Effects of solution treatment on grain coarsening and hardness of laser welds in UNS N10003 alloy contained different carbon content.

Microstructure and microhardness evolution of laser welds in low carbon UNS N10003 alloy (LC alloy) and high carbon UNS N10003 alloy (HC alloy) before and after solution treatment have been characterized and investigated in this work. The eutectic M 6 C-γ carbides have been transformed into spherical M 6 C carbides in fusion zone of HC alloy, while it can be found that the spherical M 6 C carbides were precipitated in fusion zone of LC alloy after solution treatment. The grain coarsening of fusion zone in HC alloy was slight because the migration of grain boundaries were impeded by the eutectic M 6 C-γ carbides. However, the columnar grains of fusion zone in LC alloy were transformed into the coarse equiaxed grains due to the migration of grain boundaries were not impeded. The activation energy of grain growth between 1093 °C and 1177 °C for 20 min in LC fusion zone was 144.3 kJ mol⁻¹, while that of HC fusion zone was 309.5 kJ mol⁻¹ calculated according to the classical Arrhenius equation. The microhardness of fusion zone in LC alloy was lower than that of fusion zone in HC alloy after solution treatment because of no dispersion strengthening and grain coarsening. [ABSTRACT FROM AUTHOR]