TY - JOUR
T1 - Functional fatigue of submicrometer NiTi shape memory alloy thin films
AU - Hou, Huilong
AU - Tang, Yuan
AU - Hamilton, Reginald F.
AU - Horn, Mark W.
N1 - Funding Information:
The authors thank Nichole Wonderling of Materials Characterization Laboratory, The Pennsylvania State University, for assisting the x-ray diffraction measurement. Components of this work were conducted at The Pennsylvania State University node of the National Science Foundation-funded National Nanotechnology Infrastructure Network. This work was supported by the National Science Foundation under Grant No. CMMI 1538354.
Publisher Copyright:
© 2017 American Vacuum Society.
PY - 2017/7/1
Y1 - 2017/7/1
N2 - Submicrometer NiTi alloy thin films prepared using biased target ion beam deposition (BTIBD) recently revealed ultranarrow thermal hysteresis and a B2 ⇌ R-phase transformation path. Here, the authors investigate the influence of thermal cycles on the phase transformation characteristics of near-equiatomic NiTi alloy films with 800 nm thicknesses deposited using BTIBD. Evolution of transformation temperatures, thermal hysteresis, and recovery stress over thermal cycles is tracked using the wafer curvature method, and changes in atomic crystal structures are detected using x-ray diffraction. The authors find that the submicrometer thin films exhibit stabilized transformation temperatures, consistent recovery stresses, and reproducible narrow thermal hysteresis over up to 100 cycles although Ni49.7Ti50.3 films undergo two-stage phase transformation B2 → R-phase → B19′ while Ni50.3Ti49.7 films have one-stage transformation between the B2 and R-phases. The inherent deposition mechanism and transformation-path-related lattice distortion can be responsible for the reduced fatigue of functional characteristics in submicrometer NiTi alloy thin films.
AB - Submicrometer NiTi alloy thin films prepared using biased target ion beam deposition (BTIBD) recently revealed ultranarrow thermal hysteresis and a B2 ⇌ R-phase transformation path. Here, the authors investigate the influence of thermal cycles on the phase transformation characteristics of near-equiatomic NiTi alloy films with 800 nm thicknesses deposited using BTIBD. Evolution of transformation temperatures, thermal hysteresis, and recovery stress over thermal cycles is tracked using the wafer curvature method, and changes in atomic crystal structures are detected using x-ray diffraction. The authors find that the submicrometer thin films exhibit stabilized transformation temperatures, consistent recovery stresses, and reproducible narrow thermal hysteresis over up to 100 cycles although Ni49.7Ti50.3 films undergo two-stage phase transformation B2 → R-phase → B19′ while Ni50.3Ti49.7 films have one-stage transformation between the B2 and R-phases. The inherent deposition mechanism and transformation-path-related lattice distortion can be responsible for the reduced fatigue of functional characteristics in submicrometer NiTi alloy thin films.
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U2 - 10.1116/1.4983011
DO - 10.1116/1.4983011
M3 - Article
AN - SCOPUS:85019062649
SN - 0734-2101
VL - 35
JO - Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films
JF - Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films
IS - 4
M1 - 040601
ER -