Influence of laser re-melting on density, microstructure, transformation behaviour and mechanical properties of selective laser melted Cu-Al-Ni-Mn shape-memory partsTuesday (27.09.2016) 15:15 - 15:30 Part of:
There is a major interest in Cu-based shape-memory alloys (SMAs) mainly due to their low cost and promising shape-memory properties. Yet, the applicability of these alloys is limited by their brittleness in the coarse-grained polycrystalline state, which is caused by a strong elastic anisotropy and the precipitation of intermetallic phases . Here, selective laser melting (SLM), an additive manufacturing technique, was used to tailor the phase formation and microstructure of the shape-memory alloy Cu-11.85Al-3.2Ni-3Mn (wt.%). The SLM process is capable of producing crack-free, fully martensitic (β´) samples with a reduced grain size and a high relative density of about 98.8%.
The focus of the present work is to further increase the density of the SLM specimens by re-melting the previously processed layers. In the first step, the processing parameters for the additional re-melting were optimised. The processing started with single-track experiments to evaluate the parameter window in which a sufficient volume of Cu-11.85Al-3.2Ni-3Mn is re-melted. Suitable parameter combinations were then transferred to the production of cubic samples (8 x 8 x 8 mm3). Every powder layer processed by SLM was re-melted at least once and the relative density increased to values of about 99.5%. The microstructure, phase formation, transformation behaviour and mechanical properties can be correlated with the energy introduced into the material during manufacturing and are compared with the specimens that were processed without re-melting.
The re-melting procedure during additive manufacturing of Cu-11.85Al-3.2Ni-3Mn (wt.%) proves to be an interesting tool not only to prepare samples with an increased density and enhanced deformability in tension but also to tailor the microstructures and with it the transformation temperatures and their pseudoelastic behaviour.
 K. Otsuka, C.M. Wayman (ed.). Shape Memory Materials. Cambridge: Cambridge University Press, 1998.
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