Multiscale microstructural regulation in ultrasonic-assisted laser repair of 30CrMnSiA

This study explores the synergistic effects of ultrasonic-assisted additive manufacturing (UAM) and heat treatment on the repair and enhancement of 30CrMnSiA alloy. UAM was found to significantly refine the grain structure, transforming columnar crystals into equiaxed grains and improving interlayer bonding. The subsequent heat treatment further enhanced mechanical properties by relieving residual stresses and homogenising the microstructure. The repaired alloy exhibited a tensile strength of 1902.5 MPa, a 12.65% increase compared to traditional additive manufacturing methods, and a yield strength of 439 MPa, reaching 83.22% of the original material. Fatigue resistance was significantly improved, with low-cycle fatigue life reaching 67,233 cycles, attributed to reduced defects, enhanced grain boundary density, and refined microstructure. These findings demonstrate the potential of UAM and heat treatment in repairing and enhancing high-strength structural alloys for demanding applications.