INFLUENCE OF MICROSTRUCTURE ON MECHANICAL PROPERTIES OF TWO SINGLE-BEAD FERRITIC WELD METALS.

The microstructures and mechanical properties of two single-bead ferritic weld metals are compared in the as-welded and artificially aged condition. The observed notch toughness behavior of both weld metals can only be understood, if differences between the principal microstructural constituents on a submicron scale are taken into account. These differences appear to be responsible for an increase in hardness and strength, offsetting the beneficial effects of more acicular ferrite and a finer microstructure. The individual constituents can be characterized by microhardness and crack propagation path measurements. The mutual differences are expressed in terms of a fracture sensitivity parameter, indicating a different resistance to cleavage for each microstructural constituent. It is emphasized that transmission electron microscopy, in combination with microanalytical techniques, is needed to reveal further details.