In the present report, we demonstrate how Selective laser melting (SLM) process can contribute to a 4D manufacturing of functional and structural properties of shape memory alloys (SMAs) in-situ synthesized into Ni-Ti and Cu-Al-Ni powdered systems. Correlations of specific resistance and phase structure in Ni-Ti and Cu-Al-Ni intermetallic phases after the SLM were experimentally observed. It was shown that electrical resistivity of the phases studied (austenite, rhombohedral and martensite phases) increases with temperature but the slopes are quite different. Intermediate R-phase in nitinol (NiTi – intermetallide) shows generally higher electrical resistivity than the austenite phase, but its value grows with the decrease of temperature for laser melted samples. We explained this fact by an accumulation of dislocation with the continuous increase of the R-phase with the decrease of temperature. Hysteresis loop of the electrical resistivity and phase-structural properties of SL-Melted samples are correlated with conditions of SLM process, additional heating during the layerwise process, 3D part's porosity. It will be important for perspective 4D printed biomedical applications (bio-MEMS - sensors, drug delivery systems, implants, etc.) of fabricated self- self-initiating and self-fixing SMAs.
|