Effect of tempering temperature on microstructure and mechanical properties of AISI 6150 steel

Effect of tempering temperature on the microstructure and mechanical properties of AISI 6150 steel was investigated. All samples were austenitized at 870 °C for 45 min followed by oil quenching, and then tempered at temperatures between 200 and 600 °C for 60 min. The results show that the microstructure of tempered sample at 200 °C mainly consists of tempered martensite. With increasing the tempered temperature, the martensite transforms to the ferrite and carbides. The ultimate tensile strength, the hardness and the retained austenite decrease with increasing tempered temperature, and 0.2% yield strength increases when the temperature increases from 200 to 300 °C and then decreases with increasing the temperature, but the elongation and impact energy increase with increasing the tempering temperature.