@article{23f1e7eb81724e82a309bf9461d7c4e4,
title = "Correlating microstructure and superelasticity of directed energy deposition additive manufactured Ni-rich NiTi alloys",
abstract = "Laser-based directed energy deposition (LDED) additive manufacturing of Ni-rich NiTi shape memory alloys was shown to produce inhomogeneous precipitate morphologies and characteristic grain structures consisting of columnar grains coexisting with equiaxed and subgrain structures. Post-processing solutionizing and aging heat treatments impacted microstructure and martensitic phase transformation (MT) responses underpinning superelastic shape memory responses. A solution treatment of 950 °C for 24 h was found to produce a uniform composition of the B2 austenite parent phase without affecting the coexistence of columnar and equiaxed substructures. Aging the solution treated material brought about a spatially uniform Ni4Ti3 precipitate morphology. Due to the uniform morphology, an underlying austenite-martensite interface motion accompanies the compressive stress-induced MT (SIMT). Reversible interface motion underpinned the compressive superelastic response for the solutionized and aged condition. On the other hand, strain concentrations existed at different spatial locations in the as built condition as well as when the as built material was aged. The stark contrasts in the SIMT exposed precipitate morphology as a controlling factor in tailoring the superelastic response of Ni-rich NiTi SMAs fabricated by LDED.",
author = "Hamilton, {Reginald F.} and Bimber, {Beth A.} and Palmer, {Todd A.}",
note = "Funding Information: AM work was performed at the Center for Innovative Materials Processing through Direct Digital Deposition (CIMP-3D) at Penn State with assistance from Griffin Jones and Jay Tressler. XRD analysis was performed by Scott Meredith. Microscopy and EBSD analysis was performed in the Materials Characterization Lab, at the Materials Research Institute, Pennsylvania State University. Support for B.B. comes from a National Science Foundation (United States) Graduate Fellowship under Grant No. DGE1255832 . Work was funded by National Science Foundation Grant No. CMMI 1335283 . Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation. Funding Information: AM work was performed at the Center for Innovative Materials Processing through Direct Digital Deposition (CIMP-3D) at Penn State with assistance from Griffin Jones and Jay Tressler. XRD analysis was performed by Scott Meredith. Microscopy and EBSD analysis was performed in the Materials Characterization Lab, at the Materials Research Institute, Pennsylvania State University. Support for B.B. comes from a National Science Foundation (United States) Graduate Fellowship under Grant No. DGE1255832. Work was funded by National Science Foundation Grant No. CMMI 1335283. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.",
year = "2018",
month = mar,
day = "30",
doi = "10.1016/j.jallcom.2017.12.270",
language = "English (US)",
volume = "739",
pages = "712--722",
journal = "Journal of Alloys and Compounds",
issn = "0925-8388",
publisher = "Elsevier BV",
}