Mechanisms of Ultrasonic Vibration Induced Porosity Control and Mechanical Properties Improvement in Laser Directed Energy Deposition

Ultrasonic vibration effectively reduces porosity in laser directed energy deposition by altering molten pool dynamics. To understand the interactions between bubble evolution and ultrasonic vibration (UV)‐induced melt flow, experiments utilizes 1Cr12Ni3MoVN powders containing hollow particles, enabling statistical pore analysis. Multiphysics modeling reveals that UV‐generated inertial forces dominate melt flow, competing with Marangoni forces. This interplay accelerates melt circulation, generating localized pressure sufficient for cavitation. Bubble behavior depends critically on size: Small bubbles (less than 20 μm) collapse due to cavitation; medium bubbles (20–50 μm) gain upward velocity and escape pool edges; large bubbles (100 μm) remain trapped at the pool bottom, deformed by shear forces. Crucially, UV treatment significantly enhances mechanical properties: yield strength rises from 905 to 984 MPa, tensile strength from 1283 to 1310 MPa, and elongation improves by 31%. Unlike traditional remelting (which increases elongation but reduces strength), UV method concurrently improves strength and ductility. This approach offers a promising pathway for enhancing the reliability of additively manufactured components.