Understanding the hot deformation behavior of metallic components produced via additive manufacturing (AM) is crucial, especially for applications in dynamic loads and high temperatures. This research examines the hot compression behavior of a martensitic precipitated hardened stainless steel, known as CX SS, produced through laser powder bed fusion (LPBF). Microstructural evolutions were examined on two sample types—as-built and heat-treated—subjected to hot compression at a constant 1 s⁻¹ strain rate within the temperature range of 300 °C to 650 °C. The impact of microstructural features such as cellular solidification subgrains, nanoscale NiAl precipitates, and the austenite reversion transformation on dynamic recovery (DRV) and dynamic recrystallization (DRX) as mechanisms of restoration is explored using electron backscattered diffraction (EBSD) techniques. A comparison between two sample types revealed that the presence of cellular solidification substructure in the as-built samples delays the restoration mechanism compared to heat-treated samples. Furthermore, LPBF CX specimens in the as-built state and after heat-treatment process exhibit nearly identical deformation behavior at temperatures above 450 °C. This identical deformation behavior is associated with the partial or complete destruction of cells in the as-built samples and the dissolution of NiAl particles in heat-treated ones. The dynamic softening mechanism primarily stems from DRV and partial DRX. Although discontinuous dynamic recrystallization (DDRX) was alleviated in heat-treated samples, the as-built CX SS also showed softening mechanism in form of continuous dynamic recrystallization (CDRX) accompanied by DDRX. A constitutive equation of Arrhenius model, including Zener–Hollomon parameters, evaluated strain accumulation during hot deformation, identifying regions prone to shear bands (SBs), microcracks, and voids.

This study explores the evolution of solidification microstructure of a laser powder bed fusion (L-PBF) martensitic stainless steel during solution annealing and aging. Quasi in-situ experiments using electron backscatter diffraction (EBSD) revealed that the finer, more equiaxed microstructure below the melt pool was susceptible to recrystallization and grain growth during solution annealing. The two distinct solidification microstructures below and inside the melt pool converged into a uniform grain morphology after solution annealing and aging processes. Graphical Abstract: (Figure presented.)

In this work, the effect of heating rate on the phase transformation temperatures was investigated using dilatometry analysis. Continuous heating and isothermal holding above Ac₃ temperature on microstructural evolutions in additively manufactured (AM) parts of Fe-Cr-Ni maraging stainless steel were studied. The microstructural features developed within the heating processes were characterized employing electron backscatter diffraction and transmission electron microscopy. Austenite reversion was found to take place in two steps for the AM parts by a diffusive mechanism as well as the precipitation reactions. Although grain refinement occurred during the austenite reversion of the continuously heated samples, the microstructure showed a coarser grain size after isothermal heating. The crystallographic orientations developed after the heating processes were different from those of the initial ones implying the absence of the austenite memory effect.