Chemical machined thin foils of TiNi shape memory alloy

Ti50Ni50 thin foils up to 10 mu m thickness are successfully fabricated fro m 100 mu m thickness thin plates using chemical machining. Ultrasonic agita tion is applied to enhance the chemical etching process with mixed solution s of HF/HNO3/H2O. The higher the HF/HNO3 volume ratio in the solution, the higher the etching rate and the smoother the surface will be. Thin foils ca n also be fabricated with the electropolishing process but with a much slow er etching rate. Foil thickness by these processes can only be approximatel y 10 mu m due to the side-etching effect. The martensitic transformation pe aks of thin foils shown on the DSC curve are broader for a thinner sample d ue to the effect of thermal resistance in the DSC sample pans. The enthalpy of transformation also decreases while the foil thickness is reduced due t o the effect of the foil surface energy and the energy of plastic deformati on. (C) 1999 Elsevier Science S.A. All rights reserved.