• Deep cryogenic treatment (DCT) for 200 h increases residual stress in HIP beryllium by 59.9% due to non-uniform volumetric contraction and mismatch stress.
• DCT induces grain refinement (12.3% decrease) and higher dislocation density (17.9% increase in GND), leading to improved yield and tensile strengths by 4.2% and 5.6%, respectively.
• DCT significantly enhances dimensional stability: cumulative size changes during cold exposure and cold cycling are reduced by 86% and 50%, respectively, after 200 h treatment.
• After room-temperature creep at 100 MPa for 1000 h, DCT-treated beryllium shows 12.5% higher residual tensile strength and 5.5% higher retention rate, indicating improved long-term reliability.