## 4 Discussion  
The two low-density steels, Fe-30.9 Mn-4.9 Al-4.5 Cr-0.4C and Fe-21.3 Mn-7.6 Al-4.3 Cr-1C, considered in this study were identified as austenite-based duplex low-density steel and austenitic low-density steel, respectively. Their composition and initial microstructures are consistent with the classification prescribed by [PERSON] et al. [4]. The interest in these alloys stemmed from their potential to be used as alternative bio-implant materials given their lower corrosion rates in simulated body fluids compared to commercial-grade 316L stainless steel [10]. Similar to Fe-Mn-Al-Cr-C low-density steel subjected to corrosion investigation in NaCl and NaOH in a previous study [11], pitting corrosion was observed in the two alloys that were considered in this study. However, the location of the pits differed. In previous work, the shallow and tiny pits formed on all phases in the alloy, whereas the deep pitsin these alloys formed preferentially at the inter-dendritic regions due to the dissolution of the austenite-carbide interface, resulting in the pullout of carbide particles [10]. To address this problem, we hypothesized that breaking the dendritic structures in both alloys using thermomechanical processing routes would help redistribute the alloying elements, eliminate segregation, and ultimately reduce the susceptibility of the alloys to pitting corrosion. However, the response of the alloys to hot working parameters is unknown as they have unique compositions that have not been subjected to hot working investigations previously. Additionally, previous studies on the hot working of Fe-Mn-Al-C low-density steels have only been on alloys subjected to either heat treatment or some form of forging or rolling prior to hot working experiments [15; 16; 25]. Therefore, the initial microstructure of the hot-worked Fe-Mn-Al-C low-density steels reported in the literature differs from the dendritic structure that was the focus of this work. In this study, the alloys were in the as-cast condition, and it is important to establish the most appropriate deformation conditions for breaking the alloys' dendritic structure. While the ultimate goal is to improve resistance to pitting corrosion in these alloys through microstructural control, the thrust of this study was to understand how the two low-density stainless steels respond to imposed hot working conditions. The hot working parameters considered here were selected from previous studies on the hot working of Fe-Mn-Al-C low-density steels [14; 25]. This approach differs from the common practice in previous studies [14; 15] where a wide range of strain rates and deformation temperatures were selected to establish the safe and unsafe working regime for a specific alloy. While the parameters selected for the alloys were typical safe working regimes for many Fe-Mn-Al-C low-density steels [14; 15; 25], we assessed if these parameters would be suitable for hot working of the two alloys investigated in this study. If suitable, defects such as voids, cracking, incipient melting, and adiabatic shear bands are not expected in the alloys after deformation. Although the continuous flow softening seen in the flow curves (Figure 5b) under specific working conditions (800 and 900 \({}^{\circ}\)C at 0.1 s\({}^{-1}\)) suggest the occurrence of either deformation-induced cracking or dynamic depolarization during deformation [18], the microstructural evidence showed that continuous flow softening was caused by dynamic globularization (Figure 8a,c). No cracking or other defects were seen in the deformed samples of the two alloys. This confirmed that the safe hot working parameters selected from previous works are indeed suitable for the hot working of Fe-30.9 Mn-4.9 Al-4.5 Cr-0.4C and Fe-21.3 Mn-7.6 Al-4.3 Cr-1C low-density stainless steels. From the flow behavior of the alloys in Figure 5, flow oscillations were dominant on the stress-strain curves when hot working was carried out at a strain rate of 0.1 s\({}^{-1}\).