Investigation of the Crack Propagation Mechanism of β-Ga2O3 Crystal in Wire Electrical Discharge Machining Process

Crack propagation remains one of the key process-related issues limiting machining integrity during liquid-immersion wire electrical discharge machining (WEDM) of β-Ga2O3 crystals. This study systematically investigated crack evolution during machining by combining segmented cutting experiments, energy-dispersive X-ray spectroscopy (EDS) characterization, and electric-field simulations, and proposed a practical strategy for suppressing crack propagation. In the segmented cutting experiments, a small crack was observed at the kerf end after completion of the third cutting segment and expanded further after the fourth segment was completed. EDS elemental analysis of foreign substances on the cleavage surface detected four characteristic elements, Ga, O, C, and Mo, providing indirect evidence consistent with discharge occurring within the cracks. The simplified electric-field simulations indicated that an idealized crack distorted the local electric-potential distribution, whereas full copper-sheet coverage of the crystal surfaces substantially reduced the electric-field intensity near the crack. Based on these findings, a method employing copper sheets for electrical conduction and clamping was proposed. By improving the uniformity of the electric-potential distribution, this method helped suppress discharge-induced crack propagation. Validation experiments showed that ten intact strip-shaped β-Ga2O3 specimens with no visible cracks were successfully fabricated using this method. This study provides a theoretical basis and a technical reference for low-damage machining of gallium oxide crystals from a process perspective.