TY  - JOUR
AU  - Luo, MengJie
AU  - Li, Ruidi
AU  - Zheng, Dan
AU  - Kang, JingTao
AU  - Wu, HuiTing
AU  - Deng, ShengHua
AU  - Niu, PengDa
PY  - 2023
TI  - Formation mechanism of inherent spatial heterogeneity of microstructure and mechanical properties of NiTi SMA prepared by laser directed energy deposition
JO  - International Journal of Extreme Manufacturing
SN  - 2631-8644
SP  - 035005
VL  - 5
IS  - 3
AB  - Ni51Ti49 at.% bulk was additively manufactured by laser-directed energy deposition (DED) to reveal the microstructure evolution, phase distribution, and mechanical properties. It is found that the localized remelting, reheating, and heat accumulation during DED leads to the spatial heterogeneous distribution of columnar crystal and equiaxed crystal, a gradient distribution of Ni4Ti3 precipitates along the building direction, and preferential formation of Ni4Ti3 precipitates in the columnar zone. The austenite transformation finish temperature (Af) varies from −12.65 ℃ (Z = 33 mm) to 60.35 ℃ (Z = 10 mm), corresponding to tensile yield strength (σ0.2) changed from 120 ± 30 MPa to 570 ± 20 MPa, and functional properties changed from shape memory effect to superelasticity at room temperature. The sample in the Z = 20.4 mm height has the best plasticity of 9.6% and the best recoverable strain of 4.2%. This work provided insights and guidelines for the spatial characterization of DEDed NiTi.
UR  - https://doi.org/10.1088/2631-7990/acd96f
DO  - 10.1088/2631-7990/acd96f