Mechanical Behavior of CrMo4 Steel With Dual-Phase Microstructure

Multi-phase microstructures having good ductility may replace the conventional microstructures in different technological applications such as pressure vessels. Mechanical properties including the fracture behavior and the service life of pressure vessels are strongly affected by the microstructure. The objective of this study was to investigate the correlation between different dual-phase microstructures and mechanical properties of 42CrMo4 (AISI 4140) steel. To produce the martensite-bainite (M-B), the martensite-ferrite (M-F), and the ferrite-bainite (F-B) microstructures, the step quenching heat treatment was used. Mechanical properties of heat treated samples including the strength, ductility, and impact energy were measured. Tensile experiments revealed a discontinuous yielding in the F-B specimen with ferritic matrix. Fracto\graphic results showed high concentration bright facets (BFs) on broken specimen surfaces indicating the brittle cleavage fracture was the predominant mechanism in the dual-phase microstructures.