Nitinol flanges fabricated by laser rod end melting and immediate flange processing

Abstract

Nitinol, a widely used shape memory alloy in actuator industries, often encounters limitations in joint strength, heat resistance and corrosion resistance when joined to mechanical systems using conventional joining processes such as crimping, screwing or adhesive bonding. To address these challenges, a novel process chain is introduced to produce all-in-one Nitinol micro flanges by laser rod end melting (LREM) in a unique system. A laser beam melts the end of a Nitinol wire into an accumulated spherical liquid, which is subsequently reshaped in a die cavity with different die speeds, die temperatures, and delay time between both steps. Unlike cold forming of solidified preforms, the utilization of a partially solidified melt allows for the fabrication of a flange without cracks and visible oxidation. The resulting flange comprises a partially in the initial shape solidified preform, surrounded by a newly distributed zone. The fabricated flanges show comparable surface quality, size, and microstructure distribution across the range of the studied die speeds and die temperatures. However, achieving the desired flange shape necessitates the selection of an appropriate delay time. This study creates the basis for a process to fabricate Nitinol flanges and examines the influencing factors during the flange processing.