Metallographic, Structural, and Mechanical Characterization of Weld Nuggets in Fe–Mn–Al–C Low‐Density Steels Microalloyed with Ti/B and Ce/La by Gas Tungsten Arc Welding Process

Abstract

The use of low‐density (LD) steels has become increasingly important due to the advantages they offer, such as high strength, high ductility, and principally weight reduction. However, there are few studies regarding their weldability by conventional processes due to the metallurgical complexity of these alloys, including kappa carbides precipitation and hot‐cracking associated with the high contents of Mn, Al, and C. Herein, the main objective is the characterization of the fusion zone and different heat‐affected zones of austenitic Fe–Mn–Al–C LD steels microalloyed with Ti/B and Ce/La. For this purpose, weld nuggets were prepared by autogenous gas tungsten arc welding process using heat inputs of 660 and 975 J. The weld nuggets were characterized metallographic, structural, and mechanically by light optical microscopy, scanning electron microscopy, X‐ray diffraction, and Vickers microhardness. In general, weld nuggets shows three well‐defined zones where γ‐austenite is the main phase and AlN and MnS particles act as nuclei of complex precipitated particles of microalloying elements such as TiC and (Ce, La)O. A considerable decrease in hot‐cracking was noticed in the microalloyed grades. A modulated structure of kappa‐carbide particles was responsible of the largest hardness values (≈450 Vickers microhardness) in the second heat‐affected zone.