Effect of Cr addition on hot deformation behavior and recrystallization mechanism of Cu–Ni–Si alloy

: The effect of Cr addition on the hot deformation behavior and microstructural evolution of Cu–Ni–Si alloys was systematically investigated. At 700 °C, both CuNiSi and CuNiSiCr alloys exhibit abnormally high peak stresses, pronounced post-peak softening, and severe intergranular cracking. Notably, an unconventional increase in cracking susceptibility with decreasing strain rate is observed, while dynamic recrystallization (DRX) is initiated within precipitation-free zones (PFZs) but spatially confined by boundary pinning from fine Ni 2 Si precipitates in adjacent regions. These behaviors are attributed to precipitation-related heterogeneity, including coarse grain-boundary precipitates and PFZ formation, which promote strain localization and facilitate crack initiation and propagation. The CuNiSiCr alloy exhibits reduced cracking sensitivity due to its refined grain structure, which weakens grain-boundary precipitation and reduces PFZ width. At higher temperatures (≥750 °C), deformation is governed by discontinuous DRX. In CuNiSi, recrystallization is dominated by strain-induced boundary migration. In CuNiSiCr, it is accelerated by increased grain-boundary density and particle-stimulated nucleation (PSN) associated with Cr 3 Si particles. Processing maps combined with microstructural observations indicate that optimal hot-working windows are 850–900 °C with strain rates of 0.01–0.1 s -1 for CuNiSi and 0.1–1 s -1 for CuNiSiCr. Overall, Cr addition suppresses precipitation-assisted intergranular damage at lower temperatures and enhances recrystallization at elevated temperatures. These findings provide mechanistic guidance for processing and microstructure optimization of precipitation-strengthened copper alloys.