Nano-carbide strengthened as-welded joint for precipitation-hardened austenitic Fe-Mn-Al-C lightweight alloys

To date, fusion welding the precipitation-hardened austenitic Fe-Mn-Al-C lightweight alloys still remains an insurmountable challenge. In the present study, the viability of using a Fe-28.3Mn-10.2Al-1.62C (in wt.% hereafter) as a welding filler wire for gas tungsten arc welding (GTAW) of as-hot-rolled Fe-29.2Mn-8.8Al-1.65C base material (BM) were systematically investigated. It was striking that in the as-welded condition, a high density of nano-sized k-carbide precipitates was formed by spinodal decomposition within the significantly refined austenite dendrite cells in the fusion zone (FZ). This unique feature is critical to achieve a high weld strength in virtually all fusion welded precipitation-hardened alloys. In the heat-affected zone (HAZ), the strengthening nano-sized k-carbides originally existed in the BM was also preserved with no sign of dissolution or noticeable coarsening. Consequently, the as-welded joint exhibited a fairly uniform microhardness across the FZ, HAZ and BM. More significantly, the entire as-welded joint is free of any solidification cracking and/or liquation cracking. The as-welded joint also exhibited an excellent combination of yield strength, ultimate tensile strength and ductility. (C) 2021 The Authors. Published by Elsevier B.V.

Automated summary

This study systematically investigated the feasibility of using a new welding filler material for gas tungsten arc welding of Fe-Mn-Al-C lightweight alloys. The results showed that the welded joints had high strength and uniform microhardness distribution, with the original strengthening phase preserved in the heat-affected zone. The joints exhibited excellent mechanical properties without any cracking, showing the potential for achieving high weld strength in precipitation-hardened alloys.