Acta Metallurgica Sinica (English Letters) ›› 2021, Vol. 34 ›› Issue (9): 1223-1233.DOI: 10.1007/s40195-021-01212-6

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On the Martensitic Transformation Temperatures and Mechanical Properties of NiTi Alloy Manufactured by Selective Laser Melting: Effect of Remelting

Jian-Bin Zhan1,2, Yan-Jin Lu2(), Jin-Xin Lin2()   

  1. 1College of Chemistry and Materials Science, Fujian Normal University, Fuzhou, 350007, China
    2Key Laboratory of Optoelectronic Materials Chemistry and Physics, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, 350002, China
  • Received:2020-09-21 Revised:2020-11-02 Accepted:2020-12-08 Online:2021-09-10 Published:2021-02-23
  • Contact: Yan-Jin Lu,Jin-Xin Lin
  • About author:Jin-Xin Lin, franklin@fjirsm.ac.cn
    Yan-Jin Lu, yjlu@fjirsm.ac.cn;

Abstract:

In this study, the influence of laser remelting on the relative density, martensitic transformation temperatures (MTTs), and mechanical properties of a NiTi alloy fabricated by selective laser melting (SLM) at a laser power between 15 and 75 W were investigated. A relative alloy density of approximately 99% was achieved in the power range of 45-60 W corresponding to the forming energy density range of 65.45-87.27 J/mm3. The MTTs increased with the increase in the energy density; thus, the initial contents of the B2 and B19′ phases of the SLM-produced NiTi alloy can be tailored by the utilized technique. However, the number of defects such as metallurgical pores and microcracks considerably increased at higher energy densities (> 87.27 J/mm3). Interestingly, the concentration of these defects was reduced by remelting in the energy density range of 21.82-65.45 J/mm3, while the alloy relative density increased to 99.7% ± 0.1% at a remelting energy density of 65.45 J/mm3. The results of tensile testing revealed that when the remelting energy was 75% or 100% of the forming energy input, the ultimate tensile strength and elongation of the alloy significantly increased. Therefore, the remelting strategy represents a promising route for manufacturing NiTi alloys with desired MTT ranges and mechanical properties.

Key words: Selective laser melting, NiTi alloy, Laser remelting, Martensitic transformation temperature