The role of connectivity of martensite on the tensile properties of a low alloy steel

The effects of martensitic morphology and its distribution in a ferrite matrix on tensile properties of a low alloy steel have been studied. Two distinct microstructures were developed solely by heat treatment, i.e., no thermo-mechanical processing was involved; one consisted of continuous ferrite matrix with embedded islands of martensite (MD: martensite dispersed). The other was continuous martensite phase with embedded islands of ferrite (MC: martensite continuous). The MC structure results in a tensile strength of 977 MPa as compared to 938 MPa for the MD structure, despite the fact that the latter had an 8% higher volume fraction of martensite. The increase is attributed to the continuous distribution of the martensite.