Selective electron beam melting of NiTi: Microstructure, phase transformation and mechanical properties

Microstructure, Mechanical Properties, and Martensitic Transformation in NiTi Shape Memory Alloy Fabricated Using Electron Beam Additive Manufacturing Technique

“…The microstructure of the AM-fabricated NiTi alloys consists usually of columnar grains elongated into the built direction, which was found to be associated with the epitaxial growth mechanism that takes place during the deposition. This also resulted in strong [001] texture along the build direction frequently reported for the AMmanufactured NiTi parts (Ref 7,11). However, in order to fabricate elements exhibiting high density, high-dimensional accuracy, and low fraction of defects, the deposition has to be conducted in a previously specified process window, e.g., in the case of SLM method full-density NiTi parts may be obtained at energy input of about 55 J/mm 3 (Ref 3).…”

A Review on Additive Manufacturing of Shape-Memory Materials for Biomedical Applications

“…However, some studies have been conducted to explore various aspects of dense NiTi manufactured by the EBM process. Zhou et al 190 investigated the microstructure, phase transformation, and mechanical properties of EBM-printed NiTi parts and reported excellent and stable superelasticity for the printed samples. It is worth noting that EBM-NiTi has superior tensile performance compared with the NiTi parts fabricated by SLM or LENS.…”

Additive Manufacturing from the Point of View of Materials Research

“…Mechanically produced powder Mechanical shape memory functionality was proven with a force range of 10-100 mN [119] Quality of deposited Ni-Ti was improved by increasing the scanning speed [120] E-PBF PREP atomized powder No visible shape memory and pseudoplastic effect seen [121] The authors did not recommend E-PBF for Ni-Ti alloys. Preheating was required [97] E-PBF process resulted in better tensile properties than L-DED and L-PBF [97,122] PAD Pre-alloyed powder Linear superelasticity [123] Quasi-linear superelasticity with narrow hysteresis [123,124] WAAM Wire High hardness and tensile strength [125] Cu-Al-Ni L-PBF Elemental powders High aluminum content led to dendrites and high hardness [126] Cu-Al-Ni-Mn Gas atomized powder High relative density (>92%) achieved [127][128][129] Reversible martensitic transformation with the formation of β 1 '-martensite [127][128][129] Large strain recovery after unloading (up to 18%) [127] Strong distribution of pores produced by the L-PBF sample [127,128] Additional re-melting led to smaller grain size and yielded a deformability of 14% [129] Higher strength and improved plasticity was observed for both samples (Cu-Al-Ni-Mn and Cu-Al-Ni-Mn-Zr) [128][129][130] For the Cu-Al-Ni-Mn-Zr sample, Zr-rich phase was found to precipitate at the grain boundaries during the annealing process [130] Cu-Al-Ni-Mn-Zr Cu-Al-Ni-Ti Copper alloy with Ti addition had a high hardness of about 280 HV due to the grain refinement. The relative density exceeded 99% [131] Fe-Mn-Al-Ni Reversible martensitic transformation and pseudo-elastic effect [132] MSMA Ni-Mn-Ga 3D ink printing Ink with elemental powders Reversible martensitic transformation [133] Martensitic twins [134] Binder jetting Mechanically produced powder Martensitic twins and reversible martensitic transformation after post-processing [135,…”