Strain rate and temperature effects on dynamic behavior of LPBF-GH3230 superalloy

This study investigates the dynamic compression behavior of laser powder bed fusion (LPBF)-processed Ni-based superalloy GH3230 across a wide range of strain rates (1482 - 6893 s⁻¹) and temperatures (-150 - 750 °C) using a Split Hopkinson Pressure Bar (SHPB) system. The mechanical test results revealed that as the strain rate increased from 1482 s⁻¹ to 6893 s⁻¹, the peak true stress increased from 895 MPa to 1853 MPa, with an increase of 107 %, exhibiting a significant strain rate strengthening effect. This phenomenon is mainly attributed to the enhanced dislocation interactions and reduced dynamic recovery capacity. Microstructural analysis demonstrates that increasing the strain rate promotes a transition from columnar to equiaxed grain morphology through dynamic recrystallization and grain fragmentation, reducing the average grain size from 35.7 μm to 2.36 μm. In contrast, temperature exerts a weaker influence on grain evolution: while thermal softening decreases peak stress at elevated temperatures, recrystallized fractions remain below 5 % across all tested temperatures due to the short deformation time in SHPB tests. EBSD-based texture analysis showed strain rate-induced weakening of the initial <001>//build direction (BD) texture and gradual orientation homogenization, accompanied by increased dislocation density and intragranular misorientation. These findings underscore the dominant role of strain rate in governing both the mechanical response and microstructural evolution, whereas temperature primarily affects deformation resistance through thermal activation.