GROWTH OF TINIHF SHAPE-MEMORY ALLOY THIN-FILMS BY LASER-ABLATION OF COMPOSITE TARGETS

Ti1-xNiHfx shape memory alloy thin films with Hf content up to 13.33 a t.% were fabricated using a KrF excimer laser ablation system with dif ferent composite targets in high vacuum for the first rime. As-deposit ed amorphous Ti36.63Ni50.04Hf13.33 thin film was annealed for crystall ization. The phase transformation behaviors of the thin film were char acterized by differential scanning calorimetry. Both the heating and c ooling curves exhibited double endotherms and exotherms indicating the presence of R-phase during the phase transformation. The forward mart ensitic transformation temperature is 31 degrees C, which is consisten t with the co-existence of high-temperature parent phase (austenite) a nd the low-temperature phase (martensite) at room temperature. The low er transition temperatures of the thin film compared with that of bulk material with the same composition was attributed to the refined grai n size and the Ni content, which was slightly above 50 at%. The fabric ation of TiNiHf shape memory alloy thin films by pulsed laser depositi on will contribute to the successful development of microactuators. (C ) 1998 Elsevier Science B.V.