Hot Deformation Behavior and Processing Map Analysis of As‐Cast Fe–Cr–Ni–Al–Ti Low‐Magnetic Stainless Steel

A precipitation‐strengthened Fe–Cr–Ni–Al–Ti low‐magnetic stainless steel (15A4‐A15) was designed to improve yield strength while maintaining excellent plasticity. The complex alloying composition results in pronounced dendritic segregation and interdendritic NiAl/Ti‐rich Laves phases, increasing the risk of cracking during hot working. Hot compression tests were conducted at 900–1050 °C and strain rates of 0.01–10 s ⁻¹ . The flow stress decreased with increasing temperature or decreasing strain rate, reflecting enhanced dynamic softening. A strain‐compensated constitutive model showed good predictive accuracy ( R ²  = 0.9653, AARE = 4.526%). The apparent activation energy of 437.19 kJ/mol indicates that hot deformation is governed by multiple thermally activated mechanisms rather than lattice diffusion alone. EBSD analyses revealed that hot workability is jointly controlled by dynamic recrystallization and the evolution of the heterogeneous as‐cast microstructure. Stable processing conditions promote homogeneous recrystallization and reduced stored deformation energy, whereas unstable conditions intensify strain localization and microstructural heterogeneity. Processing maps identified two favorable hot‐working windows, 900–1050 °C/0.01−0.04 s ⁻¹ and 1000–1050 °C/3–10 s ⁻¹ . Representative hot‐rolling experiments performed under typical stable and unstable conditions exhibited markedly different deformation behaviors consistent with the processing map predictions, confirming the reliability of the proposed processing map for optimizing the hot‐working parameters of as‐cast Fe–Cr–Ni–Al–Ti low‐magnetic stainless steel.