Transformações de fase termoelásticas em ligas com memória de forma a base de Cu-Al-Ni
Abstract
Shape memory alloys (SMA) have some exceptional properties such as the
shape memory effect and the superelasticity. Both are associated with a
martensitic/austenitic phase transformation. Alloys of the system Cu-Al-Ni, Cu-
Zn-Al and NiTi belong to this class of material. The interest in the study of Cubased
SMA arises from the fact that they are cheaper than NiTi and might
achieve better properties in specific applications. Considering the presented
facts, the aim of the thesis is to understand the phase transformation and its
features such as the stabilization and hysteresis using thermoelastic
thermodynamics and a theory of the compatibility between the austenite and
martensite for the system Cu-Al-Ni. This system attracts attention of the
scientific community because it is a good candidate in the application of high
temperature shape memory alloys (HTSMA), working above 100 oC. Another
aim of the thesis is to evaluate the mechanical and functional properties of one
alloy processed by spray forming, which was selected based in on the previous
study. Important correlations were observed on the thermodynamics and
crystallographic compatibility with the phase transformation characteristics of
the system Cu-Al-Ni, which also enabled the production of an alloy with good
functional properties regarding the shape memory effect.