Impact of microstructure on the mechanical properties and the toughness ofD6A steel

The present article deals with the impact of microstructure on the mechanic al properties, specifically the toughness of the D6A steel containing 0.45% C, 0.5% Ni, 0.97% Cr, 0.09% Mo and 0.06% Ti. Suitably prepared specimens w ere first austenized and then quenched using water (25 degrees C), oil (65 degrees C), salt bath (200 degrees C) or air as cooling media. They were su bsequently annealed at 500 degrees C for 120 min. The metallographic invest igations of the microstructure were performed by means of optical light mic roscope and scanning electron microscope. The effect of the microstructure on the mechanical properties, i.e. hardness, tensile strength, impact stren gth and fracture toughness of the steel involved were studied using standar d test methods. The experimentally obtained results indicate that most favo rable mechanical properties may be achieved by oil quenching (65 degrees C) and annealing the steel at 500 degrees C.