Stiffness tuning of NiTi implants through aging

Narges Shayesteh Moghaddam, Amirhesam Amerinatanzi, Soheil Saedi, Ali Sadi Turabi, Haluk Karaca, Mohammad Elahinia

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

3 Scopus citations

Abstract

NiTi alloys are interesting materials for biomedical implants since they offer unique characteristics such as superelastic behavior, low stiffness (I.e., modulus of elasticity) close to that of the cortical bone, and shock absorption. Thermal treatments are the most common and practical ways to improve the superelasticity of these alloys. In addition to the superelastic behavior of the metallic implants, it is important for the implants to have a stiffness similar to that of cortical bone in order to reduce the risk of failure caused by stress shielding. The cortical bone has a stiffness ranging from 12 to 31 GPa for different patients (e.g., sex, age, mechanical behavior of bone) and various bone locations (e.g., jaw implant, hip implant), while the untreated Ni-rich NiTi has the stiffness equal to 41.37 GPa. One recently used technique to lower the stiffness of NiTi implant is to introduce porosity into the implant. The major problem associated with the imposed porosity is stress concentration on the pore walls and the subsequent implant failure. In this work, the purpose is to tune the stiffness via changing the post-heat treatment conditions, i.e., aging time and aging temperature. In this study, several bulk specimens of Ni-rich NiTi (SLM Ni50.8Ti49.2) were additively manufactured using selective laser melting (SLM) technique. The samples were solution annealed (950°C, 5.5 h) and subsequently water quenched to provide equilibrium state in the samples. Subsequently, different aging conditions (350°C and 450°C for 5 to 18 hours) were applied to the samples. Mechanical testing (compression) was conducted on the samples and the stiffness of each sample was defined to investigate the effect of aging on the stiffness. Our results indicate that the range of 29.9 to 43.7 GPa for stiffness can be achieved through the implant via different time period and temperatures for aging. The modulus of 43.7 GPa is attributed to 10 hours heat treatment under 450°C and the modulus of 29.9 GPa is attributed to 18 hours heat treatment under 350°C.

Original languageEnglish
Title of host publicationMultifunctional Materials; Mechanics and Behavior of Active Materials; Integrated System Design and Implementation; Structural Health Monitoring
ISBN (Electronic)9780791850480
DOIs
StatePublished - 2016
EventASME 2016 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS 2016 - Stowe, United States
Duration: Sep 28 2016Sep 30 2016

Publication series

NameASME 2016 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS 2016
Volume1

Conference

ConferenceASME 2016 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, SMASIS 2016
Country/TerritoryUnited States
CityStowe
Period9/28/169/30/16

Keywords

  • Additive manufacturing
  • Post-heat treatment
  • Selective laser melting
  • Stiffness tuning
  • Superelastic NiTi

ASJC Scopus subject areas

  • Building and Construction
  • Civil and Structural Engineering
  • Control and Systems Engineering
  • Mechanics of Materials

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