Production of Cu-based alloys bulks with shape memory effect by atomization followed by selective laser fusion

Abstract

The shape memory alloys (SMA) are able to recover its original shape by heating after been plastically deformed. Cu-based alloys and NiTi based alloys are the most commun materials that have the SMA effect. However, Cu-based alloys have advantages over NiTi alloys because of the reduced cost of the alloy elements, the lower hysteresis and thermal stress, and also because of the low reactivity with oxygen. The main difficulty in the production of these alloys is the requirement of high cooling rates to avoid the transformation of the ß phase, which decomposes in the phases ± and ³2 at 565°C in conventional conditions of cooling, and deteriorates the shape memory effect of the alloy. The gas atomization process impose high cooling rates (103-105 K/s) to the melt particles and might avoid the decomposition of the b phase, enabling the formation of the martisite above room temperature. The purpose of this project is the production of complex geometry bulks with shape memory effect by atomization and consolidation of the powders by selective laser fusion (SLF). Tem nominal composition of the alloys are in wt% u-11.85Al-3.2Ni-3Mn and Cu-11.35Al-3.2Ni-3Mn-0.5Zr