite. The nature and appearance of these transformation products determine the physical and mechanical properties of given steel. The present work intended to produce a dual-phase structure in medium carbon low alloy Steel (AISI4140) and experimentally investigating the effects of pretreatments (annealing, normalizing) on austenitisation and hence dual-phase properties of AISI4140 steel. Experimental investigation shows considerable positive effect of initial room temperature structure on the characterization of the heat treated dual phase steel. Annealed dualphase steel has more hardness as compared to normalized dual-phase steel. The dual-phase steel (ferrite-bainite) formed with normalizing as pretreatment has got better impact resistance.