Caracterização mecânica e funcional de uma liga com memória de forma do sistema Cu-Al-Ni-Mn conformada por spray e deformada por HPT

Abstract

The martensitic transformations (MT) existing in shape memory alloys (SMA) are thermoelastics and are responsible for providing unique features for this class of materials, such as shape memory and pseudoelasticity, which make them interesting for applications in motion actuators, sensors, damping devices, energy absorption/release, and elastocaloric materials. The Ni-Ti system is one of the most important SMA. At high temperatures, Cu-based alloys are a low-cost alternative to replace them, with satisfactory performance of functional properties. However, they are susceptible to fragile intergranular fracture, due to their high elastic anisotropy. In this context, an alloy from the Cu-Al-Ni system was formed by Spray and exposed to a severe plastic deformation process (SPD), called High Pressure Torsion (HPT), with 0, 1/16 and 1/2 turns, in order to modify the microstructure of the alloy overcoming the difficulties previously exhibited. X-ray diffraction (XRD) was used to identify the phases formation. The mechanical behavior was evaluated by Vickers Microhardness tests. The measurement of the produced grain sizes was performed by Optical Microscopy (OM), while the morphologies were analyzed using a Transmission Electron Microscope (TEM). Aiming at understanding the variation of functional memory shape, it was carried out Differential Scanning Calorimetry (DSC), Atomic Force Microscopy (AFM), and Scanning Electron Microscopy (SEM). The results proved the effectiveness of the HPT processing, due to the increase of the hardness and reduction of the grain size. The predominance of the β’ martensite phase and the formation of self-accommodating martensitic fine plates suggested the maintenance of the shape memory functional property, which was further corroborated by the shape recovery in all processing routes used in this work.