TY - JOUR
T1 - Microscale stress-geometry interactions in an additively manufactured NiTi cardiovascular stent
T2 - A synchrotron dual imaging tomography and diffraction study
AU - Vashishtha, Himanshu
AU - Jamshidi, Parastoo
AU - Vrettou, Anastasia
AU - Kareer, Anna
AU - Goode, Michael
AU - Deyhle, Hans
AU - James, Andrew
AU - Ahmad, Sharif
AU - Reinhard, Christina
AU - Attallah, Moataz M.
AU - Collins, David M.
PY - 2024/7/1
Y1 - 2024/7/1
N2 - This study explores cardiovascular stents fabricated using laser powder bed fusion (LPBF) which is an emerging method to offer patient-specific customisable parts. Here, the shape memory alloy NiTi, in a near equiatomic composition, was investigated to deconvolve the material response from macroscopic component effects. Specifically, stress-geometry interactions were revealed, in-situ, for a minaturised cardiovascular stent subjected to an externally applied cylindrical stress whilst acquiring synchrotron X-ray imaging and diffraction data. The approach enabled the collection of spatially resolved micromechanical deformation data; the formation of stress-induced martensite and R-phase was evident, occurring in locations near junctions between stent ligaments where stress concentrations exist. In the as-fabricated condition, hardness maps were obtained through nanoindentation, demonstrating that the localised deformation and deformation patterning is further controlled by porosity and microstructural heterogeneity. Electron backscatter diffraction (EBSD) supported these observations, showing a finer grain structure near stent junctions with higher associated lattice curvature. These features, combined with stress concentrations when loaded will initiate localised phase transformations. If the stent was subjected to repeated loading, representing in-vivo conditions, these regions would be susceptible to cyclic damage through transformation memory loss, leading to premature component failure. This study highlights the challenges that must be addressed for the post-processing treatment of LPBF-processed stents for healthcare-related applications.
AB - This study explores cardiovascular stents fabricated using laser powder bed fusion (LPBF) which is an emerging method to offer patient-specific customisable parts. Here, the shape memory alloy NiTi, in a near equiatomic composition, was investigated to deconvolve the material response from macroscopic component effects. Specifically, stress-geometry interactions were revealed, in-situ, for a minaturised cardiovascular stent subjected to an externally applied cylindrical stress whilst acquiring synchrotron X-ray imaging and diffraction data. The approach enabled the collection of spatially resolved micromechanical deformation data; the formation of stress-induced martensite and R-phase was evident, occurring in locations near junctions between stent ligaments where stress concentrations exist. In the as-fabricated condition, hardness maps were obtained through nanoindentation, demonstrating that the localised deformation and deformation patterning is further controlled by porosity and microstructural heterogeneity. Electron backscatter diffraction (EBSD) supported these observations, showing a finer grain structure near stent junctions with higher associated lattice curvature. These features, combined with stress concentrations when loaded will initiate localised phase transformations. If the stent was subjected to repeated loading, representing in-vivo conditions, these regions would be susceptible to cyclic damage through transformation memory loss, leading to premature component failure. This study highlights the challenges that must be addressed for the post-processing treatment of LPBF-processed stents for healthcare-related applications.
KW - Customized stents
KW - Dual imaging and diffraction
KW - Laser powder bed fusion
KW - Stress-geometry interactions
KW - Stress-induced martensite
UR - https://www.webofscience.com/api/gateway?GWVersion=2&SrcApp=pure_starter&SrcAuth=WosAPI&KeyUT=WOS:001249505600001&DestLinkType=FullRecord&DestApp=WOS_CPL
UR - http://www.scopus.com/inward/record.url?scp=85194586122&partnerID=8YFLogxK
U2 - 10.1016/j.matchar.2024.114016
DO - 10.1016/j.matchar.2024.114016
M3 - Article
SN - 1044-5803
VL - 213
JO - Materials Characterization
JF - Materials Characterization
M1 - 114016
ER -