Effect of postweld heat treatment on the microstructure and cyclic deformation behavior of laser-welded NiTi-shape memory wires

C. W. Chan, H.C. Man, T.M. Yue

Research output: Contribution to journalArticlepeer-review

35 Citations (Scopus)

Abstract

NiTi wires of 0.5 mm diameter were laser welded using a CW 100-W fiber laser in an argon shielding environment with or without postweld heat-treatment (PWHT). The microstructure and the phases present were studied by scanning-electron microscopy (SEM), transmission-electron microscopy (TEM), and X-ray diffractometry (XRD). The phase transformation behavior and the cyclic stress–strain behavior of the NiTi weldments were studied using differential scanning calorimetry (DSC) and cyclic tensile testing. TEM and XRD analyses reveal the presence of Ni4Ti3 particles after PWHT at or above 623 K (350 °C). In the cyclic tensile test, PWHT at 623 K (350 °C) improves the cyclic deformation behavior of the weldment by reducing the accumulated residual strain, whereas PWHT at 723 K (450 °C) provides no benefit to the cyclic deformation behavior. Welding also reduces the tensile strength and fracture elongation of NiTi wires, but the deterioration could be alleviated by PWHT.
Original languageEnglish
Pages (from-to)1956-1965
Number of pages10
JournalMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Volume43
Issue number6
Early online date19 Jan 2012
DOIs
Publication statusPublished - Jun 2012

Keywords

  • Post-weld Heat-treatment
  • Laser Welding
  • NiTi
  • Cyclic Deformation

ASJC Scopus subject areas

  • Metals and Alloys

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