Effect of the intermediate quenching on fracture toughness of ferrite-martensite dual phase steels

Abstract

The main aim of the research work is to examine the fracture toughness of the dual phase steels prepared using the intermediate quenching method. The ferrite-martensite dual phase (DP) steel is produced using low carbon micro alloyed steel by the heat treatment and intercritical quenching technique using various intercritical temperatures such as 740,760,780,800 and 820oC. The samples of the produced dual phase steel are analyzed for their microstructure using optical microscope. The fracture toughness investigations for the dual phase steel have been carried out using ASTM standard testing procedure. From the results it is observed that the fine distribution and equal volume fraction of ferrite and martensite phases at 780oC. The effect of which, the A780 steel has demonstrated excellent fracture toughness which is the result of intermediate quenching technique. The fractography analysis it is clear that the ductile initiated brittle fracture is occurred which is due to the increased hard martensite phase and the increment in the stress accumulation at the ferrite which also leads to the higher elongation.

Experimental and numerical evaluation of semi‐circular bending specimen for mixed mode I/III and pure mode III fracture tests

“…On the mode I and mode II loadings, various geometries and fixtures have been suggested and used by researchers to explore the fracture behavior of materials. For example, notched beam, 1–7 rectangular plate, 8–10 Brazilian disc, 11–13 chevron bend, 14 disc‐shaped and rectangular compact tension, 15–21 semi‐circular bending (SCB), 22–26 and disc shaped 27 specimens are among the test methods that have been employed in the past years.…”