Enhancing the shape memory effect of Cu-Al-Ni alloys via partial reinforcement by alumina through selective laser melting

Cu-Al-Ni shape memory alloys (SMAs) have high thermal stability and various potential applications. The most significant factors limiting their application are their relatively low elastic strain and poor shape memory effect known as recoverable strain. In addition, the incorporation of new elements for reinforcement usually results in a polycrystalline structure with a larger grain size, which is not suitable for shape memory applications. To overcome these drawbacks, a new method is introduced in this study to increase the shape memory effect and its stability in Cu-Al-Ni SMAs through partial reinforcement with alumina (Al2O3) by selective laser melting. In this approach, the reinforcing lines are deposited in-plane at the mid-height of the printed part, i.e., in the neutral plane. To characterize the effect of partial reinforcement, partially reinforced parts with 0.3 wt% and 0.9 wt% Al2O3 are compared to fully reinforced parts. The results show that the accumulation of localized residual compressive stresses above the reinforcing lines in the neutral plane, induced during selective laser melting, increases the shape memory effect as a result of the increase in mechanical anisotropy in the building direction. Moreover, a new phenomenon named the waistband effect is observed in cyclic compressive operation, which results in incremental penetration of the reinforcing particles into the neutral plane during compression. This facilitates a higher strain recovery in the partially reinforced part. These results clearly confirm that partial reinforcement with Al2O3 significantly enhances the shape memory effect of Cu-Al-Ni SMAs. (C) 2021 The Authors. Published by Elsevier B.V.

Automated summary

The study introduced a new method to enhance the shape memory effect and stability in Cu-Al-Ni shape memory alloys by partially reinforcing with alumina through selective laser melting. Partial reinforcement accumulates localized residual compressive stresses, increasing the shape memory effect, and a waistband effect is observed during cyclic compressive operation, facilitating higher strain recovery. These results confirm that partial reinforcement with alumina significantly enhances the shape memory effect of Cu-Al-Ni shape memory alloys.