Dissertação
Caracterização microestrutural e mecânica da liga de alta entropia CrMnFeCoNi conformada por laminação
Fecha
2019-12-06Registro en:
orcid.org/0000-0002-2802-1554
Autor
Gustavo Henrique Sousa
Institución
Resumen
High-entropy alloys (HEAs) are defined as alloys that normally contain five or more
major elements in atomic fractions ranging from 5% to 35%. Despite the presence
of a large number of components, HEAs often show rather simple crystal
structures such as faces centered cubic (FCC). The distinctive feature of these
alloys was originally attributed to the high configurational entropy associated with
the mixing of a large number of constituents, allowing the formation of simple solid
solutions. Since then, this new class of alloys has been extensively studied, and
has attracted attention from academia, being reported with many interesting
properties. In some cases the properties may be considerably better than those
found in traditional materials, such as: good wear resistance, high temperatures
resistance, high hardness, good thermal stability, good fatigue resistance
characteristics and good corrosion resistance. Research for potential applications
of high entropy alloys are using thermomechanical processing involving high
deformation levels to refine the microstructure of these alloys and, cold rolling has
been shown to be the main technology to improve the strength of these alloys.
From this context, this work reports the effects of cold rolling on the final
microstructure and the mechanical properties of a CrMnFeCoNi HEA processed
by spray-formed and deformed to 30, 50, 90 and 146% of true strain. The results
presented an alloy with excellent workability and exhibited a large work hardening
capacity in cold rolling. The sample in as-sprayed condition is texture free and
during cold rolled, the samples indicated a formation of {220} type texture. During
cold rolling occurred the typical dislocation interactions dislocation-dislocation and
the other from dislocation-mechanical twin boundary interactions, with the twinning
contributing significantly to strain hardening because of the extra boundaries
introduced during twinning (i.e., the dynamic Hall-Petch effect). The LAE
CrMnFeCoNi in as-spray condition showed good results in terms of yield strength,
tensile strength and elongation, about 319,0 MPa, 671,7 MPa and 43,6%
respectively. The true strain sample of 146%, on the other hand, presented high
tensile strength and yield strength, about 1256 MPa, at the cost of ductility.