LAUSR

A microspring is an important actuating component used widely in micro-electromechanical systems. It is important to develop microforming techniques for high-fatigue life microsprings manufactured. In this work, a micro-extrusion die was designed and manufactured for a plane microspring, and a CuAl7 copper alloy plane microspring was fabricated by cold extrusion. Effects of pre-annealing treatment, extrusion velocity, and lubrication conditions on the extrusion loading, surface crack and fatigue life of the spring were studied. The spring microstructure was characterized by equiaxed grains on the spring ends, and elongated grains exhibited the spring interior. Both internal and surface cracks were present in the springs. A good lubrication condition, an appropriate pre-annealing treatment, and a suitable extrusion velocity would reduce surface cracks. The fatigue life of the spring extruded at higher velocity was larger than that extruded at lower velocity under the same surface crack density. The fatigue life decreased with increasing annealing treatment temperature and holding time. A good lubrication condition during the extrusion process would improve the fatigue life of the spring. The maximum fatigue life of these extruded microsprings was 19,260 cycles when the cycle force was 10 N.