Effect of hatch angle rotation on the thermal and mechanical properties of micro selective laser melted NiTi shape memory alloy

Jin Fu, Zhiheng Hu, Xu Song, Mingwang Fu

Research output: Chapter in book / Conference proceedingConference article published in proceeding or bookAcademic researchpeer-review

Abstract

NiTi shape memory alloy (SMA) has been widely used for biomedical and aerospace applications due to its unique properties, i.e. shape memory effect and pseudoelasticity. However, the high ductility and work-hardening effect of NiTi lead to poor machinability. Additive manufacturing (AM), with excellent capability of fabricating complicated structures, has been used to fabricate NiTi components. To meet the increasing demand of product miniaturization, micro selective laser melting (?SLM) system equipped with finer laser beam has been developed to improve manufacturing resolution. This work studies the fabrication of NiTi SMA parts by ?SLM for the first time. The effect of hatch angle rotation on the thermal and mechanical behaviors of ?SLMed NiTi is analyzed. Columnar grains accompanied with equiaxed grains are observed in ?SLMed NiTi. Laser rotation angles of 45/60/90° lead to weak crystallographic texture. Ti-rich secondary phases including Ti2Ni/Ti4Ni2Ox and TiC1-xNx are detected in the raw NiTi powder and the as-printed NiTi parts, respectively. The as-printed parts under different hatch angles show similar phase constitution. The thermal-induced transformation behavior was depressed with absence of transformation peak. The variation of hatch angle cannot activate the transformation peak. Varying hatch angle from 45 ° to 90 °, the compressive strength and ductility reduce, and the hardness increases. The depressed thermal-/stress-induced phase transformation of the ?SLM NiTi can be attributed to the Ti-rich secondary phases, which cause variation of matrix Ni/Ti ratio and inhomogeneous microstructure.

Original languageEnglish
Title of host publicationAdditive Manufacturing; Advanced Materials Manufacturing; Biomanufacturing; Life Cycle Engineering; Manufacturing Equipment and Automation
PublisherAmerican Society of Mechanical Engineers
ISBN (Electronic)9780791884256
DOIs
Publication statusPublished - Jan 2020
EventASME 2020 15th International Manufacturing Science and Engineering Conference, MSEC 2020 - Virtual, Online
Duration: 3 Sep 2020 → …

Publication series

NameASME 2020 15th International Manufacturing Science and Engineering Conference, MSEC 2020
Volume1

Conference

ConferenceASME 2020 15th International Manufacturing Science and Engineering Conference, MSEC 2020
CityVirtual, Online
Period3/09/20 → …

Keywords

  • Hatch angle rotation
  • Mechanical behaviors
  • Micro selective laser melting
  • NiTi shape memory alloy
  • Thermal

ASJC Scopus subject areas

  • Safety, Risk, Reliability and Quality
  • Materials Science (miscellaneous)
  • Control and Optimization
  • Industrial and Manufacturing Engineering
  • Mechanical Engineering

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