Influência dos precipitados de nb nas propriedades mecânicas de ligas cu-al-be passivas do efeito memória de forma

Abstract

The term Shape Memory Alloy (SMA) consists of a group of metallic materials that feature the capacity to return to their original shape when subjected to a suitable thermomechanical treatment. These alloys have been widely researched because of your unique properties, namely the Shape Memory Effect (SME) and superelasticity. The phase transformations and crystalline structure of martensite and austenite directly influence the achievement of these peculiar characteristics. Shape memory alloys have been widely used today in mechanical actuators, acoustic isolation, pipe coupling, in the medical industry among others. In particular, Cu-Al-Be alloys are used in civilian industry, such as buffers for earthquakes in buildings and bridges. The present study aims to generate Cu-Al-Be alloys, with addition of niobium in different compositions (0.5%, 1.5% and 2.5%), to evaluate the influence of niobium precipitates on the mechanical properties of the alloy , with the purpose of verifying the residual deformation in the superelasticity and the thermal hysteresis influenced by the niobium. The methodology used consisted of melting the alloy under an Indutherm MU-400 induction furnace, with subsequent solubilization in a MUFLA, Jong type furnace. The samples were tempered and submitted to microstructural analysis, DSC and traction tests. The results showed a slight reduction of grain size with the addition of niobium in the alloy composition, besides an increase of the induction and residual strain.