Anisotropy in microdevices produced by micromachining of cold-rolled NiTi sheets

The process of fabrication and characterisation of three types of NiTi micr odevice are described: a double-beam cantilever of constant beam width and two designs of cantilever of stress-optimised width profile, with thickness es ranging from 17 to 95 mu m produced by cold rolling. The technology of e lectrolytic photoetching was used as a versatile tool for micromachining. T he transformation behavior of the specimens was investigated by differentia l scanning calorimetry and electrical resistance measurements. Anisotropies caused by rolling-induced textures have been investigated by beam-bending experiments. Strong anisotropies were found in results on thickness-depende nt Young's modulus in the parent phase as well as in the beam-bending chara cteristics in the rhombohedral and martensitic phase. For beam directions t ransverse to the rolling direction, beam-bending experiments revealed a thi ckness dependence of hysteresis associated with the martensitic transformat ion, which was not observed in the rolling direction. Cantilevers with stre ss-optimised width profile display favorable beam-bending characteristics c ompared with cantilevers of constant beam width due to an optimum use of th e shape memory effect. (C) 1999 Elsevier Science S.A. All rights reserved.