Effect of morphologies of martensite–austenite constituents on impact toughness in intercritically reheated coarse-grained heat-affected zone of HSLA steel.

By using the gleeble-3500 simulator, three different two-pass weld thermal cycles were applied to base metal of a high strength low alloy (HSLA) steel with the purpose of obtaining martensite-austenite (MA) constituents of different morphologies in intercritically reheated coarse-grained heat-affected zones (ICGHAZ). Morphology of each MA constituent was characterized by maximum length, maximum width and aspect ratio (maximum length/ maximum width). Toughness of thermal simulated specimens was examined by using an instrumented Charpy impact tester. Behaviour of cracks was present by Charpy impact curve and typical data. Correlation between behaviour of cracks and morphologies of MA constituents was further analysed by observing crack propagation and microstructure of MA constituent. Fracture modes of MA constituents with slender and massive shape were proposed. Results show that slender MA constituents are more harmful to toughness compared with massive ones. [ABSTRACT FROM AUTHOR]