Welding bulk metallic glasses: Processes, key challenges, and future directions

Considerable scientific effort has been devoted to comprehending welding processes and establishing correlations between structure and properties in crystalline metals and alloys’ welded joints. However, welding of bulk-metallic glasses (BMGs) presents unique challenges. The weldability of these glasses is complex due to their lack of long-range order and high propensity to crystallization. BMGs are joined through either supercooled-liquid-phase or liquid-phase welding techniques. To maintain the integrity of the glassy structure, it is imperative to meticulously control the welding temperature and duration during supercooled-liquid-phase welding to prevent crystallization or ensure a sufficiently rapid cooling rate in liquid-phase welding to suppress solidification. In most cases, the presence of crystalline phases adversely affects the mechanical and physical properties of the joints. This review article describes and critically analyzes the key aspects influencing BMG welding and the correlations between the welding conditions and BMG joint properties. The fundamental knowledge to understand the welding of BMGs is presented, and the many welding methods used are discussed. The review also offers recommendations for various opportunities and new directions for advancing the field of BMG welding.