Fabricação de componentes miniaturizados de ligas com memória de forma Ni-Ti usando fundição de precisão.

Abstract

Shape memory alloy (SMA) have functional characteristics of apparent plastic deformation recovery and change of mechanical properties when subjected to temperature variations, providing an increasing interest for engineering applications and a new way of designing mechanical systems. In this context, it is important develop new methods to manufacture of mechanical components mainly of Ni-Ti SMA system. In addition, from end of the 20th century investment casting has become an effective alternative to forming components of titanium and its alloys for high-tech applications. However, there is no information on the use of this process for the manufacture of Ni-Ti SMA mechanical components. Thus, the aim of this thesis was to evaluate two investment casting technologies, based on melting and injection of liquid metal into a mold to obtain miniaturized Ni-Ti SMA components with functional properties. For this purpose, optimization of controllable process parameters was performed, followed by thermal and mechanical characterization of Ni-Ti SMA with shape memory effect and superelasticity properties. Subsequently, in order to validate the used investment casting processes were made different shapes of Ni-Ti SMA mini-actuators (Belleville springs, orthopedic clamps, meshes, cellular structures, springs and bolts), which were submitted to thermal and mechanical characterization, and non-destructive testing of integrity. Based on the results, it was concluded that the investment casting processes (Plasma Skull Push-Pull and Induction Melting with Centrifugal Casting employed were suitable for manufacture of Ni-Ti SMA mini-actuators with good functional properties and simple and complex geometries.