Metallic components are the cornerstone of modern industries, advancements in these field depend on the development of materials and processes such as smart materials and additive manufacturing. Especially for critical fields, optimization of materials, processes, and structure of the part are essential to achieve higher functionality and applicability of the alloy. Among the most utile smart materials is shape memory alloys (SMA) such as Cu-based, Fe-based, and NiTi. NiTi alloys have been produced conventionally and through additive manufacturing techniques especially over the past two decades [2-3]. Through which, functional defect-free parts were printed with challenges in terms of compositional sensitivity, functional and thermomechanical stability. Regarding the material aspect, multiple elements have been alloyed into NiTi to attain superior functionality as demonstrated in figure 1, on right side where the effect of ternary element on the martensite start temperature (Ms) is reported.

A convolution of both aspects of design process will be carried out in this project through: LPBF production of NiTi actuators followed by mechanical and functional characterisation. This followed by LPBF printing of NiTi-Cu actuators and reporting the added challenges in printing the part along with mechanical and functional properties of the alloy. Copper is the proposed ternary element for its capability to increase the thermal stability of produced phases thus decreasing thermal hysteresis. In addition to increasing the conductivity of NiTi thus utilising it more in smart actuators, MEMS, and micro-energy harvesting devices. To facilitate the production of these actuators, different combinations of SLM process parameters of Aconity machine will be utilised; Volumetric energy density (VED) as a initial condition insuring full densification and lack of defects such as lack of fusion, and balling. Following, which is the manipulation of laser power, scanning speed, and scanning strategy to control the grain and precipitates structure of both alloys. The goal is to manufacture isotropic defect-free part exhibiting uniform and pronounced Thermo-mechanical behaviour. As a result, contributing to further utilisation of LPBF in producing NiTi SMA for different applications.

References

[1] Chowdhury, http://dx.doi.org/10.1016/j.pmatsci.2017.03.003.

[2] S. Soheil, http://dx.doi.org/10.1016/j.actamat.2017.10.072

[3] Elahinia, https://doi.org/10.1016/j.matdes.2021.109654

Eslam Salaheldin Abdelhady (M.Sc.)