Application of in-situ nano-scanning calorimetry and X-ray diffraction to characterize Ni–Ti–Hf high-temperature shape memory alloys
Combinatorial nanocalorimetry and synchrotron X-ray diffraction were combined to study the martensite–austenite (M–A) phase transformation behavior of Ni–Ti–Hf shape memory alloys. A thin-film library of Ni–Ti–Hf samples with a range of compositions was deposited on a parallel nano-scanning calorimeter device using sputter deposition. Crystallization of each amorphous as-deposited sample by local heating at approximately 10^4 K/s produced a nanoscale grain structure of austenite and martensite. Individual samples were then cycled through the M–A transformation, while the transformation enthalpy was measured by nanocalorimetry and the low- and high-temperature phase compositions were determined by X-ray diffraction. The techniques enable correlation of the observed behavior during thermal cycling with the thermodynamic and structural properties of the samples.
© 2014 Elsevier B.V. Available online 4 August 2014. The authors thank Aaron Lyndaker for assistance with the synchrotron experiments and James MacArthur for assistance with the custom electronics. The work presented in this paper was supported by the Air Force Office of Scientific Research under Grants FA9550-08-1-0374 and A9550-12-1-0098, and by the Materials Research Science and Engineering Center at Harvard University. It was performed in part at the Center for Nanoscale Systems, a member of the National Nanotechnology Infrastructure Network, which is supported by the National Science Foundation under NSF Award ECS-0335765. The Center for Nanoscale Systems is part of the Faculty of Arts and Sciences at Harvard University.