Influência da taxa de deformação nas propriedades termomecânicas de ligas CU-AL-BE-NB-NI com memória de forma

Abstract

The interfaces with physical form memory (EMF) belong to a family of metallic materials that, even after being pseudoplastically deformed, demonstrate a recoverability of a form of age definition, since they have undergone a suitable thermomechanical process. These alloys were four phase transformation phases: Mi and Mf during the cooling, Ai and Af during heating. The halves and the images represent, respectively, and initiate the martensitic transformation, whereas the temperatures and the affinity, respectively, the beginning and end of the austenitic transformation. As the multiple properties of EMF are largely related to a thermoelastic martensitic transformation. When the alloys with EMF are a thermoelastic martensitic measure the deformation is made possible by a machining mechanism, below the transformation temperature. This (reversible) measure undergoes an inversion process, when a maze structure (martensitic) becomes the mother phase of high temperature (austenite), by heating. One can consider the martensitic transformation as a first-order structural transition presenting a uniform deformation of the crystal lattice. This process basically happens, by shear, being made possible by a machining mechanism below the transformation temperature. It is consistent to state that the martensitic transformation is thermoelastic, when the deformation that produces the transformation is absorbed by the austenite matrix around the martensite, so that there is a thermoelastic balance between the energy of chemical origin and the elastic origin, which controls the progress of transformation. Thus, the present work aims to evaluate the influence of the deformation velocity on the thermomechanical properties of Cu-Al-Be-Nb-Ni alloys with shape memory effect. Thus, it was possible to observe that the higher the test temperature, the smaller the residual deformation. It was also observed that the stress to impose at the same maximum deformation the alloy was lower, the lower the deformation temperature. In the same way, it can be stated that the heating rate during the deformation contributes to the increase of the residual deformation. And that the residual deformation increases with the decrease of the velocity of deformation and is directly associated with the martensite retained.