COMPARATIVE STUDY BY TEM, EBSD AND MICROHARDNESS OF THE MICROSTRUCTURE OF COPPER WIREDRAWN AT 77 K AND 295 K
ESTUDO COMPARATIVO USANDO MET, EBSD E MICRODUREZA DA MICROESTRUTURA DO COBRE TREFILADO A 77 K E 295 K
Marcos Paulo Pereira Leis, Sheyla Santana de Carvalho, Talita Gama Sousa, Simone Izabel Vieira de Santana, Luiz Paulo Branda
Abstract
Copper has limited application in coils of high magnetic field electromagnets because of its low mechanical strength. In this work, the mechanical strength of copper wire was increased through severe wiredrawing in several steps at 77 K and transmission electron microscopy (TEM), electron backscatter diffraction (EBSD) and Vickers microhardness were used to study the evolution of the microstructure of the material. Comparison of the results with those obtained processing the same material at room temperature (295 K) led to a better understanding of the hardening mechanisms. The wires drawn at 295 K showed dynamic recovery structures, while the wires drawn at 77 K showed a partial recrystallization microstructure. The fact that the Vickers microhardness of the wires wiredrawn at 77 K was about 50% higher than those wiredrawn at 295 K suggests that cryogenic deformation was effective in delaying the recovery of the material.
Keywords
Resumo
O cobre tem aplicação limitada em bobinas de eletromagnetos de alto campo magnético devido à sua baixa resistência mecânica. Neste trabalho, a resistência mecânica do cobre foi aumentada através de trefilação severa a 77 K em várias etapas. A microscópia eletrônica de transmissão (MET), a difração de elétrons retorespalhados (EBSD) e a microdureza Vickers foram usadas para o estudo da evolução microestrutural do material. A comparação dos resultados com o mesmo material processado em temperature ambiente (295 K) levou a uma melhor compreensão dos mecanismos de endurecimento. Fios trefilados em 295 K mostraram estruturas de recuperação dinâmica, enquanto que os fios trefilados a 77 K mostraram uma microestrutura de recristalização parcial. O fato da microdureza Vickers do fio trefilado a 77 K seja cerca de 50% maior do que os fios trefilados a 295 K sugere que a deformação criogênica foi efetiva em retardar a recuperação do material.
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References
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